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The evaluation of the long-term effectiveness of zero/low fluoroscopy workflow in ablation procedures for the treatment of paroxysmal and persistent atrial fibrillation

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The evaluation of the long-term effectiveness of zero/low fluoroscopy workflow in ablation procedures for the treatment of paroxysmal and persistent atrial fibrillation

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The Evaluation of the Long-Term Effectiveness of Zero/Low
Fluoroscopy Workflow in Ablation Procedures for the Treatment of
Paroxysmal and Persistent Atrial Fibrillation

by

Kevin Tseng

A Thesis Presented to the
FACULTY OF THE USC KECK SCHOOL OF MEDICINE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOSTATISTICS AND EPIDEMIOLOGY)

May 2023

Copyright 2023 Kevin Tseng
ii

ACKNOWLEDGEMENTS

I want to thank Dr. Wendy Mack, my committee chair, for her endless patience and kindness in
helping me explore my passion and interest during the thesis development. I would also like to
express my gratitude to my committee members Dr. Mariana Stern and Dr. Andrew Zadeh for
their immense support for my thesis.

iii

TABLE OF CONTENTS
ACKNOWLEDGEMENTS ............................................................................................................ ii
LIST OF TABLES ......................................................................................................................... iv
LIST OF FIGURES ........................................................................................................................ v
Abstract .......................................................................................................................................... vi
Chapter 1. INTRODUCTION ......................................................................................................... 1
1.1 Treatment of AF .................................................................................................................... 2
1.2 Ablation Procedure ................................................................................................................ 2
1.3 Zero or Low Fluoroscopy Workflow ..................................................................................... 4
1.4 Evolving Non-fluoroscopic Techniques ................................................................................ 5
Chapter 2. METHODS .................................................................................................................... 7
2.1 Study Population.................................................................................................................... 7
2.2 Data Collection ...................................................................................................................... 7
2.3 Statistical Analysis ................................................................................................................ 8
2.3.1 Demographics and Baseline Characteristics ................................................................... 8
2.3.2 Primary Effectiveness Endpoint ...................................................................................... 9
Chapter 3. RESULTS .................................................................................................................... 12
3.1 Demographics and Baseline Characteristics ........................................................................ 12
3.1.1 Demographics................................................................................................................ 12
3.1.2 Medical History ............................................................................................................. 16
3.1.3 Atrial Fibrillation History.............................................................................................. 20
3.2 Procedure Data .................................................................................................................... 24
3.3 Primary Effectiveness Endpoint .......................................................................................... 29
3.3.1. Primary Effectiveness Success Rates ........................................................................... 29
3.3.2. Kaplan-Meier Analyses ................................................................................................ 34
3.3.3. Cox Proportional Hazards Models ............................................................................... 42
Chapter 4. DISCUSSION ............................................................................................................. 51
Study Strength and Limitation ............................................................................................... 54
Chapter 5. CONCLUSION ........................................................................................................... 56
REFERENCES ............................................................................................................................. 57

iv

LIST OF TABLES
Table 1. Demographics of PAF and PsAF Cohort ........................................................................ 13
Table 2. Demographics of PAF and PsAF Cohorts by Fluoroscopy Groups ............................... 14
Table 3. Medical History of PAF and PsAF Cohort ..................................................................... 17
Table 4. Medical History of PAF and PsAF Cohorts by Fluoroscopy Groups............................. 18
Table 5. Atrial Fibrillation Characteristics of PAF and PsAF Cohort .......................................... 21
Table 6. Atrial Fibrillation Characteristics of PAF and PsAF Cohorts by Fluoroscopy Groups.. 22
Table 7. Ablation Procedural Data of PAF and PsAF Cohort ...................................................... 25
Table 8. Ablation Procedural Data of PAF and PsAF Cohorts by Fluoroscopy Groups .............. 27
Table 9. Recurrence of AF/AT/AFL in PAF and PsAF Cohort ................................................... 31
Table 10. Recurrence of AF/AT/AFL in PAF and PsAF Cohort by Zero/Low vs. Conventional
Fluoroscopy Groups ...................................................................................................................... 32
Table 11. Recurrence of AF/AT/AFL in PAF and PsAF Cohort by 5-Level Fluoroscopy
Groups ........................................................................................................................................... 33
Table 12. Hazard Ratios (HR) and 95% Confidence Interval (CI) Estimates for Variables
Associated AF/AT/AFL Recurrence 12 Months After Undergoing Ablation Procedures in PAF
Cohort ........................................................................................................................................... 47
Table 13. Hazard Ratios (HR) and 95% Confidence Interval (CI) Estimates for Variables
Associated AF/AT/AFL Recurrence 12 Months After Undergoing Ablation Procedures in PsAF
Cohort ........................................................................................................................................... 49

v

LIST OF FIGURES
Figure 1. THERMOCOOL SMARTTOUCH Catheter .................................................................. 4
Figure 2. CARTO 3 System ............................................................................................................ 4
Figure 3. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months Post
Procedure by PAF and PsAF Cohort ............................................................................................ 37
Figure 4. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months Post
Procedure by Zero/Low vs. Conventional Fluoroscopy Groups in PAF Cohort ......................... 38
Figure 5. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months Post
Procedure by Zero/Low vs. Conventional Fluoroscopy Groups in PsAF Cohort ....................... 39
Figure 6. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months Post
Procedure by 5-Level Fluoroscopy Groups in PAF Cohort.......................................................... 40
Figure 7. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months Post
Procedure by 5-Level Fluoroscopy Groups in PsAF Cohort ........................................................ 41

vi

ABSTRACT
Purpose: There have been long standing concerns of the negative acute and long-term health
hazards associated with radiation exposure from the fluoroscopy used in radiofrequency catheter
ablations. The primary objective of this study was to evaluate the 12-month effectiveness of the
alternative zero/low fluoroscopy radiofrequency catheter ablation workflow compared with the
conventional radiofrequency catheter ablation workflow with normal fluoroscopy in paroxysmal
and persistent atrial fibrillation ablation procedures.
Methods: Data arose from a prospective, multi-center, clinical registry study for the ablation
procedure for the treatment of atrial fibrillation. A total of 426 patients diagnosed with atrial
fibrillation in the period of June 2013 to Aug 2021 were enrolled, and 397 of them underwent
ablation procedures, including 242 PAF, 124 PsAF, and 31 subjects with long-standing AF. All
ablation procedures were conducted using the ThermoCool® SmartTouch™ catheter. Subjects
with PAF and PsAF were included in this thesis as the study population.
The primary effectiveness endpoint was defined as freedom from symptomatic AF through the
effectiveness evaluation period (91-365 days post index procedure). In this study, total
fluoroscopy time less than 3.0 minutes was defined as Zero/Low Fluoroscopy group, and the
fluoroscopy time greater than or equal to 3.0 minutes as Conventional Fluoroscopy Group. The
fluoroscopy time was also categorized into 5 strata by using the cut points of 3.0 mins and
quartiles of the overall data distribution of PAF and PsAF study subjects.
The percent of subjects who were free from symptomatic AF recurrences were summarized in
PAF and PsAF Cohorts, overall and by fluoroscopy groups. The association between the
fluoroscopy time and the primary effectiveness success rate were tested using: 1) the Chi-square
test; and 2) the Cochran-Armitage test for trend.
vii

Kaplan-Meier estimates and plots were used to characterize survival probabilities for the time to
first atrial fibrillation (AF), atrial tachycardia (AT) and atrial flutter (AFL) (hereafter, AF)
recurrence by the end of the 12 months follow-up in the PAF and PsAF cohorts, separately. The
survival probabilities of symptomatic AF recurrence over the 12-month follow-up were also
presented by fluoroscopy workflow along with the 95% confidence interval. Cox proportional
hazard models are performed to adjust for confounding effects on the hazard ratios (HR) in AF
recurrences between the fluoroscopy workflows.
Results:
Demographics and Baseline Characteristic: Patients with PsAF were slightly, though not
statistically significantly older (mean age, 62.3 vs 59.5 years; p=0.072). There was a higher
proportion of males in both PAF and PsAF cohorts (69.3% males vs 30.7% females and 73.2%
males vs 26.8% females, respectively). Similar demographic distributions were seen when
stratified by fluoroscopy groups, with the zero/low fluoroscopy group in the PAF cohort being
the youngest group (mean age, 57.7), and the conventional fluoroscopy group in the PsAF cohort
being the oldest (mean age, 62.7).
The PsAF cohort exhibited a higher proportion of medical comorbidities compared to the PAF
cohort, namely diabetes mellitus (12.7 vs. 3.9%; p=0.001), congestive heart failure (9.9 vs 1.6%;
p<0.001), and hypertension (51.4 vs 41.3%; p=0.053). Within AF cohorts, comorbidities did not
differ between fluoroscopy groups.
Procedural Data: The procedure efficiency was also demonstrated in subjects undergoing the
ablation procedure with the zero/low fluoroscopy workflow. The mean total procedure time in
PAF subjects was 109.0 (± 34.14) mins in the Zero/Low Fluoroscopy group compared with a
mean total duration of 199.98 (± 52.16) mins in the >35 mins fluoroscopy group. Even though
viii

the mean total procedure time was longer in the PsAF subjects, the time was still shortest in the
0-3 mins group (132.69 ± 51.56 min) and longest (210.51 ± 68.43) in the group of subjects with
>35 mins of fluoroscopy time.
Primary Effectiveness Results:
I. PAF Cohort
Of the 242 subjects in the PAF cohort, 67 (27.6%) subjects had recurrence of symptomatic AF
during the 12-month follow-up. Kaplan-Meier estimates of the cumulative probability of
freedom from recurrence 12 months post the procedure seems to be decreasing with the
increasing fluoroscopy time. The survival probabilities in the 0-3 mins, 3-7 mins, 7-17.5 mins,
17.5-35 mins, and >35 mins of fluoroscopy time were 76.9%, 75.0%, 71.4%, 72.4%, and 67.0%,
respectively. However, there is no significant differences of the survival curves across
fluoroscopy groups (log rank p-value=0.51).
The conventional fluoroscopy was associated with an increased risk of recurrence in subjects
undergoing ablation compared to zero/low fluoroscopy (unadjusted Hazard Rate (uHR), 1.30;
95% CI, 0.64-2.62). The results of the multivariable Cox proportional hazards model showed
that undergoing ablation procedure with conventional fluoroscopy time was associated with a
1.33-fold increased risk (adjusted Hazard Rate (aHR), 1.33; 95% CI, 0.65-2.70) comparing to
undergoing ablation procedure with zero/low fluoroscopy time, after adjustment for other
variables.
Similar results were obtained replacing the dichotomized fluoroscopy time by the 5-level
variable in the multivariable Cox proportional hazards model. After adjusting for age, sex, LA
diameter, and PV visualization using ICE/Venogram, the adjusted hazard ratios (aHRs) were
ix

non-significantly increased with the increasing length of fluoroscopy time during ablation
procedure in the PAF cohort.
II. PsAF Cohort
Of the 133 subjects in the PsAF cohort, 62 (46.6%) subjects had recurrence of symptomatic AF
during the 12-month follow-up. Kaplan-Meier Estimates of the cumulative probability of
freedom from recurrence 12 months post the procedure seems have no pattern with the
increasing fluoroscopy time. The highest survival probability of 81.0% was observed in the 3-7
mins fluoroscopy group, and the lowest probability of 37.8% in the 7-17.5 mins group. The
survival probability in the 0-3 mins, 17.5-35 mins, and >35 mins of fluoroscopy time groups
were 42.0%, 61.9%, and 51.4%, respectively. The survival curves across fluoroscopy groups
showed borderline statistical significance (log rank p-value=0.052).
Undergoing ablation with convention fluoroscopy time reduced the hazard of having
symptomatic AF recurrence by 38% (uHR, 0.62; 95% CI, 0.63-1.06) compared to zero/low
fluoroscopy time as the reference group in the PsAF cohort. Using the same reference group, the
risk was decreasing with the higher level of fluoroscopy time: the risk was 0.25 times (95% CI,
0.08-0.73) in 3.1-7.0 min fluoroscopy group, 0.95 (95% CI, 0.49-1.85) in 7.1-17.5 min
fluoroscopy group, 0.52 (95% CI, 0.23,1.19) in 17.6-35.0 min fluoroscopy group, and 0.70 (95%
CI, 0.36-1.38) in >35.0 min fluoroscopy group. The risk in subjects who underwent ablation
procedure with conventional fluoroscopy time was 0.51 times to subjects who underwent
ablation with zero/low fluoroscopy time (95% CI, 0.29-0.90), after adjustment of other factors.
Conclusion: The study results based on real-world settings provide strong support for the
zero/low fluoroscopy workflow by its profound long-term effectiveness profile in both PAF and
PsAF subjects. It appears that the effectiveness of ablation procedures using zero/low
x

fluoroscopy may vary depending on the type of atrial fibrillation (AF) being treated. In patients
with paroxysmal AF, the use of zero/low fluoroscopy may result in slightly higher success rates
compared to conventional fluoroscopy. However, in patients with persistent AF, the success rate
may be lower with zero/low fluoroscopy. Overall, the decision to use zero/low fluoroscopy
should be made on a case-by-case basis, taking into consideration the type and severity of AF
being treated.

1

CHAPTER 1: INTRODUCTION
Atrial fibrillation (AF) is a rhythm characterized by chaotic and irregular electrical activation of
the atria (the atria actually do not contract fully in AF). This activation leads to abnormal atrial
function, impaired atrial emptying due to loss of atrial contraction, increased risk of stroke, and a
loss of the usual AV synchrony in a cardiac cycle.
AF is the most common type of heart arrhythmia, affecting anywhere from 0.4% to 1% of the
general population. An estimated 12.1 million people in the United States will have AFib in 2030
(1-4). The prevalence of AFib increases with age, with an estimated 8% prevalence in persons
over 80 years of age (5,6). Globally, it was estimated that 23.1 million women and 23.2 million
men had AF in 2016 (7). The estimated prevalence was lower in women than in men (8). The
prevalence of AF is lower among African American comparing to white American (9). However,
it is unclear this is due toa lower incidence of AF or to a lack of diagnosis.
In addition to life-altering symptomatic episodes, individuals with AF have an increased long-
term risk of stroke, heart failure, and all-cause mortality (10,11). The ischemic stroke risk of AF
subjects is greater than that of individuals without AF (12,13). AF also leads to the increase of
health care utilization and have a great impact on health care resources globally (14,16). The
medical community has adopted a 3-category classification system that attempts to distinguish
and standardize the different levels of AF. The 3 AF classifications are: Paroxysmal (2 or more
AF episodes that terminate spontaneously within 7 days), Persistent (AF sustained beyond 7 days
or lasting less than 7 days but necessitating termination by intervention), and Longstanding
Persistent (AF greater than one-year duration) (6,17).
2

1.1 TREATMENT OF AF
The treatment of AF and its consequences has made AF a costly public health burden.
Approximately one-third of all hospital admissions for cardiac arrhythmias are due to AF, with
an observed increase in admissions for AF of 66% over the last 20 years in the US due to the
rising prevalence of related co-morbidities. This represents a major US healthcare burden, with
annual direct healthcare costs between (US) $4,000 and $5,000 per person when treated with
traditional therapies (i). Total annual US expenditure for the treatment of AF subjects has been
estimated at $6.65 billion, and approximately (US) $15.7 billion in the European Union (18,19).
In persons with paroxysmal AF, elimination or amelioration of symptoms is a major driving
force for therapy. Radiofrequency (RF) catheter ablation is widely considered the best treatment
method for the paroxysmal AF population (17,20,21). In a randomized clinical trial comparing
catheter ablation to antiarrhythmic drug (AAD) therapy in persons with paroxysmal AF, 66% of
patients who underwent ablation with the NAVISTAR® THERMOCOOL® catheter remained
free from symptomatic atrial arrhythmias and only 16% of patients treated with AAD were
recurrence free at one year (22).
1.2 ABLATION PROCEDURE
During the ablation procedure, the patient lies on a table and electrodes are attached to their chest
to monitor their heart rhythm. A small incision is made in the groin, and catheters are threaded
through blood vessels to the heart. The catheters are used to deliver radiofrequency energy to the
areas of the heart that are responsible for the abnormal electrical signals that cause AF. In this
study, the THERMOCOOL SMARTTOUCH catheter was used in the ablation procedures for all
subjects.
3

The THERMOCOOL SMARTTOUCH Diagnostic/Ablation Deflectable Tip Catheters with
Contact Force Sensing Capability is a multi-electrode luminal catheter with a deflectable tip
designed to facilitate electrophysiological mapping of the heart and to transmit RF current to the
catheter tip electrode for ablation purposes. The catheter has force sensing technology that
provides a real-time measurement of contact force between the catheter tip and the beating heart
wall.
The THERMOCOOL SMARTTOUCH Catheter is also designed to work with the CARTO
Cardiac Electrophysiological Mapping System (CARTO System) to provide the user with real-
time anatomical and electrophysiological information. The CARTO system helps
electrophysiologists navigate the heart by generating an accurate 3D map, as well as pinpointing
the exact location and orientation of catheters in the heart during diagnostic and the ablation
procedures. The 3D image that’s generated by the system helps doctors steer the catheter to areas
in the heart where RF energy needs to be administered (23).

4

Figure 1. THERMOCOOL SMARTTOUCH Catheter

Figure 2. CARTO 3 System

1.3 ZERO OR LOW FLUOROSCOPY WORKFLOW
During the ablation procedure, X-ray fluoroscopy has been universally established as one of the
primary imaging modalities used to position catheters in the heart, to create maps of the
chambers of the heart, to guide the transseptal puncture and electrophysiology ablation
procedures. The pre- and post-procedure imaging and multiple long fluoroscopically-guided
ablation procedures for AF has the potential to significantly add to the lifetime radiation
exposure of individual patients and electrophysiologists. The radiation exposure from
fluoroscopy during the ablation procedures for the treatment of atrial fibrillation has been a long-
standing concern, including the increased risk of skin carcinomas, leukemia, dermatitis,
cataracts, and other adverse health effects. The rise of musculoskeletal injuries due to wear-
weighted protection equipment to limit the radiation exposure and reports of head and neck
5

cancer among electrophysiologists have also been raising concerns of the indiscriminate use of
fluoroscopy.
With the advent of new ablation technologies in recent years, a growing number of operators
have alternative workflows for AF ablation that minimize exposure to zero/low fluoroscopy
without compromising safety and efficacy outcomes (24). These zero/low fluoroscopy
minimization workflows allow for extremely low to no exposure to radiation to all individuals in
the procedure room, resulting in a valuable reduction of years of lives lost and affected from
adverse health effects of medical radiation exposures.
1.4 EVOLVING NON-FLUOROSCOPIC TECHNIQUES
Techniques to reduce or even eliminate x-ray fluoroscopy during catheter ablation have been
reported for more than a decade. The radiation exposure duration or the fluoroscopy dose during
ablation procedure has not shown a deterministic effect of cancers on physicians or patients. The
concerns surrounding fluoroscopy exposures are largely focused on the potentially increased risk
of musculoskeletal injuries associated with weighted protective equipment and head and neck
cancer among ablation electrophysiologists that may be due to the cumulative exposure to the
radiation.
Several small studies have demonstrated the feasibility of eliminating x-ray fluoroscopy during
AF ablations completely. In 2002, a small study demonstrated the feasibility of using the
CARTO mapping system (BioSense Webster, Diamond Bar, CA) and eliminating the use of x-
rays in ablation procedures on the right-sided accessory pathway in 21 cases. In 2009, a study
reported the atrial fibrillation ablation technique using intracardiac echocardiography (ICE) and
electroanatomic mapping without fluoroscopy (25). A case study reported a successful
transseptal puncture for left-sided accessory pathway ablation via transesophageal
6

echocardiography guidance where no fluoroscopy was used (26). These techniques were then
gradually adapted to catheter ablation of AF. More and more studies demonstrated the feasibility
of performing the AF ablation with zero to low fluoroscopy use (27,31).
Though the availability, accuracy and resolution of 3D mapping systems has advanced over time,
the adoption of non-fluoroscopic techniques has increased slowly. This can be attributed to a
number of factors. There is a learning curve associated with adopting new techniques, and this
can be a barrier to their widespread adoption. Physicians may be reluctant to try a new technique
if they are not confident in their ability to perform it safely and effectively. Secondly, there may
be concerns about the patient safety of non-fluoroscopic techniques. Without the use of real-time
fluoroscopy, there may be a perceived risk of complications or incomplete ablation. There is also
an issue of procedure time. AF ablation is already a lengthy and complex procedure, and the use
of non-fluoroscopic techniques may add additional time and complexity.
Overall, the slow adoption of non-fluoroscopic techniques for AF ablation highlights the need for
studies to evaluate the safety and effectiveness of zero/low fluoroscopy techniques. This thesis
used data from an observational registry to address the following objectives:
 To evaluate the efficacy of zero/low fluoroscopy radiofrequency ablations in the
treatment of patients with Paroxysmal or Persistent atrial fibrillation
 To evaluate if risk of AF recurrence is associated with fluoroscopy duration
 To evaluate if the association between treatment effect and length of fluoroscopy time in
the ablation procedure is different between PAF and PsAF patients
7

CHAPTER 2: METHODS
The primary objective of this thesis is to evaluate the effectiveness of zero/low fluoroscopy
radiofrequency catheter ablation workflow in paroxysmal atrial fibrillation ablation procedures.
2.1 STUDY POPULATION
All subjects of this study were from an observational registry. The registry aims to evaluate the
safety and effectiveness of using the THERMOCOOL SMARTTOUCH Catheter for the
treatment of symptomatic atrial fibrillation. The investigation is a prospective, non-randomized,
open-label, multicenter, cohort registry conducted at approximately 30 clinical centers in Europe,
Australia and Canada. The registry population included adult (aged 18 and older) subjects with
symptomatic AF who met eligibility criteria and who, in the opinion of the clinical site
investigator, were candidates for ablation of AF. As an ablation procedure was not the first line
treatment of AF, all eligible subjects should have failed first line AF treatment of at least one
antiarrhythmic drug (AAD, class I or III, or AV nodal blocking agents such as beta blockers and
calcium channel blockers) as evidenced by recurrent symptomatic AF. Registry subjects included
AF subtypes: Paroxysmal atrial fibrillation (PAF), Persistent atrial fibrillation (PsAF), and long-
standing Persistent atrial fibrillation. All subjects were planned to be followed for 12 months
following their ablation procedures.
2.2 DATA COLLECTION
The American Heart Association and American College of Cardiology classified AF as follows:
1. Paroxysmal AF (PAF): intermittent in nature, terminating spontaneously or within 7 days
of treatment.
2. Persistent AF (PsAF): Failure to terminate in 7 days
3. Long-lasting AF: AF lasting for more than 12 months
8

4. Permanent AF: Persistent AF where rhythm strategy is no longer pursued
Subjects with PAF and PsAF were included in this thesis as the study population.
Demographics, medical history, atrial fibrillation history, and other baseline data were collected
approximately 30 days before ablation procedures. During the ablation procedure, fluoroscopy
time, RF application data, total ablation duration, pulmonary vein isolation related data were
recorded. Medical condition, concomitant medication, hospitalization history, symptomatic AF
recurrence, adverse events, and electrocardiogram data were collected at 3, 6, and 12 months
after the ablation procedures. Electronic Case Report Forms (eCRF) were used to collect all
subject data.
The fluoroscopy time was recorded during the ablation procedures, which was categorized in two
different ways in this thesis. The first grouping method considered the total fluoroscopy time less
than 3.0 minutes as Zero/Low Fluoroscopy group, and the fluoroscopy time greater than or equal
to 3.0 minutes as Conventional Fluoroscopy Group. The second method categorized the
fluoroscopy time into 5 strata by using the cut points of 3.0 mins (considered as low fluoroscopy
application), 7.0 mins (1
st
quartile), 17.5 mins (2
nd
quartile), and 35.0 mins (3
rd
quartile) based on
the overall data distribution of PAF and PsAF study subjects. The 5-Level Fluoroscopy group
were therefore: 1) Zero/Low fluoroscopy group, 2) 3.1 to 7.0 min fluoroscopy group, 3) 7.1 to
17.5 min fluoroscopy group, 4) 17.6 to 35.0 min fluoroscopy group, and 5) greater than 35.0 min
fluoroscopy group.
2.3 STATISTICAL ANALYSIS
2.3.1 DEMOGRAPHICS AND BASELINE CHARACTERISTICS
Subject demographics, medical history, atrial fibrillation history, and other baseline data were
summarized descriptively for all patients in the PAF and PsAF cohort. Procedural data such as
total procedure duration, fluoroscopy duration and dose, RF application time, balloon dwell time,
9

fluid delivery, output and balance were summarized descriptively. Descriptive summaries for
continuous variables included mean, standard deviation, median, and range. For categorical
variables, the count and percent were provided. Percentages were based on the number of
subjects with available data.
The differences of demographics and baseline characteristics between PAF and PsAF cohorts
were tested using t-test for continuous variables and Chi-square test for categorical variables.
2.3.2 PRIMARY EFFECTIVENESS ENDPOINT
The primary effectiveness endpoint was defined as freedom from symptomatic AF through the
effectiveness evaluation period (which was 91-365 days post index procedure). AF recurrences
were captured by arrhythmia monitoring devices, while symptoms associated with each episodes
were based on subjects’ self-report. The primary effectiveness success rate was calculated as the
percentage of subjects who remained free from symptomatic AF recurrences during the
evaluation period (Day 91-365 post ablation procedure), and this was analyzed separately for
different study groups based on their fluoroscopy times in the PAF and PsAF cohorts. Only
subjects who had at least 12 months of follow-up data available were included in the analysis
unless they had already experienced recurrences of AF before the 12-month mark. In other
words, if a subject had a recurrence of AF before the 12-month mark, they were still included in
the analysis, even if they did not complete the full 12-month follow-up period.
The association between the fluoroscopy time and the primary effectiveness success rate were
tested using: 1) the Chi-square test, where fluoroscopy time was dichotomized as zero/low
fluoroscopy group versus conventional fluoroscopy group; 2) the Cochran-Armitage test for
trend to test if the primary effectiveness success rates showed a monotonic trend with the
increasing duration of fluoroscopy time, where the 5-level fluoroscopy grouping was used.
10

The 12-month survival rates were estimated using the Kaplan-Meier method. Kaplan-Meier
estimates were used to estimate the probability of freedom from symptomatic AF recurrence
through the 12-month follow-up while accounting for censored observations. Kaplan-Meier
curves were presented by fluoroscopy group (dichotomized and 5-level) to display time to
symptomatic AF through the effectiveness evaluation period (91-365 days post index procedure)
in PAF and in PsAF, separately. The probability of freedom from recurrences at 12 months in
each fluoroscopy group were presented along with the corresponding two-sided 95% confidence
bound. The pointwise 95% confidence intervals were constructed with Greenwood variance. A
log-rank test was used to test for differences in the 12-month survival curves between the
fluoroscopy groups in the probability of recurrence-free.
To identify the factors associated with symptomatic AF recurrences following ablation, two Cox
proportional hazard models were conducted: one model was conducted among zero/low
fluoroscopy patients, and another model was conducted among conventional fluoroscopy
patients. Hazard ratios (HR) and 95% confidence intervals (CI) associated with the factors were
estimated in PAF and in PsAF cohort, separately. In the first step, bivariate proportional hazards
models were used to evaluate the association between time to symptom recurrence and each of
the patient demographic, cardiovascular medical history, history of atrial fibrillation, left atrial
diameter, left ventricular ejection fraction (LVEF), procedure data. In the second step, variables
with a p-value less than 0.05 in the first step were included in a multivariate model to identify the
statistically significant factors associated with risk of symptom recurrence; adjusted HRs and CIs
are reported. In the implementation of the stepwise selection method, the entry and removal
approaches for the forward selection and backward elimination methods were used to assess
contributions of effects as they were added to or removed from a model. To control for key
11

factors and confounders, fluoroscopy time, age and sex were forced into the final adjusted
model; additional variables were selected in the model using the stepwise method with the
significance level for entry at 0.15 and 0.20 for staying in the model.
As not all ablation procedure data were transferred back from the study sites, subjects with
missing data of contact force, power, temperature, impedance were individually grouped as a
category of missing when fitting into the model. As racial and ethnic data is considered an
important aspect of clinical research for identifying potential disparities in treatment outcomes.
However, in Europe, there are stricter regulations governing the collection of personal data,
including information about race and ethnicity. Therefore, race and ethnicity data were not
mandatory fields to be answered in this study and thus were not included in the analyses.

12

CHAPTER 3: RESULTS
A total of 426 subjects were enrolled in the observational registry, all patients received cardiac
ablation treatment for atrial fibrillation (AF). Of the 426 enrolled subjects, 7 subjects were
excluded from the study after enrollment because the study catheter was not used, 22 subjects
were found not meeting eligibility criteria after enrollment. A total of 396 patients with PAF and
PsAF were included in the thesis.
3.1 DEMOGRAPHICS AND BASELINE CHARACTERISTICS
3.1.1 DEMOGRAPHICS
Patients with persistent AF were slightly, though not statistically significantly older (mean age,
62.3 vs 59.5 years; p = 0.072), with both groups having most patients between 60-70 years old.
There was a higher proportion of males in both PAF and PsAF cohorts (69.3% males vs 30.7%
females and 73.2% males vs 26.8% females, respectively; p = 0.41). In both PAF and PsAF
cohorts, the majority of subjects were White, Caucasian (92.9 and 92.3%, respectively; p=0.91),
and not Hispanic nor Latino (71.3 and 81.7%, respectively; p = 0.07) (Table 1). However, due to
the stricter regulations governing the collection of personal data in Europe, 6.7% and 7.0%
subjects in the PAF and PsAF cohorts did not provide race data, while 23.2% and 14.8% of them
did not provide data of ethnicity (Table 1).
Similar demographic distributions are seen when stratified by fluoroscopy groups, with the
zero/low fluoroscopy group in the PAF cohort being the youngest group (mean age, 57.7), and
the conventional fluoroscopy group in the PsAF cohort being the oldest (mean age, 62.7) (Table
2).

13

Table 1. Demographics of PAF and PsAF Cohort
Characteristic Paroxysmal AF
(N = 254)
Persistent AF
(N = 142)
p-value
1

Age, yr, median (range) 61.0 (30.0 – 82.0) 63.0 (36.0 – 80.0) 0.07
<50 51 (20.1) 16 (11.3)
50-60 66 (26.0) 32 (22.5)
60-70 89 (35.0) 60 (42.3)
≥70 48 (18.9) 34 (23.9)
Mean (SD) 59.5 (11.1) 62.3 (9.4)
Sex, n (%) 0.41
Female 78 (30.7) 38 (26.8)
Male 176 (69.3) 104 (73.2)
Race, n (%) 0.91
White or Caucasian 236 (92.9) 131 (92.3)
Black or African American 1 (0.4) 1 (0.7)
N/A 17 (6.7) 10 (7.0)
Ethnicity, n (%) 0.07
Hispanic or Latino 14 (5.5) 5 (3.5)
Not Hispanic nor Latino 181 (71.3) 116 (81.7)
N/A 59 (23.2) 21 (14.8)
1
p-value of Chi-square test

14

Table 2. Demographics of PAF and PsAF Cohorts by Fluoroscopy Groups
Variables Paroxysmal AF
(N = 254)
Persistent AF
(N = 142)
Zero/Low
Fluoroscopy
(n=41)
Convention
Fluoroscopy
(n=213)
p-
value
1

Zero/Low
Fluoroscopy
(n=34)
Convention
Fluoroscopy
(n=108)
p-
value
1

Age, yr,
median
(range)
58.0 (35.0 –
79.0)
62.0 (30.0 –
82.0)
0.25 61.0 (42.0 –
75.0)
63.5 (36.0 –
80.0)
0.42
<50 11 (26.8) 40 (18.8) 6 (17.7) 10 (9.3)
50-60 13 (31.7) 53 (24.9) 9 (26.5) 23 (21.3)
60-70 9 (22.0) 80 (37.6) 13 (38.2) 47 (43.5)
≥70 8 (19.5) 40 (18.8) 6 (17.7) 28 (25.9)
Mean (SD) 57.7 (11.4) 59.8 (11.0) 60.7 (9.3) 62.7 (9.4)
Sex, n (%)
Female 13 (31.7) 65 (30.5) 0.88 10 (29.4) 28 (25.9) 0.69
Male 28 (68.3) 148 (69.5) 24 (70.6) 80 (74.1)
Race, n (%)
White or
Caucasian
38 (92.7) 198 (93.0) 0.90 32 (94.1) 99 (91.7) 0.81
Black or
African
American
0 (0.0) 1 (0.5) 0 (0.0) 1 (0.9)
N/A 3 (7.3) 14 (6.5) 2 (5.9) 8 (7.4)
15

Ethnicity, n
(%)

Hispanic or
Latino
0 (0.0) 14 (6.6) 0.06 1 (2.9) 4 (3.7) 0.23
Not
Hispanic nor
Latino
35 (85.4) 146 (68.5) 31 (91.2) 85 (78.7)
N/A 6 (14.6) 53 (24.9) 2 (5.9) 19 (17.6)
1
p-value of Chi-square test
16

3.1.2 MEDICAL HISTORY

Overall, the PsAF cohort exhibited a higher proportion of medical comorbidities compared to the
PAF cohort (Table 3), namely diabetes mellitus (12.7 vs. 3.9%; p=0.001), congestive heart
failure (9.9 vs 1.6%; p<0.001), and hypertension (51.4 vs 41.3%; p=0.053). Within AF cohorts,
comorbidities did not differ between fluoroscopy groups (Table 4).

17

Table 3. Medical History of PAF and PsAF Cohort
Characteristic Paroxysmal AF
(N = 254)
n (%)
Persistent AF
(N = 142)
n (%)
p-value
1

Diabetes 0.001
No 244 (96.1) 124 (87.3)
Yes 10 (3.9) 18 (12.7)
Congestive Heart Failure <0.001
No 250 (98.4) 128 (90.1)
Yes 4 (1.6) 14 (9.9)
Hypertension 0.053
No 149 (58.7) 69 (48.6)
Yes 105 (41.3) 73 (51.4)
Ischemic Cardiomyopathy 0.46
No 241 (94.9) 137 (96.5)
Yes 13 (5.1) 5 (3.5)
Hypertrophic Cardiomyopathy 0.55
No 252 (99.2) 140 (98.6)
Yes 2 (0.8) 2 (1.4)
Transient Ischemic Attacks 0.37
No 246 (96.9) 135 (95.1)
Yes 8 (3.1) 7 (4.9)
Thromboembolic events 0.25
No 249 (99.2) 136 (97.8)
Yes 2 (0.8) 3 (2.2)
1
p-value of Chi-square test
18

Table 4. Medical History of PAF and PsAF Cohorts by Fluoroscopy Groups
Characteristic Paroxysmal AF
(N = 254)
n (%)
Persistent AF
(N = 142)
n (%)
Zero/Low
Fluoroscopy
(n=41)
Convention
Fluoroscopy
(n=213)
p-
value
1

Zero/Low
Fluoroscopy
(n=34)
Convention
Fluoroscopy
(n=108)
p-
value
1

Diabetes 0.74 0.17
No 39 (95.1) 205 (96.2) 32 (94.1) 92 (85.2)
Yes 2 (4.9) 8 (3.8) 2 (5.9) 16 (14.8)
Congestive Heart
Failure
0.38 0.12
No 41 (100.0) 209 (98.1) 33 (97.1) 95 (88.0)
Yes 0 (0.0) 4 (1.9) 1 (2.9) 13 (12.0)
Hypertension 0.50 0.56
No 26 (63.4) 123 (57.8) 18 (52.9) 51 (47.2)
Yes 15 (36.6) 90 (42.3) 16 (47.1) 57 (52.8)
Ischemic
Cardiomyopathy
0.49 0.83
No 38 (92.7) 203 (95.3) 33 (97.1) 104 (96.3)
Yes 3 (7.3) 10 (4.7) 1 (2.9) 4 (3.7)
Hypertrophic
Cardiomyopathy
0.53 0.39
No 41 (100.0) 211 (99.1) 33 (97.1) 107 (99.1)
Yes 0 (0.0) 2 (0.9) 1 (2.9) 1 (0.9)
19

Transient Ischemic
Attacks
0.10 0.54
No 38 (92.7) 208 (97.7) 33 (97.1) 102 (94.4)
Yes 3 (7.3) 5 (2.4) 1 (2.9) 6 (5.6)
Thromboembolic
events
0.53 0.72
No 41 (100.0) 208 (99.1) 33 (97.1) 103 (98.1)
Yes 0 (0.0) 2 (0.9) 1 (2.9) 2 (1.9)
1
p-value of Chi-square test
20

3.1.3 ATRIAL FIBRILLATION HISTORY

Comparing characteristics of the atrial fibrillation history between PAF and PsAF cohorts, the
PAF cohort had both a longer duration of AF (mean duration 6.0 vs 4.4 years; p=0.017), and a
higher ejection fraction (59.9 vs 56 .0%; p=0.002) (Table 5). The LA diameter was significantly
larger in the PsAF cohort (mean diameter, 41.7 mm vs 39.3 mm; p=0.004). Within each AF
cohort (Table 6), the Zero/Low fluoroscopy group had a significantly higher ejection fraction
than the conventional fluoroscopy group (61.0% vs 54.4%; p<0.001) in the PAF cohort. AF
characteristics did not differ between fluoroscopy groups in the PsAF cohort (Table 6).
21

Table 5. Atrial Fibrillation Characteristics of PAF and PsAF Cohort
Characteristic Paroxysmal AF
(N = 254)
Persistent AF
(N = 142)
p-value
1

History of Atrial Flutter, n (%) 0.25
No 204 (80.3) 107 (75.3)
Yes 50 (19.7) 35 (24.7)
Atrial Tachycardia, n (%) 0.22
No 231 (90.9) 134 (94.4)
Yes 23 (9.1) 8 (5.6)
LA Diameter (mm) 0.004
Median (range) 40.0 (20.0 – 54.0) 42.0 (26.0 – 60.0)
Mean (SD) 39.3 (6.1) 41.7 (6.3)
Ejection Fraction (%) 0.002
Median (range) 60.0 (15.0 – 76.0) 60.0 (0.0 – 77.0)
Mean (SD) 59.9 (7.5) 56.0 (12.4)
Duration of AF (yrs) 0.017
Median (range) 3.0 (0.0 – 56.0) 2.0 (0.0 – 24.0)
Mean (SD) 6.0 (7.9) 4.4 (5.0)
Previous Ablation for any
Arrhythmias, n (%)
0.81
No 168 (66.4) 96 (67.6)
Yes 85 (33.6) 46 (32.4)
1
p-value of Chi-square test for categorical variables and t-test for continuous variables

22

Table 6. Atrial Fibrillation Characteristics of PAF and PsAF Cohorts by Fluoroscopy
Groups
Paroxysmal AF
(N = 254)
Persistent AF
(N = 142)
Characteristic Zero/Low
Fluoroscopy
(n=41)
Convention
Fluoroscopy
(n=213)
p-
value
1

Zero/Low
Fluoroscopy
(n=34)
Convention
Fluoroscopy
(n=108)
p-
value
1

History of Atrial
Flutter, n (%)
0.41 0.86
No 31 (75.6) 173 (81.2) 26 (76.5) 81 (75.0)
Yes 10 (24.4) 40 (18.8) 8 (23.5) 27 (25.0)
Atrial Tachycardia,
n (%)
0.051 0.44
No 34 (82.9) 197 (92.5) 33 (97.1) 101 (93.5)
Yes 7 (17.1) 16 (7.5) 1 (2.9) 7 (6.5)
LA Diameter (mm) 0.35 0.11
Median (range) 39.0 (20.0 –
49.0)
40.0 (20.0 –
54.0)
38.0 (31.0 –
55.0)
42.0 (26.0 –
60.0)

Mean (SD) 38.2 (6.6) 39.5 (6.0) 39.8 (5.7) 42.3 (6.4)
Ejection Fraction
(%)
0.32 <0.001
Median (range) 63.0 (40.0 –
75.0)
60.0 (15.0 –
76.0)
60.0 (45.0 –
72.0)
57.0 (0.0 –
77.0)

Mean (SD) 61.1 (6.8) 59.7 (7.6) 61.0 (6.3) 54.4 (13.5)
Duration of AF
(yrs)
0.84 0.62
23

Median (range) 2.0 (0.0 –
56.0)
3.0 (0.0 – 40.0) 2.0 (0.0 –
20.0)
2.0 (0.0 –
24.0)

Mean (SD) 5.7 (10.1) 6.0 (7.5) 4.1 (4.5) 4.5 (5.2)
Previous Ablation
for any
Arrhythmias, n
(%)
0.84 0.99
No 26 (65.0) 142 (66.7) 23 (67.7) 73 (67.6)
Yes 14 (35.0) 71 (33.3) 11 (32.3) 35 (32.4)
1
p-value of Chi-square test for categorical variables and t-test for continuous variables
24

3.2 PROCEDURE DATA
Patients with PAF had a significantly shorter total ablation procedure time compared to patients
with PsAF (mean time, 143.5 vs 172.0 minutes; p<0.001) (Table 7). On the other hand, the
average impedance during procedure was significantly lower in patients with PsAF compared to
patients with PAF (mean impedance, 125.5 vs 133.6 Ohms; p<0.008). When stratified by
fluoroscopy groups, the Zero/Low fluoroscopy groups had shorter total procedural times in the
PAF cohort (mean time, 105.8 vs 148.4 minutes; p<0.001), as well as the PsAF cohort (117.1 vs
178.2; p = 0.009) (Table 8). By definition, the Zero/Low fluoroscopy groups had significantly
shorter total fluoroscopy times in the PAF cohort (mean time, 2.3 vs 24. 5 minutes; p<0.001),
and the PsAF cohort (mean time, 2.5 vs 26.8 minutes; p<0.001). The Zero/low Fluoroscopy
group showed significantly higher average power in the PAF cohort (mean power, 29.0 vs 26.7
Watts; p=0.014) and a significantly lower average temperature in the PsAF cohort (mean
temperature, 37.1 vs 38.2 degrees Celsius; p=0.003) (Table 8). As not all subjects’ procedure
data were collected (231 of the 254 subjects in the PAF cohort, and 117 of the 142 subjects in the PsAF
cohort with available procedure data), the analyses were performed in subjects with available data.

25

Table 7. Ablation Procedural Data of PAF and PsAF Cohort
Characteristic Paroxysmal AF
(N = 231
1
)
Persistent AF
(N = 117
1
)
p-value
2

Total Procedure Time (min) <0.001
Median (range) 130.0 (39.0 – 400.0) 162.0 (65.0 – 382.0)
Mean (SD) 143.5 (56.3) 172.0 (64.9)
Total Fluoroscopy Time (min) 0.36
Median (range) 16.0 (1.0 – 95.0) 17.0 (1.0 – 96.0)
Mean (SD) 22.1 (19.2) 24.1 (21.0)
PV visualized using ICE, n (%) 0.67
No 225 (97.4) 113 (96.6)
Yes 6 (2.6) 4 (3.4)
PV Visualized using
Venogram, n (%)
0.48
No 174 (75.3) 84 (71.8)
Yes 57 (24.7) 33 (28.2)
Average Contact Force (g) 0.82
Median (range) 17.0 (8.0 – 53.0) 17.0 (9.0 – 53.0)
Mean (SD) 18.2 (6.6) 18.0 (6.2)
Average Power (W) 0.92
Median (range) 27.5 (16.0 – 45.0) 27.0 (18.0 – 56.0)
Mean (SD) 26.9 (4.6) 27.0 (5.8)
Average Temperature (C) 0.87
Median (range) 38.0 (13.0 – 48.0) 38.5 (27.0 – 43.0)
Mean (SD) 38.1 (3.9) 38.2 (2.8)
26

Average Impedance (Ohms) 0.008
Median (range) 130.0 (45.0 – 190.0) 124.0 (84.0 – 185.0)
Mean (SD) 133.6 (21.7) 125.5 (19.1)
1
Included subjects with available procedural data
2
p-value of Chi-square test for categorical variables and t-test for continuous variables

27

Table 8. Ablation Procedural Data of PAF and PsAF Cohorts by Fluoroscopy Groups
Paroxysmal AF
(N = 231
1
)
Persistent AF
(N = 117
1
)
Characteristic Zero/Low
Fluoroscopy
(n=28
1
)
Convention
Fluoroscopy
(n=203
1
)
p-
value
2

Zero/Low
Fluoroscopy
(n=15
1
)
Convention
Fluoroscopy
(n=102
1
)
p-
value
1

Total Procedure
Time (min)
<0.001 0.009
Median (range) 102.5 (39.0 –
216.0)
139.5 (50.0 –
400.0)
120.0 (80.0
– 175.0)
166.5 (79.0
– 382.0)

Mean (SD) 105.8 (35.3) 148.4 (57.5) 117.1 (28.9) 178.2 (65.1)
Total Fluoroscopy
Time (min)
<0.001 <0.001
Median (range) 2.0 (1.0 – 3.0) 21.0 (3.5 –
95.0)
3.0 (1.0 –
3.0)
19.5 (4.0 –
96.0)

Mean (SD) 2.3 (0.7) 24.5 (19.2) 2.5 (0.7) 26.8 (21.1)
PV visualized
using ICE, n (%)
0.73 0.44
No 27 (96.4) 198 (97.5) 15 (100.0) 98 (96.1)
Yes 1 (3.6) 5 (2.5) 0 (0.0) 4 (3.9)
PV Visualized
using Venogram,
n (%)
0.07 0.17
No 25 (89.3) 149 (73.4) 13 (86.7) 71 (69.6)
Yes 3 (10.7) 54 (26.6) 2 (13.3) 31 (30.4)
28

Average Contact
Force (g)
0.82 0.48
Median (range) 17.0 (8.0 –
40.0)
17.0 (8.0 –
53.0)
15.0 (14.0 –
16.0)
17.0 (9.0 –
53.0)

Mean (SD) 17.8 (8.2) 18.3 (6.5) 15.0 (1.4) 18.1 (6.2)
Average Power
(W)
0.014 0.16
Median (range) 30.0 (24.0 –
32.0)
27.0 (16.0 –
45.0)
26.0 (26.0 –
26.0)
27.0 (18.0 –
56.0)

Mean (SD) 29.0 (2.5) 26.7 (4.7) 26.0 (0.0) 27.0 (6.0)
Average
Temperature (C)
0.22 0.003
Median (range) 37.0 (35.0 –
41.0)
38.0 (13.0 –
48.0)
37.2 (37.0 –
37.2)
39.0 (27.0 –
43.0)

Mean (SD) 37.3 (1.9) 38.2 (4.0) 37.1 (0.1) 38.2 (2.9)
Average
Impedance
(Ohms)
0.65 0.94
Median (range) 131.0 (110.0 –
170.0)
130.0 (45.0 –
190.0)
133.0
(109.0 –
137.0)
123.0 (84.0
– 185.0)

Mean (SD) 132.3 (15.1) 133.8 (22.2) 126.3 (15.1) 125.8 (19.4)
1
Included subjects with available procedural data

2
p-value of Chi-square test for categorical variables and t-test for continuous variables
29

3.3 PRIMARY EFFECTIVENESS ENDPOINT
3.3.1. PRIMARY EFFECTIVENESS SUCCESS RATES
Table 9 shows that the primary effectiveness success of freedom from AF/AT/AFL recurrence
within the 12-months of follow-up after the ablation procedures was higher in the PAF (72.4%)
than in the PsAF Cohort (53.4%). There were significant differences in the proportion of
recurrences between the two types of arrhythmias (p-value <0.001).
Table 10 and Table 11 present the primary effectiveness success rates of group of subjects
undergoing ablation procedure with different fluoroscopy time in PAF and PsAF cohorts,
separately. The association between the fluoroscopy group and the recurrence rates were
examined by using the Chi-square test.
Table 10 shows that the primary effectiveness success rate was slightly higher in the Zero/Low
fluoroscopy group (76.9%) than in the Conventional Fluoroscopy group (71.6%) in PAF cohort;
however, this difference was not statistically significant (p-value = 0.49). The primary
effectiveness success rate was slightly lower in the Zero/Low fluoroscopy group (42.4%) than in
the Conventional Fluoroscopy group (57.0%) in the PsAF cohort where subjects were in a more
progressed disease status; however, this difference was also not statistically significant (p-value
= 0.15).
Table 11 shows the primary effectiveness success rates of subjects in PAF and PsAF cohort by
the 5-Level fluoroscopy group. The primary effectiveness success rates were 76.9% in the
Zero/Low fluoroscopy group, 75.0% in group with 3.1 to 7.0 min fluoroscopy time, 71.4% in
group with 7.1 to 17.5 min fluoroscopy time, 72.4% in group with 17.6 to 35.0 min fluoroscopy
time, and 67.4% in group with greater than 35.0 min fluoroscopy time in the PAF cohort.
30

The primary effectiveness success rates showed a trend of decreasing success rates with the
increasing duration of fluoroscopy time. However, there was no statistically significant
monotonic trend between the increasing duration of fluoroscopy time and the success rates based
on the Cochran-Armitage test result (p-value = 0.32).
A significant association between the primary effectiveness success rates and fluoroscopy time
was observed in the PsAF Cohort based on the Chi-square test (p-value = 0.027). The success
rates ranged around 40% to 60% with different level of fluoroscopy time, except for the highest
success rate in the 3.1-to-7.0 min fluoroscopy group where success rate reached 80%. The
insignificant result (p-value = 0.72) implied that there was no monotonic dose-response
relationship between the fluoroscopy time and the effectiveness success rates.

31

Table 9. Recurrence of AF/AT/AFL in PAF and PsAF Cohort
Type of Arrhythmia
Recurrence
p-value
2

Yes
n (%)
No
n (%)
PAF (n
1
=247) 67 (27.6) 176 (72.4)
0.0002
PsAF (n
1
=129) 62 (46.6) 71 (53.4)
1
Included subjects with available recurrence outcome data
1
p-value of chi-square test

32

Table 10. Recurrence of AF/AT/AFL in PAF and PsAF Cohort by Zero/Low vs.
Conventional Fluoroscopy Groups
PAF Recurrence

PsAF Recurrence

Fluoroscopy
Time (min)
Yes
n (%)
No
n (%)
p-value
1

Fluoroscopy
Time (min)
Yes
n (%)
No
n (%)
p-value
1

Zero/Low
Fluoroscopy
9 (23.1) 30 (76.9)
0.49
Zero/Low
Fluoroscopy
19 (57.6) 14 (42.4)
0.15
Convention
Fluoroscopy
58 (28.4) 146 (71.6)
Convention
Fluoroscopy
43 (43.0) 57 (57.0)
1
p-value of Chi-square test for association

33

Table 11. Recurrence of AF/AT/AFL in PAF and PsAF Cohort by 5-Level Fluoroscopy
Groups
PAF Recurrence

PsAF Recurrence

Fluoroscopy
Time (min)
1

Yes
n (%)
No
n (%)
p-value
2,3

Fluoroscopy
Time (min)
Yes
n (%)
No
n (%)
p-value
2,3

<=3 9 (23.1) 30 (76.9)
0.89
2

0.32
3

<=3 19 (57.6) 14 (42.4)
0.027
2

0.72
3

3.1 to 7.0 11 (25.0) 33 (75.0) 3.1 to 7.0 4 (19.1) 17 (80.9)
7.1 to 17.5 16 (28.6) 40 (71.4) 7.1 to 17.5 16 (61.5) 10 (38.5)
17.6 to 35.0 16 (27.6) 42 (72.4) 17.6 to 35.0 8 (38.1) 13 (61.9)
>35.0 15 (32.6) 31 (67.4) >35.0 15 (46.9) 17 (53.1)
1
grouping by 3.0 min, Q1, Q2, and Q3 of fluoroscopy time as cut points
2
p-value of Chi-square test for association
3
p-value of Cochran-Armitage Test for Trend

34

3.3.2. KAPLAN-MEIER ANALYSES
The cumulative probability of freedom from recurrence of AF at 12 months post index procedure
was 72.4% (95% CI 66.3%, 77.5%) in the PAF cohort and was 53.4% (95% CI 44.1%, 61.1%) in
the PsAF cohort. The cumulative probability of freedom from recurrence at the end of 12 months
of follow up was higher in the PAF cohort than in the PsAF cohort; this difference in cumulative
probability of freedom from recurrence between type of arrhythmia was statistically significant
(log-rank p-value<0.001) (Figure 3).
Figure 4 and Figure 5 present the summary of lifetable analysis results for the primary
effectiveness endpoints based on completed follow-up data of subjects in the PAF and PsAF
cohorts by the Zero/Low vs. Conventional Fluoroscopy workflow using Kaplan-Meier analyses.
Figure 4 Error! Reference source not found.characterizes cumulative survival probability from
the time from index procedure to the first recurrence of AF in the PAF Cohort. The cumulative
probability of freedom from recurrence of AF at 12 months post index procedure was 76.9%
(95% CI 60.3%, 87.3%) in the Zero/Low fluoroscopy group compared to the probability of
72.1% (95% CI 65.4%, 77.7%) in the conventional fluoroscopy group. The probability of
freedom from recurrence at the end of 12 months of follow up was slightly higher in the
Zero/Low fluoroscopy group than in the conventional fluoroscopy group (76.9% vs. 72.1%) in
the PAF cohort; this difference between fluoroscopy groups was not statistically significant (log-
rank p-value = 0.47).
Figure 5 characterizes the lifetable analysis for the time from index procedure to the first
recurrence of AF in the PsAF Cohort. The cumulative probability of freedom from recurrence of
AF at 12 months post index procedure was 42.0% (95% CI 25.1%%, 58.0%) in the Zero/Low
fluoroscopy group compared to the cumulative probability of 56.6% (95% CI 46.2%, 65.7%) in
35

the conventional fluoroscopy group. The probability of freedom from recurrence at the end of 12
months of follow up was much lower in the Zero/Low fluoroscopy group than in the
Conventional fluoroscopy group (42.0% vs. 56.6%) in the PsAF cohort; this difference between
fluoroscopy groups was not statistically significant (log-rank p-value = 0.08). Consistent with
Figure 3, the effectiveness of freedom from recurrence in PsAF subjects with more advanced
disease progress was relatively lower (40-50% range) comparing to subjects having PAF,
regardless of using Zero/Low or Conventional fluoroscopy during the ablation procedures.
Figure 6Error! Reference source not found. and Figure 7 present the summary of lifetable
analysis results for the primary effectiveness endpoints based on completed follow-up data of
subjects in the PAF and PsAF cohorts by the 5-Level Fluoroscopy group using Kaplan-Meier
analyses.
Figure 6Error! Reference source not found.Error! Reference source not found. characterizes
the cumulative survival probabilities by time from index procedure to the first recurrence of AF
in the PAF Cohort by 5-Level Fluoroscopy group. The probability of freedom from recurrence of
AF at 12 months post index procedure was 76.9% (95% CI 60.3%, 87.3%) in the Zero/Low
fluoroscopy group, 75.0% (95% CI 59.4%, 85.3%) in group with 3.1 to 7.0 min fluoroscopy
time, 71.4% (95% CI 57.7%, 81.4%) in group with 7.1 to 17.5 min fluoroscopy time, 72.4%
(95% CI 59.0%, 82.1%) in group with 17.6 to 35.0 min fluoroscopy time, and 67.0% (95% CI
51.3%, 78.6%) in group with greater than 35.0 min fluoroscopy time.
The point estimates of the probability of recurrence-free showed a trend of decreasing with
increasing duration of fluoroscopy time. The point estimates were 76.9%, 75.0%, 71.4%, 72.4%,
and 67.0% showing a possible dose response relationship between the fluoroscopy time and the
36

effectiveness of recurrence-free in the PAF cohort. The differences among 5 fluoroscopy groups
were not statistically significant (log-rank p-value = 0.85).
Figure 7 Error! Reference source not found.characterizes the cumulative survival probability
by time from index procedure to the first recurrence of AF in the PsAF Cohort by 5-Level
Fluoroscopy group. The probability of freedom from recurrence of AF at 12 months post index
procedure was 42.0% (95% CI 25.1%, 58.0%) in the Zero/Low fluoroscopy group, 81.0% (95%
CI 56.9%, 92.4%) in group with 3.1 to 7.0 min fluoroscopy time, 37.8% (95% CI 19.6%, 55.8%)
in group with 7.1 to 17.5 min fluoroscopy time, 61.9% (95% CI 38.1%, 78.8%) in group with
17.6 to 35.0 min fluoroscopy time, and 51.4% (95% CI 32.4%, 67.5%) in group with greater than
35.0 min fluoroscopy time.
While there was no apparent dose-response relationship between the fluoroscopy time and the
effectiveness of recurrence-free in the PsAF cohort, borderline significant differences were
observed in the time-to-recurrence curves among the 5 levels of fluoroscopy groups in the PsAF
cohort (log-rank p-value = 0.052).
37

Figure 3. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months
Post Procedure by PAF and PsAF Cohort

Note: log-rank p-value <0.001
38

Figure 4. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months
Post Procedure by Zero/Low vs. Conventional Fluoroscopy Groups in PAF Cohort

Note: log-rank p-value = 0.47

39

Figure 5. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months
Post Procedure by Zero/Low vs. Conventional Fluoroscopy Groups in PsAF Cohort

Note: log-rank p-value = 0.08

40

Figure 6. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months
Post Procedure by 5-Level Fluoroscopy Groups in PAF Cohort

Note: log-rank p-value = 0.85

41

Figure 7. Kaplan-Meier Analysis of Time to First Recurrence of AF through 12 Months
Post Procedure by 5-Level Fluoroscopy Groups in PsAF Cohort

Note: log-rank p-value = 0.052

42

3.3.3. COX PROPORTIONAL HAZARDS MODELS
I. PAF Cohort
In Cox proportional hazards regression, the factors associated with recurrences of AF/AT/AFL
of subjects in the PAF cohort are presented in Table 12. When the fluoroscopy time was
dichotomized, conventional fluoroscopy was associated with an increased risk of recurrence in
subjects undergoing ablation compared to zero/low fluoroscopy (unadjusted Hazard Rate (uHR),
1.30; 95% CI, 0.64-2.62). Using the same reference group, the uHR was increasing with the
higher level of fluoroscopy time: uHR was 1.07 (95% CI, 0.44-2.57) in 3.1-7.0 min fluoroscopy
group, 1.33 (95% CI, 0.59-3.00) in 7.1-17.5 min fluoroscopy group, 1.29 (95% CI, 0.57-2.91) in
17.6-35.0 min fluoroscopy group, and 1.52 (95% CI, 0.66-3.47) in >35.0 min fluoroscopy group.
LA diameter was associated with an increased risk of symptomatic AF recurrence. Compared to
LA diameter < 40.0 mm, LA diameter ≥40.00 mm was associated with a 1.66-fold increased risk
(uHR, 1.66; 95% CI, 1.02-1.70). Other variables, such as age, sex, duration of AF history,
undergoing ablation for arrhythmias previously, history of atrial flutter, ejection fraction,
congestive heart failure, hypertension, ischemic cardiomyopathy, transient ischemic attacks, total
procedure time, PV visualized using ICE/ Venogram during procedure, average contact force,
average power, average temperature, and average impedance did not show significant
associations with time to symptomatic AF recurrence.
On multivariable Cox proportional hazards modeling, the key variable of interest (fluoroscopy
time, dichotomized or 5-level categories) and other clinically important factors (age and sex)
were forced into the model. Then a stepwise procedure was used to select additional variables
into the final model. The results showed that undergoing ablation procedure with conventional
fluoroscopy time was associated with a 1.33-fold increased risk (aHR, 1.33; 95% CI, 0.65-2.70)
43

comparing to undergoing ablation procedure with zero/low fluoroscopy time, after adjustment
for other variables. The adjusted hazard ratios (aHRs) in the final model were 1.63 (95% CI,
0.80-3.33) for age 50-60, 0.84 (95% CI, 0.40-1.78) for age 60-70, and 0.84 (95% CI, 0.34-1.97)
for age ≥70 vs age <50. Males had 0.77 times the risk of having recurrence when compared with
females (aHR, 0.77, 95% CI, 0.46-1.30). Compared to LA diameter < 40.0 mm, LA diameter
≥40.00 mm was associated with a 1.79-fold increased risk (uHR, 1.79; 95% CI, 1.09-2.95).
Using ICE/Venogram for PV visualization during procedure was associated with a 1.41-fold
increased risk (95% CI, 0.79-2.52) compared to no visualization technic used. Only a larger LA
diameter was statistically significantly associated with a higher risk of symptomatic AF
recurrence, while other factors did not show a significant association in the final model.
Similar results were obtained replacing the dichotomized fluoroscopy time by the 5-level
variable in the multivariable Cox proportional hazards model. After adjusting for age, sex, LA
diameter, and PV visualization using ICE/Venogram, the adjusted hazard ratios (aHRs) were
0.89 (95% CI, 0.36-2.18) for undergoing ablation procedure with fluoroscopy time 3.1 to 7.0
min, 1.32 (95% CI, 0.58-3.01) for fluoroscopy time 7.1 to 17.5 min, 1.52 (95% CI, 0.66-3.50) for
fluoroscopy time 17.6 to 35.0 min, 1.79 (95% CI, 0.76-4.22) for fluoroscopy time >35.0 vs
zero/low fluoroscopy time. The results showed that the risk of symptomatic AF recurrence was
non-significantly increased with the increasing length of fluoroscopy time during ablation
procedure in the PAF cohort.
II. PsAF Cohort
The factors associated with recurrences of AF/AT/AFL of subjects in the PsAF cohort are
presented in Table 13. When the fluoroscopy time was dichotomized, undergoing ablation with
44

convention fluoroscopy time reduced the hazard of having symptomatic AF recurrence by 38%
(uHR, 0.62; 95% CI, 0.63-1.06) compared to zero/low fluoroscopy time as the reference group.
Using the same reference group, the risk was decreasing with the higher level of fluoroscopy
time: the risk was 0.25 times (95% CI, 0.08-0.73) in 3.1-7.0 min fluoroscopy group, 0.95 (95%
CI, 0.49-1.85) in 7.1-17.5 min fluoroscopy group, 0.52 (95% CI, 0.23,1.19) in 17.6-35.0 min
fluoroscopy group, and 0.70 (95% CI, 0.36-1.38) in >35.0 min fluoroscopy group. The results
showed that using zero/low fluoroscopy during ablation procedure for subjects with more
progressed arrhythmia might have a higher risk of symptomatic AF recurrences compared to
subjects undergoing ablation procedures with longer fluoroscopy time.
Two variables were associated with increased risk of AF recurrence. Compared to LA diameter <
42.0 mm, LA diameter ≥42.0 mm was associated with a 1.81-fold increased risk (uHR, 1.81;
95% CI, 1.10-2.98). The use of ICE or Venogram for PV visualization during procedure showed
protective effect on AF recurrence. The risk in subjects who had ICE or Venogram for PV
visualization during procedure was 0.52 times (95% CI, 0.32-0.87) to subjects who did not use
had ICE or Venogram for PV visualization. Other variables, such as age, sex, duration of AF
history, undergoing ablation for arrhythmias previously, history of atrial flutter, ejection fraction,
congestive heart failure, hypertension, ischemic cardiomyopathy, transient ischemic attacks, total
procedure time, average contact force, average power, average temperature, and average
impedance did not show significant increased/decreased hazard rates.
To identify the factors associated with the symptomatic AF recurrences in the PsAF cohort, a
multivariable Cox proportional hazard model forced in the key variable of interest (fluoroscopy
time, dichotomized or 5-level categories) and other clinically important factors (age and sex).
The risk of recurrence was lower in subjects who had longer fluoroscopy time in the ablation
45

procedure. The risk in subjects who underwent ablation procedure with conventional fluoroscopy
time was 0.51 times to subjects who underwent ablation with zero/low fluoroscopy time (95%
CI, 0.29-0.90), after adjustment of other factors. Compared to subjects aged less than 50, the risk
of recurrence was 0.45 times (95% CI, 0.19-1.01) for age 50-60, 0.49 (95% CI, 0.23-1.06) for
age 60-70, and 0.91 (95% CI, 0.41-2.03) for age ≥70. Males had 0.57 times the risk of having
recurrence when compared with females (95% CI, 0.33-1.01). A large LA diameter of ≥42.0 was
associated with a 1.93-fold increased risk comparing to LA diameter <42.0 mm (95% CI, 1.15-
3.24). Having PV visualized by ICE/Venogram during ablation procedure had a protective effect
of 0.55 times risk compared to no visualization technic used (95% CI, 0.33-0.93).
The results showed a protective effect on the risk of symptomatic AF when conventional
fluoroscopy time was applied in the ablation procedure in subjects with persistent AF compared
to zero/low fluoroscopy. Large LA diameter was associated with a higher risk of symptomatic
AF recurrence and using ICE/Venogram for PV visualization was associated with lower risk of
symptomatic AF recurrence. All other factors did not show a significant association in the final
model.
Similar results were obtained replacing the dichotomized fluoroscopy time by the 5-level
variable in the multivariable Cox proportional hazards model. After adjusting for age, sex, LA
diameter, and PV visualization using ICE/Venogram, the adjusted hazard ratios (aHRs) were
0.26 (95% CI, 0.09-0.80) for undergoing ablation procedure with fluoroscopy time 3.1 to 7.0
min, 0.74 (95% CI, 0.38-1.47) for fluoroscopy time 7.1 to 17.5 min, 0.58 (95% CI, 0.25-1.35) for
fluoroscopy time 17.6 to 35.0 min, 0.40 (95% CI, 0.19-0.86) for fluoroscopy time >35.0 vs
zero/low fluoroscopy time. The results showed that the risk of having symptomatic AF
recurrence were lower with the increasing length of fluoroscopy time during ablation procedure.
46

The risk of having symptomatic AF recurrence were significantly lower in the group of subjects
with the longest length of fluoroscopy time (>35.0 min) when comparing to the zero/low
fluoroscopy group (aHR, 0.40, 95% CI, 0.19-0.86).

47

Table 12. Hazard Ratios (HR) and 95% Confidence Interval (CI) Estimates for Variables
Associated AF/AT/AFL Recurrence 12 Months After Undergoing Ablation Procedures in
PAF Cohort

Variables
PAF Cohort
n/N
1

Unadjusted HR
(95% CI)
Adjusted HR
2

(95% CI)
Adjusted HR
3

(95% CI)
Fluoroscopy Time (min)
Zero/Low
Fluoroscopy
9/39 1.00 1.00
Convention
Fluoroscopy
58/204 1.30 (0.64-2.62) 1.33 (0.65-2.70)
Fluoroscopy Time (min)
<=3.0 9 / 39 1.00 1.00
3.1 to 7.0 11 / 44 1.07 (0.44- 2.57) 0.89 (0.36-2.18)
7.1 to 17.5 16 / 56 1.33 (0.59- 3.00) 1.32 (0.58-3.01)
17.6 to 35.0 16 / 58 1.29 (0.57- 2.91) 1.52 (0.66-3.50)
>35.0 15 /46 1.52 (0.66- 3.47) 1.79 (0.76-4.22)
Age, y
<50 11/48 1.00 1.00 1.00
50-60 25/65 1.71 (0.84-3.48) 1.63 (0.80-3.33) 1.73 (0.84-3.56)
60-70 20/85 1.00 (0.48-2.09) 0.84 (0.40-1.78) 0.86 (0.41-1.83)
≥70 11/45 1.07 (0.46-2.47) 0.82 (0.34-1.97) 0.86 (0.36-2.07)
Sex
Female 23/75 1.00 1.00 1.00
Male 44/168 0.83 (0.50-1.37) 0.77 (0.46-1.30) 0.73 (0.43-1.24)
Duration of AF History,
y

<3.0 28/103 1.00
≥3.0 39/140 1.04 (0.64-1.69)
Previous Ablation for
any Arrhythmias

No 41/163 1.00
Yes 26/79 1.35 (0.83-2.21)
History of Atrial Flutter
No 58/196 1.00
Yes 9/47 0.61 (0.30 -1.24)
LA Diameter (mm)
<40.0 39/167 1.00 1.00 1.00
≥40.0 28/76 1.66 (1.02-2.70) 1.79 (1.09-2.95) 1.96 (1.17-3.27)
Ejection Fraction (%)
<60.0 25/99 1.00
≥60.0 42/144 1.17 (0.71-1.92)
Congestive Heart
Failure

No 66/239 1.00
Yes 1/4 0.85 (0.12-6.13)
Hypertension
No 35/142 1.00
Yes 32/101 1.28 (0.79-2.06)
48

Ischemic
Cardiomyopathy

No 62/230 1.00
Yes 5/13 1.55 (0.62-3.85)
Transient Ischemic
Attacks

No 63/235 1.00
Yes 4/8 1.84 (0.67-5.07)
Total Procedure Time
(min)

<130.0 35/124 1.00
≥130.0 32/119 0.99 (0.61-1.59)
PV visualized using
ICE/ Venogram

No 15/62 1.00 1.00 1.00
Yes 52/181 1.25 (0.70-2.22) 1.41 (0.79-2.52) 1.68 (0.89-3.17)
Average Contact Force
(g)

<17.0 47/160 1.00
≥17.0 20/83 0.81 (0.44-1.51)
Missing 27/90 1.04 (0.59-1.86)
Average Power (W)
<27.5 50/168 1.00
≥27.5 17/75 0.78 (0.41-1.49)
Missing 30/95 1.16 (0.66-2.04)
Average Temperature
(C)

<38.0 51/163 1.00
≥38.0 16/80 0.56 (0.30-1.07)
Missing 29/95 0.91 (0.52-1.59)
Average Impedance
(Ohms)

<130.0 49/165 1.00
≥130.0 18/78 0.84 (0.44-1.60)
Missing 30/95 1.19 (0.67-2.12)
1
n/N, number of subjects with recurrence/total number of subjects, in that category.
2
The Cox model forced in the dichotomized variable of fluoroscopy time of Zero/Low and Conventional
Fluoroscopy, age, sex, and visual
3
The Cox model forced in the 5-level categorical variable of fluoroscopy time, age, sex, and visual

49

Table 13. Hazard Ratios (HR) and 95% Confidence Interval (CI) Estimates for Variables
Associated AF/AT/AFL Recurrence 12 Months After Undergoing Ablation Procedures in
PsAF Cohort
Variables
PsAF
n/N
1

Unadjusted HR
(95% CI)
Adjusted HR
2

(95% CI)
Adjusted HR
3

(95% CI)
Fluoroscopy Time (min)
Zero/Low Fluoroscopy 43/100 1.00 1.00
Convention Fluoroscopy 19/33 0.62 (0.63-1.06) 0.51 (0.29-0.90)
Fluoroscopy Time (min)
<=3.0 19/33 1.00 1.00
3.1 to 7.0 4/21 0.25 (0.08-0.73) 0.26 (0.09-0.80)
7.1 to 17.5 16/26 0.95 (0.49-1.85) 0.74 (0.38-1.47)
17.6 to 35.0 8/21 0.52 (0.23,1.19) 0.58 (0.25-1.35)
>35.0 15/32 0.70 (0.36-1.38) 0.40 (0.19-0.86)
Age, y
<50 10/16 1.00 1.00 1.00
50-60 11/32 0.43 (0.18-1.02) 0.45 (0.19-1.01) 0.49 (0.20-1.20)
60-70 22/53 0.51 (0.24-1.07) 0.49 (0.23-1.06) 0.56 (0.26-1.23)
≥70 19/32 0.93 (0.43-1.99) 0.91 (0.41-2.03) 1.07 (0.48-2.39)
Sex
Female 20/35 1.00 1.00 1.00
Male 43/98 0.60 (0.35-1.02) 0.57 (0.33-1.01) 0.52 (0.29-0.94)
Duration of AF History, y
<2.0 16/45 1.00
≥2.0 46/88 1.59 (0.90-2.81)
Previous Ablation for any
Arrhythmias

No 42/90 1.00
Yes 20/43 1.01 (0.59-1.72)
History of Atrial Flutter
No 50/100 1.00
Yes 12/33 0.75 (0.40-1.41)
LA Diameter (mm)
<42.0 33/87 1.00 1.00 1.00
≥42.0 29/46 1.81 (1.10-2.98) 1.93 (1.15-3.24) 1.95 (1.15-3.32)
Ejection Fraction (%)
<60.0 33/68 1.00
≥60.00 29/65 0.98 (0.59-1.61)
Congestive Heart Failure
No 50/119 1.00
Yes 10/14 1.94 (0.98-3.82)
Hypertension
No 29/64 1.00
Yes 33/69 1.05 (0.64-1.73)
Ischemic Cardiomyopathy
No 60/128 1.00
Yes 2/5 0.96 (0.23-3.92)
Transient Ischemic Attacks
50

No 58/128 1.00
Yes 4/5 2.19 (0.79-6.04)
Total Procedure Time (min)
<162.0 13/77 1.00
≥162.0 23/56 0.79 (0.47-1.32)
PV visualized using ICE/
Venogram

No 27/44 1.00 1.00 1.00
Yes 35/89 0.52 (0.32-0.87) 0.55 (0.33-0.93) 0.54 (0.30-0.95)
Average Contact Force (g)
<17.0 48/99 1.00
≥17.0 14/34 1.17 (0.53-2.58)
Missing 37/72 1.41 (0.72-2.77)
Average Power (W)
<27.0 45/98 1.00
≥27.0 17/35 1.70 (0.80-3.63)
Missing 34/67 1.65 (0.84-3.26)
Average Temperature (C)
<38.5 47/103 1.00
≥38.5 15/13 1.64 (0.77-3.51)
Missing 35/68 1.67 (0.87-3.22)
Average Impedance
(Ohms)

<124.0 53/100 1.00
≥124.0 9/33 0.38 (0.17-0.84)
Missing 62/133 0.84 (0.48-1.49)
1
n/N, number of subjects with recurrence/total number of subjects, in that category.
2
The Cox model forced in the dichotomized variable of fluoroscopy time of Zero/Low and Conventional
Fluoroscopy, age, and sex
3
The Cox model forced in the 5-level categorical variable of fluoroscopy time, age, and sex

51

CHAPTER 4: DISCUSSION
This registry study included patients with paroxysmal atrial fibrillation and persistent atrial
fibrillation who underwent ablation procedures using the ThermoCool® SmartTouch™ catheter
with the various length of fluoroscopy time per physician’s discretion.
The study shows that the primary effectiveness success rate was slightly higher in the Zero/Low
fluoroscopy group than in the Conventional Fluoroscopy group in the PAF cohort, and slightly
lower in the Zero/Low fluoroscopy group than in the Conventional Fluoroscopy group in the
PsAF cohort. Using a 5-level categorization, the primary effectiveness success rates were
decreased with the increasing duration of fluoroscopy time in the PAF cohort. In the PsAF
cohort, there was a significant association between the primary effectiveness success rates and
fluoroscopy time, but no significant monotonic dose-response relationship was found between
fluoroscopy time and effectiveness success rates in either cohort.
While there was no significant dose-response relationship between the fluoroscopy time and the
effectiveness of recurrence-free, borderline significant differences were observed in the survival
curves among the 5 levels of fluoroscopy groups in the PsAF cohort, which might be due to the
exceptional high success rate in one fluoroscopy group.
There are several studies that have investigated the relationship between fluoroscopy time during
ablation procedures and AF recurrence rates. A study compared the outcomes of AF ablation
procedures performed with low-fluoroscopy guidance (less than 10 minutes of total fluoroscopy
time) and those performed with conventional fluoroscopy guidance (more than 30 minutes of
total fluoroscopy time) (32). The study found no significant difference in AF recurrence rates
between the two groups at one year of follow-up. Another study compared the outcomes of AF
52

ablation procedures performed with near-zero fluoroscopy guidance (less than 1 minute of total
fluoroscopy time) and those performed with conventional fluoroscopy guidance. This study also
had no significant findings (33).
Comparing to previous studies, more findings were observed and provided by this study. It is
important to note that the definition of low or near-zero fluoroscopy time can vary from study to
study as there is no standardized definition available yet. In current study, we used a different
approach by categorizing fluoroscopy time using both a dichotomized variable and a 5-level
categorical variable. This approach allows for not only comparing the effectiveness between two
fluoroscopy groups, but also examining the dose-response relationship between fluoroscopy time
and the effectiveness success rates.
Literature showed that there are some important factors that may influence AF recurrence rates,
such as patient age, comorbidities, and procedure parameters used while performing the ablation
procedure (34). Additionally, the use of low-fluoroscopy or near-zero fluoroscopy techniques
may require specialized equipment and expertise and may not be suitable for all patients or all
types of AF ablation procedures. The study conducted Cox Proportional Modeling to control
potential cofounding effects and found that undergoing an ablation procedure with conventional
fluoroscopy time may be associated with a higher risk of symptomatic AF recurrence compared
to zero/low fluoroscopy time in patients with PAF. Furthermore, using a 5-level variable to
represent fluoroscopy time in the model and adjusted for various factors, the risk of symptomatic
AF recurrence seemed to increase with increasing fluoroscopy time. In contrast, the analyses of
the PsAF cohort showed that undergoing ablation with longer fluoroscopy time had a protective
association compared to those with zero/low fluoroscopy time, which is opposite to the findings
in the PAF cohort. These findings suggest that the relationship between fluoroscopy time and AF
53

recurrence rates may differ depending on the type of AF and highlight the importance of
considering multiple factors when interpreting study results.
To further understand the baseline characteristics of our study population, we examine the age,
sex, medical history, AF history, and procedural data between PAF and PsAF cohort, and also
among fluoroscopy groups. Consistent with earlier studies, this study showed that patients with
persistent AF were slightly older, more males, and had greater percentages of baseline
comorbidities such as congestive heart failure, diabetes, had larger LA diameters, ejection
fraction, and longer history of AF compared to patients with PAF. Persistent AF patients also
had longer total procedure time and lower average impedance than patients with paroxysmal AF.
The total fluoroscopy time were comparable in both cohorts. The demographics and baseline
characteristics were similar between subjects undergoing ablation procedure with zero/low and
convention fluoroscopy time. This may suggest that the patient characteristics and procedural
parameters may be different between PAF and PsAF cohorts, but the use of low or near-zero
fluoroscopy techniques may not be determined by patient characteristics in this study.
Although literatures suggested some important factors that may influence the AF recurrences, we
only found that large LA diameter and using ICE/Venogram for PV visualization were
associated with the risk of symptomatic AF recurrence in the final Cox proportional model. All
other factors of demographics, medical history, history of AF, procedural data, did not show a
significant association in the final model. The reason of insignificant findings for some factors,
such as age, sex, and comorbidities, may be due to the small sample size of the study. With
relatively small sample size in PAF and PsAF cohorts, the study may not have enough statistical
power to detect significant differences among fluoroscopy groups being compared.
54

Our study results showed that the use ICE or Venogram for PV visualization during procedure
may have a protective effect on the risk of recurrences comparing to those who did not use in the
PsAF patients. Intracardiac echocardiography (ICE) and advanced mapping systems such as
three-dimensional mapping systems can provide real-time visualization of catheter placement
and cardiac structures, allowing for improved confidence in achieving effective ablation while
minimizing fluoroscopy exposure. Additionally, using ICE or venography for visualization of
pulmonary veins during the procedure may reduce the risk of AF recurrence compared to not
using these imaging techniques. These findings highlight the importance of using advanced
imaging and mapping technologies in AF ablation procedures to achieve optimal outcomes while
minimizing radiation exposure, especially in patients with more advance AF status.
This study adds to the existing literature on the relationship between fluoroscopy time during AF
ablation procedures and recurrence rates and provides valuable insights into the potential impact
of fluoroscopy time on efficacy outcomes separately for PAF and PsAF patients.
STUDY STRENGTH AND LIMITATION
Overall, Strengths of the study include the use of a registry, which allowed the examination of
the effectiveness of ablation procedures using different lengths of fluoroscopy time per the real-
world practice of AF ablation. The study used a different approach by categorizing fluoroscopy
time using both a dichotomized variable and a 5-level categorical variable, which allowed for not
only comparing the effectiveness between two fluoroscopy groups but also examining the dose-
response relationship between fluoroscopy time and effectiveness success rates. The study
controlled for potential confounding effects using Cox Proportional Modeling. The study also
examined baseline characteristics of the study population and found that the patient
characteristics and procedural parameters may be different between the paroxysmal atrial
55

fibrillation (PAF) and persistent atrial fibrillation (PsAF) cohorts, but the use of low or near-zero
fluoroscopy techniques may not be determined by patient characteristics nor by the type of
arrhythmia at current medical practice.
Limitations of this study with small sample sizes is that the results may not be representative of
the larger population. With a small sample size, there is a greater chance of random variation and
the results may not accurately reflect the true effect of the technique of low/zero fluoroscopy.
This may limit the generalizability of the findings to other patient populations or clinical settings.
In addition, with a small sample size, there may be limited statistical power to detect significant
differences or associations. Therefore, it is important to interpret the results of this study with
caution and to consider the need for larger, more definitive studies to confirm the findings. It
will also be important to evaluate the feasibility, safety, and efficacy of these fluoroscopy
reduction techniques more broadly among the wider EP community. Although it is probable that
our findings may be widely applicable, site-specific contextual factors could lead to different
results across sites or operators.

56

CHAPTER 5: CONCLUSION
Considering the potential addition to the lifetime radiation exposure to the ablation physicians if
longer fluoroscopically-guided ablation procedures are performed, it may be reasonable to
minimize the fluoroscopy time during the ablation procedure if zero/low fluoroscopy ablation
techniques are safe and effective. Our findings suggest that the effectiveness of ablation
procedures using zero/low fluoroscopy may vary depending on the type of atrial fibrillation (AF)
being treated. After controlling potential confounding effects, the study results showed that
undergoing an ablation procedure with conventional fluoroscopy time may be associated with a
higher risk of symptomatic AF recurrence compared to zero/low fluoroscopy time in patients
with PAF. Furthermore, using a 5-level variable to represent fluoroscopy time in the model, the
risk of symptomatic AF recurrence seemed to increase with increasing fluoroscopy time. In
contrast, PsAF patients who underwent ablation with longer fluoroscopy time seemed to have a
protective effect on risk of recurrence when compared to those with zero/low fluoroscopy time.
However, in patients with persistent AF (PsAF), the success rate may be lower with zero/low
fluoroscopy. The results suggest that the type of AF and multiple factors, such as patient’s
anatomical characters and methods of cardiac mapping, should be considered before the use of
zero/low fluoroscopy techniques. Overall, the decision to use zero/low fluoroscopy should be
made on a case-by-case basis, taking into consideration the type and severity of AF being
treated.

57

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Abstract (if available)

Abstract Purpose: There have been long-standing concerns of the negative acute and long-term health hazards associated with radiation exposure from the fluoroscopy used in radiofrequency catheter ablations. The primary objective of this study was to evaluate the 12-month effectiveness of the alternative zero/low fluoroscopy radiofrequency catheter ablation workflow compared with the conventional radiofrequency catheter ablation workflow with normal fluoroscopy in paroxysmal and persistent atrial fibrillation ablation procedures.
Methods: Data arose from a prospective, multi-center, clinical registry study for the ablation procedure for the treatment of atrial fibrillation. A total of 426 patients diagnosed with atrial fibrillation in the period of June 2013 to Aug 2021 were enrolled, and 397 of them underwent ablation procedures, including 242 PAF, 124 PsAF, and 31 subjects with long-standing AF. All ablation procedures were conducted using the ThermoCool® SmartTouch™ catheter. Subjects with PAF and PsAF were included in this thesis as the study population.
The primary effectiveness endpoint was defined as freedom from symptomatic AF through the effectiveness evaluation period (91-365 days post index procedure). In this study, total fluoroscopy time less than 3.0 minutes was defined as Zero/Low Fluoroscopy group, and the fluoroscopy time greater than or equal to 3.0 minutes as Conventional Fluoroscopy Group. The fluoroscopy time was also categorized into 5 strata by using the cut points of 3.0 mins and quartiles of the overall data distribution of PAF and PsAF study subjects.
The percent of subjects who were free from symptomatic AF recurrences were summarized in PAF and PsAF Cohorts, overall and by fluoroscopy groups. The association between the fluoroscopy time and the primary effectiveness success rate were tested using: 1) the Chi-square test; and 2) the Cochran-Armitage test for trend.
Kaplan-Meier estimates and plots were used to characterize survival probabilities for the time to first atrial fibrillation (AF), atrial tachycardia (AT) and atrial flutter (AFL) (hereafter, AF) recurrence by the end of the 12 months follow-up in the PAF and PsAF cohorts, separately. The survival probabilities of symptomatic AF recurrence over the 12-month follow-up were also presented by fluoroscopy workflow along with the 95% confidence interval. Cox proportional hazard models are performed to adjust for confounding effects on the hazard ratios (HR) in AF recurrences between the fluoroscopy workflows.
Results:
Demographics and Baseline Characteristic: Patients with PsAF were slightly, though not statistically significantly older (mean age, 62.3 vs 59.5 years; p=0.072). There was a higher proportion of males in both PAF and PsAF cohorts (69.3% males vs 30.7% females and 73.2% males vs 26.8% females, respectively). Similar demographic distributions were seen when stratified by fluoroscopy groups, with the zero/low fluoroscopy group in the PAF cohort being the youngest group (mean age, 57.7), and the conventional fluoroscopy group in the PsAF cohort being the oldest (mean age, 62.7).
The PsAF cohort exhibited a higher proportion of medical comorbidities compared to the PAF cohort, namely diabetes mellitus (12.7 vs. 3.9%; p=0.001), congestive heart failure (9.9 vs 1.6%; p<0.001), and hypertension (51.4 vs 41.3%; p=0.053). Within AF cohorts, comorbidities did not differ between fluoroscopy groups.
Procedural Data: The procedure efficiency was also demonstrated in subjects undergoing the ablation procedure with the zero/low fluoroscopy workflow. The mean total procedure time in PAF subjects was 109.0 (± 34.14) mins in the Zero/Low Fluoroscopy group compared with a mean total duration of 199.98 (± 52.16) mins in the >35 mins fluoroscopy group. Even though the mean total procedure time was longer in the PsAF subjects, the time was still shortest in the 0-3 mins group (132.69 ± 51.56 min) and longest (210.51 ± 68.43) in the group of subjects with >35 mins of fluoroscopy time.
Primary Effectiveness Results:
I. PAF Cohort
Of the 242 subjects in the PAF cohort, 67 (27.6%) subjects had recurrence of symptomatic AF during the 12-month follow-up. Kaplan-Meier estimates of the cumulative probability of freedom from recurrence 12 months post the procedure seems to be decreasing with the increasing fluoroscopy time. The survival probabilities in the 0-3 mins, 3-7 mins, 7-17.5 mins, 17.5-35 mins, and >35 mins of fluoroscopy time were 76.9%, 75.0%, 71.4%, 72.4%, and 67.0%, respectively. However, there is no significant differences of the survival curves across fluoroscopy groups (log rank p-value=0.51).
The conventional fluoroscopy was associated with an increased risk of recurrence in subjects undergoing ablation compared to zero/low fluoroscopy (unadjusted Hazard Rate (uHR), 1.30; 95% CI, 0.64-2.62). The results of the multivariable Cox proportional hazards model showed that undergoing ablation procedure with conventional fluoroscopy time was associated with a 1.33-fold increased risk (adjusted Hazard Rate (aHR), 1.33; 95% CI, 0.65-2.70) comparing to undergoing ablation procedure with zero/low fluoroscopy time, after adjustment for other variables.
Similar results were obtained replacing the dichotomized fluoroscopy time by the 5-level variable in the multivariable Cox proportional hazards model. After adjusting for age, sex, LA diameter, and PV visualization using ICE/Venogram, the adjusted hazard ratios (aHRs) were non-significantly increased with the increasing length of fluoroscopy time during ablation procedure in the PAF cohort.
II. PsAF Cohort
Of the 133 subjects in the PsAF cohort, 62 (46.6%) subjects had recurrence of symptomatic AF during the 12-month follow-up. Kaplan-Meier Estimates of the cumulative probability of freedom from recurrence 12 months post the procedure seems have no pattern with the increasing fluoroscopy time. The highest survival probability of 81.0% was observed in the 3-7 mins fluoroscopy group, and the lowest probability of 37.8% in the 7-17.5 mins group. The survival probability in the 0-3 mins, 17.5-35 mins, and >35 mins of fluoroscopy time groups were 42.0%, 61.9%, and 51.4%, respectively. The survival curves across fluoroscopy groups showed borderline statistical significance (log rank p-value=0.052).
Undergoing ablation with convention fluoroscopy time reduced the hazard of having symptomatic AF recurrence by 38% (uHR, 0.62; 95% CI, 0.63-1.06) compared to zero/low fluoroscopy time as the reference group in the PsAF cohort. Using the same reference group, the risk was decreasing with the higher level of fluoroscopy time: the risk was 0.25 times (95% CI, 0.08-0.73) in 3.1-7.0 min fluoroscopy group, 0.95 (95% CI, 0.49-1.85) in 7.1-17.5 min fluoroscopy group, 0.52 (95% CI, 0.23,1.19) in 17.6-35.0 min fluoroscopy group, and 0.70 (95% CI, 0.36-1.38) in >35.0 min fluoroscopy group. The risk in subjects who underwent ablation procedure with conventional fluoroscopy time was 0.51 times to subjects who underwent ablation with zero/low fluoroscopy time (95% CI, 0.29-0.90), after adjustment of other factors.
Conclusion: The study results based on real-world settings provide strong support for the zero/low fluoroscopy workflow by its profound long-term effectiveness profile in both PAF and PsAF subjects. It appears that the effectiveness of ablation procedures using zero/low fluoroscopy may vary depending on the type of atrial fibrillation (AF) being treated. In patients with paroxysmal AF, the use of zero/low fluoroscopy may result in slightly higher success rates compared to conventional fluoroscopy. However, in patients with persistent AF, the success rate may be lower with zero/low fluoroscopy. Overall, the decision to use zero/low fluoroscopy should be made on a case-by-case basis, taking into consideration the type and severity of AF being treated.

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Creator Tseng, Kevin (author)

Core Title The evaluation of the long-term effectiveness of zero/low fluoroscopy workflow in ablation procedures for the treatment of paroxysmal and persistent atrial fibrillation

School Keck School of Medicine

Degree Master of Science

Degree Program Applied Biostatistics and Epidemiology

Degree Conferral Date 2023-05

Publication Date 04/27/2023

Defense Date 04/26/2023

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag atrial fibrillation,cardiac ablation,catheter ablation,efficacy,electrophysiology,fluoroscopy,long-term effectiveness,OAI-PMH Harvest,Quality of life,radiation exposure

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Advisor Mack, Wendy Jean (committee chair), Stern, Mariana (committee member), Zadeh, Andrew (committee member)

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