Introduction: 
Recent trials demonstrating a lack of benefit for adjunctive ablation beyond pulmonary vein isolation (PVI) 1 and a belief that PVI alone is insufficient for catheter ablation of persistent atrial fibrillation (AF), has resulted in left atrial posterior wall (LAPW) isolation being the preferred ablation strategy for persistent AF at many institutions. Aside from pathophysiologic and embryological rationales for this strategy, multiple randomized trials have demonstrated favorable outcomes associated with LAPW isolation2–4. Reported techniques for LAPW isolation include ablation at the periphery without ablation within the LAPW5 as well as high-density ablation of all sites of electrical activity within the LAPW. Within this latter approach there are numerous potential ablation strategies including: debulking, single ring, box isolation of fibrotic areas, and varying sizes of box lesions2,6–8. Given that each of these disparate ablation strategies is considered “LAPW isolation,” we aimed to ascertain if the benefits of more extensive ablation (i.e. atrial debulking, electrical isolation of fibrotic areas, trigger elimination, and avoidance of reconnection across linear ablation) outweigh the increased risk of more extensive ablation (i.e. esophageal injury, and prolonged procedure time). The optimal technique for LAPW isolation remains unclear.
Methods:
Patient Selection :
We evaluated 110 patients undergoing first-time catheter ablation of persistent AF at New York University (NYU) Langone Health between 8/2018-12/2018. Data collection and analysis were performed according to protocols approved by the NYU Langone Health Institutional Review Board. All authors had full access to data, take responsibility for the integrity of the data, and have agreed to the paper as written.
Electrophysiology Study :
All procedures were done under general anesthesia. Surface and intracardiac electrograms (ECGs) were digitally recorded and stored (EP Workmate, St. Jude Medical, Inc., Diamond Bar California). Non-fluoroscopic 3-dimensional electroanatomic mapping (EAM) was performed using the Carto 3 (Biosense-Webster, Inc.) mapping system. A 10- or 20-pole circumferential PV mapping catheter (Lasso, Biosense-Webster, Inc.) or a five-spline mapping catheter (PentaRay Nav, Biosense-Webster, Inc.) was utilized for left atrial mapping and recording. Left atrial three-dimensional anatomy was created with manipulation of the multi-electrode mapping catheter. Voltage mapping was performed and areas with local bipolar electrogram amplitude <0.5mV were considered to be abnormal9.
Ablation was performed with an open-irrigated, 3.5-mm RFA catheter (ThermoCool SmartTouch, Biosense Webster Inc.). Ablation lesions were generated in a point-by-point fashion in power-controlled mode applying 20 to 35 W for 20 to 40 s per lesion during irrigation at a rate of 17 to 30-mL/min while maintaining a goal ACT of > 350 s. All electroanatomic map lesion markers were created using automated lesion annotation (VisiTag, Biosense Webster, Inc.) in the CFS group. Lesion set dimensions and degree of ablation within the LA posterior wall were at the operators’ discretion. All lesion sets were rendered unexcitable utilizing a pace-ablate technique10. Left atrial posterior wall and pulmonary vein entrance block and exit block with pacing output > 10mA @ 2ms were confirmed after a 30-minute waiting period and infusion of adenosine.
Lesion Density Calculation :
The area of the posterior wall and total LA surface area was calculated within the EAM system. The number of RF applications within the outer boundary of the LAPW isolation lesion set was subsequently tallied using automated lesion annotation (VisiTag, Biosense Webster, Inc.). The total ablated surface area was estimated by assigning a diameter of each non-overlapping lesion as 0.5cm, resulting in an ablation area of 0.8cm2 per lesion. Lesion density was calculated by dividing the total RF lesion surface area by the area of the posterior wall (Figure 1). The proportion of electrically isolated LA surface area was calculated by dividing the wide antral circumferential area by the total LA surface area.
Arrhythmia Recurrence :
Patients were followed for up to 2 years after the date of their procedure. Patient follow-up was censored for the purposes of survival analyses at time of last follow up if less than 2 years after their ablation procedure. Patients were followed in clinic at 1-month post-ablation and subsequently at three-month intervals. At each visit, study assessments included a detailed medical history, physical exam, and 12-lead ECG. A 2-week mobile cardiac outpatient telemetry (MCOT) monitor was performed prior to each scheduled in-office visit in patients without implanted arrhythmia monitoring. Arrhythmia recurrence was defined as either a sustained atrial arrhythmia within the 90-day blanking period that required a repeat ablation, or an atrial arrhythmia that occurred after the 90-day blanking period and was captured on a resting 12-lead ECG or lasted longer than 30 s on an ambulatory monitor.
Statistical Analysis :
Data were reported as mean ± standard deviation for continuous variables with normal distributions and the number of events (proportion) for categorical variables. Continuous variables with non-normal distributions were reported as means ± non-parametric bootstrap standard deviation (based on 5000 replicates). The normality of data was assessed with Shapiro-Wilk testing. To assess statistical significance, the Student’s t-test and analysis of variance tests were used for normal continuous variables, while Mann-Whitney U and Kruskal-Wallis testing was used for non-normal continuous variables. Chi-square or Fisher exact testing was used to assess statistical significance for categorical variables as appropriate. Multivariable Cox proportional regression analysis was performed to assess predictors of arrhythmia recurrence yielding hazard ratios with 95% confidence intervals. Predictors of AF recurrence noted in Kece et. Al. were tested in a univariate model. Subsequently variables with P values ≤0.05 were included in the multivariate analysis using the “enter” method in The R Project. P values ≤0.05 were considered significant; all are reported as 2-sided.