Faculty Bibliography

Background: Biophysical markers of effective lesion formation during radiofrequency (RF) ablation include impedance decline, stable catheter-tissue contact and local unipolar electrogram change suggesting lesion transmurality The interactions between these factors as well as the implications of lesion sequence are not well understood. Objective: To analyze the impact of catheter stability and lesion sequence on markers of lesion formation during atrial fbrillation (AF) ablation. Methods: Sequential or time-spaced paired RF lesions with goal force-time integral (FTI) 400 gs were placed in prespecifed locations in 20 patients undergoing frst time RF ablation for paroxysmal AF. Custom developed software (MATLAB, Mathworks, USA) was used to extract and analyze lesion data, and 3D catheter position sampled at 60Hz from the CARTO3 mapping system (Biosense Webster, Inc.). All cases were performed using jet ventilation and irrigated force-sensing catheters. Results: 282 ablation lesions were studied, with mean FTI 410.8+/-18.2 gs. Mean impedance decline was greater for the frst lesion in a given pair, 13.6+/-7.9OMEGA vs. 10.7+/-4.6OMEGA, (p < 0.01). Compared to time-spaced lesions, sequential lesions resulted in signifcantly smaller impedance decline (9.8+/-3.8OMEGA vs. 11.8+/-5.2OMEGA, p<0.01), but increased probability of achieving transmurality, as evident by unipolar signal change (68% vs 42% p=0.01). Mean catheter excursion for a single lesion was 0.67+/-0.54mm and maximal catheter excursion was 1.64+/-1.3mm. Ablation catheter spatial stability was found to be inversely related to both amplitude (rho=0.51, p<0.0001) and maximal rate (dI/dT) of impedance decline (rho=0.32, p<0.0001). Conclusion: Lesion sequence and catheter spatial stability were major modifers of impedance change and unipolar electrographic evidence of lesion transmurality during RF ablation. Sequential ablation resulted in transmural lesions more frequently, despite lesser impedance decline. In contrast to previously reported positive association between contact-force and impedance decline, increased ablation catheter spatial stability was associated with lesser impedance decline

Background: Recent studies suggest RF ablation at high power for short durations may be safer and more effcient than using conventional power levels. Comparative data exploring the kinetics and safety of lesion formation at high power/short duration vs. conventional methods is lacking. Objective: The goal of this study is to compare lesion formation and safety across study conditions in an intracardiac model. Methods: Canines (n=24) were anesthetized and intracardiac RF energy was applied in both ventricles over a wide range of conditions (20-50 W, 5-60 s, 5-40 g) in a quasi-random fashion using a contact force, irrigated RF ablation catheter. Hearts were then stained with 1% TTC and formalin fxed Hearts were sectioned and lesions measured A common regression model for lesion width, depth and steam pop likelihood was created, and subsequently realized for three RF powers (see fgure). With these models, the time to achieve target lesion sizes and the relative steam pop risk were compared. Results: Of the 228 lesions created, 227 were found (99%). At 50 W, the maximum lesion width growth rate was 1.4 mm/s, vs. 0.9 mm/s (40 W) and 0.7 mm/s (30 W). Steam pop risk grew by 0.25%/s when ablating at 30 W vs. 1.1%/s at 50 W. Comparable lesions could be created at 30 W and 50 W power with similar steam pop risk (e.g., 30 W took 42 s to create a 10 mm wide lesion vs. 10 s at 50 W with similar risk). Conclusion: In this study, RF ablation lesions can be created about two times faster when using 50 W vs. 30 W; however the steam pop risk increased 4.4 fold. Though lesions are created more effciently, there is a much lower margin for error when ablating at 40-50 W. [Figure Presented]

Background: Optimal contact-force during atrial fbrillation (AF) radiofrequency (RF) ablation is associated with improved procedural outcomes The extent to which ablation catheter spatial stability varies between patients and predicts procedural success is unknown. Objective: To examine the prognostic signifcance of intra-procedure ablation catheter spatial stability on one year arrhythmia recurrence following ablation of paroxysmal atrial fbrillation. Methods: 100 consecutive patients undergoing frst time RF ablation for paroxysmal AF under general anesthesia were analyzed. Spatial localization of the ablation catheter sampled at 60 Hz during RF application was extracted from the CARTO3 system (Biosense Webster, Inc.) and analyzed using custom software (MATLAB, Mathworks, USA) to determine mean and maximum catheter excursion relative to mean catheter location during point-by-point RF ablation. All lesions for a given patient were then averaged to form composite measures of catheter stability The primary end point was freedom from documented recurrence of atrial arrhythmia lasting longer than 30 seconds after a single ablation procedure. Results: At one year, 86% of patients were free from recurrent AF. There was no signifcant difference in clinical and echocardiographic baseline characteristics between patients with and without recurrent arrhythmia There was no signifcant difference in lesion number, average contact-force, average impedance decrease, or RF time between patients who did recur and those who did not. For all patients, maximum catheter excursion was 2.84 +/- 0.40mm and mean catheter excursion was 0.99 +/- 0.16mm. Patients with arrhythmia recurrence had signifcantly greater maximum (3.07 +/- 0.38mm vs 2.80 +/- 0.40mm, p = 0.03) and mean (1.08 +/- 0.13mm vs 0.98 +/- 0.17mm, p = 0.01) catheter excursion compared to those without recurrence. Univariate regression demonstrated that maximal catheter excursion was a signifcant predictor of arrhythmia recurrence (OR 5.1 per 1mm excursion increase, 95% CI 1.2-21.9, p=0.03). Conclusion: Quantitative measures of ablation catheter spatial stability may be novel and potentially modifable predictors of procedural success during RF ablation of AF

Background: Catheter ablation has become an increasingly common elective therapy for symptomatic atrial fbrillation (AF). Few data are available regarding outcomes of urgent AF ablation performed during AF related hospital admission, and the impact of these procedures on healthcare utilization. Objective: To evaluate patient characteristics, procedural outcomes, and impact on healthcare utilization in patients undergoing urgent AF ablation. Methods: Procedural outcomes of patients undergoing urgent frst-time AF ablation during an AF related hospital admission between 1/2014 and 8/2017 at a single tertiary care medical center were compared to those of 2:1 matched control patients undergoing frst-time elective AF ablation. An inverse probability weighted marginal structural model was constructed and the weighted means of the average hospital days and number of hospital visits in the six-months post ablation were compared. Results: 25 patients (1% of frst-time AF ablations) underwent an urgent procedure. There were no major procedural complications in either group. Incidence of arrhythmia recurrence within one year was similar in urgent and elective patients (20% vs. 18%, respectively, p=0.85). Urgent ablation patients had a greater number of hospital utilization days in the 6-months pre-ablation (mean 8.9+/-4.5 vs 2.6+/-1.1, p<.001) and a similar number of hospital utilization days in the 6-months post-ablation (1.8+/-4.5 vs 0.59+/- 1.07, p=.05) The marginal structural model of the change in number of hospital visits due to being in the urgent ablation group was-0.924 (-1.43 to-0.41; P <0.001). Conclusion: Urgent ablation for treatment resistant, symptomatic AF is feasible and safe with procedural outcomes were similar to those of elective AF ablation. There is and increased rate of healthcare utilization in prior to ablation in the urgent group, and a statistically signifcant reduction in healthcare utilization following urgent AF ablation. Defning the cost-effectiveness of and optimal patient selection for urgent ablation requires further investigation

Background: Unfavorable outcomes for stepwise linear ablation of non-paroxysmal atrial fbrillation (NPAF) in clinical trials may be attributable to pro-arrhythmic effects of incomplete ablation lines. It is unknown if recurrent arrhythmia following stepwise linear ablation is more likely to be successfully ablated compared to recurrent arrhythmia following a more limited initial procedure The optimal ablation strategy for catheter ablation of NPAF using a contact-force sensing (CFS) radiofrequency ablation (RFA) catheter remains unclear. Objective: To compare 2-procedure outcomes of stepwise linear RFA to left atrial posterior wall isolation in patients undergoing NPAF ablation using a CFS RFA catheter. Methods: We compared clinical outcomes of two cohorts of 100 consecutive NPAF patients undergoing frst-time RFA using a CFS RFA catheter. Group 1: stepwise linear ablation (July 2014-July 2015); Group 2: left atrial posterior wall isolation (October 2015-June 2016). Arrhythmia recurrence was assessed using 2-week event monitors at 3-month intervals following ablation procedures. Results: Baseline characteristics of the two groups were similar. Mean follow-up time was 656 +/- 361 days for Group 1 and 436 +/- 228 days for Group 2. At 24-month follow up, Kaplan-Meier estimated single procedure arrhythmia free survival was signifcantly greater in Group 2 compared to Group 1 (76% vs 59%, respectively; p = 0.01), primarily driven by a higher rate of recurrence of atrial tachycardia (12% vs 35%, respectively; p < 0.001). Among patients with recurrent arrhythmia after a single procedure, Group 2 patients were less likely to require repeat ablation compared to Group 1 (6/24 vs 34/41, respectively; p < 0.001) and less likely to recur after repeat ablation (1/6 vs 13/34, respectively; p = 0.001). Conclusion: Compared to stepwise linear ablation, LA posterior wall isolation for catheter ablation of NPAF resulted in a lower incidence of recurrent arrhythmia at 2 years, a lower likelihood of requiring repeat ablation amongst patients with recurrence, and a lower likelihood of recurrence following a second ablation

OBJECTIVES/OBJECTIVE:This study sought to investigate the effect of pacing mediated heart rate modulation on catheter-tissue contact and impedance reduction during radiofrequency ablation in human atria during atrial fibrillation (AF) ablation. BACKGROUND:In AF ablation, improved catheter-tissue contact enhances lesion quality and acute pulmonary vein isolation rates. Previous studies demonstrate that catheter-tissue contact varies with ventricular contraction. The authors investigated the impact of modulating heart rate on the consistency of catheter-tissue contact and its effect on lesion quality. METHODS:Twenty patients undergoing paroxysmal AF ablation received ablation lesions at 15 pre-specified locations (12 left atria, 3 right atria). Patients were assigned randomly to undergo rapid atrial pacing for either the first half or the second half of each lesion. Contact force and ablation data with and without pacing were compared for each of the 300 ablation lesions. RESULTS:Compared with lesion delivery without pacing, pacing resulted in reduced contact force variability, as measured by contact force SD, range, maximum, minimum, and time within the pre-specified goal contact force range (p < 0.05). There was no difference in the mean contact force or force-time integral. Reduced contact force variability was associated with a 30% greater decrease in tissue impedance during ablation (p < 0.001). CONCLUSIONS:Pacing induced heart rate acceleration reduces catheter-tissue contact variability, increases the probability of achieving pre-specified catheter-tissue contact endpoints, and enhances impedance reduction during ablation. Modulating heart rate to improve catheter-tissue contact offers a new approach to optimize lesion quality in AF ablation. (The Physiological Effects of Pacing on Catheter Ablation Procedures to Treat Atrial Fibrillation [PEP AF]; NCT02766712).

Introduction Objectives: The AutoMark feature of the EnSite PrecisionTM electroanatomical mapping system allows physicians to create RF ablation lesion markers automatically. Additionally, the lesion markers can be scaled and colored based on up to two metrics of the RF energy delivery including: RF energy, RF duration, impedance drop magnitude, impedance drop (%), average RF power, maximum RF power, average temperature, maximum temperature, average force, and maximum force. Data exploring the optimal use of the AutoMark feature for creating consistent lesions are currently lacking. This study seeks to determine which combinations of two AutoMark metrics yield the best prediction of lesion diameter. Methods: In 24 canines, ventricular focal lesions were created using a contact force sensing, irrigated, RF ablation catheter over a wide range of ablation conditions (20-50W, 5-40 g, 5-60 seconds). Animals were sacrificed, hearts explanted and stained with 1% TTC, and fixed in 10% formalin. Lesions were identified, photographed, and digitally measured. Pairs of AutoMark metrics were exhaustively explored to find optimal combinations of metrics and success criteria for predicting consistent lesion diameter. Results: A total of 228 lesions were created with 227 found at dissection (> 99%). Within the IFU recommended contact force range (10- 30 g, n = 167 lesions), the combinations of energy and impedance drop (%); energy and average power; and average power and impedance drop (%) provided accurate indications for predicting lesion diameter equal to or exceeding 8 mm. The combination of energy >=473 J and impedance drop >=14% resulted in 92.1% lesions with a diameter of at least 8 mm versus only 50% when one or both criteria were not met (P < 0.001). Similarly, energy >=473 J and average RF power >=27 W yielded 95.1% of lesions with a diameter of at least 8 mm versus only 44.6% when one or both criteria were not met (P < 0.001). When RF power was at least 29 W and impedance drop was at least 14%, 100% of the lesions had a diameter of at least 8 mm versus only 54.4% when one or both criteria were not met (P < 0.001). Conclusions: The size and color of lesion markers placed using the AutoMark feature assisted in the identification of lesions of a desired dimension in this acute, preclinical model. Clinical use of theAutoMark featuremay facilitate creation of efficacious lesions

Background: Unfavorable outcomes observed with stepwise linear ablation of non-paroxysmal AF (NPAF) in large clinical trials utilizing ablation catheters without contact-force sensing (CFS) may be attributable to pro-arrhythmic effects of incomplete ablation lines. The optimal ablation strategy for catheter ablation of NPAF using a contact force sensing radiofrequency (RF) ablation catheter remains unclear. Objective: To compare catheter ablation outcomes of stepwise linear ablation to left atrial (LA) posterior wall isolation in patients undergoing NPAF ablation using a CFS RF ablation catheter. Methods: We performed pulmonary vein antral isolation (PVAI) followed by isolation of the LA posterior wall in 80 consecutive patients undergoing first-time NPAF ablation between November 2015 and March 2016 (Group 1) and compared clinical outcomes to those of 112 consecutive patients who underwent PVAI followed by step-wise linear ablation for NPAF between May 2014 and November 2015 (Group 2). All ablation procedures were performed using the Carto 3 mapping system and SmartTouch RF ablation catheter (Biosense Webster, Inc.). Arrhythmia recurrence was assessed using 2-week event monitors at 3-month intervals. Arrhythmia-free survival at 12 months was estimated using the Kaplan-Meier method. Results: Baseline characteristics of Group 1 and Group 2 were similar. At 12 months follow-up, arrhythmia-free survival was significantly greater in Group 1 patients compared with Group 2 (81.9% vs. 67.5%, respectively; p=0.0318). There was no significant difference in survival free from AF between group 1 and group 2 (89% vs. 84.1%, respectively; p=0.3431), however group 1 patients developed significantly fewer post-ablation atrial tachycardias (AT) than group 2 patients (8.1% vs 30.1%, respectively; p<0.001). Conclusion: Among patients undergoing NPAF ablation using a contact force sensing RF ablation catheter, LA posterior wall isolation resulted in fewer recurrent atrial arrhythmias than a stepwise linear approach. The reduction in recurrent atrial arrhythmias is driven primarily by a reduction in recurrent AT