Faculty Bibliography

PURPOSE/OBJECTIVE:Elimination of pace-capture along pulmonary vein isolation (PVI) lesion sets reduces atrial fibrillation (AF) recurrence in catheter ablation of paroxysmal AF. Pacing from the RF ablation electrode during RF application is prevented within the CARTO electroanatomic mapping system (Biosense Webster, Inc.) due to theoretical safety considerations. We evaluated a method of pacing the distal ablation electrode during RF application in the CARTO system, thus avoiding repeated activation and inactivation of the pacing channel and facilitating immediate recognition of pace-capture loss. We investigated the safety, feasibility, and utility of simultaneous pace-ablate (SPA) during AF ablation with the CARTO-3 system and a contact-force sensing RF ablation catheter. METHODS:Safety of feasibility of SPA was evaluated in 250 patients undergoing first-time AF ablation. Frequency and regional distribution of pace-capture following PVI was evaluated in a cohort of 50 consecutive patients undergoing catheter ablation of paroxysmal AF. RESULTS:SPA was successfully performed in all 250 patients without adverse event. At least one pace-capture site was noted in 22 of 50 PAF patients (44%), and pace-capture following PVI was most common at anterior and superior left atrial sites. There were 2.0 ± 3.3 RF applications during pacing via the distal ablation electrode per patient, and all lesions sets were successfully rendered unexcitable. CONCLUSIONS:Pace-capture along the completed PVI lesion set remains common despite utilization of contact-force sensing RF ablation catheters and automated lesion annotation. Simultaneous pace-ablate in AF ablation using the CARTO system may be safely used to render atrial lesion sets unexcitable.

OBJECTIVE:Cardiac catheter cryoablation is a safer alternative to radiofrequency ablation for arrhythmia treatment, but electrophysiological (EP) effects during and after freezing are not adequately characterized. The goal of this study was to determine transient and permanent temperature induced EP effects, during and after localized tissue freezing. METHODS:Conduction in right (RV) and left ventricles (LV) was studied by optical activation mapping during and after cryoablation in paced, isolated Langendorff-perfused porcine hearts. Cryoablation was performed endocardially (n=4) or epicardially (n=4) by a cryoprobe cooled to -120 °C for 8 minutes. Epicardial surface temperature was imaged with an infrared camera. Viability staining was performed after ablation. Motion compensation and co-registration was performed between optical mapping data, temperature image data, and lesion images. RESULTS:Cryoablation produced lesions 14.9 +/- 3.1 mm in diameter and 5.8 +/- 1.7 mm deep. A permanent lesion was formed in tissue cooled below -5 +/- 4 °C. Transient EP changes observed at temperatures between 17 and 37 °C during cryoablation surrounding the frozen tissue region directly correlated with local temperature, and include action potential (AP) duration prolongation, decrease in AP magnitude, and slowing in conduction velocity (Q10=2.0). Transient conduction block was observed when epicardial temperature reached <17 °C, but completely resolved upon tissue rewarming, within 5 minutes. CONCLUSION/CONCLUSIONS:Transient EP changes were observed surrounding the permanent cryo lesion (<-5 °C), including conduction block (-5 to 17 °C), and reduced conduction velocity (>17 °C). SIGNIFICANCE/CONCLUSIONS:The observed changes explain effects observed during clinical cryoablation, including transient increases in effective refractory period, transient conduction block, and transient slowing of conduction. The presented quantitative data on temperature dependence of EP effects may enable the prediction of the effects of clinical cryoablation devices.

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: 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: 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).

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

Background: Analysis of the local unipolar electrogram aids premature ventricular contraction (PVC) localization in catheter ablation of idiopathic, outflow tract PVCs. A unipolar electrogram QS complex may be seen in the region of PVC origin, but the specificity of this finding is low. The unipolar anodal electrode utilized for PVC mapping is typically Wilson central terminal (WCT) or an indifferent electrode placed within the inferior vena cava (IVC). The optimal unipolar electrode selection for unipolar PVC mapping is unknown. Objective: To compare unipolar mapping of idiopathic outflow tract PVCs using WCT to unipolar mapping using an IVC electrode. Methods: PVC mapping and ablation was performed in 20 consecutive patients presenting for first-time ablation of idiopathic, outflow tract PVCs. The unipolar electrode utilized for initial mapping was randomly assigned and blinded to the operator. Mapping was performed using the CARTO 3 mapping system and SmartTouch RF ablation catheter (Biosense Webster, Inc.). Activation mapping and pace-mapping was performed at the discretion of the operator. Locations with a QS complex were annotated on the electroanatomic map. After a complete map was created blinded mapping was repeated with the alternate unipolar electrode prior to RF application. Results: PVCs were localized to the right ventricular outflow tract in 18 patients (90%) and to the left ventricular outflow tract in 2 patients (10%). Complete unipolar mapping could not be completed in 4 of 20 (20%) of cases due to infrequency of PVCs. In the 16 remaining patients, QS complex surface area was significantly larger with WCT than with the IVC electrode (3.11 +/- 1.8 cm² vs. 1.3 +/- 0.8 cm², p < 0.001). The IVC electrode QS area was completely within the WCT QS area in all cases, and the ratio of WCT QS area to IVC electrode QS area was 2.6 +/- 0.8 (range 1.8 to 4.4). The area of RF application at which PVCs were durably suppressed was within the IVC electrode QS area in all patients. Conclusion: Utilization of an indifferent IVC electrode may improve precision and specificity of unipolar mapping in catheter ablation of idiopathic, outflow tract PVCs

Background: Pre-procedure time outs are integral to medicine to improve quality and safety. We hypothesized that a radiation safety time out for EP procedures would reduce radiation exposure levels for patients and staff. Objective: To design, implement and assess the effect of a radiation safety time out on radiation exposure in the EP lab. Methods: Baseline data on all adult EP procedures were collected for 6 months prior to implementation of the radiation safety time out. Upon implementation of the time out, data were collected prospectively with analyses to be performed every 3 months for up to 12 months. The primary endpoint was mean dose area product (DAP). Secondary endpoints were reference dose, fluoroscopy time, use of additional shielding, and use of alternative imaging. Results: The study was halted after three months. In total, 592 cases prior to the time out and 448 cases during implementation of the time out were included. Use of the time out resulted in a 22% reduction in the DAP (p = 0.013). The mean reference dose was also reduced by 26%. The use of additional radiation shields and ultrasound imaging for venous access increased significantly during the time out period. These differences remained significant when adjusted for BMI, proceduralist, and procedure type. There was no increase in procedure time or complications with the time out (Table). Conclusion: Implementation of a radiation safety time out significantly reduces radiation exposure during EP procedures. EP laboratories, as well as other areas of medicine that use fluoroscopy, should strongly consider the use of radiation safety time outs to reduce radiation exposures and improve safety. (Table presented)

Introduction: LA ablation for persistent AF that achieves organization to atrial tachycardia (AT) or sinus rhythm (SR) predicts greater long term ablation success. However, extensive LA ablation increases the risks of recurrent AT, adverse atrial remodeling and procedural complications. Preclinical and observational studies suggest that right atrial ablation may reduce AF risk. We hypothesized that CTI ablation may reduce the extent of LA ablation required to achieve organization of persistent AF. Methods: Persistent AF patients (n=107) were randomized to two arms (CTI-first or CTI-last) in a single center, prospective, single blind study. Excluding the CTI ablation, stepwise linear LA ablation was performed in a prespecified order. The primary endpoint was the percentage of patients who organized to AT or SR. The secondary endpoint was number of steps to organization. Results: CTI ablation first versus last during AF ablation did not significantly alter the percentage of patients who organized (Table). Among those who organized, the number of steps to organization did not differ between the two arms. No significant differences were found when patients were stratified by LA size or AF duration. Conclusions: CTI ablation does not alter the extent of LA ablation needed to achieve organization of AF. The utility of right atrial ablation for persistent AF ablation remains unclear. (Table presented)