Faculty Bibliography

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

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).

Esophageal perforation is a dreaded complication of atrial fibrillation ablation that occurs in 0.1% to 0.25% of atrial fibrillation ablation procedures. Delayed diagnosis is associated with the development of atrial-esophageal fistula (AEF) and increased mortality. The relationship between the esophagus and the left atrial posterior wall is variable, and the esophagus is most susceptible to injury where it is closest to areas of endocardial ablation. Esophageal ulcer seems to precede AEF development, and postablation endoscopy documenting esophageal ulcer may identify patients at higher risk for AEF. AEF has been reported with all modalities of atrial fibrillation ablation despite esophageal temperature monitoring. Despite the name AEF, fistulas functionally act 1 way, esophageal to atrial, which accounts for the observed symptoms and imaging findings. Because of the rarity of AEF, evaluation and validation of strategies to reduce AEF remain challenging. A high index of suspicion is recommended in patients who develop constitutional symptoms or sudden onset chest pain that start days or weeks after atrial fibrillation ablation. Early detection by computed tomography scan with oral and intravenous contrast is safe and feasible, whereas performance of esophageal endoscopy in the presence of AEF may result in significant neurological injury resulting from air embolism. Outcomes for esophageal stenting are poor in AEF. Aggressive intervention with skilled cardiac and thoracic surgeons may improve chances of stroke-free survival for all types of esophageal perforation.

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)

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: 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