Atrial Fibrillation Substrate and Catheter Ablation Outcomes in MYBPC3- and MYH7-Mediated Hypertrophic Cardiomyopathy.

BACKGROUND: The effects of disease-causing MYBPC3 or MYH7 genetic variants on atrial myopathy, atrial fibrillation (AF) clinical course, and catheter ablation efficacy remain unclear. OBJECTIVES: The aim of this study was to characterize the atrial substrate of patients with MYBPC3- or MYH7-mediated hypertrophic cardiomyopathy (HCM) and its impact on catheter ablation outcomes. METHODS: A retrospective single-center study of patients with HCM who underwent genetic testing and catheter ablation for AF was performed. Patients with MYBPC3- or MYH7-mediated HCM formed the gene-positive cohort; those without disease-causative genetic variants formed the control cohort. High-density electroanatomical mapping was performed using a 3-dimensional mapping system, followed by radiofrequency ablation. RESULTS: Twelve patients were included in the gene-positive cohort (mean age 55.6 ± 9.9 years, 83% men, 50% MYBPC3, 50% MYH7, mean ejection fraction 59.3% ± 13.7%, mean left atrial [LA] volume index 51.7 ± 13.1 mL/m2, mean LA pressure 20.2 ± 5.4 mm Hg) and 15 patients in the control arm (mean age 61.5 ± 12.6 years, 60% men, mean ejection fraction 64.9% ± 5.1%, mean LA volume index 54.1 ± 12.8 mL/m2, mean LA pressure 19.6 ± 5.41 mm Hg). Electroanatomical mapping demonstrated normal voltage in 87.7% ± 5.03% of the LA in the gene-positive cohort and 94.3% ± 3.58% of the LA in the control cohort (P < 0.001). Of the abnormal regions, intermediate scar (0.1-0.5 mV) accounted for 6.33% ± 1.97% in the gene-positive cohort and 3.07% ± 2.46% in the control cohort (P < 0.01). Dense scar (<0.1 mV) accounted for 5.93% ± 3.20% in the gene-positive cohort and 2.61% ± 2.19% in the control cohort (P < 0.01). Freedom from AF at 12 months was similar between the gene-positive (75%) and control (73%) cohorts (P = 0.92), though a greater number of procedures were required in the gene-positive cohort. CONCLUSIONS: Patients with MYBPC3- or MYH7-mediated HCM undergoing AF ablation have appreciably more low-amplitude LA signals, suggestive of fibrosis. However, catheter ablation remains an effective rhythm-control strategy.

Utilizing median and maximum QTc values improves prediction of breakthrough cardiac events in pediatric long QT syndrome.

INTRODUCTION: Although prior studies indicate that a QTc > 500 ms on a single baseline 12-lead electrocardiogram (ECG) is associated with significantly increased risk of arrhythmic events in long QT syndrome (LQTS), less is known about the risk of persistent QT prolongation. We sought to determine QTc persistence and its prognostic effect on breakthrough cardiac events (BCEs) among pediatric patients treated for LQTS. METHODS: We performed a retrospective analysis of 433 patients with LQTS evaluated, risk-stratified, and undergoing active guideline-based LQTS treatment between 1999 and 2019. BCEs were defined as arrhythmogenic syncope/seizure, sudden cardiac arrest (SCA), appropriate VF-terminating ICD shock, and sudden cardiac death (SCD). RESULTS: During the median follow-up of 5.5 years (interquartile range [IQR] = 3-9), 32 (7%) patients experienced a total of 129 BCEs. A maximum QTc threshold of 520 ms and median QTc threshold of 490 ms were determined to be strong predictors for BCEs. A landmark analysis controlling for age, sex, genotype, and symptomatic status demonstrated models utilizing both the median QTc and maximum QTc demonstrated the highest discriminatory value (c-statistic = 0.93-0.95). Patients in the high-risk group (median QTc > 490 ms and maximum QTc > 520 ms) had a significantly lower BCE free survival (70%-81%) when compared to patients in both medium-risk (93%-97%) and low-risk (98%-99%) groups. CONCLUSIONS: The risk of BCE among patients treated for LQTS increases not only based upon their maximum QTc, but also their median QTc (persistence of QTc prolongation). Patients with a maximum QTc > 520 ms and median QTc > 490 ms over serial 12-lead ECGs are at the highest risk of BCE while on guideline-directed medical therapy.

Arrhythmic manifestations and outcomes of definite and probable cardiac sarcoidosis.

BACKGROUND: The 2014 Heart Rhythm Society consensus statement defines histological (definite) and clinical (probable) diagnostic categories of cardiac sarcoidosis (CS), but few studies have compared their arrhythmic phenotypes and outcomes. OBJECTIVE: The purpose of this study was to evaluate the electrophysiological/arrhythmic phenotype and outcomes of patients with definite and probable CS. METHODS: We analyzed the arrhythmic/electrophysiological phenotype in a single-center North American cohort of 388 patients (median age 56 years; 39% female, n = 151) diagnosed with definite (n = 58) or probable (n = 330) CS (2000-2022). The primary composite outcome was survival to first ventricular tachycardia/fibrillation (VT/VF) event or sudden cardiac death. Key secondary outcomes were also assessed. RESULTS: At index evaluation, in situ cardiac implantable electronic devices and antiarrhythmic drug use were more common in definite CS. At a median follow-up of 3.1 years, the primary outcome occurred in 22 patients with definite CS (38%) and 127 patients with probable CS (38%) (log-rank, P = .55). In multivariable analysis, only a higher ratio of the 18F-fluorodeoxyglucose maximum standardized uptake value of the myocardium to the maximum standardized uptake value of the blood pool (hazard ratio 1.09; 95% confidence interval 1.03-1.15; P = .003, per 1 unit increase) was associated with the primary outcome. During follow-up, patients with definite CS had a higher burden of device-treated VT/VF events (mean 2.86 events per patient-year vs 1.56 events per patient-year) and a higher rate of progression to heart transplant/left ventricular assist device implantation but no difference in all-cause mortality compared with patients with probable CS. CONCLUSION: Patients with definite and probable CS had similarly high risks of first sustained VT/VF/sudden cardiac death and all-cause mortality, though patients with definite CS had a higher overall arrhythmia burden. Both CS diagnostic groups as defined by the 2014 Heart Rhythm Society criteria require an aggressive approach to prevent arrhythmic complications.

Predictors of nonpulmonary vein triggers for atrial fibrillation: A clinical risk score.

BACKGROUND: Targeting non-pulmonary vein triggers (NPVTs) after pulmonary vein isolation may reduce atrial fibrillation (AF) recurrence. Isoproterenol infusion and cardioversion of spontaneous or induced AF can provoke NPVTs but typically require vasopressor support and increased procedural time. OBJECTIVE: The purpose of this study was to identify risk factors for the presence of NPVTs and create a risk score to identify higher-risk subgroups. METHODS: Using the AF ablation registry at the Hospital of the University of Pennsylvania, we included consecutive patients who underwent AF ablation between January 2021 and December 2022. We excluded patients who did not receive NPVT provocation testing after failing to demonstrate spontaneous NPVTs. NPVTs were defined as non-pulmonary vein ectopic beats triggering AF or focal atrial tachycardia. We used risk factors associated with NPVTs with P <.1 in multivariable logistic regression model to create a risk score in a randomly split derivation set (80%) and tested its predictive accuracy in the validation set (20%). RESULTS: In 1530 AF ablations included, NPVTs were observed in 235 (15.4%). In the derivation set, female sex (odds ratio [OR] 1.40; 95% confidence interval [CI] 0.96-2.03; P = .080), sinus node dysfunction (OR 1.67; 95% CI 0.98-2.87; P = .060), previous AF ablation (OR 2.50; 95% CI 1.70-3.65; P <.001), and left atrial scar (OR 2.90; 95% CI 1.94-4.36; P <.001) were risk factors associated with NPVTs. The risk score created from these risk factors (PRE2SSS2 score; [PRE]vious ablation: 2 points, female [S]ex: 1 point, [S]inus node dysfunction: 1 point, left atrial [S]car: 2 points) had good predictive accuracy in the validation cohort (area under the receiver operating characteristic curve 0.728; 95% CI 0.648-0.807). CONCLUSION: A risk score incorporating predictors for NPVTs may allow provocation of triggers to be performed in patients with greatest expected yield.

Identifying Origin of Nonpulmonary Vein Triggers Using 2 Stationary Linear Decapolar Catheters: A Novel Algorithm.

BACKGROUND: Targeting nonpulmonary vein triggers (NPVTs) of atrial fibrillation (AF) after pulmonary vein isolation can be challenging. NPVTs are often single ectopic beats with a surface P-wave obscured by a QRS or T-wave. OBJECTIVES: The goal of this study was to construct an algorithm to regionalize the site of origin of NPVTs using only intracardiac bipolar electrograms from 2 linear decapolar catheters positioned in the posterolateral right atrium (along the crista terminalis with the distal bipole pair in the superior vena cava) and in the proximal coronary sinus (CS). METHODS: After pulmonary vein isolation in 42 patients with AF, pacing from 15 typical anatomic NPVT sites was conducted. For each pacing site, the electrogram activation sequence was analyzed from the CS catheter (simultaneous/chevron/inverse chevron/distal-proximal/proximal-distal) and activation time (ie, CSCTAT) between the earliest electrograms from the 2 decapolar catheters was measured referencing the earliest CS electrogram; a negative CSCTAT value indicates the crista terminalis catheter electrogram was earlier, and a positive CSCTAT value indicates the CS catheter electrogram was earlier. A regionalization algorithm with high predictive value was defined and tested in a validation cohort with AF NPVTs localized with electroanatomic mapping. RESULTS: In the study patient cohort (71% male; 43% with persistent AF, 52% with left atrial dilation), the algorithm grouped with high precision (positive predictive value 81%-99%, specificity 94%-100%, and sensitivity 30%-94%) the 15 distinct pacing sites into 9 clinically useful regions. Algorithm testing in a 98 patient validation cohort showed predictive accuracy of 91%. CONCLUSIONS: An algorithm defined by the activation sequence and timing of electrograms from 2 linear multipolar catheters provided accurate regionalization of AF NPVTs to guide focused detailed mapping.

Complexity analysis of electrical activity during endocardial and epicardial biventricular mapping of ventricular fibrillation.

BACKGROUND: Ventricular fibrillation (VF) is a lethal cardiac arrhythmia that is a significant cause of sudden cardiac death. Comprehensive studies of spatiotemporal characteristics of VF in situ are difficult to perform with current mapping systems and catheter technology. OBJECTIVE: The goal of this study was to develop a computational approach to characterize VF using a commercially available technology in a large animal model. Prior data suggests that characterization of spatiotemporal organization of electrical activity during VF can be used to provide better mechanistic understanding and potential ablation targets to modify VF and its substrate. We therefore evaluated intracardiac electrograms during biventricular mapping of the endocardium (ENDO) and epicardium (EPI) in acute canine studies. METHODS: To develop thresholds for organized and disorganized activity, a linear discriminant analysis (LDA)-based approach was performed to the known organized and disorganized activities recorded in ex vivo Langendorff-perfused rat and rabbit hearts using optical mapping experiments. Several frequency- and time-domain approaches were used as individual and paired features to identify the optimal thresholds for the LDA approach. Subsequently, VF was sequentially mapped in 4 canine hearts, using the CARTO mapping system with a multipolar mapping catheter in the ENDO left and right ventricles and EPI to capture the progression of VF at 3 discrete post-induction time intervals: VF period 1 (just after induction of VF to 15 min), VF period 2 (15 to 30 min), and VF period 3 (30 to 45 min). The developed LDA model, cycle lengths (CL), and regularity indices (RI) were applied to all recorded intracardiac electrograms to quantify the spatiotemporal organization of VF in canine hearts. RESULTS: We demonstrated the presence of organized activity in the EPI as VF progresses, in contrary to the ENDO, where the activity stays disorganized. The shortest CL always occurred in the ENDO, especially the RV, indicating a faster VF activity. The highest RI was found in the EPI in all hearts for all VF stages, indicating spatiotemporal consistency of RR intervals. CONCLUSION: We identified electrical organization and spatiotemporal differences throughout VF in canine hearts from induction to asystole. Notably, the RV ENDO is characterized by a high level of disorganization and faster VF frequency. In contrast, EPI has a high spatiotemporal organization of VF and consistently long RR intervals.

Impact of Median Sternotomy on Safety and Efficacy of the Subcutaneous Implantable Cardioverter Defibrillator.

BACKGROUND: Subcutaneous implantable cardioverter defibrillators (S-ICDs) are an attractive alternative to transvenous ICDs among those not requiring pacing. However, the risks of damage to the S-ICD electrode during sternotomy and adverse interactions with sternal wires remain unclear. We sought to determine the rates of damage to the S-ICD lead during sternotomy, inappropriate shocks from electrical noise due to interaction with sternal wires, and failure to terminate spontaneous or induced ventricular arrhythmias. METHODS: Retrospective, multicenter study of patients undergoing sternotomy before or after S-ICD implantation. Clinical, procedural, and device-related data were collected by each center and analyzed by the coordinating center. These data were compared with a historical control cohort of nonsternotomy patients. RESULTS: Of 196 identified patients (52±16 years, 47 women), 166 underwent S-ICD implantation after sternotomy and 30 sternotomy after S-ICD. There was no damage to any lead among those who underwent sternotomy after S-ICD. Defibrillation threshold testing was performed in 63% at implant, with 91% first shock success. During a median follow-up of 29 months (range, 1-188), S-ICD first shocks successfully terminated spontaneous ventricular arrhythmias in 31 of 32 patients (97%). Inappropriate shocks occurred in 22 patients, most commonly related to T wave oversensing (n=14). Compared with the nonsternotomy controls, there were no differences in rates of first shock success for induced or spontaneous arrhythmias or rate of inappropriate shocks. CONCLUSIONS: Sternotomy before or after S-ICD does not confer additional risk relative to a historical control group without sternotomy.

Effects of Pulsed Electric Fields on the Coronary Arteries in Swine.

BACKGROUND: Previous animal studies have shown no significant vascular injury from pulsed electrical field (PEF) ablation. We sought to assess the effect of PEF on swine coronary arteries. METHODS: We performed intracoronary and epicardial (near the coronary artery) PEF ablations in swine pretreated with dual antiplatelet and antiarrhythmic therapy. Intracoronary PEF was delivered using MapiT catheters (Biotronik, Berlin), whereas epicardial PEF was delivered using EPT catheters (Boston Scientific, MA). PEF pulse duration was microseconds (Nanoknife 3.0, Angio Dynamics, NY) or nanoseconds (CellFX, Pulse Biosciences, CA). RESULTS: We performed 39 intracoronary ablations in 10 swine and 20 epicardial-pericoronary ablations in 4 separate swine. Intracoronary PEF was delivered at higher energy compared with epicardial PEF (46 [interquartile range, IQR 20-85] J versus 10 [IQR 10-11] J, P < 0.01). Reversible coronary spasm occurred in 49% intracoronary ablations and 45% epicardial ablations (P=0.80). At the end study, fixed coronary stenosis was demonstrated in 44% intracoronary ablations (80% for microsecond PEF and 18% for nanosecond PEF) and 0% epicardial ablations. Visible hemorrhagic and/or fibrotic myocardial lesions were observed at necropsy with similar frequency between intracoronary and epicardial PEF (45% versus 50%, P=0.70). Nanosecond PEF (49 ablations in 11 swine), when compared with microsecond PEF (10 intracoronary ablations in 3 swine), resulted in lower energy delivery (21 [IQR 10-46] J versus 129 [IQR 24-143] J, P=0.03) and less incidence of fixed coronary stenosis (18% versus 80%, P=0.04). CONCLUSIONS: In the swine model, intracoronary PEF resulted both in significant coronary spasm and fixed coronary stenosis. Epicardial PEF, delivered at lower energy, resulted in reversible spasm but no fixed coronary stenosis.

Novel insights into the substrate involved in maintenance of ventricular fibrillation: results from continuous multipolar mapping in a canine model.

BACKGROUND: While the triggers for ventricular fibrillation (VF) are well-known, the substrate required for its maintenance remains elusive. We have previously demonstrated dynamic spatiotemporal changes across VF from electrical induction of VF to asystole. Those data suggested that VF drivers seemed to reside in the distal RV and LV. However, signals from these areas were not recorded continuously. The aim of this study was to map these regions of significance with stationary basket electrodes from induction to asystole to provide further insights into the critical substrate for VF rhythm sustenance in canines. METHODS: In six healthy canines, three multipolar basket catheters were positioned in the distal right ventricle (RV), RV outflow tract, and distal left ventricle (LV), and remained in place throughout the study. VF was induced via direct current application from an electrophysiologic catheter. Surface and intracardiac electrograms were recorded simultaneously and continuously from baseline, throughout VF, and until asystole, in order to get a complete electrophysiologic analysis of VF. Focused data analysis was also performed via two defined stages of VF: early VF (immediately after induction of VF to 10 min) and late VF (after 10 min up to VF termination and asystole). RESULTS: VF was continuously mapped for a mean duration of 54 ± 9 min (range 42-70 min). Immediately after initiation of VF in the early phase, the distal LV region appeared to drive the maintenance of VF. Towards the terminal stage of VF, the distal RV region appeared to be responsible for VF persistence. In all canines, we noted local termination of VF in the LV, while VF on surface ECG continued; conversely, subsequent spontaneous termination of VF in the RV was associated with termination of VF on surface ECG into a ventricular escape rhythm. Continuous mapping of VF showed trends towards an increase in peak-to-peak ventricular electrogram cycle length (p = 0.06) and a decrease in the ventricular electrogram amplitude (p = 0.06) after 40 min. Once we could no longer discern surface QRS activity, we demonstrated local ventricular myocardial capture in both the RV and LV but could not reinitiate sustained VF despite aggressive ventricular burst pacing. CONCLUSIONS: This study describes the evolution of VF from electrical initiation to spontaneous VF termination without hemodynamic support in healthy canines. These data are hypothesis-generating and suggest that critical substrate for VF maintenance may reside in both the distal RV and LV depending on stage of VF. Further studies are needed to replicate these findings with hemodynamic support and to translate such findings into clinical practice. Ventricular fibrillation maintenance may be dependent on critical structures in the distal RV. ECG: electrocardiogram; LV: left ventricle; RV: right ventricle; RVOT: right ventricular outflow tract; VF: ventricular fibrillation.

Ventricular nanosecond pulsed electric field delivery using active fixation leads: a proof-of-concept preclinical study.

BACKGROUND: Mid-myocardial ventricular arrhythmias are challenging to treat. Cardiac electroporation via pulsed electric fields (PEFs) offers significant promise. We therefore tested PEF delivery using screw-in pacemaker leads as proof-of-concept. METHODS: In 5 canine models, we applied nanosecond PEF (pulse width 300 ns) across the right ventricular (RV) septum using a single lead bipolar configuration (n = 2) and between two leads (n = 3). We recorded electrograms (EGMs) prior to, immediately post, and 5 min after PEF. Cardiac magnetic resonance imaging (cMRI) and histopathology were performed at 2 weeks and 1 month. RESULTS: Nanosecond PEF induced minimal extracardiac stimulation and frequent ventricular ectopy that terminated post-treatment; no canines died with PEF delivery. With 1 lead, energy delivery ranged from 0.64 to 7.28 J. Transient ST elevations were seen post-PEF. No myocardial delayed enhancement (MDE) was seen on cMRI. No lesions were noted on the RV septum at autopsy. With 2 leads, energy delivery ranged from 56.3 to 144.9 J. Persistent ST elevations and marked EGM amplitude decreases developed post-PEF. MDE was seen along the septum 2 weeks and 1 month post-PEF. There were discrete fibrotic lesions along the septum; pathology revealed dense connective tissue with < 5% residual cardiomyocytes. CONCLUSIONS: Ventricular electroporation is feasible and safe with an active fixation device. Reversible changes were seen with lower energy PEF delivery, whereas durable lesions were created at higher energies. Central illustration: pulsed electric field delivery into ventricular myocardium with active fixation leads.

Cardiac ablation with pulsed electric fields: principles and biophysics.

Pulsed electric fields (PEFs) have emerged as an ideal cardiac ablation modality. At present numerous clinical trials in humans are exploring PEF as an ablation strategy for both atrial and ventricular arrhythmias, with early data showing significant promise. As this is a relatively new technology there is limited understanding of its principles and biophysics. Importantly, PEF biophysics and principles are starkly different to current energy modalities (radiofrequency and cryoballoon). Given the relatively novel nature of PEFs, this review aims to provide an understanding of the principles and biophysics of PEF ablation. The goal is to enhance academic research and ultimately enable optimization of ablation parameters to maximize procedure success and minimize risk.

Leak closure following left atrial appendage exclusion procedures: A multicenter registry.

BACKGROUND: Though infrequent, incomplete left atrial appendage closure (LAAC) may result from residual leaks. Percutaneous closure has been described though data is limited. METHODS: We compiled a registry from four centers of patients undergoing percutaneous closure of residual leaks following LAAC via surgical means or with the Watchman device. Leak severity was classified as none (no leak), mild (1-2 mm), moderate (3-4 mm), or severe (≥5 mm). Procedural and clinical success was defined as the elimination of leak or mild residual leak at the conclusion of the procedure or follow-up, respectively. RESULTS: Of 72 (age 72.2 ± 9.2 years; 67% male) patients, 53 had undergone prior LAAC using the Watchman device and 19 patients surgical LAAC. Mean CHADS2 -VA2 Sc score was 4.0 ± 1.8. The median leak size was 5 mm, range: 2-13). A total of 13 received Amplatzer Vascular Plug-II, 18 received Amplatzer Duct Occluder-II and 40 patients received coils. One underwent closure using a 21 mm-Watchman. Procedural success was 94%. Zero surgical and nine Watchman patients (13%) had a residual leak at procedural-end (five mild, three moderate, and one severe)-only one patient had no reduction in leak size. Overall leak size reduction was 94%. Two (3%) had intraoperative pericardial effusion. There were no device embolizations, device-related thrombi, or procedural deaths. Clinical success was maintained at 94%. Two had cerebrovascular accidents-at 2 days (transient ischemic attack) and 10 months postprocedure. Two had major bleeding outside the 30-day periprocedural window. CONCLUSION: Percutaneous closure of residual leaks following left atrial appendage closure is feasible and associated with good outcomes. The procedural risk appears to be satisfactory.

Outcomes of Direct Oral Anticoagulants Co-Prescribed with Common Interacting Medications.

Direct oral anticoagulants (DOACs) can potentially interact with multiple prescription medications. We examined the prevalence of co-prescription of DOACs with interacting medications and its impact on outcomes in patients with atrial fibrillation (AF). Patients with AF treated with a DOAC from 2010 to 2017 at the Mayo Clinic and co-prescribed medications that are inhibitors or inducers of the P-glycoprotein and/or Cytochrome P450 3A4 pathways were identified. The outcomes of stroke, transient ischemic attack, or systemic embolism, major bleeding, and minor bleeds were compared between patients with and without an enzyme inducer. Cox proportional hazards model was used to assess the association between interacting medications and outcomes. Of 8,576 patients with AF (mean age 70 ± 12 years, 35% female) prescribed a DOAC (38.6% apixaban, 35.8% rivaroxaban, 25.6% dabigatran), 2,610 (30.4%) were on at least 1 interacting agent: the majority were on an enzyme inhibitor (n = 2,592). Prescribed medications included non-dihydropyridine calcium channel blocker (n = 1,412; 16.5%), antiarrhythmic medication (n = 790; 9.2%), antidepressant (n = 659; 7.7%), antibiotic/antifungal (n = 77; 0.90%), antiepileptics (n = 17; 0.2%) and immunosuppressant medications (n = 19; 0.2%). Patients on an interacting medication were more likely to receive a lower dose of DOAC than indicated by the manufacturer's labeling (15.0% vs 11.4%, p <0.0001). In multivariable analysis, co-prescription of an enzyme inhibitor was not associated with risk of any bleeding (hazard ratio 0.87 [0.71 to 1.05], p = 0.15) or stroke, transient ischemic attack, or systemic embolism (hazard ratio 0.82 [0.51 to 1.31], p = 0.39). In conclusion, DOACs are co-prescribed with medications with potential interactions in 30.4% of patients with AF. Co-prescription of DOACs and these drugs are not associated with increased risk of adverse embolic or bleeding outcomes in our cohort.

Regional and Temporal Variation of Ventricular and Conduction Tissue Activity During Ventricular Fibrillation in Canines.

[Figure: see text].

Sinus rhythm heart rate increase after atrial fibrillation ablation is associated with lower risk of arrhythmia recurrence.

BACKGROUND: Pulmonary vein isolation (PVI) with autonomic modulation may be more successful than PVI alone for atrial fibrillation (AF) ablation and may be signaled by changes in sinus rhythm heart rate (HR) post ablation. We sought to determine if a change in sinus rhythm HR predicted AF recurrence post PVI. METHODS: Patients who underwent AF ablation from 2000 to 2011 were included if sinus rhythm was noted on ECG within 90 days pre and 7 days post ablation. Basic ECG interval and HR changes were analyzed and outcomes determined. RESULTS: A total of 1152 patients were identified (74.3% male, mean age 57 ± 11 years). Mean AF duration was 5.2 ± 5.3 years. Paroxysmal AF was noted in 712 (61.8%) of the patients. Mean EF was 61% ± 6%. Sinus rhythm HR was 61 ± 11 pre-ablation and 76 ± 13 bpm post-ablation (27% ± 24% increase, p < .001). The ability of relative HR change post-ablation to predict AF recurrence was borderline (hazard ratio 0.65 [0.41-1.01], p = .067). With patients separated into quartiles based on the relative HR change, the upper quartile with the largest relative increase in HR had a significantly lower rate of AF recurrence compared to the lowest quartile following multi variable modeling (p = .038). There were significant changes in PR (171 ± 28 to 167 ± 30 ms) and QTc (424 ± 25 to 434 ± 29 ms) intervals (both p < .001) but these were not predictive of outcome. CONCLUSION: Relative changes in HR post AF ablation correlates with AF recurrence. Further prospective studies are needed to confirm this relationship.