Atrial fibrillation is significantly associated with morbidity and mortality and erodes the quality and quantity of life. It is standard of care to treat patients with AF and an increased risk of stroke with oral anticoagulation therapy, but the more daunting question many clinicians face is whether to pursue a “rate-only” or “rhythm” control strategy. Historical studies over the years have sought to answer this question but have found no significant difference in major clinical outcomes between the two strategies. There are opportunities based on new data to improve the natural history of the disease. The EAST AFnet trial for the first time revealed a significant morbidity and mortality advantage to rhythm control therapy when performed early in the disease process of AF and in the setting of comprehensive medical management that was maintained. The CABANA trial clearly demonstrated that catheter ablation was a more effective long-term treatment of AF in general and significantly lowers risk of AF progression compared to medical therapy. Like multiple prior trials of rhythm management strategies, when rhythm control was effective in these trials, independent of therapy assignment, there was a significantly lower risk of adverse outcomes and death. These contemporary data provide optimism that the pervasive mortality risk in patients with AF observed over the past 50 years may be improved by the timing, use, and efficacy of use of therapeutic interventions.

Introduction: Antitachycardia pacing (ATP) is used to terminate ventricular tachycardia (VT) by delivering rapid, low energy pacing to the right ventricle (RV). Unfortunately, ATP is not effective against all VT episodes and can result in adverse outcomes, such as VT acceleration and degeneration into ventricular fibrillation (VF). Improving ATP is therefore desirable. Our objective was to compare the efficacy and safety of ATP delivered at the His bundle to traditional ATP. Methods: Six dogs were anesthetized and pacing leads were implanted in the RV and His bundle. The lateral anterior descending artery (LAD) was occluded for 2 hours to create an ischemic injury. In a study 4-7 days later, a 128-electrode sock was placed snugly around the ventricles and VT was induced using rapid pacing. ATP was delivered from either the His bundle or RV lead, then attempted at the other location if unsuccessful. Success rates and instances of VT acceleration and degeneration into VF were calculated. Results: We induced 83 runs of VT and attempted ATP 128 times. RV ATP was successful in 36% of attempts; His ATP was successful in 38% of attempts. RV ATP resulted in significantly more adverse outcomes. RV and His ATP induced VT acceleration in 9% and 3% of trains respectively, and induced degeneration into VF in 5% and 1% of trains, respectively. Conclusion: His bundle ATP is safer, but not significantly more effective, than RV ATP.

Response to “Delay in AF ablation costs lives”Andrew J. Sessions BS1, Heidi T. May, PhD, MSPH2, Brian G. Crandall, MD2, John D. Day, MD3, Michael J. Cutler DO, PhD2, Christopher A. Groh MD4, Leenapong Navaravong MD4, Ravi Ranjan MD, PhD4, Benjamin A. Steinberg MD, MHS4, T. Jared Bunch, MD4Corresponding Author: Dr. T. Jared BunchUniversity of Utah School of Medicine, Salt Lake City, Utah, USADepartment of Cardiology, Intermountain Heart Institute, Intermountain Medical Center, Salt Lake City, Utah, USASt. Marks Hospital, Salt Lake City, UtahDepartment of Internal Medicine, Division of Cardiology, University Hospital, Salt Lake City, Utah, USAAddress for correspondence: T. Jared Bunch, M.D.University of Utah School of Medicine Division of Cardiology, Department of Internal Medicine 50 N Medical Drive Salt Lake City, Utah 84132 Phone: 801-585-7676Short Title: Impact of delays in catheter ablationFunding : None

Background: Recent randomized controlled trials (RCT) suggest that ablation is superior to antiarrhythmic drugs (AAD) as an initial therapy for paroxysmal atrial fibrillation (pAF) to prevent arrhythmia recurrences. We performed an updated meta-analysis of RCTs, to include recent data from cryoballoon-based ablation, and to compare arrhythmia-free survival and adverse events between ablation and AAMs. Methods: We searched MEDLINE and EMBASE from inception to December 2020. We included RCT comparing patients with pAF undergoing ablation or receiving AADs as an initial therapy. We combined data using the random-effects model to calculate hazards ratio (HR) for arrhythmia-free survival and odds ratio (OR) for adverse events. Results: Five studies from 2005-2020 involving 985 patients were included (495 patients and 490 patients underwent ablation and medication as initial therapy, respectively). Patients who underwent ablation had higher freedom from atrial tachyarrhythmias (AT) during the 12-24 months follow-up period (pooled HR=0.48, 95% CI:0.40-0.59, p<0.001) (Figure 2). In a subgroup analysis of ablation method used, both cryoablation group (pooled HR=0.49, 95% CI:0.38-0.64, p<0.001) (Figure 2A) and radiofrequency ablation group (pooled HR=0.47, 95%CI:0.35-0.64, p<0.001) (Figure 2B) showed reduction in AT recurrence compared to AAD group. There were no differences in adverse events including cerebrovascular accident, pericardial effusion or tamponade, pulmonary vein stenosis, acute coronary syndrome, deep vein thrombosis and pulmonary embolism, and bradycardia requiring a pacemaker. Conclusion: Catheter ablation (both cryoablation and radiofrequency ablation) is superior to AAD as an initial therapy for pAF in efficacy for reducing AT recurrences without a compromise in adverse events.