This weekend, I was fortunate to attend the American Heart Association (AHA) Scientific Sessions 2019 in Philadelphia. Based on my career interest, I was keen to attend sessions related to the field of arrhythmia and electrophysiology. While late-breaking trials such as ISCHEMIA, COLCOT and DAPA-HF have appropriately and expectedly dominated the highlights of the scientific sessions, I would like to use the next few lines to talk about a few selected arrhythmia and electrophysiology studies that were presented at AHA, and have important clinical implications in my opinion.
Early morning on Saturday, Dr Larry Chinitz from New York University Langone Health, presented the primary results of the prospective, multicenter Micra Atrial tRacking using a Ventricular accelerometer (MARVEL 2) study.1 This innovative study examined the safety and efficacy of an accelerometer-based atrial sensing algorithm in patients with atrioventricular (AV) block who are implanted with a Micra leadless pacemaker. The primary efficacy endpoint (which was available in 40 patients) was the superiority of the algorithm in providing AV synchronous pacing (i.e. VDD) compared to the conventional Micra VVI pacing. The novel algorithm was successful in maintaining AV synchronous pacing (≥70% of the time at rest, during normal sinus rhythm and complete heart block) in 95% of the patients, compared to 0% in the Micra VVI pacing (P<0.001). VDD pacing was associated with 8.8% increase in stroke volume. There were no pauses (i.e. oversensing) or episodes of pacemaker-mediated tachycardia during VDD pacing. The automatic algorithm was successful in mode switching between VVI during intrinsic AV conduction and VDD during AV block. The algorithm is not commercially available yet, however, based on this exciting data, it seems that we should expect VDD leadless pacemakers to be available in the market shortly. Furthermore, the revolutionary leadless pacing technology is likely to expand in the coming few years, with potentially atrial leadless pacemakers and multicomponent systems such as cardiac resynchronization therapy with leadless left ventricular pacemaker and the possible combination of leadless pacemaker with subcutaneous defibrillator.
Later in the day, Dr Sean Pokorney from Duke Clinical Research Institute, presented the results of the RENal hemodialysis patients ALlocated apixaban versus warfarin in Atrial Fibrillation (RENAL-AF) trial.2 The study tackles a very important question regarding the safety and efficacy of NOAC (compared to warfarin) in hemodialysis patients with atrial fibrillation and elevated stroke risk (CHA2DS2-VASc score ≥2). A total of 154 patients were randomized 1:1 to apixaban 5 mg bid (N=82, 29% received a reduced dose of 2.5 mg bid due to increased age or low body weight) or warfarin with a target INR of 2-3 (N=72). At 1-year of follow up, there was no significant difference in the primary outcome of International Society on Thrombosis and Hemostasis (ISTH) major or clinically relevant non-major bleeding between the 2 groups (31.5 vs. 25.5% for apixaban and warfarin, respectively; p > 0.05). Similarly, the secondary outcomes of ISTH major bleeding (8.5 vs. 9.7%), major intracranial (1.2 vs. 1.4%) or gastrointestinal bleeding (2.4 vs. 6.9%), stroke (2.4 vs. 2.8%) and death (25.6 vs 18.1%) were not significantly different between both groups. Dr Pokorney clarified that the study was terminated prematurely due to slower than anticipated enrollment, and that the power was limited by small sample size. However, this remains the only randomized data currently available for the comparative safety and effectiveness of NOAC vs. warfarin for non-valvular atrial fibrillation in this challenging patient population that is at increased risk of both thromboembolic and bleeding events. For the time being, it seems that apixaban is a reasonable anticoagulant option for hemodialysis patients.
Last but not least, Dr Arthur Labovitz from the University of South Florida presented the Apixaban for Early Prevention of Recurrent Embolic Stroke and Hemorrhagic Transformation (AREST) trial.3 The study was a randomized, open-label, pilot trial that included patients with atrial fibrillation who had recent cerebral ischemic symptoms (0-48 hours). The patients were randomized to apixaban (to start 0-3 days after transient ischemic attack [TIA], 3-5 days after small stroke and 7-9 days after medium stroke, N=41) or warfarin (to start 7±5 days after TIA, or 14±5 days after small or medium stroke, N=47). At 180 days, early use of apixaban resulted in less fatal stroke, recurrent ischemic stroke or TIA (19.5 vs 27.7%, p=0.46) but this did not reach statistical significance. Early apixaban use was not associated with increased risk of intracranial bleeding. The authors concluded that the early use of apixaban is safe in this patient population and may be associated with improved outcomes.
Whether you are a fan of innovative technologies that revolutionize the way we treat our arrhythmia patients, or you are an admirer of rigorous clinical trials that address common challenging scenarios in clinical electrophysiology, the high-quality science presented this year at AHA will sure satisfy your taste. Stay tuned!
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Amr F. Barakat is a Clinical Cardiac Electrophysiology Fellow at the University of Pittsburgh Medical Center in Pittsburgh, PA. He is invested in academic electrophysiology and clinical outcomes research, and is a believer in the role of social media in medical education (tweets @AmrFBarakat). He volunteers for the AHA FIT & Early Career Blogging Program.