Impaired sinus response during ventricular arrhythmia predicts adverse outcomes in implantable cardioverter-defibrillator recipients

Background Sinus rhythm (SR) acceleration has been shown to be associated with better hemodynamic tolerance of induced ventricular tachycardia during an electrophysiological study. Whether atrial behavior during ventricular arrhythmias (VAs) has prognostic value outside the lab remains largely unexplored. Purpose To assess the proportions of patients that either exhibit SR acceleration, absence of SR acceleration or predominantly retrograde conduction (RC) during VA, and to assess whether this behavior is associated with adverse events in implantable cardioverter-defibrillator (ICD) patients. Methods In this single-center retrospective study, patients with an ischemic (ICM) or non-ischemic cardiomyopathy who received appropriate ICD therapy with an interpretable SR immediately prior to and during the treated VA were included. Patients were considered to exhibit SR acceleration if the SR increased with 5 beats per minute or more. In case of atrial pacing prior to, followed by a more rapid intrinsic SR during the VA, patients were considered to exhibit SR acceleration. EGMs were interpreted by three cardiologists blinded for outcome. The analyzed endpoints were a composite endpoint of all-cause mortality, heart transplantation or implantation of a ventricular assist device (Mort/HTx/VAD), and a new, subsequent appropriate ICD intervention. Time to event statistical methods were applied. Results After excluding 1,065 patients without appropriate ICD therapy and another 466 patients that did not meet inclusion criteria, either due to single-chamber devices, atrial fibrillation, atrial pacing or absent recordings, 84 patients were included (17% female, 61% ICM, median age of 62 years [IQR 57 – 68]). SR acceleration was the most common (40%), followed by no acceleration (36%) and predominantly RC (24%). Patients that exhibited SR acceleration were younger, had better renal function, had less often ICM, took more beta blockers, and had VAs of shorter cycle length (CL), however none of these observations reached statistical significance. SR acceleration was significantly associated with a lower incidence of the composite endpoint when compared to absent SR acceleration with an incidence ratio of 0.25 (Figure 1). This association remained statistically significant (HR 0.33, 95%CI 0.12 – 0.94, p=0.038) in a multivariable Cox regression including ICM, use of beta blockers or class III anti-arrhythmic drugs, patient age, and the CL of the treated VA. Atrial behavior was not significantly associated with subsequent appropriate ICD interventions (Figure 2). Conclusion During VAs, SR acceleration is the most common pattern. SR acceleration is significantly and independently associated with a lower incidence of Mort/HTx/VAD when compared to patients without SR acceleration, while showing no association with subsequent appropriate ICD interventions. Atrial behavior may currently be underappreciated as a potential risk stratifier in ICD patients.