In children with single-ventricular circulation, a permanent ventricular pacemaker (PPMv) is associated with an increased risk of heart transplantation or death, according to a new international retrospective study. Henry Chubb, MA, MBBS, PhD, of Stanford University, and colleagues reported this and other findings in a manuscript published online Monday and in the Aug. 30 issue of the Journal of the American College of Cardiology. Single-ventricle palliation offers youth with congenital heart disease a chance at survival. The multistep procedure is completed with great medical and technical care; however, issues inherent to the solution inevitably arise down the line. Importantly, heart failure may lead to a cascade of events ultimately ending in transplant or death. Due to arrhythmia, pacemaker implantation is often considered in these patients, though with necessary caution, as ventricular pacing and the dyssynchrony that is induced can accelerate heart failure and further decline. Even so, existing evidence is largely anecdotal. Chubb and colleagues attempt to address this important clinical question in their study. The group completed a multicenter, international retrospective review of cases patients with single-ventricle circulation who received pacemakers. The primary outcome was death or transplantation, while secondary outcomes included those related to pacemaker implantation and function. The study identified 236 patients, of whom and 213 were matched to controls by ventricular morphology, sex, center and age. The patients’ average year of birth was 2002, the majority (59.5%) were male, average age at enrollment was 5 years, and nearly half (48.3%) had systemic left ventricle. Key Findings The authors noted several important findings are noted: the pacemaker cohort (PPMv) was at increased risk of death and transplant (hazard ratio [HR]: 3.8; 95% confidence interval [CI] 1.9-7.6; P < 0.001). Further insight into the mechanistic causes for increase in primary outcome are offered: Within the PPMv population, median percent ventricular pacing (Vp) was 90.8% and in multivariable analysis increasing ventricular pacing percentage, higher QRS z-score and non-apical lead position were all associated with increased risk of death/transplantation The findings suggest that more pacing, wider QRS and non-apical lead placement are associated with poor outcome. Importantly, taking away the choice of pacemaker or not, these parameters represent possible areas for modifications: the authors state, “Dose response is important not only in confirmation of causality, but also as a modifiable risk factor.” A limitation of this study pertains to the difficulty with lack of randomizations; the PPM and non PPM cohorts may be very different even after matching, but the authors state, “This study, with a large, well-characterized, control cohort, demonstrated that the association with poor outcomes persists after controlling for the increased morbidity of those subjects receiving a Vp system.” “Disease complexity, as anticipated, was higher at baseline in the PPMv group. Subjects with PPMv were more likely to be on inotropic support and antiarrhymic medications as baseline,” the authors write. Refining Pacing In an accompanying editorial, Salim F. Idriss, MD, PhD, of Duke University Medical Center, and M. David Weiland, MD, of the University of Mississippi Medical Center, further contextualize the present study. They first state regarding the issue inherent to retrospective review in this population: “It remained difficult to conclude whether pacing independently worsened the clinical status or whether the cards were dealt and the patient’s already poor cardiac substrate resulted in both the need for pacing and the clinical decline.” The editorial notes that refining pacing toward the minimal needed and with optimal synchronization may provide benefit. However, when placing leads in this patient population, which must be epicardial, the editorialists note that ‘the enemy of good is better’ thinking, often results in ventricular leads being placed on the epicardium of the free wall closer to the sternal incision. However, as this study clearly demonstrates, meticulous attention to lead placement is extremely important for patient longevity.” Sources: Chubb H, Bulic A, Mah D, et al. Impact and Modifiers of Ventricular Pacing in Patients With Single Ventricle Circulation. J Am Coll Cardiol 2022;80:902–914. Idriss SF, Weiland MD. Ventricular Pacing in Single Ventricle Circulation: Making the Best of a Difficult Situation. J Am Coll Cardiol 2022;80:915–917. Image Credit: Gina Sanders – stock.adobe.com