Ventricular pacing in single ventricles—A bad combination Anica Bulic, MD,* Frank J. Zimmerman, MD, FHRS, † Scott R. Ceresnak, MD,* Ira Shetty, MD, † Kara S. Motonaga, MD,* Anne Freter, APN, † Anthony V. Trela, NP,* Deb Hanisch, NP,* Lisa Russo, RN, † Kishor Avasarala, MD,* Anne M. Dubin, MD, FHRS* From the *Division of Pediatric Cardiology, Lucile Packard Children’s Hospital, Stanford University, Palo Alto, California, and † Advocate Children’s Heart Institute, Oak Lawn, Illinois. BACKGROUND Chronic ventricular pacing (VP) is associated with systolic dysfunction in a subset of pediatric patients with heart block and structurally normal hearts. The effect of chronic VP in congenital heart disease is less well understood, specifically in the single-ventricle (SV) population. OBJECTIVE To determine the longitudinal effect of VP in SV patients. METHODS SV patients with heart block and dual-chamber pacemakers requiring .50% VP were compared with nonpaced (controls) SV patients matched for age, sex, and SV morphology. Patients were excluded if a prepacing echocardiogram was not avail- able. Echocardiogram and clinical parameters were compared at baseline (prepacing) and at last follow-up in the paced group, and in controls when they were at ages similar to those of their paced-group matches. RESULTS Twenty-two paced and 53 control patients from 2 institu- tions were followed for similar durations (6.665 years vs 7.667.6 years; P 5 .59). There was no difference between groups regarding baseline ventricular function or the presence of moderate-to-severe atrioventricular valvar regurgitation (AVVR). Paced patients were more likely to develop moderate-to-severe systolic dysfunction (68% vs 15%; P , .01) and AVVR (55% vs 8%; P , .001) and require heart failure medications (65% vs 21%; P , .001). Chronic VP was also associated with a higher risk of transplantation or death (odds ratio, 4.9; 95% confidence interval, 1.05–22.7; P 5 .04). CONCLUSIONS SV patients requiring chronic VP are at higher risk of developing moderate-to-severe ventricular dysfunction and AVVR with an increased risk of death or transplantation compared with controls. New strategies to either limit VP or improve synchro- nization in this vulnerable population is imperative. KEYWORDS Congenital heart disease; Heart block; Pacemaker; Pediatrics; Single ventricle (Heart Rhythm 2017;14:853–857) © 2017 Heart Rhythm Society. All rights reserved. Introduction Chronic ventricular pacing has been associated with poor systolic function in a subset of pediatric patients with com- plete heart block and structurally normal hearts. 1–6 The effect of chronic ventricular pacing in congenital heart disease is less well understood, especially in patients with single-ventricle physiology. To date, there has been no study in the literature specifically evaluating the effects of chronic ventricular pacing in this complex population. The objective of this study is to determine the longitudinal effect of ventric- ular pacing in children with single-ventricle congenital heart disease. We hypothesized that single-ventricle patients requiring chronic ventricular pacing would have worse out- comes than single-ventricle patients who did not require ven- tricular pacing. Methods Study cohort This was a retrospective cohort study across 2 institutions from 1990 to 2015 that investigated patients with single-ventricle congenital heart disease and dual-chamber epicardial pacemakers who had 50% ventricular pacing (based on the most recent pacemaker interrogation). Dual- chamber pacemaker modes DDD, DDI, DDIR, and DDDR were included. Patients with ventricular pacing were compared with a control group of single-ventricle patients without pacemakers who were matched for age, sex, and single-ventricle morphology and had similar follow-up pe- riods; there was a 1:2 ratio of paced-group participants to controls. Patients were excluded if a prepacing Attention HRS Members and Journal Subscribers Visit the HRS Learning Center at www.hrsonline.org/HRJ-CME to earn CME credit through an online activity related to this article. Certificates are available for immediate access upon successful completion of the activity. Address reprint requests and correspondence: Dr Anica Bulic, Division of Pediatric Cardiology, Stanford University, 750 Welch Road, Suite 325, Palo Alto, CA 94304. E-mail address: anica@stanford.edu. 1547-5271/$-see front matter © 2017 Heart Rhythm Society. All rights reserved. http://dx.doi.org/10.1016/j.hrthm.2017.03.035