136 New-Onset Heart Failure After Permanent Right Ventricular Apical Pacing in Patients with Acquired High-Grade Atrioventricular Block and Normal Left Ventricular Function XUE-HUA ZHANG, M.D., * ,† HUA CHEN, M.D.,† CHUNG-WAH SIU, M.B.B.S.,† KAI-HANG YIU, M.B.B.S.,† WING-SZE CHAN, M.B.B.S.,† KATHY L. LEE, M.B.B.S.,† HON-WAH CHAN, M.B.B.S.,† STEPHEN W. LEE, M.B.B.S.,† GUO-SHENG FU, M.D., * CHU-PAK LAU, M.D.,† and HUNG-FAT TSE, M.D., PH.D.† From the * Cardiology Division, the Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou; and the †Cardiology Division, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China RV Apical Pacing and Heart Failure. Introduction: Emerging data have suggested that right ven- tricular (RV) apical pacing results in progressive left ventricular (LV) dysfunction and contributes to the development of heart failure (HF). This study aimed to investigate the prevalence and clinical predictors for the development of new-onset HF after long-term RV apical pacing in patients with acquired atrioven- tricular (AV) block who require permanent pacing. Methods: We studied the clinical outcomes after long-term RV apical pacing for acquired AV block in 304 patients without a prior history of HF. All patients had >90% ventricular pacing as determined by device diagnostic data. Results: After a median follow-up of 7.8 years, 79 patients (26.0%) developed new-onset HF after RV apical pacing. Univariate Cox-regression analysis revealed that older age at the time of pacemaker implantation (P < 0.001), the presence of coronary artery disease (CAD) (P < 0.001) or atrial fibrillation (P = 0.03), VVI pacemaker (P < 0.001), wider paced QRS duration (P < 0.001), and new-onset myocardial infarction (P < 0.001) were predictors for HF. Multivariate analysis revealed that older age at implantation (Hazard ratio [HR] 1.06, 95% confidential interval [CI] 1.04–1.09, P < 0.001), CAD (HR 1.98, 95% CI 1.12–3.50, P < 0.05), and a wider paced QRS duration (HR 1.27 for each 10 ms increment, 95% CI 1.11–1.45, P = 0.001) were independent predictors of HF. Furthermore, cardiovascular mortality was significantly increased in those with HF (36.7% vs. 2.7%, P < 0.001). Conclusions: After a median follow-up of 7.8 years, permanent RV apical pacing was associated with HF in 26% of patients. Elderly age at the time of implant, a wider paced QRS duration and the presence of CAD independently predicted new-onset HF. More importantly, HF after RV apical pacing was associated with a higher cardiovascular mortality. (J Cardiovasc Electrophysiol, Vol. 19, pp. 136-141, February 2008.) right ventricular apex, pacing, heart failure, atrioventricular block Introduction Due to aging of the populations worldwide, cardiac pac- ing has been increasingly used for the treatment of cardiac rhythm disturbances. 1,2 Among different possible ventricu- lar pacing sites, right ventricular (RV) apex has been selected as the conventional site for lead positioning. This is because of the easy accessibility of RV apical site to allow safe and stable long-term pacing using endocardial pacing leads. How- ever, emerging clinical data have demonstrated that chronic RV apical pacing can lead to adverse clinical outcome. 3-5 In patients with congenital 6 or acquired 7-9 atrioventricular (AV) block, chronic RV apical pacing was associated with left ven- tricular (LV) dyssynchrony, and deterioration of LV systolic Address for correspondence: Prof. Hung-Fat Tse, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China. Fax: (852) 2818-6304; E-mail: hftse@hkucc.hku.hk Manuscript received 14 July 2007; Revised manuscript received 31 August 2007; Accepted for publication 4 September 2007. doi: 10.1111/j.1540-8167.2007.01014.x and diastolic function. Recent studies have shown that up to 31–50% of pacemaker patients had LV dysfunction. 9,10 Currently, there are very limited data on the long-term clinical outcome after RV apical pacing in patients with ac- quired AV block. In UKPACE, 11 the annual incidence of heart failure (HF) was rather low, with 3.2% in the single-chamber pacing group and 3.3% in the dual-chamber pacing group after a mean of 3 years of follow-up. However, in patients with normal baseline LV function, the adverse LV remodel- ing induced by RV apical pacing may take a very long term to manifest. 12 Therefore, the aim of this study was to investigate the prevalence and clinical predictors for development of HF after long-term RV apical pacing in patients implanted with a pacemaker for acquired AV block. Methods Study Population The study population consisted of 420 consecutive patients with a permanent pacemaker implanted for acquired second- or third-degree AV block at our center. All patients were implanted with a ventricular pacing lead at the RV apical position. Demographic characteristics, electrocardiogram,