The Prevalence of Pacing-Induced Cardiomyopathy (PICM) in Patients With Long Term Right Ventricular Pacing - Is it a Matter Of Definition?

Background Chronic right ventricular pacing may contribute to deterioration in left ventricular ejection fraction (LVEF). The aim of the study was to identify the prevalence of pacing-induced cardiomyopathy (PICM) in patients with chronic right ventricular pacing. Methods Patients attending a pacemaker clinic were retrospectively identified as having had transthoracic echocar-diographic LVEF measurement during the 12 months prior to device implantation. Those with card cardioverter-defibrillators or biventricular devices were excluded. The remaining patients were invited back for a repeat echocardiogram. Three (3) different definitions of PICM were employed: 1) follow-up LVEF of <= 40% if baseline LVEF was >= 50%, or an absolute reduction in LVEF >= 5% if baseline LVEF was <50%; 2) follow-up LVEF of <= 40% if baseline LVEF was >= 50%, or an absolute reduction in LVEF >= 10% if baseline LVEF was <= 50%; 3) absolute reduction in LVEF >= 10% irrespective of baseline LVEF. Alternate causes of cardiomyopathy were excluded following a chart review. Results The study cohort of 118 included 67 males (mean age 77.8 +/- 10.5 years) and 51 females (mean age 76.8 +/- 11.2 years). The mean time between baseline and follow-up echocardiograms was 3.5 + 1.4 years (range 1.5-6.4 years). The prevalence of PICM ranged from 5.9 to 39.0% depending on PICM definition. Multivariate analysis found that PICM was significantly associated with ventricular pacing burden (p = 0.013). Conclusions The prevalence of pacing induced cardiomyopathy is dependent on current accepted clinical definitions. A clear definition of PICM is required for a better understanding of the clinical implications of right ventricular pacing.