NEW YORK (Reuters Health) – In patients with bradycardia and a normal ejection fraction, biventricular pacing can prevent the adverse ventricular remodeling and drop in ejection fraction seen with standard right ventricular apical pacing, according to findings from the Pacing to Avoid Cardiac Enlargement (PACE) trial.

“Preclinical data suggested that biventricular pacing might preserve myocardial performance better than right ventricular apical pacing in patients with atrioventricular block and normal systolic function,” Dr. Cheuk-Man Yu, from Chinese University of Hong Kong, and co-researchers explain.

To determine whether this beneficial effect applies to patients with bradycardia and normal ejection fraction, the researchers examined left ventricular (LV) ejection fraction and LV end-systolic volume in 177 subjects who had been randomized to receive biventricular pacing or conventional pacing after pacemaker implantation.

In the November 15th issue of The New England Journal of Medicine, the authors report that at 12 months, the LV ejection fraction in the biventricular pacing group was significantly greater than in the conventional pacing group: 62.2% vs. 54.8% (p < 0.001). The LV end-systolic volume, by contrast, was lower in the biventricular pacing group: 27.6 vs. 35.7 mL (p < 0.001). Eight subjects in the standard pacing group versus just one in the biventricular pacing group had ejections fractions below 45% (p = 0.02). One death occurred in the standard pacing group compared with none in the biventricular pacing group. Six patients in the standard pacing group and five in the biventricular pacing group were hospitalized for heart failure. “Despite the use of right ventricular apical pacing for decades, its association with the development of heart failure and even death has been recognized only in the past 7 years with the publication of…various large-scale trials,” the researchers point out. They add, “The results of our study suggest that in patients who require a high percentage of ventricular pacing – especially patients with atrioventricular block – a biventricular-pacing strategy is preference to right ventricular apical pacing.” The authors admit to several limitations of the study, including the small sample size and inadequate power to detect differences in clinical events. Thus, they call for further randomized trials with larger samples and longer follow-up periods to investigate this topic. Reference:
N Engl J Med 2009.