Biventricular pacing is superior to right ventricular pacing in bradycardia patients with preserved systolic function: 2-year results of the PACE trial

The Pacing to Avoid Cardiac Enlargement (PACE) trial is a prospective, double-blinded, randomized, multicentre study that reported the superiority of biventricular (BiV) pacing to right ventricular apical (RVA) pacing in the prevention of left ventricular (LV) adverse remodelling and deterioration of systolic function at 1 year. In the current analysis, we report the results at extended 2-year follow-up for changes in LV function and remodelling. Patients (n 177) with bradycardia and preserved LV ejection fraction (EF epsilon 45) were randomized to receive RVA or BiV pacing. The co-primary endpoints were LVEF and LV end-systolic volume (LVESV). Eighty-one (92) of 88 in the RVA pacing group and 82 (92) of 89 patients in the BiV pacing group completed 2-year follow-up with a valid echocardiography. In the RVA pacing group, LVEF further decreased from the first to the second year, but it remained unchanged in the BiV pacing group, leading to a significant difference of 9.9 percentage points between groups at 2-year follow-up (P 0.001). Similarly, LVESV continues to enlarge from the first to the second year in the RVA pacing group, leading to a difference of 13.0 mL (P 0.001) between groups. Predefined subgroup analysis showed consistent results with the whole study population for both co-primary endpoints, which included patients with pre-existing LV diastolic dysfunction. Eighteen patients in the BiV pacing group (20.2) and 55 in the RVA pacing group (62.5) had a significant reduction of LVEF (of epsilon 5, P 0.001). Left ventricular adverse remodelling and deterioration of systolic function continues at the second year after RVA pacing. This deterioration is prevented by BiV pacing.