His or para-His pacing preserves left ventricular function in atrioventricular block: a double-blind, randomized, crossover study

To compare left ventricular function after a long-term His or para-His pacing (HP) and right ventricular septal pacing (RVSP) in patients with atrioventricular block (AVB). We included consecutive patients with AVB, a narrow QRS < 120 ms, and a preserved left ventricular ejection fraction (LVEF) > 0.40, in a prospective, randomized, double-blinded, crossover design. All patients were treated with 12 months HP and 12 months RVSP. A total of 38 patients [mean age, 67 +/- 10 years; 30 (79%) men] were included. The primary endpoint was LVEF, which was significantly lower after a 12 months RVSP (0.50 +/- 0.11) than after 12 months of HP (0.55 +/- 0.10), P = 0.005. We measured the difference in time-to-peak systolic velocity between opposite basal segments in the apical views by using tissue Doppler imaging. In the four-chamber view, the difference was 58 (+/- 7) ms after RVSP and 49 (+/- 7) ms after HP, P = 0.27; in the two-chamber view, the difference was 45 (+/- 5) ms after RVSP and 31 +/-(4) ms after HP, P = 0.02, and in the apical long-axis view, the difference was 63 (+/- 6) after RVSP and 44 (+/- 7) after HP, P = 0.03. There was no difference in New York Heart Association class, 6-min hall walk test, quality-of-life assessments, or device-related complications. The mean threshold was significantly higher in HP leads than in RVSP leads. His or para-His pacing preserves LVEF and mechanical synchrony as compared with RVSP after 12 months pacing in patients with AVB, narrow QRS, and LVEF > 0.40.