Early improvement of diastolic dyssynchrony and myocardial relaxation time after upgrade of longstanding right ventricular apical to right ventricular septal pacing

Oral Abstracts Session & Young Investig Awards 33-47INTRODUCTION: Chronic right ventricular septal (RVS) pacing appears to be superior to right ventricular apical (RVA) pacing in preserving systolic function. However, limited data exists on left ventricular (LV) diastolic dyssynchrony and diastolic function. METHODS: We compared diastolic synchronicity and myocardial relaxation time and velocity in 20 pts (age: 73±12 yrs, 8 M) with permanent RVA pacing (>90% ventricular pacing, pacing duration: 13.3±9 yrs) admitted for device replacement. Pts were randomly assigned to continue in RVA (n=10) or RVS (n=10) pacing. Tissue Doppler echocardiogram from apical 4, 2 and 3 chamber views was acquired both in baseline and 6-9 months follow-up. Time interval between the onset of QRS complex to peak systolic and diastolic myocardial velocities were derived. LV dyssynchrony was defined by maximum delay >65ms between peak systolic velocities amongst the LV basal, mid septal/lateral and inferior/anterior wall. RESULTS: At baseline, LV dyssynchrony existed in 94% of pts with RVA pacing. At follow-up, pacing QRS duration decreased from 163±13 to156±10 ms (p=0.034) in RVS group, but remained unchanged in the RVA group. The standard deviation of time to peak early diastolic myocardial relaxation (Te-SD) significantly decreased compared with baseline in RVS group (40±4 vs.24±7ms, p=0.04). Furthermore, time to peak early myocardial relaxation (Te) significantly prolonged compared with baseline in RVS group (585±83 vs. 635±78 ms, p=0.016). (figure) However, there was no change in LV ejection time, LV isovolumic contraction, relaxation time and index of systolic dyssynchrony in 2 groups from baseline to follow-up. CONCLUSIONS: RVS pacing is superior to RVA pacing in improving diastolic dyssynchrony and myocardial relaxation