Abstract 2299: Characteristics of Left Ventricular Synchrony in Patients with Right Ventricular Apical Pacing and Normal Left Ventricular Function
Backgrounds: There are several studies demonstrate that right ventricular apical (RVA) pacing creates abnormal left ventricular (LV) contraction. However, these adverse effects are not always manifested in RVA paced patients.To provide insights into this discrepancy, we evaluated characteristics of LV synchrony in these patients.
Methods: 80patients (40male, 76±10y) who presented normal LV function (LVEF≥50%) with either of chronic RVA pacing (n=36) or preserved intrinsic ventricular conduction (n=44) were enrolled. We assessed LV synchrony using ECG-gated myocardial SPECT imaging applying newly developed software to quantify regional myocardial motion (cardioGRAF) . For assessment of quantitative LV synchrony, LV was divided into 17 segments and measured time from R wave to end myocardial systolic contraction (TES, msec) . Average TES of 5lateral, 5septum, 3anterior and 3posterior segments were calculated. LV synchrony were evaluated using dyssynchrony index;DI=difference between the average TES of the septum and the lateral(s-l), or between the average TES of the anterior and the posterior(a-p) /R-R interval x100).
Results: In patients with preserved intrinsic ventricular conduction, DI from between s-l and a-p did not differ (1.9 ± 2.2 vs. 1.9±1.9, p=0.99). However, in patients with RVA pacing, DI of a-p(6.6±23.3) showed high standard deviation more significantly than l-s(2.8±3.1)(Fig⇓)
Conclusions:In some RVA paced patients with normal LV function, despite loss of the synchrony between LV anterior and posterior, the synchrony between LV septum and lateral were preserved. This finding may explain that RVA pacing does not always cause LV pump failure.