Abstract
Objectives: Traditional right ventricular apical (RVA) pacing may induce ventricular dyssynchrony in patients with normal left ventricular (LV) function. The purpose of this study is to elucidate the influence of pacing sites on the ventricular dyssynchrony, using ultrasound speckle-tracking imaging and tissue Doppler imaging. Methods: We investigated 24 patients with normal LV function who underwent DDD pacemaker implantation. Right ventricular lead position was apex in 18 patients and septum in 6 patients. Radial strain and circumferential strain were measured using ultrasound speckle-tracking imaging (Vivid 7, GE) from short axis view at papillary muscle level. Myocardial velocity was measured by tissue Doppler imaging in mid-segments from apical 4-chamber view. The difference of time to peak radial strain, circumferential strain, and systolic myocardial velocity between septal and lateral wall were compared between during patients’ intrinsic rhythm and pacing rhythm, and between patients with RVA pacing and right ventricular septal (RVS) pacing. Results: In 18 patients with RVA pacing, difference of time to peak circumferential strain and systolic myocardial velocity between septal and lateral wall were larger during pacing rhythm than during patients’ intrinsic rhythm (circumferential strain: 118±57 vs 59±48msec, p<0.01, myocardial velocity: 75±47 vs 52±40msec, p<0.05). On the other hand, in 6 patients with RVS pacing, difference of time to peak radial strain, circumferential strain and systolic myocardial velocity during pacing rhythm were the same as those during patients’ intrinsic rhythm. Difference of time to peak circumferential strain between septal and lateral wall was smaller in patients with RVS pacing than patients with RVA pacing (37±50 vs 118±57msec, p<0.005). Conclusions: Ventricular synchrony can be preserved by RVS pacing compared with RVA pacing.
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