Non-Apical Right Ventricular Pacing Reducing Left Ventricular Systolic Impairment

Background: Right ventricular apical (RVA) pacing deleterious effects on left ventricular ejection fraction (LVEF) had been demonstrated. Non-apical pacing such as right ventricular mid-septal (RVMS) pacing appear as useful alternative. Our purpose is to evaluate the effect of alternate sites of right ventricular (RV) pacing on left ventricular (LV) function and hemodynamics in patients with bradyarrhythmias.

Methods: We observed 54 patients (age 58±27 years, 32 men) with AV block III, who underwent permanent dual chamber pacemaker implantation. To 32 patients RV lead has implanted middle area of RV septum (RVMS) and 22 patients’ RV lead has implanted traditionally to right ventricular apex (RVA). Color tissue velocity imaging was performed to analyze time to peak systolic velocity (Ts) in a 12 segment model of the LV for each pacing site. Measurements included standard deviation of time to peak systolic velocity (SD-Ts) for all segments, maximal difference in Ts between any 2/6 basal (Ts-B), any 2/6 mid segments (Ts-M) and maximal Ts difference between any 2/12 segments (Ts-12). Stroke volume was estimated using Doppler velocity time integral (TVI) in the left ventricular outflow tract (LVOT). QRS width for each site was recorded. Measurements were observed by transthoracic echocardiography and electrocardiography, before and 12 month later after implantation.

Results: Ts-12 was significantly higher with RVA - pacing (107 ms, p=0.003) compared to RVMS - pacing (81 ms) sites. SD-Ts was significantly higher with RVA - pacing (38.5 ms, p=0.01) than RVMS - pacing (28.7 ms). QRS duration was longest for RVA - pacing (157 ms) while significantly shorter RVMS - pacing (115 ms, p<0.001). LVOT VTI was significantly higher for RVMS - pacing than for RVA (p=0.0014) pacing.

Conclusions: Right ventricular mid-septal pacing may reduce electro-mechanical dyssynchrony compared to RVA pacing and RVMS – pacing to effect better LV function and hemodynamics than RVA pacing in patients with permanent pacemaker implantation.