Relation of right ventricular pacing site to left ventricular mechanical synchrony.

Transvenous pacing leads are regularly placed in the right ventricular (RV) apex. Pediatric patients can develop myopathic changes after long-term RV apical pacing. Left ventricular (LV) mechanical dyssynchrony, estimated with echocardiography, may explain the acute decrease in LV function and long-term histopathologic changes. Ts-4w is an established echocardiographic measurement of LV synchrony, using tissue Doppler imaging (TDI). The purpose of this study was to determine whether TDI could identify acute changes in LV synchrony during pacing from different RV sites. We prospectively measured Ts-4w and Doppler-derived cardiac output after 5 minutes of pacing in 19 subjects undergoing catheter ablation. Each subject underwent pacing at 4 sites in random order: high right atrium, high RV septum (septal), RV outflow tract, and RV apex. Ts-4w was measured during sinus rhythm and each pacing protocol, with a value >65 ms defining mechanical dyssynchrony. Ts-4w during high right atrial (32.6 +/- 17.6 ms) and septal (28.9 +/- 10.9 ms) pacing were not different from sinus rhythm (39.5 +/- 15.5 ms). RV apex (85.7 +/- 18.4 ms) and RV outflow tract (84.2 +/- 20.4 ms) pacing induced mechanical dyssynchrony (p <0.0001). In conclusion, TDI demonstrated significant differences in LV synchrony related to pacing site. Ts-4w may be useful to determine ideal lead placement because it correlates with acutely improved hemodynamics.