Larger interventricular conduction time enhances mechanical response to resynchronization therapy.

Background: Previous studies have reported that the left ventricular (LV) pacing site is a major determinant of the hemodynamic response to cardiac resynchronization therapy (CRT). However, lead positioning in a lateral or posterolateral cardiac vein may not be optimal for every patient. The objective of this study was to assess the relationship between the right ventricular (RV)-to-LV conduction time and the systolic function during CRT on the basis of changes to LV pressure-volume loops.

Methods: Left ventricular pressure and volume data were determined using a conductance catheter during CRT device implantation in 10 patients. Four endocardial LV sites were systematically assessed at four atrioventricular delays. The RV-to-LV conduction time was measured as the time interval between spontaneous peak R waves, recorded through the RV lead and the LV catheter.

Results: The optimal pacing site varied among patients. However, the pacing site associated with the maximum RV-to-LV conduction time resulted in a stroke volume improvement comparable to the pacing site identified through individual hemodynamic optimization (41 ± 17 mL vs 44 ± 18 mL, P = 0.266). Moreover, the RV-to-LV conduction time recorded at each endocardial pacing site correlated positively with the increase in stroke volume (r = 0.537; P < 0.001), stroke work (r = 0.642; P < 0.001), and the pressure-derivative maximum (r = 0.646; P < 0.001) obtained with CRT.

Conclusions: An optimal acute response to CRT can be obtained by positioning the LV lead at the site associated with the maximum RV-to-LV conduction time. A significant correlation appears to exist between RV-to-LV conduction time and the improvement in systolic function with CRT.