Estimation of the optimal VV delay by an IEGM-based method in cardiac resynchronization therapy.

Determination of the optimal interventricular (VV) delay in cardiac resynchronization therapy currently relies on costly, time-consuming echocardiographic (ECHO) methods. This study evaluated the performance of a new intracardiac electrogram (IEGM)-based VV method compared to the aortic velocity time integral (AVTI) method of VV delay optimization. The study included two patient groups. Eleven patients enrolled by a single center in the Rhythm II ICD trial underwent prospective comparisons of the AVTI at the VV interval determined by the IEGM VV method versus the maximum AVTI at the echocardiographically determined optimal VV delay. In 61 patients enrolled in the RHYTHM VV trial, the same testing methods were compared retrospectively. In the prospective study, the maximum AVTI by the ECHO-based method (24.3 +/- 7.9 cm), was closely correlated with maximum AVTI by the IEGM-based method (23.9 +/- 7.9 cm; concordance correlation coefficient = 0.99; 95% confidence, lower limit of 98%. Likewise, in the retrospective analysis, the ECHO-determined maximum AVTI (22.1 +/- 8.2 cm) was similar to that determined by the IEGM-based method (20.9 +/- 8.3 cm; concordance correlation coefficient = 0.98; 95% confidence, lower limit of 97%).