Comparison of segmental and global markers of dyssynchrony in predicting clinical response to cardiac resynchronization

Abstract

Cardiac resynchronization therapy (CRT) reduces inter- and intraventricular dyssynchrony and shortens total isovolumic time (t-IVT). We compared the extent to which the values of ventricular dyssynchrony and t-IVT predict clinical benefits of CRT. Ventricular dyssynchrony was assessed in 39 patients with heart failure before and 6 months after CRT. Segmental dyssynchrony was identified from time to onset and peak systolic velocity of wall motion. T-IVT (s/min) was derived as [60-(total ejection time+total filling time)]. The difference between ventricular pre-ejection periods (D-PEP) was calculated. Outcome measures were fall in New York Heart Association (NYHA) class and increase in cardiac output (CO). Following CRT, NYHA class fell in 29/39 patients, CO increased (by 1.0 L/min, P < 0.001), and intraventricular delay (Intra-VD), interventricular delay (Inter-VD), t-IVT, and D-PEP shortened (by 25 ms, 72 ms, 6 s/min, and 38 ms, P < 0.01). NYHA class and CO were unchanged with CRT in 10/39, and Intra-VD, Inter-VD, t-IVT, and D-PEP lengthened (by 43 ms, 52 ms, 7 s/min, and 35 ms, P < 0.05). Though univariate predictors of CO increment with CRT were Intra-VD, Inter-VD, t-IVT, and D-PEP, only pre-CRT values of CO (P < 0.001), t-IVT (P < 0.001), and D-PEP (P = 0.025) were independent. Global, rather than segmental, measures of ventricular dyssynchrony are powerful, independent predictors of clinical response to CRT.