Criteria predicting response to CRT: is more better?

Abstract

The quest for the perfect parameter to predict response to cardiac resynchronization therapy (CRT) suffered a major setback when two prospective trials (PROSPECT and ReTHINQ) demonstrated limitations in the potential clinical value of the much-touted tissue Doppler velocity-based criteria.1,2 Until then there was a steady stream of ‘highly accurate’ predictors of response to CRT.3–5 Notwithstanding the bevy of potential technical issues plaguing these studies, they did successfully raise serious doubts about how the clinical community and vendors were going about identifying patients likely to respond to CRT. We have always been of the opinion that attempting to solve a complex issue such as predicting response to CRT by means of a single binary parameter, such as tissue Doppler velocity-derived delays, is overly simplistic. For what it is worth, several studies over thousands of patients do indicate some value to testing dyssynchrony using tissue velocities.6 In a similar vein, our take on PROSPECT and ReTHINQ is that they do not convincingly repudiate the notion that a dyssynchronous heart is more likely to respond to CRT. In that regard it is heartening to see a study examine the value of using multiple parameters to predict response to CRT. Lafitte and colleagues examined parameters of dyssynchrony at multiple functional levels including atrioventricular, interventricular and intraventricular.7 The strengths of this study include: size ( n = 181), multicentre design, all patients fulfilled standard clinical criteria for CRT (New York Heart Association class II–IV, ejection fraction 120 ms) and a large proportion of ‘responders’ to CRT (57%). The authors used a relatively well-validated index of response, namely a ≥15% decrease in left ventricular end-systolic volume. Feasibility of measurement was high (∼80%) at acceptable variability of … *Corresponding author. Tel: +1 410 502 7974, Fax: +1 410 955 1509, Email: tabraha3{at}jhmi.edu