Abstract 4342: The RethinQ Trial Echocardiographic Sub Study: Insights from Analysis of TDI Data on Mechanical Dyssynchrony in a Randomized Clinical Trial of Cardiac Resynchronization Therapy in Narrow QRS Patients with Heart Failure
Tissue Doppler Imaging (TDI) of myocardial velocities is the method of choice to characterize mechanical dyssynchrony (MD) in the failing heart. TDI identified candidates for the RethinQ trial, a prospective, randomized, multicenter, double-blind, parallel-controlled trial evaluating the efficacy of Resynchronization Therapy (CRT) in pts with EF <35%, NHYA class III, QRS <130 ms and MD by TDI. Peak MVO2 at 6 months was the primary endpoint. The purpose of this study was to determine whether:
degree of MD by TDI and opposing wall delay (OPWD) correlated with outcome;
resynchronization by TDI parameters of MD was achieved by CRT; and
if other TDI parameters of MD were predictive of outcome.
Methods: A retrospective analysis of prospectively acquired echo data. Pts underwent an echo exam at baseline and 6 months which included color TDI enabling determination of the OPWD ≥65 ms required for enrollment into the trial. Other recognized parameters of MD such as the pre-ejection period (PEP) and 12 segment standard deviation of time-to-peak myocardial velocity were collected but not part of the selection criteria used to randomize pts to CRT. For the purpose of this analysis responders (R) were defined by improved MVO2 and reduction in LVESV> 15%. All echo data was adjudicated by a Core Lab.
Results: Degree of dyssynchrony pre implant (OPWD > 65, > 80, > 100ms) did not impact response to CRT. Both R and Non responders (NR) exhibited a decrease in OPWD at 6 months though R had a greater median change than NR -33(−29+42) ms vs 0(−3+45) ms, p=0.01. When pts exhibited OPWD ≥65ms, 12 segment standard deviation ≥34ms and PEP > 100ms there was a trend toward being able to identify R to CRT pre implant. 18/65 (28%) pts receiving CRT and meeting all 3 MD criteria were categorized as R vs. 6/47 (13%) not receiving CRT, p=0.052.
Conclusions: Analysis of the echo TDI data revealed that degree of MD did not impact outcome, improvement of dyssynchrony was achieved with CRT and a combination of OPWD≥65ms, 12 segment standard deviation ≥34ms and pre ejection period > 100ms showed promise in predicting improvement in pts with narrow QRS, low EF and MD.