Coronary flow reserve and functional improvement after resynchronization therapy

Objective: The aim of the study was to evaluate the relation of coronary flow reserve (CFR) with left ventricular functional improvement after cardiac resynchronization therapy (CRT). Background: In patients with non-ischemic dilated cardiomyopathy, CFR is related to microvascular function and viability. Abnormal CFR <2, has been shown to be independent predictor of bad prognosis. Method: Forty one patient (mean age 60±10 years, male 38) with heart failure (EF 26±5%) and QRS duration of 159±22ms underwent CFR measurement with transthoracic Doppler echocardiography before CRT implantation, during hyperemia induced with adenosine. CFR was calculated as a ratio of hyperemic and basal flow velocities. Responders were defined by decrease in end-systolic volume (ESV) ≥15%, 6 months after CRT implantation. Results: At inclusion, left ventricular ejection fraction (EF), end-systolic volume, end-diastolic volume, QRS duration, 6 min walk test and coronary flow velocity at rest did not differ in responder vs. nonresponder group (p=ns). Before CRT implantation, responders showed a greater increase in coronary flow velocities during hyperemia, and consequently higher CFR: 2.23±0.59 vs. 1.67±0.54 (p=0.010). We found significant correlation between CFR before CRT and EF improvement after 6 months (r=0.492, p=0.008). End systolic and end diastolic diameters, left bundle branch block (LBBB), and CFR before CRT were predictors of LV functional recovery. By multivariate analysis, only CFR before CRT and LBBB were independent predictors of left ventricular recovery in the follow-up period (p=0.011). Conclusion: We have found that adequate CFR response, which means preserved coronary microcirculation and LBBB, as an ECG surrogate of dyssynchrony were independent predictors of LV reverse remodeling.