Background: Overall response rate to cardiac resynchronization therapy (CRT) is still not optimal. The aim of the study was to evaluate the influence of the regional myocardial contractile reserve during dobutamine infusion in the area of left ventricular (LV) electrode on the response rate and reverse remodeling LV in patients receiving CRT.
Methods: Biventricular pacemaker was implanted in 41 consecutive patients (33 men, mean age 62 ± 10 years) with LV ejection fraction (LVEF) ≤ 35%, New York Heart Association class III and QRS duration ≥ 120 ms. Myocardial contractile reserve was assessed by LV strain during dobutamine infusion (20 μg/kg/min) using speckle tracking echocardiography. Patients were classified as responders if an increase in LVEF ≥ 5% or decrease in end-systolic volume ≥ 15% was observed after 6 months of CRT.
Results: Twenty-four patients were responders and 17 were non-responders. During dobutamine infusion at a rate of 20 μg/kg/min, responders showed significant increase in regional deformation (Δ strain) when compared to non-responders (2.14 ± 2.9 vs. - 0.94 ± 1.74, p = 0.042). Patients with increased deformation in the LV lead area during dobutamine stimulation were more likely to be responders to CRT compared to patients without increased deformation in this area (81% vs. 20%, p = 0.0002). They exhibited significant increase in LVEF (8.8% ± 10.3% vs. 0.3% ± 6.4%, p = 0.01). LV electrode localization in viable myocardium was a good predictor of response to CRT (AUC 0.852, p < 0.0001).
Conclusions: Regional contractile reserve assessed by strain rate echocardiography during dobutamine infusion predicts the response to CRT.