Abstract 2018: Inotropic Contractile Reserve is a Strong Predictor of Response to Cardiac Resynchronization Therapy
Background and Objective Approximately one third of patients treated with cardiac resynchronization therapy (CRT) do not respond. Pts who fare poorly may have inadequate inotropic contractile reserve (ICR). The effect of ICR of left ventricular (LV) segments in predicting response to CRT has not been studied.
Methods 28 pts (68±11yrs;71%male) with end-stage heart failure (NYHA III/IV), LV ejection fraction (EF) ≤35%, QRS >120ms and LBBB were included. ICR was assessed with low dose (5–20 μg/kg/min) dobutamine stress echocardiography (LDDSE). LV dyssynchrony (DYS) was assessed at baseline and immediately post CRT. DYS was defined as > 65ms opposing LV wall delay in peak systolic contraction by Tissue Synchronization Imaging. LVEF were assessed at baseline and at 6 mths follow-up. ICR in ≤ 5 segments was considered as positive. Responders were defined by post CRT improvement in LVEF of ≤15 % from baseline.
Results 7 pts (25%) did not demonstrate ICR. In contrast to patients with ICR these pts showed a low response rate (29% vs. 81%, p=0.01) and LV DYS remained unchanged post CRT (73 ± 25 ms vs. 67 ± 20 ms, ns).Pts with ICR+ DYS showed the best response rate of 88% and LV DYS diminished (74 ± 23 ms vs. 26 ± 10 ms; p= 0.03) significantly. Univariate and multi variate analysis showed that compared to DYS ;ICR is a stronger predictor of response to CRT (chi sq = 6.33, p = 0.019 ; RR = 13.5, 95% CI = 1.54 –125, p =0.019) independent of DYS.
Conclusion Presence of inotropic contractile reserve is a strong predictor of response to CRT, independent of mechanical LV dyssynchrony. ICR should be routinely evaluated in all patients referred for CRT to predict response to therapy.