Inotropic Contractile Reserve and Response to Cardiac Resynchronization Therapy in Patients with Markedly Remodeled Left Ventricle

Background: Recently concluded multicenter studies have shown that none of an array of echocardiographic indicators of ventricular dyssynchrony have enough sensitivity and specificity for predicting response to cardiac resynchronization therapy (CRT). Inotropic contractile reserve (ICR) on dobutamine stress echocardiography can differentiate viable myocardium from scar and is a predictor of improvement in regional and global left ventricular function in patients with cardiomyopathy. Its role in patients undergoing CRT is unknown. The aim of this study was to evaluate the role of ICR in predicting response to CRT in patients with markedly remodeled left ventricles. Methods: Fifty-four patients (mean age, 69 +/- 11 years; 63% men) referred for clinically indicated CRT were evaluated. All patients underwent low-dose dobutamine stress echocardiography to assess for ICR, defined as an improvement in contractility in more than five of 16 left ventricular segments. Results: During a mean follow-up period of 206 +/- 167 days, 31 patients (57%) were responders, as defined by a 5-point increase in ejection fraction after CRT. The presence of ICR was a stronger predictor of response to CRT (area under the curve, 0.94; chi(2) = 39.0; P < .0001) compared with dyssynchrony (area under the curve, 0.74; chi(2) = 10.07; P = .002). It was a significant predictor of response (odds ratio, 2.84; 95% confidence interval, 1.59 to 5.09; P < .0001), even after controlling for the other predictors, and provided incremental prognostic value beyond that provided by QRS duration and dyssynchrony (increase in area under the curve from 0.47 to 0.75 to 0.93; P = .030 and P = .008). Conclusions: In patients referred for CRT, ICR was a stronger predictor of response and provided incremental value beyond that of current known predictors of response to CRT (dyssynchrony and QRS duration). Dobutamine stress echocardiography may have an important role in identifying CRT responders, and further multicenter studies are needed to confirm this. (J Am Soc Echocardiogr 2011;24:91-7.)