Prediction of cardiac resynchronization therapy response: value of calibrated integrated backscatter imaging.

BACKGROUND: Left ventricular (LV) fibrosis is important for the response to cardiac resynchronization therapy (CRT). Calibrated integrated backscatter derived by 2D echocardiography quantifies myocardial ultrasound reflectivity, which may provide a surrogate of LV fibrosis. The aim of the study was first, to investigate the relation of myocardial ultrasound reflectivity assessed with calibrated integrated backscatter on CRT response, and second, to explore the "myocardial ultrasound reflectivity-CRT response" relation in patients with ischemic and nonischemic heart failure (HF).

METHODS AND RESULTS: One hundred fifty-nine patients with HF referred for CRT underwent an extensive echocardiographic evaluation at baseline and at 6-month follow-up. LV dyssynchrony was derived from speckle-tracking analysis. Calibrated integrated backscatter was obtained from the parasternal long-axis view. The mean value of calibrated integrated backscatter of the anteroseptal and posterior wall was used to estimate myocardial ultrasound reflectivity. CRT response was defined as reduction >/=15% of LV end-systolic volume. At baseline, LV dyssynchrony was significantly larger in responders as compared with nonresponders (188+/-96 ms versus 115+/-68 ms, P<0.001), and CRT responders showed less myocardial ultrasound reflectivity as compared with nonresponders (-20.8+/-3.0 dB versus -17.0+/-3.0 dB, P<0.001). In multivariable logistic regression analysis, independent predictors for CRT response were LV dyssynchrony, renal function, and myocardial ultrasound reflectivity. Importantly, myocardial ultrasound reflectivity provided an incremental value to CRT response (chi(2) change=40, P<0.001). Considering patients with ischemic HF, the only independent predictor of CRT response was myocardial ultrasound reflectivity, whereas in patients with nonischemic HF, independent predictors of LV reverse remodeling were myocardial ultrasound reflectivity, LV dyssynchrony, and renal function.

CONCLUSIONS: Assessment of myocardial ultrasound reflectivity is important in the prediction of CRT response in ischemic and nonischemic patients.