Role of the old and new echocardiographic technologies in cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is an important tool for the treatment of patients with chronic heart failure, as it can correct the heterogeneity of regional left ventricular mechanical contraction, known as dyssynchrony. Although this therapy is strongly indicated in patients with both heart failure with left ventricular systolic dysfunction and wide Q-, R- and S-waves (QRS) on electrocardiogram, about one-third of these patients are non-responders. Since the degree of mechanical dyssynchrony can vary greatly, it is interesting to quantify dyssynchrony by means of imaging methods, such as echocardiography, which might be able to lead to a better selection of CRT candidates. This article will review the role of old and new echocardiographic techniques to predict CRT response.