Echocardiography in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is a new treatment modality for eligible patients with congestive heart failure (CHF). The premise of CRT is that it decreases inter and intra ventricular inhomogeneity during systolic contraction thereby improving efficiency of cardiac pump function. Presence of cardiac dyssynchrony appears to be a prerequisite for a response to CRT. Traditionally this inhomogeneity in contraction has been determined by electrocardiographic QRS widening. More recently several echocardiographic methods of assessment of dyssynchrony have become available. These methods utilize conventional M-mode and pulsed wave (PW) Doppler as well tissue Doppler imaging (TDI) methods. These echocardiographic parameters have been shown to be more important predictors of response to CRT than conventional QRS widening. This article will discuss echocardiographic methods of assessment of dyssynchrony and their role in predicting response to CRT. In addition role of echocardiography in post CRT pacemaker programming will also be discussed.