Selection of candidates for cardiac resynchronization therapy: late gadolinium enhanced cardiac magnetic resonance as a new and promising predictor of intraventricular dyssynchrony

Cardiac resynchronization therapy (CRT) is an important therapeutic option for patients with intraventricular conduction delay and has been shown to reduce mortality and morbidity in selected heart failure patients. Several echocardiographic methods have been proposed to define intraventricular delay and to select candidates for CRT, such as color coded tissue Doppler echocardiography and speckle tracking. Since, up to 30% of these carefully selected patients do not receive benefit; predictors of response to CRT still remain a topic of ongoing investigations. Recently, myocardial fibrosis defined by late gadolinium enhancement on cardiac magnetic resonance (CMR) imaging has been introduced as promising predictor of both intraventricular dyssynchrony and response to CRT. The focus of the present review is the major echocardiographic modalities to select CRT candidates, the potential role of cardiac fibrosis detected by CMR in this respect, and the possible relation of it with the presence of intraventricular dyssynchrony.