Current and future role of cardiovascular magnetic resonance in cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) has revolutionized the treatment of selected patients with systolic heart failure. It is well recognized, however, that the symptomatic response to and the outcome of CRT is highly variable. The degree of pre-implant mechanical dyssynchrony and the extent as well as the localization of myocardial scarring are known to contribute to this variability. Cardiovascular magnetic resonance (CMR) is the gold-standard imaging modality for the assessment of myocardial structure and function. Recently, CMR has also been shown to be useful in assessing cardiac dyssynchrony and in guiding left ventricular lead deployment away from scarred myocardium. This review explores the current role of CMR in risk stratification and in guiding LV lead deployment. The potential of CMR in identifying the arrhythmogenic substrate is also discussed.