Cardiac resynchronization therapy.

It is now well established that electrical and mechanical dyssynchrony are not clinically synonymous; however, at present no individual noninvasive method can reliably and consistently identify the criteria for mechanical dysfunction correctable through device therapy. The results of the PROSPECT (Predictors of Response to CRT) trial not only highlight the complicated nature of this dilemma, but also emphasize the importance of broadening our approach to this topic. Not only do the capabilities of real-time three-dimensional echocardiography and cardiac magnetic resonance imaging need to be maximized, but the strengths and weaknesses of each modality need to be more selectively matched to the heterogeneity of this particular patient population and subsequently studied in a robust clinical fashion.