Patient selection and echocardiographic assessment of dyssynchrony in cardiac resynchronization therapy.

Appropriate cardiac resynchronization therapy (CRT) enhances quality of life and improves survival in patients with refractory heart failure due to systolic dysfunction and mechanical dyssynchrony. On the assumption that the main therapeutic mechanism of CRT is the correction of dyssynchronous myocardial contraction, imaging-based measures of dyssynchrony have been intensely investigated with the aim of predicting response to therapy. Numerous echocardiographic dyssynchrony parameters have been proposed, but no large prospective trial have been published to prove the clinical utility of any of these indexes. Moreover, the methodology to derive the proposed dyssynchrony indexes has not been standardized. Therefore, the purpose of this article is to critically review the current status of proposed dyssynchrony indexes by echocardiography for patient selection and to recommend future investigations in this area.