Prognostic Implications of Echocardiographic Left Ventricular Dyssynchrony

Abstract Normal regional left ventricular (LV) mechanical contraction is synchronous, resulting in efficient ejection. Abnormalities in electrical activation or myocardial diseases may affect the timing of regional contraction, resulting in discoordinated or dyssynchronous contraction, which is inefficient. This article reviews various approaches to quantify dyssynchrony, focusing on LV dyssynchrony, that have been principally related to cardiac resynchronization therapy (CRT). Several attempts have been made to improve patient selection for CRT by use of echocardiographic dyssynchrony; however, none have gained clinical acceptance. This review focuses on the different reasons for the existence LV dyssynchrony, the dyssynchronous strain patterns indicative of CRT response, and the prognostic implications of dyssynchrony. Interest in echocardiographic dyssynchrony remains high because of its mechanistic and prognostic importance. Dyssynchrony may occur from electrical or nonelectrical causes. Patients with a wide QRS complex who have baseline dyssynchrony from electrical delay in general have a favorable response to CRT, whereas patients with nonelectrical dyssynchrony (from contractile heterogeneity or scar) at the baseline have a worse prognosis. New insights into the meaning of mechanical dyssynchrony continue to emerge, and this article reviews the important lessons learned from experience, prognostic implications, and promise for future applications.