Cardiac resynchronization in 2008: an echo approach.

Dyssynchrony is the abnormality in timing of regional ventricular mechanical activation in patients with heart failure. Dyssynchrony is one of the principal pathophysiologic features that improves with cardiac resynchronization therapy (CRT). Several echocardiographic approaches over the past several years have been described to quantify mechanical dyssynchrony in an attempt to improve patient selection over the electrocardiographic QRS complex width, which is a surrogate for dyssynchrony. Although no ideal method exists, this article focuses on the strengths and limitations of measures of longitudinal velocity using color tissue Doppler, radial strain using speckle tracking, and interventricular mechanical delay using routine pulsed Doppler. Recent results using these methods are exciting; however, they have not yet replaced routine clinical implant criteria for CRT. Echocardiographic assessment of dyssynchrony continues to evolve, with new information being added continually, and appears to have promise for future clinical applications.