2011 Volume 75 Issue 2 Pages 465-471
Contraction delay of the lateral left ventricular free wall can be improved by biventricular pacing. Cardiac resynchronization therapy (CRT) is based on the principle of resynchronizing un-uniformed contraction of the ventricle. Prolongation of the QRS duration on an electrocardiogram served as an indirect marker to identify mechanical dyssynchrony. One of the greatest problems is approximately 30% of the patients who met the criteria do not respond for CRT. One possible explanation for the lack of response for CRT could be the absence of sufficient dyssynchrony to allow the therapy to have any impact. Direct assessments of mechanical dyssynchrony might better select responder patients for CRT. However, RethinQ study demonstrated that patients with heart failure and narrow QRS intervals might not benefit from CRT, even with dyssynchrony. Moreover, the results of the PROSPECT study suggest given the modest sensitivity and specificity in the multicenter setting, despite training and central analysis, no single echocardiographic measurement of dyssynchrony could be recommended to improve patient selection for CRT beyond current guidelines. At present, assessment of mechanical dyssynchrony is not necessary in determining CRT indication. Current indication including QRS width is recommended as selection criteria to identify patients suitable for CRT. (Circ J 2011; 75: 465-471)
