Cardiac resynchronization therapy: Is ECG criterion satisfying? What are the alternative modalities?

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality markedly in patients with heart failure and prolonged QRS duration. Although QRS duration seems to be the main inclusion criterion for CRT in major randomized studies, nonresponders account for nearly 30% to 40% of the patients. We reviewed information on and measurement of electrical and mechanical dyssynchrony, difficulties and weaknesses of electrocardiographic and echocardiographic indices of dyssynchrony, new and alternative diagnostic modalities, and controversial issues on predicting response to treatment. Although echocardiographic assessment together with new modalities seems to be reliable and applicable in clinical practice, appropriate patient selection remains challenging for large prospective randomized trials.

Keywords: Cardiac pacing, artificial, cardiomyopathy, dilated; echocardiography, Doppler; electrocardiography; heart conduction system/physiopathology; heart failure/therapy; myocardial contraction; ventricular dysfunction, left.