Emerging Role of Cardiac Resynchronization Therapy in Heart Failure

Morbidity and mortality due to heart failure remains high in spite of advances in its medical management. During the last decade a new modality has emerged that has now proven to be beneficial in a select group of patients with heart failure. This is the cardiac resynchronization therapy (CRT), which is based on correcting various types of cardiac dyssynchrony that many patients with heart failure have. Though a large number of trials have demonstrated clinical and hemodynamic benefits of CRT, it is only recently that mortality benefits have been shown. The mortality benefit is further improved when CRT is combined with intracardiac defibrillator in selected patients of heart failure. Based on the existing criteria for selection of heart failure patients for CRT (NYHA III or IV, depressed left ventricular ejection fraction < 35% and presence of left bundle branch block with QRS duration > 120 ms), 30-40% patients do not respond favorably. Newer modalities like speckle tracking imaging and three-dimensional echocardiography are being validated to differentiate responder from nonresponder. This is extremely important in view of the high cost of the device. This review article highlights logic behind CRT, criteria for selection of cases, problems of non response, role of combined CRT-defibrillator and other related issues.