Cardiac resynchronization therapy: clinical results and evolution of candidate selection

Cardiac resynchronization therapy (CRT) is now a recommended treatment in patients with severe heart failure, a poor left ventricular (LV) ejection fraction and wide QRS of >120 ms. The implementation of CRT in the current guidelines for the treatment of chronic heart failure occurred after the results of different clinical trials including more than 4000 patients, especially the COMPANION and CARE-HF trials. These trials showed that CRT over and above optimal drug treatment improves symptoms, quality of life, exercise tolerance, but more importantly reduces mortality and morbidity. Another major finding was that CRT reverses LV remodelling, a major prognostic factor in heart failure. However, the rate of responders remains only 65–70%. So far, the only validated criterion of cardiac dyssynchrony is the QRS width on the surface ECG, which is probably not optimal. Echocardiographic techniques have shown interesting perspectives for optimizing patient selection, but still have to be validated. Moreover, new indications for CRT (patients with atrial fibrillation, narrow QRS, or mild heart failure) will probably be validated in the near future. The recent and future technical developments in the device will help to optimize the therapy and also to improve heart failure monitoring using sensors in the device and home monitoring by telephone or Internet.