[Resynchronization therapy for heart failure--still many question marks].

At present, the potential benefit of resynchronization therapy, i.e. an improved quality of life and prolonged survival in patients with heart failure, is not achieved in every patient. The 30% non-response has prompted a search for new criteria predicting patient response to resynchronization treatment. An absence of mechanical dyssynchrony, viability of the myocardium and an inadequate positioning of the intracardiac left ventricular lead probably limit the response to resynchronization therapy. ECG remains essential for the selection of suitable patients.