Abstract
Cardiac resynchronization therapy (CRT) is an important adjunct to medical therapy of heart failure. Necessary preconditions for a successful application of CRT are mechanical and electrical dyssynchrony of the left ventricle. Small clinical studies with a short follow-up time in patients with advanced systolic heart failure, structural heart disease, low LV ejection fraction (< 35 %) and a wide QRS complex (> 150 ms) demonstrated the beneficial effect of bi-ventricular pacing showing improvement of cardiac function and reduction of heart failure symptoms within a few weeks or months after initiation of CRT.
Large randomized trials (COMPANION and CARE-HF) in patients with advanced heart failure showed a decrease of overall mortality and less heart failure hospitalizations besides improvement of NYHA class. ICD backup in CRT devices proved to be important to reduce sudden arrhythmic death. Since the benefit of decreased overall mortality is limited in severe heart failure, three important trials (REVERSE, MADIT-CRT and RAFT) were launched in order to test the effect of CRT in patients with mild or asymptomatic heart failure (NYHA class I and II). The results of these trials with different study designs, follow-up time and primary endpoints demonstrated that significant „reverse remodeling“, reduction of overall mortality and decrease of heart failure hospitalization can be best achieved in patients with left bundle branch block (LBBB) configuration, a broad QRS complex ≥ 130 ms, sinus rhythm, female gender and non-ischemic cardiomyopathy.
Therefore, prevention of heart failure progression is easier to achieve at an early stage of heart failure by using bi-ventricular pacing with ICD backup. The long-term benefit of CRT in patients that fulfill the effectiveness criteria of CRT is more pronounced in patients with mild- instead of advanced heart failure.
