Cardiac Resynchronization Therapy in Heart Failure

Heart failure pharmacotherapy including beta-blockers (BB), angiotensin converting enzyme inhibitors/Angiotensin II Receptor Blockers (ACEi/ARB), and aldosterone antagonists have resulted in dramatic improvements in the morbidity and mortality of patients with heart failure (HF) with a reduced ejection fraction. However, in many patients, medical management alone is insufficient to achieve adequate symptom control and HF associated morbidity and mortality remains high. In a subgroup of these patients with prolonged QRS duration, particularly with left bundle branch block (LBBB) morphology, cardiac resynchronization therapy (CRT) has demonstrated additional benefit. Currently CRT is indicated for patients with NYHA functional class II-IV heart failure, severe systolic dysfunction (left ventricular ejection fraction (LVEF) ≤35 %) and interventricular conduction delay. Over the last two decades it has become a key component of the staged treatment of HF (Jessup and Brozena N Engl J Med 348(20):2007–18, 2003).