The primary objective of this study is to demonstrate that in patients with recuperated/normalized left ventricular function, defined as an ejection fraction (EF) ≥ 50%, after implantation of cardiac resynchronization therapy, device treatment is sufficient and neurohumoral blocker therapy can safely be withdrawn

Inclusion Criteria:

• ≥18 years

• CRT implantation

  • based on class I recommendations of ESC (European society of CArdiology) guidelines:
  • Left bundle branch block (LBBB) with QRS duration >150 ms and left ventricular ejection fraction (LVEF) ≤35% who remained NYHA functional class II, III and ambulatory IV despite adequate medical treatment
  • LBBB with QRS duration 120-150 ms and LVEF ≤ 35% who remain in NYHA functional class II, III and ambulatory IV despite adequate medical treatment

• At the moment of inclusion: ≥ 6 months after implantation

• At the moment of inclusion: normalised LVEF (≥ 50%), LVIDD/BSA (left ventricular internal diastolic diameter indexed to body surface area) ≤3.2 cm/m²(woman) en ≤3.1 cm/m² (men) or LVDV/BSA (left ventricular diastolic volume indexed to body surface area) ≤75 ml/m² (women) or ≤75 ml/m² (men)

• euvolemic clinical state and functioning in NYHA class I

Exclusion Criteria:

• contraindication for withdrawal of ACE-I/ARB such as diabetic nephropathy and proteinuria > 1g / 24 h
• severe ventricular arrythmia (sustained VT or ventricular fibrillation) occuring at the time LV function was normalized
• ischemic cardiomyopathy with evidence of scarring (scarring on MRI or severe hypokinesia/akinesia in >1 LV wall segment on echocardiography)
• known severe coronary atherosclerosis (stenosis ≥ 80%)