Inclusion Criteria:  Patient with a CRT device for at least one year due to the presence of LBBB and LVEF <40% of non-ischemic origin Current LVEF ≥50% and normal volumes in two consecutive echocardiographic studies, separated at least 3 months, and the last one performed in the previous 6 months. Normally functioning CRT device with stimulation> 95%. NYHA functional class I-II. Absence of admissions for HF in the last year. NT-proBNP <450pg/ml in sinus rhythm and <900pg/ml in patients with atrial fibrillation, in the previous 6 months. Pharmacological treatment with beta-blockers, ACEIs/AIIRA/RNAI with or without MRA. Older than 18 years. Patients who have given their informed consent in writing.  Exclusion Criteria:  Previous episode of sustained ventricular tachycardia/recovered sudden death/appropriate shock (in the case of a patient with an implantable cardioverter-defibrillator associated with CRT). Uncontrolled arterial hypertension (figures> 140/90 mmHg). Need to use beta-blockers at the medical discretion for other indications such as heart rate (HR) control in atrial fibrillation (in the absence of ablation of the atrioventricular node) or to control other supra or ventricular arrhythmias. Severe valve disease. Diabetic or hypertensive with microalbuminuria or proteinuria. Renal failure with creatinine clearance <30ml/min/1.73m2. Fertile women who are neither using contraceptives nor surgically sterilized; pregnant or lactating women. Patients are currently participating in a clinical trial or have participated in the past 30 days.