Patients with severe systolic disfunction (left ventricle ejection fraction<40%) heart failure that remain functional class II, III or IV after at least 3 months of optimal treatment and after being evaluated by the cardiologist by doing an echocardiography, blood test and clinical evaluation, start Sacubitril-Valsartan treatment.

Evaluation of the Sacubitril-Valsartan treatment effectiveness.

As there are three possible doses, during the first 30 days of treatment 3 evaluations will be carried out (every 10 days) for dose titration based on safety and tolerability as well as a blood test the 30rd day of treatment.

Afterwards the patient will be evaluated after 3 and 6 months of treatment with a blood test and in the final visit (6 months) an echocardiography will be carried out and the final clinical evaluation will be made.

Verify if there is any difference in the response to the treatment with Sacubitril-Valsartan depending on the ventricular dysfunction etiology, ischemic or non-ischemic (idiopathic/familiar,toxic, volume overload,etc) excluding enolic, of patients with severe systolic heart failure.

Study of the microRNA genetic profile in heart failure as an indicator of the cardiac remodeling process and see its response and changes after undergoing Sacubitril-Valsartan treatment.

Demonstrate if there´s a possible relation between the biomarkers levels in heart failure and an improvement in the cardiac remodeling.