Sacubitril-Valsartan in Heart Failure With Preserved Ejection Fraction and Secondary Mitral Valve Regurgitation

Inclusion Criteria: * Age \> 18 years. * New York Heart Association class II to IV. * Written informed consent. * Left ventricular (LV) ejection fraction ≥ 50%. * Objective evidence of cardiac structural and/or functional abnormalities consistent with the presence of LV diastolic dysfunction/raised LV filling pressures, including raised natriuretic peptides. * ≥ moderate functional MR assessed by transthoracic echocardiography within the previous year. Exclusion Criteria: * Systolic blood pressure \< 100 mmHg. * Potassium ≥ 5.2 mmol/L. * Estimated Glomerular Filtration Rate ≤ 25 ml/min/1.73m². * History of angioedema or unacceptable side effects during receipt of angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARB). * Structural mitral valve disease and previous or planned mitral valve intervention. * Already receiving angiotensin receptor neprilysin inhibitor (ARNI, sacubitril-valsartan) therapy. * Severe comorbid condition limiting life expectancy \< 24 months or inability to perform a maximal CPETecho. * Myocardial infarction, unstable angina, coronary revascularization within 12 weeks prior enrolment. * Severe aortic, tricuspid or pulmonary valve disease. * Pregnancy, lactation, or use of any method of contraception that is not highly effective.