Clinical Research Directory

General Inclusion Criteria * Participant is willing and able to give informed consent for participation in the study. * Participant aged at least 18 years old. 6.2.2 Additional inclusion criteria for participants in the HFpEF arm * Clinical diagnosis of HFpEF * HFA-PEFF score ≥ 5 6.2.3 Additional inclusion criteria for participants in the healthy and matched control arm * HFA-PEFF \< 3 * No known diagnosis of heart failure 6.3 Exclusion criteria * Participant is unwilling or unable to give informed consent * Any impediment to communication which, in the opinion of the investigator, might prevent the investigator communicating effectively with the patient during the study which could cause a safety or reliability concern. * Any other condition which, in the opinion of the investigator, might affect the safety of the participant or reduce the reliability of the study results * Involvement in any other research project where the procedures would affect the outcomes of this study. * Individuals with NYHA class IV symptoms * Known ischaemic heart disease, ICD, or CRT in situ. * Individuals on oral magnesium supplementation * Insulin dependent diabetes * Standard contraindications to magnetic resonance imaging (MRI), (Metal clips or metallic foreign body, prior injury to the eye involving fragments of metal, prior shrapnel injuries, any other metallic or electronic implants affected by the magnetic field, history of severe claustrophobia, history of chronic kidneys disease, egg, or soya allergy) * Heart transplant recipient * Cardiomyopathy from infiltrative or storage diseases, muscular dystrophies, or with reversible causes, hypertrophic cardiomyopathy * Moderate or greater valvular heart disease * Acute HF requiring iv diuretics, inotropes, vasodilators, or hospitalisation within 6 weeks of screening * BMI\>40kg/m2 (due to MRS sensitivity). * Pregnancy (due to magnesium infusion). * Chronic kidney disease stage 4/5 (due to contrast injection)