Does oral intake of exogenous ketone salt improve heart function measured by cardiac MRI in heart failure compared to oral intake of a carbohydrate placebo?

This study will help to quantify heart and kidney ketone uptake with or without an exogenous ketone salt in heart failure condition.

Participants will have 2 different cardiac MRI to perform:

1. Fasting with exogenous ketone salt supplement
2. Fasting with exogenous carbohydrate supplement

Inclusion Criteria:

• Patients with heart failure with left ventricle ejection fraction of 40%
• Heart failure of ischemic or dilated etiology
• Ambulatory patient with a NYHA functional class of II-III;
• Stable symptoms and no change in medical therapy in the last month.

Exclusion Criteria:

• Diabetes
• Patients treated with any SGLT2i;
• Chronic kidney disease
• Acute coronary syndrome in the last 3 months;
• Use of parenteral inotropic agents;
• Persistent or permanent atrial fibrillation or atrial flutter;
• Presence of pacemaker or defibrillator;
• Medical condition that causes malabsorption of the test material;
• Under ketogenic diet, or using exogenous ketone supplements
• Use of nicotinamide adenine dinucleotide (NAD) precursor supplements

Triple (Participant, Investigator, Outcomes Assessor) Investigators, participants and outcome assessors will be fully blinded.