Study Design:~The MECHAD study is an explorative prospective cohort study with matched controls including patients with heart failure with reduced ejection fraction (HFrEF, EF≤40%) due to DCM in NYHA-class II-IV, ≥18 years, referred to Department of Cardiology/Sahlgrenska for heart failure work-up. A control group will be collected with age, gender and body mass index (BMI) matched controls without heart failure from the electrophysiology laboratory.~Study Site:~Sahlgrenska University Hospital is a tertiary center for patients in the need of heart failure evaluation, staging and therapy. Further, Sahlgrenska University Hospital is included in the assignment as one of the national centers for heart transplantation in Sweden. Patients with advanced HF are referred from the western and northern parts of Sweden and as part of clinical evaluation they most often undergo transthoracic echocardiogram (TTE), cardiopulmonary exercise test (CPET) as well as right-sided heart catheterization (RHC) with biopsy from the right ventricle septum or the lateral wall in the left ventricle. The site receives approximately 150 patients for evaluation every year and about 70% have clinically DCM.~Patient information and consent:~The Principal Investigator (or delegated sub investigator) will provide each patient with verbal and written information regarding the objectives and procedures of the study and possible risks involved. The patients will be informed about their right to withdraw from the study at any time. Prior to any study related procedures, the informed consent will be reviewed, signed and dated by the patient and investigator. The research unit at the Department of Cardiology/Sahlgrenska University hospital have dedicated research nurses who will facilitate coordination of the study.~Study timetable:~The inclusion in the study is planned to start in Q1 2022 and will continue until 30 patients with HF and 60 patients without HF (controls) are included. The investigators estimate to be able to include one patient per week in average.~Power Calculation and statistical analyses The investigators aim to include 30 patients with HF and 60 matched patients without HF as controls. To calculate the power, data was used from one study in humans showing an increase in 3-hydroxybutanoyl from 0.29 pmol/mg in a non-failing heart to 0.59 pmol/mg in failing heart. This large difference would result in only 2 patients in each group. However, the estimated increase in 3-hydroxybutanoyl does not directly transmitted to our cohort of DCM, therefore a larger sample was chosen.
The overall aim of the study is to explore the energy metabolism of the failing heart.~Primary objective is to understand the differences in the energy metabolism in patients with DCM and heart failure compared to matched controls without heart failure. Secondary objectives, is to understand if optimal medical therapy, including sodium-gucose transporter 2 inhibitors (SGLT2i), alter the cardiac metabolism in DCM-patients. The investigators will also examine if changes in cardiac metabolism happens during exercise in patients with DCM.~This will be done with invasive measurements of a range of energy substrate metabolites in the coronary sinus of the heart in patients with heart failure due to DCM and controls without heart failure respectively. A range of other clinical characteristics will also be examined to characterize patients and controls.