For DCM cohort (Group A):  Inclusion Criteria:  Age ≥16. Able to give informed consent. Confirmed DCM with symptom-onset within the last 6 months and LVEF ≤ 45%. The diagnosis of DCM will be confirmed using the European Society of Cardiology definition, based on reduced LVEF and elevated LV end-diastolic volume indexed to body surface area, compared to published age- and sex-specific reference values  Exclusion Criteria:  Significant coronary artery heart disease, defined as a stenosis of >50% of an epicardial coronary artery affecting the proximal or mid-portion of the vessel on invasive angiography or computed tomography coronary angiography (CTCA), previous percutaneous coronary intervention, CMR late gadolinium enhancement pattern suggestive of previous myocardial infarction of ≥ 2 segments of ≥ 50% transmural infarction of the LV wall. High suspicion of concomitant hypertrophic cardiomyopathy, amyloidosis, Fabry disease, sarcoidosis, active myocarditis, Chagas disease or hemochromatosis. History of primary valvular heart disease or congenital heart disease. Severe, untreated or untreatable hypertension (systolic blood pressures routinely >180 mm Hg and/or diastolic blood pressures >120 mm Hg) Pregnancy and/or breastfeeding. Severe renal disease (GFR <15 mls/min).  For healthy volunteer cohort (Group B):  Inclusion Criteria:  Age ≥16. Able to give informed consent.  Exclusion criteria:  Participants with any clinically significant cardiovascular or metabolic disease. Participants taking prescription medicines for significant cardiovascular or metabolic disease. Female subjects if they are pregnant or breastfeeding at the time of recruitment.