Examining the Effects of Mitochondrial Oxidative Stress in DCM

Inclusion criteria 1. idiopathic or familial DCM 2. LVEF ≤45% on 2 imaging studies of any modality ≥3 months apart (may include CMR scan at baseline visit) 3. on guideline therapy for ≥3 months as determined by usual clinicians 4. sinus rhythm on 12-lead electrocardiogram 5. plasma NT-pro-BNP \>250ng/L for those \>65 years and \>100ng/L for those aged ≤65 years within the last 6 months (may include sample at baseline visit) Exclusion criteria 1. current persistent atrial fibrillation 2. contraindication to CMR 3. estimated glomerular filtration rate (eGFR) \<30mls/min 4. current or planned pregnancy or current breast-feeding 5. clear environmental trigger such as excess alcohol intake, cardiotoxic chemotherapy or peripartum presentation 6. fibrosis burden \>25% on CMR 7. current cancer (other than non-melanoma skin cancers) 8. current use of CoQ10 9. current participation in another randomised controlled trial