Despite recent advances and even when receiving optimal therapy, patients with chronic heart failure (CHF) suffer poor quality of life, with recurrent hospitalisations and persistent symptoms. The investigators have shown that patients attending the Leeds Integrated Heart Failure Service are also frequently deficient in vitamin D and that the severity of the deficiency relates to the levels of symptoms, exercise capacity, diuretic requirements and response to optimal medical therapy. Vitamin D contributes to cardiac and skeletal muscle contractile function, immune function, pancreatic insulin release, and neuro-hormonal homeostasis. A randomised, placebo-controlled proof of concept study in 60 CHF patients has demonstrated improvements in submaximal exercise capacity and symptoms. VINDICATE will be a randomised, placebo-controlled developmental clinical study in 250 patients with CHF and vitamin D deficiency. The present study is designed to detect whether vitamin D has pathophysiologically important effects, as well as providing preliminary evidence of efficacy and safety by examining cardiac function (using cardiac magnetic resonance imaging) and submaximal exercise capacity (by 6-minute walk test). This will provide pertinent data to inform a larger multi-centre efficacy and effectiveness study.

This is a randomized placebo-controlled trial of vitamin D versus placebo in people with heart failure. Primary endpoint is 6 minute walk distance.

Inclusion Criteria:

• Class II or III CHF
• Stable symptoms (on otherwise optimally tolerated medical therapy)
• Able to give written informed consent

Exclusion Criteria:

• Currently taking vitamin D supplementation
• Untreated valvular heart disease
• Existing class I indication for vitamin D therapy
• History of primary hyperparathyroidism, tuberculosis, sarcoidosis, malignancy or hypercalcaemia
• Heart failure due to anaemia or thyrotoxicosis
• Renal failure (GFR <30l/min)