Diabetes increases the risk of heart failure. This is mainly due to a disease of the blood vessels supplying the heart muscle and/or high blood pressure, but abnormal metabolism may also contribute. We plan to study the mechanisms involved in this abnormal metabolism, whilst also assessing the effects of a drug called Perhexiline which improves the abnormal metabolism that is present in diabetic patients before the development of heart failure.

Inclusion Criteria:

• Diabetes Mellitus(WHO definition)
• HbA1C <9
• No history of chest pain
• No evidence of Coronary Artery Disease or peripheral vascular disease
• Left ventricular ejection fraction over 50%
• No evidence of respiratory disease

Exclusion Criteria:

• Patients < 16years or who cannot provide informed consent
• Evidence of significant epicardial coronary artery disease
• Evidence of peripheral vascular disease
• Abnormal liver function tests
• Clinically apparent peripheral neuropathy
• Severe chronic renal failure (creatinine >250) or diabetic nephropathy
• Concomitant use of Amiodarone, Quinidine, Haloperidol or Selective serotonin (5HT) uptake inhibitors such as Fluoxetine and Paroxetine which may inhibit the CYP2D6 enzyme
• Patients on statin therapy for primary dyslipidemia.
• Patients with recurrent hypoglycaemia
• Women of child bearing age who are not using effective contraception (or if pregnancy test positive)