Hypertrophic cardiomyopathy (HCM) is a complex and relatively common genetic cardiac disease and it is the most common cause of sudden cardiac death in young people, including trained athletes. In a recent study using in vivo cardiac MR spectroscopy resting PCr/ATP ratio was diminished in patients with sarcomeric HCM, indicating reduced energy availability. Importantly patients with genotypic HCM who did not yet have hypertrophy had a similar degree of impairment of cardiac PCr/ATP ratio as do patients with marked hypertrophy, implying that the disturbance may be an early feature of the disease and is not simply due to the hypertrophy. In medically refractory patients with obstruction, surgical myectomy or alcohol septal ablation may be very effective. However in patients with non obstructive HCM with symptoms refractory to standard drug therapy, there are no therapeutic options (apart from cardiac transplant in very severe cases). Recently, our group showed that Perhexiline, an antianginal agent with an oxygen-sparing metabolic effect which increases the efficiency of energy production by shifting substrate utilisation from free fatty acids towards glucose, was highly effective in improving symptoms, exercise capacity (Vo2max) and cardiac function in patients with systolic heart failure of both ischaemic and non ischaemic aetiology.