Open-heart surgery causes injury of the heart muscle. Although this is usually mild, temporary and reversible, if it is severe it can endanger life and require additional high cost care. During surgery, techniques are used to protect the heart from injury, but these remain imperfect. Patients with a thickened wall of the heart (left ventricular hypertrophy) may be at greater risk. This study assesses the effect of facilitating sugar metabolism (a more efficient fuel) by the heart muscle using the drug Perhexiline given before the operation.