Refractory Angina Pectoris

REGENERATE-COBRA will examine whether autologous stem cell treatment can improve angina symptoms and quality of life for patients with refractory angina. Patients will be randomised (randomly allocated with a 50:50 chance) to either the 'treatment' or the 'sham' group - they will not know which group they are in. In the 'treatment' group: * Stem cells will be collected from bone marrow in the patient's hip under local anaesthetic (a bone marrow aspiration). * Under local anaesthetic, the stem cells will be infused into the arteries that supply blood to the heart through a small tube inserted either in the wrist or the groin. * The follow-up involves a phone call at 1 month and 12 months and clinic visit at 6 months. In the 'sham' group: * A sham bone marrow aspiration is performed - a 3mm nick in the skin will be made under local anaesthetic. * A sham cell infusion is performed - a small tube is inserted either in the wrist or groin under local anaesthetic. * The follow-up involves a phone call at 1 month and 12 months and clinic visit at 6 months.