If diagnostic tests indicate a blockage in the coronary arteries the commonest remedial measure is the coronary-artery bypass -although as early as the 1950s, my colleagues and I were exploring other methods of improving blood-supply to the heart. Experiments on dogs using the mammary artery were successful: we joined the mammary artery to the coronary artery and then ligated (tied-off) the coronary artery. These were some of the first experiments in direct revascularizing of the heart muscle.

It is estimated that in the USA 120000 people a year undergo coronary-bypass surgery, a procedure pioneered in the early 1960s by Dr. Michael DeBakey and Dr. Edward Garrett of Houston. They first removed a section of a patient's leg-vein and used it as a graft to bypass a clogged section of artery, promptly relieving the pain of angina and allowing the patient to survive another nine years.

Subsequently Dr. DeBakey carried out a study following up the outcome of bypass surgery on 3500 patients. He found that over 80 percent survived ten years or so after surgery, with half of those under the age of 65 working full-time. In other countries bypass surgery, although regularly performed, is less popular than in the USA. In the UK, for example, it seems that only one operation is carried out for every 12 in the USA, per capita; the Swiss come somewhere in the middle. Why these national differences should exist is a difficult question. The operations are not especially cheap to undertake, and not all doctors agree about the life-prolonging effects of a bypass. Still others argue that resources are better channelled into preventive measures, the bypass being only a palliative procedure, doing nothing to strike at the root cause of the disease. And so the debate continues.

It has to be said that, because this operation is a money-spinner, it can be over-used, like tonsillectomies were 20 years ago. The most important indication that a bypass operation is desirable is uncontrollable angina; where there are only minor symptoms, the operation should be carried out only if there is evidence of other life-threatening lesions, such as an obstruction of the main left coronary artery.