Heart bypass - or coronary artery bypass graft (CABG) - is a radical procedure that has become the most frequently performed of all surgical operations, with around 500,000 carried out every year in the US alone. Around 10 per cent of all heart patients will undergo a cardiac bypass, especially if they have one or more coronary arteries that are either blocked or severely narrowed.
In an operation that can last from two to six hours, the surgeon removes (or ‘harvests’) veins from the patient’s leg, forearm or chest. These are then attached or grafted to a part of the artery that is not blocked, so bypassing the blocked section. Three or more bypasses may be created, depending on the number of blocked arteries.
The traditional approach is known as ‘on-pump’, where the heart is stopped for several hours to allow the surgeon to perform the graft. The patient is attached to a heart-lung machine, or pump, so that the blood supply can be diverted from the heart and sent through the pump, where it is oxygenated and then pumped back to the vital organs.
But a newer technique, which some surgeons believe is safer and less traumatic, is known as ‘off-pump’ or ‘beating-heart bypass surgery’. While the grafting procedure for both approaches is the same, ‘off-pump’ is performed with a heart that continues to beat, stabilised by special equipment.
The ‘off-pump’ technique was developed as a response to the high risk of a serious adverse reaction, such as a stroke, heart attack or even death, following ‘on-pump’ surgery. A study from Yale University, for example, found that 27 per cent of ‘on-pump’ patients suffered a heart contraction after surgery (JAMA, 1996; 276: 300-6), while another study discovered that 6 per cent of patients suffer a stroke afterwards, 5 per cent of which are fatal; and half of the stroke victims suffer deterioration of their mental faculties (N Engl J Med, 1996; 335: 1857-63). A grimmer picture was painted by another study that found that 23 per cent of all CABG patients suffer some degree of mental decline after the operation (JAMA, 2002; 287: 1405-12).
However, mental health problems can occur with either procedure. This is because microscopic blood clots dislodged during surgery can then make their way to the brain (Stroke, 2000; 31: 707-13).
But considering it’s such a new procedure, ‘off-pump’ is already raising concerns of its own. On the heels of several studies suggesting that the technique was safe, a new study among 102 patients at the Royal Brompton Hospital in London has found that grafts following ‘off-pump’ surgery are six times more likely to close up within three months compared with those inserted ‘on-pump’ (N Engl J Med, 2004; 350: 21-8).
The researchers suggest this may be down to the experience of the surgeons - and very few surgeons are likely to be highly competent in a technique that is so new. An ‘off-pump’ operation is a far more difficult procedure as the surgeon is working in a more restricted space and on a heart that is still beating.
What happens later on?
Most bypass studies have concentrated on problems that arise immediately after surgery, but what happens to the patient after he is allowed to go home? One analysis of 17,857 three-artery-bypass patients found that 590 of them - or 3.3 per cent - died within the first year after surgery. However, the rate dropped slightly - to 2.7 per cent - in patients who had two-vessel bypasses (J Am Coll Cardiol, 1999; 33: 63-72).