Other Uses

Helping the heart
It is now recommended that aspirin in smaller doses than those used for pain relief is given to people with angina pectoris, people in the acute stages of myocardial infarction ("heart attack"), and people who have had coronary artery surgery, whether of the bypass, balloon or stent type.

Common to all these people is the need to prevent blood clotting in the coronary arteries, the arteries feeding blood and therefore oxygen, to the heart muscle. The initial stage of blood clots in small arteries such as the coronaries is the aggregation ("clumping together") of platelets, the smallest solid elements - they are sub-cellular particles - in the circulation.

A small dose of aspirin - the dose used is usually 75mg - 150mg per day, or less than half of a standard aspirin tablet - is enough to prevent platelet aggregation. This is of crucial benefit to people with narrowed coronary arteries, or in the throes of a heart attack, or whose first need is to keep open coronary arteries that have just undergone surgery or dilation by balloon or stent.

In particular, timing of treatment of heart attacks is vital to survival. One third of all heart attacks cause death within two hours of the first symptom - yet many sufferers do not reach hospital within four hours. What is needed is an effective treatment on the spot that needs the minimum technical expertise and carries the minimum risk. aspirin answers that specification perfectly, and has been proved to save many lives in trials involving thousands of people.

Saving lives in heart diseases - the evidence
Professor Richard Peto and his team at Oxford University have analysed the findings of 215 trials of antiplatelet agents, including aspirin, in over 100,000 patients with various circulation disorders, worldwide. There was no reasonable doubt that aspirin conferred real benefit.

Professor Peto concluded that "regular use of aspirin could save huge numbers of lives". A daily dose of 75mg aspirin was enough to prevent thrombosis in patients with angina and 150mg - 300mg should be given to patients having a heart attack.

The professor listed the men and women who would benefit from daily aspirin as those with:

• a history of heart attack
• angina
• coronary bypass grafts and angioplasty
• surgery for disorders circulation in the limbs

Such aspirin treatment, according to Professor Peto, leads to the avoidance of serious vascular events in a quarter of all patients in these classes. The benefit was in men and women of all ages, regardless of whether they had other diseases such as high blood pressure or diabetes. Concerns that reducing the blood's ability to clot might increase numbers of strokes were dispelled, as most strokes are caused by clots ("thromboses") and not by bleeding. Any small risk of increased bleeding was more than offset by the benefit of preventing thrombotic stroke.

In fact, analysis of the randomised trials of anti-platelet therapy involving 70,000 people defined as at high risk of a serious vascular event showed that their estimated numbers of non-fatal myocardial infarctions and stroke were each reduced by a third. Since they suffered no increased risk of non-vascular death, it was confirmed that overall mortality was significantly reduced in these high risk patients. Moreover, in the trials lasting three years, there was significantly more benefit after three years than after one year, showing that the benefit not only lasts but increases with longer treatment.

With coronary bypass
Coronary bypass surgery, coronary balloon angioplasty and the insertion of stents are now standard treatments for coronary artery disease. All aim to widen the "bore" of the narrowed arteries. However, thrombosis often occurs in the newly grafted, or the manipulated, vessel. aspirin has been shown to reduce the risk of such thrombosis, so that everyone undergoing these procedures is given aspirin just before, during and after them, and is strongly advised to take it permanently thereafter.

Dr David Dunbabin, of Edinburgh, has calculated that if 1,000 coronary artery bypass patients were treated with aspirin for one year, this would prevent 150 occlusions (blockages) and 37 other blood vessel events.

Preventing stroke
According to Dr Christian Blomstrand, of Goteborg, Sweden, 85% of strokes are caused by infarctions due to thromboses, and not to bleeds - so aspirin should be valuable in their prevention. The Anti-Platelet Trialists' Collaboration (BMJ 1994 308 81-106) showed that in high risk patients - those with a previous stroke or who have transient ischaemic attacks ("drop attacks" - sudden but transient loss of consciousness, mostly in the elderly, known to be precursors of stroke) - the effect of aspirin is clearly beneficial, reducing the risk of stroke by around 35%. There was no difference in the benefit between people at high and moderate risk of stroke.

The Swedish aspirin Low Dose Trial (SALT) compared a daily aspirin dose of 75mg with placebo. There was a significantly lower risk of stroke or death in patients taking aspirin (77/671 patients) than in those on placebo (102/684 patients). This reduction was far greater than the excess of 6 deaths in the aspirin group due to haemorrhagic stroke.

This conclusion is strongly supported by Dr Peter Sandercock, of Edinburgh who has calculated the aspirin-linked reduction of strokes among people with peripheral blood vessel disease as 40%, and in those with the commonest form of irregular heartbeat, atrial fibrillation, as 46%.