At low risk for cardiovascular events? Aspirin still recommended

Aspirin has long held a place in the secondary prevention of heart attack and death. In other words, there is no controversy about aspirin’s use if you have the diagnosis of atherosclerotic disease. In fact, this is a Class 1A (the highest level) indication in Cardiovascular Guidelines for practice.The controversy is: can we prevent heart attacks and death in patients who have no knowledge of their atherosclerotic burden. This is not a small group of people. It is estimated that 50 million Americans use low dose aspirin regularly for cardioprophylaxis.

Multiple trials have been done with the seminal trial being the Physicians Health Study that started in the mid 1980’s. Basically 22,071 male physicians who were age 40-84 were enrolled. The first problem was they were all men so no knowledge of women’s benefit was gained. They were randomized to take 325mg of aspirin every other day or placebo. Since even physicians are limited, they took the pills from a blister pack and in the aspirin group every other pill was a placebo.

The trial was stopped early because if you were over 50 years of age and a male you had a 44% reduction in heart attacks. A small group had chronic stable angina (i.e. secondary prevention). Although they were “enrolled improperly” the risk reduction of heart attack was 87%. Reduction of stroke and cardiovascular death were found to be inconclusive because of very low rates of occurrence.

Women got their chance in the Women’s Health Study a 40,000 patient trial that showed low dose aspirin did not lower the risk of MI but did lower the risk of stroke.

In 1994 the Antiplatelet Trialist Group published their overview of 174 randomized trials of antiplatet agents. This study included 70,000 high risk patients and 30,000 low risk patients. Again the number of females was unknown. The findings were that long-term antiplatet therapy in patients at high risk of vascular disease offers significant protection against MI, stroke and death. Cardiovascular Guidelines state that among patients with a 10-year cardiovascular risk greater than or equal to 10% this therapy is warranted. See 09/04/09 blog regarding calculating your risk.

Low dose aspirin is used. This is defined as 75-325mg a day. The use of enteric coated does not appear to reduce the risk of GI bleeding complications contrary to common belief. The lower the dose of aspirin used the lower the risk of GI bleeding.

Confused yet? Most doctors are. The best summary is that if patients who are at low risk for cardiovascular events take aspirin for an average of 6.4 years three cardiovascular events are prevented per 1000 women and four cardiovascular events are prevented for men. 2.5 major bleeding events per 1000 occurred among woman and 3.0 per 1000 men.

Tags: aspirin, Atherosclerotic Disease, cardioprophylaxis, Heart attack, Stroke

This entry was posted on Thursday, October 1st, 2009 at 2:20 pm and is filed under Atherosclerotic Heart Disease, Heart Failure. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.