Last month the United States Preventative Services Task Force became the latest of several organisations to suggest decreasing the use of aspirin as an agent for primary prevention. We have had several of our patients ask whether this is advice that affects them and their care. Thus, we thought this would be an interesting topic for our readership at large.

The first thing to note is that the above advice does not apply to patients who have established cardiac or cardiovascular disease. That is, patients who have been diagnosed with heart attacks or strokes, or who have established atherosclerotic disease – cholesterol that has deposited in the walls of arteries. For these patients, the use of aspirin is termed secondary prevention. These patients are at considerable risk for future morbid events such as heart attack, stroke, and cardiovascular death and, in these patients, the use of aspirin significantly improves outcome. Primary prevention refers to measures that are being used to reduce risk in patients with no evidence of cholesterol deposition and no clinical disease. Low dose aspirin has for many years been thought to improve outcome, particularly in terms of reducing the risk of stroke and heart attack. It has, however, become clear that the use of aspirin in primary prevention is associated with side effects and, for large groups of patients, these side effects outweigh any possible benefit that the use of aspirin may provide.

What is aspirin?

The chemical name of aspirin is acetyl-acetic acid and records of its use date back to antiquity. In nature, the compound is found in the bark of the willow tree. Physicians in ancient Greece and Egypt are known to have used tea made with willow bark to treat fever and inflammation. Aspirin has effects on the generation of chemicals in the blood that lead to its therapeutic effects. These therapeutic effects include an anti-inflammatory effect, which is clinically useful in rheumatic fever, Kawasaki’s disease, and certain rheumatologic diseases. Aspirin also has anti-pyretic effects, which can be useful for treating fevers and lastly, an anti-thrombotic effect which inhibits clotting of the blood. It is this last effect that is useful clinically when treating atherosclerotic disease, but which also potentially leads to side effects. As we have previously discussed cholesterol that is present in the arteries can serve as a focal point for clotting. This clotting process can progress to occlusion of the artery, leading to heart attack and stroke. The use of aspirin in patients who have cholesterol deposition protects against intra-arterial clotting and thus reduces the risk for heart attack and stroke.

What are the potential side effects of aspirin use?

The side effects of aspirin use are related to its clinical benefits. The inhibition of clotting on the inside of arteries can be clinically useful in patients with atherosclerosis but can be a problem in other areas. The use of aspirin is associated with an increase in the risk of bleeding. This bleeding can be minor, for example, bruising or cuts. It may also be major, as in bleeding within the brain or from the gastrointestinal tract. The bleeding risk with aspirin increases with age. Other factors increasing the risk of bleeding with aspirin include a prior history of bleeding, smoking, male sex, peptic ulcer disease, liver disease, and hypertension. Certain medications, including non-steroidal anti-inflammatory drugs and steroids, also increase bleeding risk. Aspirin also has the effect of decreasing the protective barrier in the stomach, thereby increasing the risk of stomach inflammation and ulcer, which can then lead to bleeding. When we consider the use of aspirin in an individual patient, we are weighing the benefit that the patient will obtain in terms of reduction in cardiovascular risk versus the potential harm that may result from bleeding. If the benefit outweighs the harm to a significant degree, these are patients in whom aspirin can be used safely.

For whom is aspirin useful?

The use of aspirin for cardiac and cardiovascular disease is based on a large body of data that found benefit in patients with acute heart attack, coronary artery disease, patients undergoing coronary bypass surgery, patients who received coronary stents, had strokes, and who have laid down cholesterol particularly in the arteries to the brains and legs. The risk reduction in these groups of patients with aspirin use is significant (15-30 per cent) with a risk for major bleeding in aspirin that averages 1 to 3 episodes per thousand people treated for one year. For these patients, who comprise a large segment of our cardiac patient population, the continued use of aspirin is important and is highly recommended.

In whom should aspirin be avoided?

Given the success of aspirin in these patients with established cardiac disease, it was thought that patients at elevated risk for developing cardiac disease would also benefit (primary prevention) and indeed the initial studies were encouraging. However, what has become clear more recently is that the benefits in patients without established disease is much less and certain subgroups of people are at quite substantial risk of bleeding on aspirin. In a study of patients above the age of 70 years with no diagnosed cardiovascular disease, the use of aspirin did not reduce the risk of heart attack or stroke but did increase the risk of major bleeding by 38 per cent and the risk of dying by 14 per cent. A study of diabetic patients again found no protective effect but a 29 per cent increase in risk of bleeding. A large meta-analysis, which included thirteen studies with 164,000 patients, found that aspirin use increased the risk of major bleeding by slightly more than it reduced the risk of cardiovascular death.

What are the current recommendations for aspirin use in patients without cardiovascular disease?

Patients at increased risk of bleeding should not use aspirin for primary prevention. One of the most important risk factors is age. The United States preventative task force recommend that people above the age of 60 should not use aspirin for primary prevention. The European cardiac society guidelines have suggested 70 years as the age above which aspirin use for primary prevention should be avoided. For patients below the cut-off – ages 40-60 years in the US guidelines and below 70 in the European guidelines – both organisations report that the likely benefit to be obtained is small. There, however, is not much data on patients who are at extremely high risk in this age range, and both societies recommend an informed discussion between a patient and their physician during which an estimate of likely benefit and harm are assessed. Clearly, patients with risk factors that put them at considerable risk of bleeding should avoid aspirin use for primary prevention.

So what should I do?

Currently the evidence would suggest avoiding aspirin as a treatment to prevent heart attack and stroke if no diagnosed cardiovascular disease is present and the risk for future cardiac disease is not extremely high. Importantly, as age increases, so does the risk of bleeding on aspirin. It is important to emphasise that patients with cardiovascular disease do benefit from aspirin use and should continue to take this important medication. For patients felt to be at extremely high risk for future cardiovascular disease, it is important to realise that other measures have been shown to reduce risk. These include lifestyle measures of diet, exercise, avoiding smoking, and good control of hypertension, diabetes, and blood cholesterol. If aspirin use is considered in this context a discussion with your primary care physician, along with cardiac or neurologic consultation may prove useful and aid in decision-making. For those patients who are currently taking aspirin without an underlying diagnosis, discussion with your primary care physician as to the trade off between risk and benefit is advised.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Correspondence to info@caribbeanheart.com or call 876-906-2107