Patients who are resistant to aspirin are more than four times more likely to suffer a heart attack, stroke or even die from a pre-existing heart condition, Canadian research has found.
Patients who are labelled aspirin resistant have platelets that are not affected in the same way as those of patients responsive to the drug. There is currently no agreed method of accurately determining who is aspirin resistant.
The researchers identified and reviewed 20 studies involving 2,930 patients with cardiovascular disease who had been prescribed aspirin as a way of preventing clots; 28% of these were classified as aspirin resistant.
The results published by BMJ online today showed all aspirin-resistant patients, regardless of their underlying clinical condition, were at greater risk of suffering a heart attack, stroke or even dying. In particular they found that 39% of aspirin-resistant patients compared to 16% of aspirin-sensitive patients suffered some sort of cardiovascular event.
The researchers also found that taking other drugs to thin the blood, such as clopidogrel or tirofiban, did not provide any benefit to these aspirin-sensitive patients.
Professor Michael Buchanan from the department of pathology and molecular medicine thrombosis and haemostasis at McMaster University Health Sciences Centre, Canada said further studies were needed to identify the most useful test for determining aspirin resistance. Aspirin resistance: “is a biological entity that should be considered when recommending aspirin as antiplatelet therapy,” he added.