Aspirin is the standard treatment when it comes to optimal medical treatment in the context of secondary prevention of coronary artery disease, in patients with diagnosed, established atherosclerosis.
Even though bleeding risk is rather small in the short period an acute event takes place, it increases substantially over time.
However, the evidence clearly supports the use of aspirin in the context of secondary prevention.
On the other side of the spectrum, there are patients that have never presented an event, despite the above-mentioned risk, and these are the ones that challenge the risk/benefit ratio of aspirin.
A recent meta-analysis (Zheng and Roddick et al) has reported significant reduction of cardiovascular death, non-fatal infarction and non-fatal stroke with aspirin in primary prevention (even though major bleeding risk was higher). But these data should be thoroughly looked into given the large number of potential confounders.
This meta-analysis could have been exposed to false positives (type 1 errors) and false negatives (type 2 errors), given the large number of non-significant tests and the lack of statistical power (characteristic of non-randomized trials, which disregard the necessary number of patients to test any given hypothesis).
The present meta-analysis has taken into account all these technical points and this might lead to a completely different conclusion.
And, in fact, for the global population, aspirin is not associated to a benefit in survival (always in the context of primary prevention).
Moreover, aspirin was associated to more intracranial and gastrointestinal bleeding, also speaking of the global population.
For diabetics, results were inconclusive. There were benefits, but not significant in terms of stroke or infarction.
For low risk patients, results show that there is no benefit in primary cardiovascular prevention of events such as death or stroke, but there is an increase in bleeding events. Bleeding risk probably cancels the marginal ischemic benefit in this population.
In the diabetic population, and also in patients with higher cardiovascular risk at baseline, data are inconclusive, and this calls for further studies with adequate statistical power.
We could conclude that aspirin should be indicated on a case by case basis with careful balancing of potential benefits with ischemic risk and ─more importantly─ bleeding risk.
Original Title: Aspirin for Primary Prevention of Cardiovascular Disease.
Reference: Babikir Kheiri et al. Circ Cardiovasc Qual Outcomes. 2019;12:e005846.
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