Role of aspirin for primary prevention of cardiovascular events

Role of aspirin for primary prevention of cardiovascular events

The role of aspirin in secondary prevention of major cardiovascular events is well established. But the role of aspirin in primary prevention is less clear. Earlier guidelines had recommended the use of aspirin for primary prevention beyond a certain risk level. But a meta analysis using primary data from several trials by Antithrombotic Trialists Collaboration [1] evaluated both primary prevention and secondary prevention studies. They could include data from 95,000 persons involving 660,000 person years and 3554 vascular events from six primary prevention trials and 17,000 persons involving 43,000 person years and 3306 vascular events from 16 secondary prevention trials. They found a 12% reduction in serious vascular events with aspirin in the primary prevention trials, most of which was due to decrease in non-fatal myocardial infarction. But the net effect on stroke was not significant, nor was the effect on vascular mortality. At the same time, aspirin increased the risk of major gastrointestinal and extracranial bleeds (0·10% vs 0·07% per year, 0·0001). They also found that main risk factors for coronary artery disease were also risk factors for bleeding episodes. There was a higher reduction of serious vascular events in the secondary prevention trials (6·7% vs 8·2% per year, p<0.0001).
The authors concluded that the value of aspirin for primary prevention is uncertain because the reduction in occlusive vascular events has to be weighed against the risk of increase in major bleeding episodes. They think that treatment of hypertension and statins for dyslipidemia will have a better risk benefit ratio and adding aspirin to this regimen may not produce much additional gain. Absolute benefits in primary prevention is an order of magnitude lesser than that in secondary prevention.
The six primary prevention trials included in the analysis were: British Doctors’ Study, US Physicians’ Health Study, Thrombosis Prevention Trial (UK), Hypertension Optimal Treatment Trial (Europe, North and South America, Asia), Primary Prevention Project (Italy) and Women’s Health Study (USA). These trials were published between 1988 and 2005.

An analysis of 15 randomized controlled trials including 165,502 participants (aspirin n = 83,529, control n = 81,973) concluded that aspirin when used as primary prevention reduces non fatal ischemic events, but there is a significant increase in non fatal bleeding events [2].

References

1. Antithrombotic Trialists’ (ATT) Collaboration; Colin Baigent, Lisa Blackwell, Rory Collins, Jonathan Emberson, Jon Godwin, Richard Peto, Julie Buring, Charles Hennekens, Patricia Kearney, Tom Meade, Carlo Patrono, Maria Carla Roncaglioni, Alberto Zanchetti. Aspirin in the primary and secondary prevention of vascular disease: collaborative meta-analysis of individual participant data from randomised trials. Lancet. 2009 May 30;373(9678):1849-60.
2. Hesham K Abdelaziz, Marwan Saad, Naga Venkata K Pothineni, Michael Megaly, Rahul Potluri, Mohammed Saleh, David Lai Chin Kon, David H Roberts, Deepak L Bhatt, Herbert D Aronow, J Dawn Abbott, Jawahar L Mehta. Aspirin for Primary Prevention of Cardiovascular Events. J Am Coll Cardiol. 2019 Jun 18;73(23):2915-2929.