Wednesday 22 July 2015

Aspirin cardiac prevention

 
Because of a generally lower baseline risk, there will be less absolute benefit from aspirin in primary prevention for the same relative risk reduction.8-12 On the other hand, the adverse effects of aspirin appear unrelated to thrombotic risk, and hence there will be a lower ratio of benefit to risk for aspirin in primary, compared with secondary, prevention. Although the major effect of aspirin is thought to be in inhibiting thrombosis, benefits were observed in the Physicians’ Health Study, particularly in those with elevated high-sensitivity C-reactive protein levels, raising the possibility of an anti-inflammatory mechanism.

Discussion of the role of aspirin in secondary and primary prevention of cardiovascular disease (not considering cancer prevention), including individuals at moderate to high risk for CVD, is presented separately. However, this position statement does not consider the potential use of aspirin in prophylaxis of venous thromboembolism.


Non-valvular atrial fibrillation three primary prevention and three secondary prevention trials of people with atrial fibrillation, aspirin reduced the incidence of stroke by 22% (95% CI, 2%–38%) (E1).16 However, in three trials examining the relative benefits and risks of warfarin and aspirin, it was found that warfarin about halved the risk of stroke compared with aspirin (E1).16 Thus, aspirin should be preferred to warfarin only in low-risk patients with atrial fibrillation (age < 65 years and no other risk factor for thromboembolism). (See "Benefits and risks of aspirin in secondary and primary prevention of cardiovascular disease" and "NSAIDs (including aspirin): Role in prevention of colorectal cancer".)

In three primary prevention and three secondary prevention trials of people with atrial fibrillation, aspirin reduced the incidence of stroke by 22% (95% CI, 2%–38%) (E1).16 However, in three trials examining the relative benefits and risks of warfarin and aspirin, it was found that warfarin about halved the risk of stroke compared with aspirin (E1).16 Thus, aspirin should be preferred to warfarin only in low-risk patients with atrial fibrillation (age < 65 years and no other risk factor for thromboembolism).

Aspirin therapy for colorectal cancer prevention: The evidence ...

Evidence exists mainly for clopidogrel as an effective oral antiplatelet agent that can be used as an alternative or in addition to aspirin.20 In the CAPRIE (clopidogrel versus aspirin in patients at risk of ischaemic events) trial, among 19 185 patients with a history of myocardial infarction, stroke, or peripheral arterial disease, treated over 1.9 years, clopidogrel reduced serious vascular events by 8.7% (95% CI, 0.3%–16.5%) compared with aspirin.23 The overall safety profile of clopidogrel was at least as good as that of aspirin.23 The recent CURE trial has also provided evidence that in patients with unstable angina, including those who undergo coronary angioplasty, clopidogrel produces additional benefits when combined with aspirin.24 Therefore clopidogrel is a suitable alternative when aspirin is contraindicated, and should be considered in combination with aspirin for patients who have recurrent cardiac or cerebral ischaemic events while taking aspirin (E2).

Randomised controlled trials have proven that antiplatelet therapy (mainly with aspirin) is effective in reducing the risk of non-fatal myocardial infarction, non-fatal stroke or vascular death among patients with established arterial disease.1 When used for secondary prevention, the benefit from aspirin substantially outweighs possible harm of therapy (E1) (for an explanation of level-of evidence codes, see Box 1). A personalized approach to the decision whether or not to advise aspirin use for primary prevention, factoring an individual’s health risks and personal values, is likely to be optimal .

Although the benefit of aspirin in secondary prevention is well established, its net beneficial effect in persons without known cardiovascular disease is less certain. Recent controlled trials have also indicated a favourable risk–benefit ratio for aspirin in primary prevention among persons who are at higher risk of coronary heart disease (CHD) and who are not at increased risk of bleeding complications (E1).3 An accurate assessment of individual cardiovascular risk is necessary when considering use of aspirin for primary prevention. These effects of aspirin on the development of cancer and subsequent adverse outcomes might alter recommendations for the use of aspirin for primary prevention. Accumulating data suggest aspirin may also have a favorable impact on cancer incidence, metastasis, and mortality. Box 2 outlines definite and possible indications for aspirin prophylaxis based on the current clinical trial evidence. The role of aspirin in the prevention of colorectal cancer (not considering cardiovascular disease) is discussed separately as well. Historically, only the potential cardiovascular benefits of aspirin, including reductions in the rates of cardiovascular death, myocardial infarction, or stroke, have been considered when making decisions about its use for primary prevention.

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