Does aspirin attenuate the effect of angiotensin-converting enzyme inhibitors in hypertension or heart failure?

There is a wealth of data that suggests an important interaction between aspirin and angiotensin-converting enzyme inhibitors in patients with chronic stable cardiovascular disease. The interaction is less obvious in the postinfarction setting, possibly reflecting the fact that many patients stop their aspirin therapy within a few months of such an event. An interaction is biologically plausible, because there is considerable evidence that angiotensin-converting enzyme inhibitors exert important effects through increasing the production of vasodilator prostaglandins, whereas aspirin blocks their production through inhibition of cyclooxygenase, even at low doses. There is some evidence that low-dose aspirin may raise systolic and diastolic blood pressure. There is also considerable evidence that aspirin may entirely neutralize the clinical benefits of angiotensin-converting enzyme inhibitors in patients with heart failure. In addition, aspirin may have an adverse effect on outcome in patients with heart failure that is independent of any interaction with angiotensin-converting enzyme inhibitors, possibly by blocking endogenous vasodilator prostaglandin production and enhancing the vasoconstrictor potential of endothelin. The evidence is not sufficient to justify advising long-term aspirin therapy for patients with cardiovascular disease in general, and for those with heart failure in particular. Thus, the lack of evidence of benefit with aspirin in patients with heart failure and coronary disease, along with growing evidence that aspirin is directly harmful in patients with heart failure and that aspirin may negate the benefits of angiotensin-converting enzyme inhibitors suggest that, unless there is an opportunity to randomize the patient into a study of antithrombotic strategies, then aspirin should be withdrawn or possibly substituted with an anticoagulant or an antiplatelet agent that does not block cyclooxygenase. In contrast, there is fairly robust evidence for a benefit of both aspirin and angiotensin-converting enzyme inhibitors during the first 5 weeks after a myocardial infarction, with little evidence of an interaction. The combination of aspirin and angiotensin-converting enzyme inhibitors is warranted during this period, after which discontinuation or substitution of aspirin with another agent should be considered.