All but which of the following statements about aspirin (ace

All but which of the following statements about aspirin (acetylsalicylic acid) are true?

A. Aspirin acts by irreversibly inhibiting cyclooxygenase (COX).
B. Aspirin reduces mortality in patients with unstable angina and myocardial infarction.
C. Aspirin reduces morbidity and mortality in patients who have had a stroke.
D. Aspirin is first-line therapy in elderly patients (over 65 years of age) with atrial fibrillation.
E. There is evidence for primary prevention of death and myocardial infarction in patients with risk factors for coronary artery disease.

The answer is D.

Aspirin acts by irreversibly inhibiting cyclooxygenase activity in platelets. This prevents thromboxane synthesis and impairs platelet secretion and aggregation. The effects peak at 1 h and last for the duration of the platelets' life span: approximately 1 week. Toxicities include gastrointestinal discomfort, blood loss, and systemic bleeding. Aspirin has a number of convincing indications. It has been shown to reduce morbidity and mortality in patients with acute myocardial infarction (MI), unstable angina, transient ischemic attacks, and stroke. It prevents recurrent cardiovascular events (secondary prevention) in patients with a history of MI or stroke. In patients older than 50 years who have risk factors for coronary heart disease, there is evidence for a primary prevention benefit with aspirin. The risk of thrombosis in patients with atrial fibrillation increases with age, prior events, risk factors for coronary heart disease, and LEFT ventricular dysfunction. Aspirin is indicated in patients with atrial fibrillation who are younger than 65 years of age and have no structural heart disease. In these patients the yearly stroke risk is less than 1%. However, in elderly patients warfarin provides significant risk reduction and should be considered the first-line treatment.