Aspirin and prevention of myocardial infarction

Targeting the urine and plasma determinants of thromboxane A2 metabolism in detection of aspirin effectiveness

Detection of reduced aspirin effectiveness has gained significant importance since clinical consequences of aspirin resistance were reported. Nevertheless, due to differentiated molecular basis of aspirin resistance, the conflicting choice of referential method for detection of acetylsalicylic acid ineffectiveness has become troublesome. This study, using a rat model of antiplatelet therapy, examines the aptitude of selected TXB2 metabolism-based methods in the detection of acetylsalicylic acid effectiveness. We hypothesized that ex-vivo whole blood spontaneous TXB2 generation assay could be, contrary to basal TXB2 and urine 11-dTXB2, a novel surrogate measure for impaired acetylsalicylic acid-dependent inhibition of thromboxane synthesis. To address this hypothesis, we evaluated the sensitivity of TXB2 generation assay in hirudinized whole blood to detect acetylsalicylic acid-mediated inhibition of cyclooxygenase activity in healthy rats and diabetic rats treated with acetylsalicylic acid. In diabetic and control animals, both acetylsalicylic acid drenches in the dose-independent manner contributed to significant attenuation of basal plasma TXB2 and urinary 11-dTXB2 formation. Urinary concentrations of 11-dTXB2 were, contrary to basal TXB2, significantly higher, regardless of acetylsalicylic acid dose, among all diabetic groups, compared with corresponding control groups. Determination of TXB2 generation in whole blood enabled sensitive detection of dose-related acetylsalicylic acid effect in both groups, as well as increased TXB2 formation in diabetes. We showed for the first time that evaluation of spontaneous generation of TXB2 in hirudinized whole blood enables, contrary to basal plasma TXB2 and urine 11-dTXB2 concentrations, to sensitively determine the acetylsalicylic acid effect in healthy and diabetic subjects.

Rationale for a primary prevention study using low-dose aspirin to prevent coronary and cerebrovascular disease in the elderly

The benefits of prophylactic aspirin therapy to prevent cardiovascular and cerebrovascular disease in asymptomatic individuals remains unclear. The rationale for developing a multicentered, double-blind, placebo-controlled clinical trial to determine whether low-dose aspirin (100 mg daily) prevents cardiovascular and cerebrovascular morbidity and mortality in persons aged 70 years and over with no evidence of pre-existing cardiovascular or cerebrovascular disease is described. Sample size calculations have indicated that 15,000 subjects would be required over a 4-year follow-up period in order to demonstrate a 20% reduction in overall cardiovascular mortality at the 0.01 level with a power of 0.8. Such a large-scale community-based clinical trial has never been conducted in Australia in this age group. Therefore the PACE (prevention by low-dose aspirin of cardiovascular disease in the elderly) pilot study has been developed to test recruitment strategies and methods and ascertaining disease end-points.