PLATELET FUNCTION ASSOCIATED WITH EXERCISE INDUCED MYOCARDIAL ISCHAEMIA: MODIFICATION BY COMBINED BETA-BL0CKER AND CALCIUM ENTRY BLOCKER THERAPY

Abstract

The relationship between platelet activation and exercise induced myocardial ischaemia is controversial, and the presence of measurable effects of anti-anginal drugs on platelet function requires further clarification. This study addresses these questions in patients with coronary artery disease (CAD), treated with metoprolol and nifedipine. Twenty seven clinically stable males aged 35 to 69 years (mean 53) with proven CAD, ceased all medications for 5 days, were maximally exercised on a treadmill, and then commenced treatment for 4 weeks. They were exercised to the same workload on treatment and again without drugs one week later. Blood samples were collected immediately before and after exercise in each of the three tests, to measure serum thromboxane B2 (TXB2). Myocardial ischaemia was assessed by ST segment depression. Statistical analysis was performed on paired and grouped data using the appropriate T-test. Baseline TXB2 levels were significantly lower in patients with exercise induced ischaemia, and this group had a significant increase in TXB2 production after exercise (Table). This increase was inhibited by therapy. .Those with a negative test had higher baseline TXB2 levels which not increase with exercise.It is concluded that myocardial ischaemia is associated with a lower potential for TXB2 production. It is also associated with an exercise induced increase in TXB2 which is prevented by anti-ischaemic drugs. It is suggested that continuous platelet activation may occur in CAD patients with ischaemia, depleting the potential for TXB2 production.