[Effects of ticlopidine on platelet function at rest and after exercise in patients with previous myocardial infarct. An acute crossover double-blind study].

The effects of Ticlopidine on platelet function at rest and after exercise test in 12 patients with a history of myocardial infarction but no risk factors and/or residual angina, were investigated. The patients were treated with 500 mg per diem Ticlopidine or placebo for 15 days in a crossover double-blind study. Blood samples were taken before and 3 minutes after maximum effort exercise cycle tests. Blood samples from 25 healthy volunteers of comparable age and sex were used for control purposes. The parameters examined were: platelet aggregation induced by ADP (1 and 3 mumol/l), Arachidonic Acid (AA) (1.3 mmol/l) and collagen (2 micrograms/ml); the presence of circulating platelet aggregates and plasmatic fibrinogen levels. When compared with the controls, the patients showed higher levels of aggregation caused by ADP, AA and collagen as well as circulating aggregates. Exercise produced a statistically significant increase in platelet activation, while Ticlopidine significantly inhibited the platelet aggregation induced by ADP, AA and collagen as well as circulating aggregates both at rest and after the exercise test. Fibrinogen levels were higher in the heart attack patients than the controls especially after exercise, but not to a statistically significant degree. Treatment with Ticlopidine did not influence plasma fibrinogen levels. It is not known whether the patients with signs of effort-induced platelet aggregation run a higher risk of ischaemic cardiopathy or whether drug treatment could prevent this eventuality.