The influence of combined treatment with propranolol and acetylsalicylic acid on platelet aggregation in coronary heart disease.

Antiaggregating agents are frequently prescribed alone or together with β-adrenergic receptor blocking agents in patients after myocardial infarction. The present study was designed to examine the effects of combined treatment with propranolol and acetylsalicylic acid (ASA) on platelet aggregability. Spontaneous platelet aggregation and aggregation induced by fibrinogen and adrenaline were studied in a group of patients with coronary heart disease before treatment, after treatment with propranolol (0.75-1.0 mg/kg daily), and after combined treatment with propranolol in same dose and ASA (20-25 mg/kg daily). Twenty-one patients with stable angina pectoris and/or after myocardial infarction and twelve healthy men were included in the study. There were no significant differences in both spontaneous and induced platelet aggregation between patient and control group before treatment. Propranolol influenced fibrinogen-induced aggregation: it lowered maximal amplitude of aggregation ( < 0.05), but it did not change the reaction time. ASA in combination with propranolol affected both spontaneous and induced aggregation: it diminished the number of pathological spontaneous aggregations ( < 0.025), it inhibited the second wave of adrenaline-induced aggregation ( < 0.01), prolonged the reaction time of fibrinogen-induced aggregation ( < 0.01) and lowered the maximal amplitude of aggregation ( < 0.05). The study showed that propranolol besides its well-known hemodynamic effects had an additional antiaggregating property. The action of combined treatment with propranolol and ASA on platelet aggregation is probably additive.