Production of circulating platelet aggregates by exercise in coronary patients.

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Abstract
To determine the effect of exercise on the in vivo formation of circulating platelet aggregates in patients with severe coronary artery disease (CAD), platelet aggregate ratios (PAR) (normal 0.8-1.1) were measured immediately before and after treadmill exercise and 30 min after exercise in 17 CAD patients (group 1, mean age 55 yr), 12 age-matched normal subjects (group 2) and 13 young normals (mean age 27 yr, group 3). Coronary patients had lower resting PAR than group 3 (0.79 .+-. 0.05 vs. 0.98 .+-. 0.03; P < 0.01), while group 2 had an intermediate value 0.86 .+-. 0.04 (P > 0.05 vs. CAD and group 3). Immediately after exercise, group 1 PAR declined from 0.79 .+-. 0.05 to 0.53 .+-. 0.04 (P < 0.001), while groups 2 and 3 were unchanged (P > 0.05; both P < 0.001 vs. group 1); 30 min after exercise, PAR in group 1 rose to 0.66 .+-. 0.05 (P < 0.05 vs. pre- and immediately postexercise); groups 2 and 3 remained unchanged vs. pre- and immediately postexercise (P > 0.05; both P < 0.001 vs. group 1). Six group 1 patients received 1300 mg aspirin daily for 10 days and repeated the protocol. Resting PAR were unchanged (P > 0.05) from resting values without aspirin. The exercise-induced decline in PAR was attenuated by aspirin: without aspirin, 0.73 .+-. 0.02 preexercise to 0.54 .+-. 0.04 postexercise; with aspirin, 0.73 .+-. 0.03 to 0.82 .+-. 0.03 (P < 0.05 vs. no aspirin). Platelet aggregation evidently occurs with exercise in CAD. Aspirin evidently exerts a significant inhibitory effect on exercise-induced platelet aggregation in CAD patients.