Aspirin decreases fibrinolytic potential during venous occlusion, but not during acute physical activity

It has previously been observed that aspirin diminishes the increase in blood fibrinolytic activity during arm venous occlusion. We studied the duration of this inhibitory effect on fibrinolytic response during 20 minutes arm venous occlusion and its effect on fibrinolytic response during acute physical activity (standardized stress testing on treadmill) in 10 healthy male volunteers. Fibrinolytic activity was measured with euglobulin clot lysis time and fibrin plates before and after both stimuli, and t-PA release estimated as the difference between post- and prestimulation values (fibrinolytic potential: FP). Venous occlusions were performed before aspirin ingestion and then on the first, second, third, and fourth to eighth day after aspirin. Stress testing was carried out on two successive days before and after aspirin ingestion. Aspirin did not affect basal fibrinolytic activity, but significantly decreased FP during occlusion. This effect was sustained for the whole period of observation. To the contrary, aspirin did not influence FP during acute physical activity. The different effect of aspirin on fibrinolytic response during venous occlusion and physical activity suggested that different mechanisms were involved in t-PA release during both stimuli.