It is well known that coronary arterial thrombosis plays an important role in the pathogenesis of acute coronary syndrome and this has focused interest on the role of the fibrinolytic system, especially tissue plasminogen activator(t-PA) and plasminogen activator inhibitor-1(PAI-1), which are major determinants of fibrinolytic system. But there are considerable variations in the reported association between these two components and acute coronary syndrome.

To evaluate association between t-PA, PAI-1 and myocardial infarction, plasma level of t-PA and PAI-1 in resting state and after venous occlusion were measured and analysed in patients with previous myocardial infarction at least 6 months after the acute phase, who showed less than 70% luminal narrowing angiographically and control group. The relationship between t-PA, PAI-1 antigen and activity and relation to age, serum triglyceride, cholesterol, and peak creatine kinase(CK) enzyme were also analyzed.

1) In resting state, there was a significant difference of plasma level of both t-PA and PAI-1 antigen, activity between patient and control group(10.72±3.28 vs 8.16±4.03ng/ml, 0.53±0.34 vs 0.02±0.07U/ml, 26.24±8.30 vs 20.82±8.82ng/ml, 14.62±5.97 vs 6.99±6.44U/ml)(p<0.05), and resting plasma level of PAI-1 activity showed a good correlation with peak creatine kinase(CK) enzyme(r=0.76, p<0.01).

2) After venous occlusion, plasma level of t-PA antigen was significantly increased(8.16±4.03 vs 9.87±3.86ng/ml)(p<0.05) whereas t-PA activity and PAI-1 antigen were not significantly changed in control group. In patient group, t-PA antigen, t-PA activity and PAI-1 antigen were significantly inceased after venous occlusion(10.72±3.28 vs 14.66±5.41ng/ml, 0.53±0.34 vs 1.41±1.69U/ml, 26.24±8.30 vs 29.87±8.78ng/ml)(p<0.05). PAI-1 activity was significantly decreased after venous occlusion in both groups(6.99±6.44 vs 6.06±5.99U/ml, 14.62±5.97 vs 12.67±6.46U/ml)(p<0.05).

Both fibrinolytic and anti-fibrinolytic systems are augmented in resting and after fibrinolysis stimulation test in patient group. These findings suggested a impairment of fibrinolytic system in patient group and a possibility that both elevated plasma levels of t-PA and PAI-1 may be markers of coronary artery disease.