Effects of different thrombolytic agents on blood rheology in acute myocardial infarction

In 89 patients with acute myocardial infarction, the time course and extent of changes in whole-blood viscosity at 115 sec⁻¹ and 5.75 sec⁻¹, plasma viscosity, erythrocyte aggregation and fibrinogen concentration were measured during the first week. 71 patients received thrombolytic therapy: 1.5 MU of streptokinase (n=20), 2 MU of urokinase (n=25), 30 mg of APSAC (n=26). The remaining 18 patients received placebo. Thrombolytic treatment led to a reduction in viscosity parameters beginning after 3 h and lasting for 24 to 48 hours. A comparison of the different drugs revealed that the effects of APSAC are most pronounced and last longer (up to 72 h), whereas viscosity changes induced by urokinase - most probably dose-dependent - are only moderate. In contrast, with placebo, blood viscosity and fibrinogen increase continuously until day 7. We conclude that reduced blood viscosity may improve microcirculation in the infarcted area and thus play a protective role in acute myocardial infarction. It seems to be necessary to include blood rheology in the assessment of thrombolytic agents, since differences in the efficacy of the different drugs with respect to blood rheology may be of importance.