Can Streptokinase Produce Beneficial Effects Additional to Coronary Recanalization? Quantitative Microvascular Analysis of Critically Injured Reperfused Myocardium

The aim of this study was to evaluate whether streptokinase (SK) may produce beneficial effects at the level of microvascular circulation in addition to coronary recanalization. Twenty mongrel dogs weighing 28.4 ± 4.6 kg were randomized to receive SK (16,000–72,000 U/kg) or 20 ml saline (control) in an open-chest anterior descending artery occlusion (3 h) and reperfusion (2 h) model. Myocardial blood flow was measured by the radioactive microsphere technique and the state of microvascular circulation (red blood cell containing capillary counts and tissue red blood cell content) was evaluated in the infarcted subendocardial zone using computerized image analysis. The percentage (mean ± SE) of cell-containing vessels normalized to nonischemic control areas was 166.5 ± 7.5 in SK-treated infarcts while in untreated control infarcts it was more variable (130.0 ± 15.6%) (2P > 0.1). The red blood cell content of infarcts treated with 2.0 megaunits SK was 3.9 ± 0.6% compared with 6.7 ± 0.9% in untreated control infarcts (2P = 0.029). Plasma viscosity was slightly reduced in SK-treated dogs (2P = 0.05), but no significant changes in blood fibrinogen, hemoglobin, blood flow, and high energy phosphate levels between control and SK-treated infarcts were observed. SK reduces congestion and results in more even reperfusion of the microvasculature in severely ischemic myocardium to which blood flow has been restored. This effect may be beneficial in the salvage and healing of clinical infarctions.