Effects of streptokinase on infarct size in rabbits in the presence and absence of coronary artery recanalization.

Despite variable efficacy in achieving recanalization, different thrombolytic agents demonstrate similar abilities to reduce mortality following myocardial infarction. We investigated whether factors other than the ability to achieve coronary artery recanalization are important in mediating the beneficial effects associated with thrombolytic therapy during acute myocardial infarction using anaesthetized rabbits. Coronary artery occlusion was produced using either a single ligature (which was released to initiate reperfusion) or by placing two ligatures 5 mm apart to allow the formation of an intraluminal thrombus. In this case, ligature removal followed by thrombolysis was required for recanalization to occur. Experiments were performed in the presence and absence of streptokinase. Streptokinase was most effective in reducing myocardial necrosis when associated with thrombolytic recanalization (total left ventricular infarct size was reduced from 37 +/- 7% to 13 +/- 1%, P < 0.01). However, streptokinase also reduced infarct size in the absence of reperfusion (45 +/- 4% vs 35 +/- 2%, P < 0.05), although further work is needed to clarify the mechanisms.