Relationship of the lytic state to successful reperfusion with standard- and low-dose intracoronary streptokinase.

The influence of a systemic lytic state on reperfusion obtained after intracoronary streptokinase (SK) therapy has been evaluated in 15 patients with acute myocardial infarction and complete coronary occlusion. Coronary angiographic studies and measurements of blood fibrinolytic parameters were repeated at 15 min intervals during the infusion of a standard dose of SK and were compared with the results with approximately one-tenth the standard dose. Successful reperfusion was obtained in only 20% (2/10) of patients receiving the low dose, compared with a 75% to 80% success rate in patients receiving the standard dose as initial treatment (4/5) or as follow-up treatment of patients in whom low-dose therapy failed (6/8). There was a striking association between reperfusion and development of the lytic state in that all 12 treatments resulting in reperfusion also caused a lytic state and all seven treatments that failed to produce a lytic state also failed to induce reperfusion (p less than .001). Among the successfully treated patients, the dose of SK that induced a lytic state was relatively constant. However, coronary arterial thrombi differed in susceptibility to treatment. Sensitive thrombi (5/12) dissolved before the lytic state occurred and at a lower SK dose than that needed to cause a lytic state; more resistant thrombi (7/12) required a longer time and a significantly larger SK dose to dissolve. These results indicate that intrinsic properties of the thrombus influence the rate and outcome of treatment and that a minimal dose of SK (about 200,000 U) is required to ensure lasting reperfusion in susceptible patients.(ABSTRACT TRUNCATED AT 250 WORDS)