Changes in left ventricular function after intracoronary streptokinase infusion in clinically evolving myocardial infarction

Abstract

Left ventricular (LV) contrast cineventriculograms were obrained in 174 patients with evolving acute myocardial infarction (AMI) treated by intracoronary streptokinase (SK) infusion. Ejection fraction (EF) increased slightly, from 52% +/- 13% before admission SK intervention to 58% +/- 13% immediately after early recanalization of the completely obstructed coronary vessel (p less than 0.0005, n = 68), while local wall motion usually improved. Immediately improved LV function appears to be the result of early reperfusion and/or decreased LV afterload. In 55 chronic (long-term follow-up) post-AMI (2 to 4 weeks after successful early SK reperfusion) patients, repeat angiography revealed late reocclusion of the infarct vessel in nine patients. Chronic EF was not significantly different from pre-SK intervention EF in these nine patients with late reocclusion, whereas in the remaining 46 patients with persistent patency, EF increased mildly from 52% +/- 13% (before SK intervention) to 56% +/- 16% (in long-term recanalization) (p less than 0.025). Ventricular loading conditions were not different at pre-SK intervention angiography and chronic angiography. EF rose modestly from 51% +/- 14% to 57% +/- 18% in the 23 patients recanalized on follow-up, in whom pre-SK intervention angiography revealed collaterals to the infarcting area (p less than 0.025), whereas there was no EF change in the 23 chronically recanalized patients without pre-SK collaterals. In the eight patients recanalized at late follow-up, who had preadmission chest pain for less than 3 hours and successful SK reperfusion within 4 hours of symptom onset (group A), EF increased significantly from 51% +/- 12% to 65% +/- 6% (p less than 0.025). In the 25 chronically recanalized patients admitted 3 to 6 hours after onset of chest pain, in whom SK reperfusion was successful (group B), EF was unchanged at late study. In the 13 chronically recanalized patients with preadmission chest pain lasting longer than 6 hours, in whom SK reperfusion was successful (group C), EF increased from 52% +/- 13% before SK intervention to 56% +/- 16% at late study (p less than 0.025). Pre-SK intervention angiography revealed collateral vessels to the infarct area in 69% of group C patients but in only 42% of patients in groups A and B. These findings suggest that the critical interval for myocardial salvage, as well as for early and long-term improvement of LV function by SK reperfusion at admission, is 4 hours after onset of chest pain in the majority of AMI patients. This time interval may be longer in patients with well-developed collateral supply to the region of the acute infarct.