Limitation of myocardial infarct size after primary angioplasty: Is a higher patency the only mechanism?

Background Several studies demonstrate a better outcome after primary angioplasty compared with thrombolysis. The mechanism is assumed to be a higher rate of open infarct–related vessels. Methods And Results We conducted a randomized trial of primary coronary angioplasty compared with thrombolysis. A total of 401 patients with acute myocardial infarction were randomly assigned to either primary angioplasty or thrombolytic therapy. Radionuclide left ventricular ejection fraction was performed before hospital discharge. Infarct size was estimated by measurement of serial lactate dehydrogenase activity (LDH Q72). Separate analyses were performed in patients with an open infarct–related vessel, either after thrombolysis or angioplasty. Baseline characteristics were comparable between the 2 treatment groups. Of the 197 patients treated with angioplasty, 176 (89%) had an open infarct–related vessel compared with 126 (62%) of the 204 patients treated with thrombolysis (P < .001). In patients with an open infarct–related vessel, those treated with primary angioplasty had a lower enzyme release compared with those treated with thrombolysis: LDH Q72 949 (748) and 1200 (1117), respectively (P < .05). Compared with angioplasty, patients treated with thrombolysis had a lower left ventricular ejection fraction. In the subgroup of patients with an open infarct–related vessel, after thrombolysis or angioplasty, patients treated with thrombolysis still had a lower ejection fraction (47% vs 50%, P < .05). Multivariate analysis, adjusting for differences in several clinical variables, did not change these results. Patients with an open infarct–related vessel and thrombolysis had a higher risk of an ejection fraction <40% compared with patients treated with primary angioplasty (relative risk 1.9, 95% confidence interval 1.0 to 2.7). Conclusions Despite successful thrombolysis, with sustained patency of the infarct-related vessel, primary angioplasty remains superior to thrombolytic therapy with regard to left ventricular function and enzymatic infarct size. This may be caused by adverse effects of fibrinolytics on infarcted myocardium. (Am Heart J 1999;137:1169-72.)