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

Background several studies demonstrate a better outcome after primary angio plasty 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 ang ioplasty compared with thrombolysis. A total of 401 patients with acute myo cardial infarction were randomly assigned to either primary angioplasty or thrombolytic therapy. Radionuclide left ventricular ejection fraction was p erformed before hospital discharge. Infarct size was estimated by measureme nt of serial lactate dehydrogenase activity (LDH Q72). separate analyses we re performed in patients with an open infarct-related vessel, either after thrombolysis or angioplasty. Baseline characteristics were comparable betwe en the 2 treatment groups. Of the 197 patients treated with angioplasty, 17 6 (89%) had an open infarct-related vessel compared with 126 (62%) of the 2 04 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, pa tients treated with thrombolysis had a lower left ventricular ejection frac tion. In the subgroup of patients with an open infarct-related vessel, afte r thrombolysis or angioplasty, patients treated with thrombolysis still had a lower ejection fraction (47% vs 50%, P < .05). Multivariate analysis, ad justing 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 potency of the infarct-related vessel, primary angioplasty remains superior to thrombolyti c therapy with regard to left ventricular function and enzymatic infarct si ze. This may be caused by adverse effects of fibrinolytics on infarcted myo cardium.