Objectives: The ST segment monitoring substudy of the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) trial compared the speed and stability of ST segment recovery among four thrombolytic strategies for acute myocardial infarction.
Background: Rapid resolution of ST segment elevation has been suggested as a noninvasive marker of infarct-related artery patency. We expected that patients treated with accelerated recombinant tissue-type plasminogen activator (rt-PA) would show a quicker recovery than that of other patients but that those treated with streptokinase would show greater stability of recovery.
Methods: ST segment monitoring was initiated in 1,067 patients within 30 min of the start of thrombolysis and continued for > 18 h with the use of a three-channel continuous vectorcardiographic monitor, a 12-lead continuous electrocardiographic (ECG) monitor or a three-channel (V2, V5, aVF) Holter ambulatory ECG monitor.
Results: Time to 50% recovery could be assessed in 618 patients and was similar in the four treatment groups: median 45 min with streptokinase/subcutaneous heparin, 45 min with streptokinse/intravenous heparin, 42 min with accelerated rt-PA and 47 min with combination therapy (p = 0.7). No significant difference among the thrombolytic regimens was shown with the three monitors used. Time to initiation of ST segment analysis was directly related to time to 50% recovery (p = 0.0001) and was its best predictor in a multiple regression model. ST segment elevation recurred equally in each treatment group (approximately 36%, p = 0.9) but was significantly more common in patients with a patent infarct-related artery (p = 0.033) or a low ejection fraction (p = 0.001).
Conclusions: The greater 90-min patency seen with accelerated rt-PA in the angiographic substudy did not correlate with a shorter time to 50% ST segment recovery, possibly because of technical limitations and study design. The similar rates of recurrent ischemia (as assessed by ST elevation) among the regimens support the similar infarction and reocclusion rates seen in the main trial and angiographic substudy.