NONINVASIVE ASSESSMENT OF SPEED AND STABILITY OF INFARCT-RELATED ARTERY REPERFUSION - RESULTS OF THE GUSTO ST SEGMENT MONITORING STUDY

Objectives. The ST segment monitoring substudy of the Global Utilizati on of Streptokinase and Tissue Plasminogen Activator for Occluded Coro nary Arteries (GUSTO-I) trial compared the speed and stability of ST s egment recovery among four thrombolytic strategies for acute myocardia l infarction. Background, Rapid resolution of ST segment elevation has been suggested as a noninvasive marker of infarct-related artery pate ncy. We expected that patients treated with accelerated recombinant ti ssue-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 monitori ng was initiated in 1,067 patients within 30 min of the start of throm bolysis and continued for >18 h with the use of a three-channel contin uous vectorcardiographic monitor, a 12-lead continuous electrocardiogr aphic (ECG) monitor or a three-channel (V-2, V-5, aVF) Holter ambulato ry 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 streptokinase/int ravenous heparin, 42 min with accelerated rt-PA and 47 min with combin ation therapy (p = 0.7). No significant difference among the thromboly tic regimens was shown with the three monitors used. Time to initiatio n 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 (simil ar to 36%, p = 0.9) but was significantly more common in patients,vith a patent infarct-related artery (p = 0.033) or a low ejection fractio n (p = 0.001). Conclusions. The greater 90-min patency seen with accel erated rt-PA in the angiographic substudy did not correlate with a sho rter time to 50% ST segment recovery, possibly because of technical li mitations and study design. The similar rates of recurrent ischemia (a s assessed by ST elevation) among the regimens support the similar inf arction and reocclusion rates seen in the main trial and angiographic substudy.