Continuous ST-segment monitoring associated with infarct size and left ventricular function in the GUSTO-I trial

BACKGROUND The aim of this study was to evaluate whether in patients with m yocardial infarction, the intensity and duration of myocardial ischemia as measured by continuous ST monitoring ore associated with infarct size and r esidual left ventricular function. Methods and Results The analyses included patients with myocardia infarctio n, receiving thrombolytic therapy, who were enrolled in the electrocardiogr aphic substudy of GUSTO-I, monitored by a vector-derived 12-lead electrocar diographic recording system, and in whom either infarct size (defined as cu mulative release of alpha-hydroxybutyrate dehydrogenase activity per liter of plasma over a 72-hour period [Q(72)]) or left ventricular election fract ion (LVEF) was determined. With the use of linear regression analysis, we i nvestigated the association of various ST-trend characteristics with Q(72) (206 patients) and with LVEF (180 patients). A higher area under the ST tre nd since thrombolysis until 50% ST recovery and a higher area under recurre nt ischemic episodes (ST reelevations) were significantly associated with a higher Q(72), whereas only a higher area under recurrent ischemic episodes was significantly associated with a lower LVEF. These associations remaine d after adjusting for other patient characteristics such as age, sex, infar ct location, and time to treatment. CONCLUSIONS These findings support the physiologic hypothesis that bath the intensity and duration of myocardial ischemia (both reflected by the estim ated areas under the ST-trend curve) determine myocardial damage and thus a re associated with infarct size and election fraction in patients with acut e myocardial infarction who receive thrombolytic therapy.