The spontaneous course of ST-segment elevation (2ZST) in 24 patients with acute anterior myocardial infarction (AMI) was studied by precordial ST-segment mapping, which was recorded at 2-hour intervals during the first 48 hours after admission. Change of 2ST between two registrations was expressed as mV/hr, and was compared with clinical and hemodynamic parameters, course of MB-CK curve, calculated infarct mass and arrhythmias. After an initial rapid increase, there was a decrease of ZST, which reaches a plateau-like curve approximately 12 hours after the onset of chest pain. A second new increase of ZST exceeding a value of 0.6 mV/hr correlates well with extension of necrosis, verified by re-elevation of MB-CK. During the first 2 days, extension of necrosis could be detected in 50% of our patients.
As new ischemic episodes and extension of necrosis in AMI occur frequently and are promptly indicated by an increase of ZST, the physician should, while monitoring therapeutic interventions, concentrate on such a second increase rather than on a decrease of ZST (which may occur spontaneously), as has been suggested in most previous reports