Variability of acute ST-segment predicted myocardial infarct size in the absence of thrombolytic therapy☆

Abstract The consistency of the predictions using the formulas of Aldrich et al 1 is dependent on the stability of the ST-segment deviations. In the present study, it was determined that 2 3 of patients were in a period of ST-segment stability, and 1 3 of patients were in a period of ST-segment lability. The clinical decision regarding reperfusion therapy will typically be made on the basis of the appearance of the initial ECG. Continuous ST-segment monitoring during the time required to administer this therapy should determine whether the individual patient is in the stable majority or the labile minority. In a study by Hackett et al 7 of 38 patients with acute pain and ST-segment elevation, 8 had documented ST-segment lability before thrombolytic therapy. Because such transient episodes cannot be determined from a single ECG, continuous ST-segment monitoring should be used until the ST segments remain sufficiently stable for the application of the formulas. A further study is required to identify the length of ST monitoring time required to determine the stability of ST-segment deviation in individual patients.