SUMMARY The spontaneous changes in left ventricular ejection fraction (LVEF) during the first 24 hours of a first transmural infarction were assessed in 34 patients by serial gated cardiac blood pool imaging. Major therapeutic interventions with a view to limit infarct size were not used. Four determinations of LVEF were performed. Study 1 was performed as soon as possible after admission to the hospital. Studies 2 and 3 were performed 2 and 4 hours, respectively, after study 1. Tlwenty-four patients (70%) had study I within 6 hours after the onset of acute chest pain and 10 had it 6-12 hours after the onset of chest pain. Study 4 was performed 24 hours after the onset of chest pain. Compared with study 1, 19 of 34 patients (56%) had spontaneous changes in LVEF in at least one of the subsequent studies, exceeding the expected variability in stable patients. The changes ranged from a 32% increase to 14% absolute decrease. LVEF improved in 11 patients and deteriorated in eight. These spontaneous changes in left ventricular performance indicate that a single assessment of LVEF during the early hours of transmural myocardial infarction may not properly characterize cardiac performance in an individual patient and may not be the most appropriate reference against which to compare subsequent evolution of left ventricular function. These data may have implications for studies of the effects of early therapeutic interventions on LVEF.IN EXPERIMENTAL MODELS of infarction, ischemic myocardium can be salvaged by interventions that improve the balance between myocardial oxygen supply and demand. [1][2][3][4][5][6] However, such clear-cut therapeutic benefit in human myocardial infarction has not been demonstrated.7 -3 One reason for this may be limitations in the techniques suitable for objective documentation of myocardial salvage in man. Recently, radionuclide techniques such as multigated cardiac blood pool imaging have been proposed for noninvasive assessment of global cardiac performance at the patient's bedside, thereby providing functional estimates of myocardial salvage. However, little is known about the spontaneous evolution of left ventricular (LV) performance during the early hours of acute infarction. It is during the first 6-12 hours that interventions probably will have their greatest therapeutic impact. In order for these measurements to be applied to this patient population, their variability during this period must be established. Thus, we performed serial assessment of LV ejection fraction (LVEF) using gated cardiac blood pool imaging during the first 24 hours of acute transmural myocardial infarction in a group of patients in whom major therapeutic interventions were not used. Our All patients underwent bedside serial multigated equilibrium cardiac blood pool imaging studies. Study 1 was performed as soon as possible after arrival in the coronary care unit. Twenty-four (70%) of the 34 patients had the first multigated cardiac blood pool study performed within 6 hours (range 3-6 hours) after the onset o...

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