Identification of viable myocardium by echocardiography during dobutamine infusion in patients with myocardial infarction after thrombolytic therapy: Comparison with positron emission tomography

Abstract

To assess the presence of viable myocardium salvaged by coronary artery reperfusion, 17 patients with acute anterior myocardial infarction were studied. Each received intravenous thrombolysis within the first 3 h of symptoms and underwent two-dimensional echocardiography before and during dobutamine infusion (10 μg/kg per min) 7 ± 4 days after admission and positron emission tomography 9 ± 5 days after admission. Echocardiography and positron emission tomography were again performed 9 ± 7 months later. Six comparable segments specific for the territory of the left anterior descending artery were selected for comparison of the two techniques. Wall thickening was evaluated by using an echocardiographic score index. Segmental perfusion and glucose uptake were measured and normalized to the peak activity. A ratio of glucose uptake to perfusion was calculated for each segment.Concordant interpretation of the two techniques was found in 79% of affected segments for both acute and follow-up studies. Positron emission tomography revealed the presence of viable myocardium in 11 patients (group 1); perfusion was within normal limits in 5 of these (group 1A). Myocardial thickening improved with dobutamine infusion in these five patients, the echocardiographic score index decreasing from 12 ± 2 at rest to 7.8 ± 1.3 during dobutamine infusion (p = 0.003). Functional recovery was demonstrated in all five patients (follow-up score index 7.4 ± 1.7). Six patients exhibited decreased perfusion but an abnormally high glucose to perfusion ratio (group 1B); their score index improved with dobutamine from 14.8 ± 2.2 to 12 ± 2.1 (p = 0.05), but late functional recovery was found in only one of the six patients (mean follow-up score index in group 1B 16 ± 1.7). In the six remaining patients in whom no viable myocardium was detected with positron emission tomography (group 2), the echocardiographic score index did not change with dobutamine (15 ± 0.9 to 14.7 ± 0.8, p = NS) and there was no functional recovery (follow-up score index 15.5 ± 1.0).Echocardiography during dobutamine infusion is a promising method to unmask viable myocardium in acute myocardial infarction. Early recovery of perfusion in the area at risk is associated with a good functional outcome, whereas a high glucose to perfusion ratio indicates jeopardized myocardium that frequently loses viability.