Significance of ST-segment elevation during dobutamine-stress echocardiography in patients with acute myocardial infarction treated with thrombolysis.

Abstract

Stress-induced ST-segment elevation in patients with recent myocardial infarction treated with thrombolysis has not been extensively investigated. According to the results of previous studies it may represent residual myocardial ischaemia or dyskinesia in the infarcted region. The aim of the study was to analyse the significance of dobutamine-induced ST-segment elevation in the infarcted area in a consecutive group of patients (n = 42, 41 men, mean age 53 +/- 7 years) with a first acute myocardial infarction treated with thrombolysis within 6 h from symptoms onset. All patients underwent dobutamine-stress echocardiography (up to 40 micrograms.kg-1.min-1 + atropine) 7 +/- 3 days from the acute event and coronary arteriography within 1 month from the test. Significant ST-segment elevation was defined as a shift > or = 1 mm during dobutamine compared to baseline in at least two contiguous infarct-related leads; a correlation was made between the site of ST-segment elevation and wall motion changes during dobutamine. Dobutamine-induced ST-segment elevation in 23/42 (55%) patients (group 1) while no changes were observed in 19/23 (45%) patients (group 2). Compared to group 2, group 1 patients showed a higher asynergy score index (1.72 +/- 0.24 vs 1.50 +/- 0.32, P < 0.02) and a higher number of asynergic segments (5.04 +/- 1.9 vs 4.11 +/- 1.8), at baseline, a higher incidence of baseline and/or stress-induced dyskinesia (39 vs 10%, P < 0.05) in the infarct-related region and a higher percentage of occluded infarct-related arteries (48 vs 0%, P < 0.001). In the 42 patients studied, a significant correlation was found between baseline ST-segment elevation and baseline asynergy score index (RS = 0.56, P < 0.001) and between ST-segment elevation and asynergy score index at peak stress (RS = 0.55, P < 0.001). The incidence of reversible wall motion abnormalities indicative of myocardial viability and residual myocardial ischaemia was similar in the two groups (87 vs 84% and 74 vs 68%, respectively), while the number of segments with irreversible akinesia indicative of myocardial necrosis was higher in group 1 compared to group 2 (1.5 +/- 1.4 vs 0.9 +/- 1.4). Among the 23 patients of group 1 with dobutamine-induced ST-segment elevation, six had no reversible wall motion abnormalities indicative of myocardial ischaemia; of the 17 patients with myocardial ischaemia, 11 had > or = 50% and six had < or = 50% of basally asynergic segments showing reversible wall motion abnormalities. In patients with recent thrombolyzed myocardial infarction dobutamine-induced ST-segment elevation is associated with a larger akinetic area in basal conditions and either with reversible wall motion abnormalities indicative of myocardial ischaemia or with irreversible or minimally reversible wall motion abnormalities in the infarct area during the test. Thus, dobutamine echocardiography provides useful information for the interpretation of stress-induced ST-segment elevation and clinical management of these patients.