EVALUATION BY QUANTITATIVE 99M-TECHNETIUM MIBI SPECT AND ECHOCARDIOGRAPHY OF MYOCARDIAL PERFUSION AND WALL-MOTION ABNORMALITIES IN PATIENTSWITH DOBUTAMINE-INDUCED ST-SEGMENT ELEVATION

ST-segment elevation during exercise testing has been attributed to my ocardial ischemia and wall motion abnormalities (WMA). However, the fu nctional significance of ST-segment elevation during dobutamine stress testing (DST) has not been evaluated in patients referred for diagnos tic evaluation of myocardial ischemia. DST (up to 40 mu g/kg/min) with simultaneous echocardiography and technetium-99m sestamibi single-pho ton emission computed tomography (SPECT) was performed in 229 consecut ive patients with suspected myocardial ischemia who were unable to per form an adequate exercise test; 127 (55%) had a previous acute myocard ial infarction (AMI). ST elevation was defined as greater than or equa l to 1 mm new or additional J point elevations with a horizontal or up sloping ST segment lasting 80 ms. Reversible perfusion defects on SPEC T and new or worsening WMA during stress on echocardiography were cons idered diagnostic of ischemia. ST elevation occurred in 40 patients (1 7%) during the test; 34 of them (85%) had previous AMI. All patients w ith ST-segment elevation had abnormal scintigrams (fixed or reversible defects, or both) and abnormal wall motion (fixed or transient defect s, or both) at peak stress. In patients who had ST elevation and no pr evious AMI (n = 6), ischemia was detected in all by echocardiography a nd in 5 (83%) by SPECT. In patients with previous AMI, the prevalence of ischemia was not different with or without ST elevation (53% vs 43% by echocardiography and 53% vs 48% by SPECT, respectively). Baseline regional wall motion score in the infarct zone was higher in patients with ST elevation. In conclusion, myocardial perfusion defects and WMA at peak stress are a hallmark in patients with ST-segment elevation d uring DST. However, ST-segment elevation is a specific marker of ische mia only in patients without previous AMI.