Dobutamine-induced hypoperfusion without transient wall motion abnormalities: Less severe ischemia or less severe stress?

Objectives. This study sought to compare the clinical characteristics, hemodynamic response and severity of ischemia in patients with coronary artery disease and reversible perfusion defects on dobutamine 2-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography (SPECT) with or without transient wall motion abnormalities. Background. The occurrence of reversible perfusion defects without concomitant wall motion abnormalities in patients with coronary artery disease was attributed to less severe ischemia. However, little data are available to support this observation. Methods. Fifty-four consecutive patients with significant coronary artery disease and reversible perfusion defects on dobutamine (up to 40 mu g/kg body weight per min) MIBI SPECT were studied (mean [+/-SD] age 59 +/- 11 years; 38 men, 16 women). All patients underwent simultaneous echocardiography. The myocardium was divided into six matched segments, and ischemic perfusion score was quantitatively derived in myocardial segments with reversible defects. Results. New or worsening wall motion abnormalities occurred in 40 patients (74%) (group A) and were absent in 14 (26%) (group B), There was no significant difference between the two groups with respect to age, previous myocardial infarction, number of abnormal coronary arteries (1.8 +/- 0.8 vs. 1.6 +/- 0.9), number of reversible perfusion defects (1.6 +/- 0.9 vs, 1.8 +/- 0.7) or ischemic perfusion score (412 +/- 750 vs, 526 +/- 553). Patients in group A had a higher prevalence of male gender (80% vs, 43%, p < 0.01), higher peak systolic blood pressure (147 +/- 30 vs. 127 +/- 31 mm Hg, p < 0.05), higher peak rate-pressure product (19,632 +/- 4,081 vs. 16,939 +/- 4,344, p < 0.01) and a higher prevalence of angina (53% vs. 14%) and ST segment depression (55% vs. 14%) than group B (p < 0.05 for both). Conclusions. In patients with coronary artery disease and ischemia on dobutamine MIBI SPECT, the absence of transient wall motion abnormalities is associated with a similar extent and severity of reversible perfusion defects, a lower stress rate-pressure product and a higher prevalence of female gender than patients with transient wall motion abnormalities. Mechanically silent ischemia should not be regarded as a marker of less severe ischemia on myocardial perfusion scintigraphy.