Detection and location of myocardial infarction using technetium-99m sestamibi imaging at rest

Abstract

Technetium-99m (Tc-99m) sestamibi imaging at rest has been used to detect and localize myocardial infarction. The largest study to date is a cooperative study of 146 patients in 17 institutions. There were 24 normal subjects and 122 patients with documented myocardial infarction based on clinical, enzymatic or electrocardiographic criteria. The presence of segmental myocardial perfusion defects was compared to the presence of a Q wave on the electrocardiogram or wall motion abnormality on gated blood pool scans, performed within 48 hours of the Tc-99m sestamibi study. Of the 122 infarct patients, 118 (97%) showed perfusion abnormalities by Tc-99m sestamibi imaging. A perfusion defect was found in 110 (99%) of 111 patients with a Q wave and a wall motion abnormality, 113 (99%) of 114 patients with a wall motion abnormality and 113 (98%) of 115 patients with a Q wave. Of the 24 normal subjects, 22 (92%) had normal Tc-99m sestamibi images. In 75% of 1,986 segments, both a Tc-99m sestamibi defect and a regional wall motion abnormality on gated blood scans were present. In 11% of segments, wall motion was normal but Tc-99m sestamibi imaging was abnormal; in 14% of segments, wall motion was abnormal and Tc-99m sestamibi images were normal. In the 24 control subjects, 99% of the segments were normal. Thirty-eight patients had coronary angiography. A close relation existed between the coronary anatomy and myocardial Tc-99m sestamibi uptake. All 9 territories supplied by an occluded vessel and poor collaterals had grade 0 uptake (scale 0 to 2: 0 = markedly reduced; 2 = normal). Among totally occluded vessels with good collaterals, 73% had reduced uptake and 27% had normal uptake. In 26 of these patients, the Tc-99m sestamibi uptake was compared to regional wall motion. Overall, wall motion correlated with Tc-99m sestamibi uptake. Abnormal wall motion occurred in 74% of territories with perfusion grade 0, 61% of those with grade 1 uptake and 30% of those scored as grade 2. However, 26% of territories with grade 0 uptake had normal wall motion. Furthermore, of 13 territories with reduced Tc-99m sestamibi uptake, 12 had improved uptake after coronary bypass surgery. These data suggest that resting Tc-99m sestamibi imaging in humans is a reliable means of detecting and localizing myocardial infarction. As a rule, uptake of Tc-99m sestamibi indicates myocardial viability, whereas reduced uptake occurs in nonviable regions. However, some, regions of reduced resting Tc-99m sestamibi uptake may consist of viable but abnormally perfused myocardium.