Positron emission tomography detects evidence of viability in rest technetium-99m sestamibi defects.
OBJECTIVE
The purpose of this study was to determine the relative value of single-photon emission computed tomographic (SPECT) imaging at rest using technetium-99m methoxyisobutyl isonitrile (technetium-99m sestamibi) with positron emission tomography for detection of viable myocardium.


BACKGROUND
Recent studies comparing positron emission tomography and thallium-201 reinjection with rest technetium-99m sestamibi imaging have suggested that the latter technique underestimates myocardial viability.


METHODS
Twenty patients with a previous myocardial infarction underwent rest technetium-99m sestamibi imaging and positron emission tomography using fluorine (F)-18 deoxyglucose and nitrogen (N)-13 ammonia. In each patient, circumferential profile analysis was used to determine technetium-99m sestamibi, F-18 deoxyglucose and N-13 ammonia activity (expressed as percent of peak activity) in nine cardiac segments and in the perfusion defect defined by the area having technetium-99m sestamibi activity < 60%. Technetium-99m sestamibi defects were graded as moderate (50% to 59% of peak activity) and severe (< 50% of peak activity). Estimates of perfusion defect size were compared between technetium-99m sestamibi and N-13 ammonia.


RESULTS
Sixteen (53%) of 30 segments with moderate defects and 16 (47%) of 34 segments with severe defects had > or = 60% F-18 deoxyglucose activity considered indicative of viability. Fluorine-18 deoxyglucose evidence of viability was still present in 50% of segments with technetium-99m sestamibi activity < 40%. There was no significant difference in the mean (+/- SD) technetium-99m sestamibi activity in segments with viable (40 +/- 7%) and nonviable segments (49 +/- 7%, p = 0.84). Of the 18 patients who had adequate F-18 deoxyglucose studies, the area of the technetium-99m sestamibi defect was viable in 5 (28%). In 16 patients (80%), perfusion defect size determined by technetium-99m sestamibi exceeded that measured by N-13 ammonia. The difference in defect size between technetium-99m sestamibi and N-13 ammonia was significantly greater in patients with viable (21 +/- 9%) versus nonviable segments (7 +/- 9%, p = 0.007).


CONCLUSIONS
Moderate and severe rest technetium-99m sestamibi defects frequently have metabolic evidence of viability. Technetium-99m sestamibi SPECT yields larger perfusion defects than does N-13 ammonia positron emission tomography when the same threshold values are used.
Sawada
S G
SG
Department of Internal Medicine, University of Michigan, Ann Arbor.
Allman
K C
KC
Muzik
O
O
Beanlands
R S
RS
Wolfe
E R
ER
Gross
M
M
Fig
L
L
Schwaiger
M
M
D000328:Adult; D000368:Aged; D002470:Cell Survival; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology; D011237:Predictive Value of Tests; D017256:Technetium Tc 99m Sestamibi; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon
D017256:Technetium Tc 99m Sestamibi