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Relation between perfusion defects on stress technetium-99m sestamibi SPECT scintigraphy and the location of a
G L Miller1, S D Herman, G V Heller
1Division of Cardiology, Roger Williams Medical Center, Providence, Rhode Island 02908, USA.
Insights
Myocardial perfusion imaging defects correlate with acute myocardial infarction (AMI) but do not always predict its exact location. While most AMIs occur at prior defect sites, a significant number happen in areas without prior SPECT imaging abnormalities.
Area of Science:
- Cardiology
- Nuclear Medicine
- Radiology
Background:
- Stress myocardial perfusion imaging (MPI) identifies perfusion defects correlating with future cardiac events like acute myocardial infarction (AMI).
- The predictive value of MPI for the precise location of subsequent AMIs remains unclear.
Purpose of the Study:
- To investigate whether the location of an acute myocardial infarction (AMI) can be predicted by the location of previous myocardial perfusion defects identified on single-photon emission computed tomographic (SPECT) imaging.
Main Methods:
- Retrospective analysis of 25 patients who experienced AMI after undergoing technetium-99m sestamibi SPECT MPI.
- Correlation of the infarct territory with the location of pre-existing perfusion defects (reversible or fixed) or normal perfusion on prior SPECT scans.
Main Results:
- A prior SPECT perfusion defect was present in 96% of patients who later had an AMI.
- AMIs occurred in territories with reversible defects (56%), fixed defects (12%), and no prior defect (32%).
- Infarction incidence was highest in territories with reversible defects (54%), followed by fixed defects (43%), and territories with no defect (19%) (p=0.011).
Conclusions:
- While prior myocardial perfusion defects, both reversible and fixed, are associated with a higher incidence of AMI, they do not reliably predict the exact location of infarction.
- A substantial proportion of AMIs occur in myocardial territories without evidence of prior perfusion defects on SPECT imaging.
- SPECT abnormalities are markers of significant coronary disease and increased AMI risk but lack precise localization predictive power for infarct location.
Abstract:
Although the presence of perfusion defects on stress myocardial perfusion imaging has been shown to correlate with future cardiac events, including acute myocardial infarction (AMI), it is unknown whether the location of the AMI can be predicted. Therefore, for 25 patients who had an AMI following a stress technetium-99m sestamibi single-photon emission computed tomographic (SPECT) imaging study and whose infarct location could be determined, the territory of infarction was correlated with the location of previous myocardial perfusion defects. A SPECT perfusion defect had been present in 24 patients (96%). The AMI occurred in territories that showed a reversible defect in 14 patients (56%), whereas 3 infarctions (12%) were in territories that revealed a fixed defect, and 8 infarctions (32%) were in territories that had not shown a defect on prior SPECT imaging. Whereas the incidence of infarction in territories with a reversible defect was highest at 14 of 26 (54%), the incidence of infarction in territories with a fixed defect was 3 of 7 (43%), and in territories with no defect was 8 of 42 (19%) (p = 0.011). Neither the time interval between SPECT imaging and infarction, nor the perfusion defect severity, was related to the correlation between perfusion defect and infarct location. Thus, although AMI occurs most often at the site of previous perfusion defects, reversible or fixed, a substantial percentage occur in territories without a perfusion defect. These findings suggest that abnormalities on SPECT perfusion imaging, although they serve as markers of significant coronary disease and increase the likelihood of infarction, do not always predict the exact location of infarction.