The aim of this study was to compare treadmill exercise (TEX) and dipyridamole stress on the uptake and retention of N-13 ammonia.
Background
Size and severity of stress-induced myocardial perfusion defects are clinically important. Because ammonia uptake and retention seems to be related to perfusion, viability, and metabolism, exercise stress might induce larger perfusion defects than dipyridamole stress.
Methods
Twenty-six patients underwent TEX and dipyridamole stress N-13 ammonia positron emission tomography (PET). Images were assessed with a 17-segment model and a five-point score. Summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated. Left ventricular (LV) defect sizes were measured quantitatively with a 70% threshold for abnormal perfusion.
Results
Compared with dipyridamole stress, TEX yielded larger SSS (9.1 ± 5.7 vs. 6.9 ± 5.9; p < 0.01), SDS (5.8 ± 4.7 vs. 3.7 ± 4.6; p < 0.02), and percentage of LV stress defect (19.3 ± 11.5% vs. 13.8 ± 13.6%; p < 0.02).
Conclusions
In patients achieving adequate exercise, TEX N-13 ammonia PET myocardial perfusion imaging (MPI) yields larger stress perfusion defects than dipyridamole stress and might reflect the true myocardial ischemic burden. Treadmill exercise might be the preferred method of stress for routine N-13 ammonia PET MPI.
Abbreviations and Acronyms
CAD
coronary artery disease
LV
left ventricle/ventricular
MPI
myocardial perfusion imaging
PET
positron emission tomography
SDS
summed difference score
SPECT
single-photon emission tomography
SRS
summed rest score
SSS
summed stress score
TEX
treadmill exercise
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This research was supported in part by the Ontario Research and Development Challenge Fund (#00-May-0710) for the Ontario Consortium of Cardiac Imaging.