Abstract
BACKGROUND: There has been a disproportionate increase in the rate of extreme obesity (EO), defined as BMI 40 kg/m, in North America in recent decades. The optimal myocardial perfusion imaging modality for the diagnosis of coronary artery disease (CAD) in EO patients has not been determined. This study evaluated the performance of Technetium-99m (Tc-99m) single photon emission computed tomography (SPECT) and rubidium-82 (Rb-82) positron emission tomography (PET) in patients with EO. METHODS: Weretrospectively identified all patientswith aBMI 40 kg/m who underwent angiography for evaluation of CAD in our centre between January 2007 and August 2010 and had been evaluated by either SPECT or PET within the previous six months.A cohort ofEOpatientswith a 50% and >70% as cutoffs. RESULTS: 108 patients who underwent Tc-99m SPECT (N 1⁄4 57, mean age 52.6 10.9, mean BMI 46.4 6.5) and Rb-82 PET (N1⁄4 51, mean age 50.0 11.4, mean BMI 45.6 5.0) were identified. 42/57 (73.7%) of SPECT studies used a two day protocol allowing a larger Tc-99m dose for better image quality. There were similar rates of angiographic multivessel disease (SPECT 15.8%, PET 15.7%) and left main coronary artery disease (SPECT 3.5%, PET 2.0%). Scan interpretation was classified as definitely normal or abnormal in 92.2% of PET and 66.7% of SPECT scans respectively (P 1⁄4 0.002). Using cutoffs of 50% and 70%, there were no significant differences in sensitivity, specificity, or diagnostic accuracy between the two modalities. At the 50% stenosis cutoff, there were trends towards increased specificity (SPECT 59.0% vs. PET 78.4%, P 1⁄4 0.087) and diagnostic accuracy (SPECT 61.4% and PET 78.4%, P 1⁄4 0.063) with PET. PET also demonstrated greater sensitivity in the detection of multivessel or left main coronary artery disease (SPECT 50% vs. PET 100%, P 1⁄4 0.036). CONCLUSIONS: InpatientswithEO,PETenabledmoredefinitive scan interpretation and providedhigher sensitivity in the detection ofmultivessel or leftmain coronary artery disease in comparison to SPECT. There was a trend towards increased specificity and diagnostic accuracy for PETrelative to SPECT.Basedon this data, PET may have added value in patients with EO.
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