Combined PET-CT: A Novel Noninvasive Method for Targeting High-Risk Plaques | CardioSource WorldNews
Journal Wrap | In a prospective clinical trial published recently in Lancet, Joshi et al. examined patients with acute myocardial infarction (AMI; n = 40) and stable angina (n = 40) who underwent invasive coronary angiography, and compared these results with findings from noninvasive imaging (PET-CT using the radioactive tracer 18F-NaF and 18F-FDG). In patients with AMI, 18F-NaF uptake on culprit plaque was compared with the highest uptake in nonculprit vessels and histology in carotid endarterectomy; in patients with stable angina, 18F-NaF uptake was compared to intravascular ultrasound (IVUS) findings between plaques with or without significant uptake. The primary endpoint was the comparison of 18F-fluoride tissue-to-background ratios of culprit and nonculprit coronary plaques in patients with AMI.
The highest coronary uptake by 18F-NaF in AMI patients was observed in culprit lesions in 37 cases (93%), where the median peak tissue-to-background ratio was significantly different between culprit and nonculprit lesions: 1.66 (interquartile range [IQR] 1.40–2.25) vs. 1.24 (IQR 1.06–1.38; p < 0.0001). Using 18F-FDG, however, there was no significant difference observed between culprit and nonculprit lesions, and the 18F-FDG uptake was commonly obscured by myocardial uptake. The investigators observed marked 18F-NaF uptake at the site of all carotid plaque ruptures; this uptake was associated with histological evidence of active calcification, macrophage infiltration, apoptosis, and necrosis.
In patients with stable angina, the highest coronary uptake by 18F-NaF was observed in culprit lesions in 18 cases (45%). Median peak tissue-to-background ratio was 1.90 (IQR 1.61–2.17), and this was associated with more high-risk features on IVUS than those without uptake, including:
- positive remodeling on remodeling index: 1.12 (IQR 1.09–1.19) vs. 1.01 (IQR 0.94–1.06; p = 0.0004)
- microcalcification: 73% vs. 21% (p = 0.002)
- necrotic core: 24.6% (20.5–28.8) vs. 18% (14.0–22.4; p = 0.001)
There was a high rate of agreement between focal uptake and ruptured plaque in patients with AMI, and, in patients with stable angina, lesions were positively associated with high-risk plaque features on IVUS.
"The use of noninvasive imaging to identify ruptured or high-risk coronary atherosclerotic plaques would represent a major clinical advance for prevention and treatment of coronary artery disease," the authors wrote. Results of the current study suggest that combined PET-CT with 18F-NaF represents a novel, noninvasive method to identify culprit plaques.
Joshi NV, Vesey AT, Williams MC, et al. Lancet. 2014;383:705-13.
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