Background
: It has been well demonstrated that inflammation is strongly associated with ruptured plaques. Invasive angiographic studies have shown that vulnerable plaques tend to be clustered proximally in the coronary arteries. We tested the hypotheses that patients with ACS have a higher overall level of inflammation in their proximal coronary vessels compared to patients with stable coronary disease and that a gradient of inflammatory activity is seen within the coronary vasculature.
Methods
: Twenty-five patients (mean age 57.9 ± 9.8 years, 72% male) who underwent coronary angiography for chest pain were studied. Ten patients underwent PCI for ACS, 5 underwent PCI for chronic stable angina; and 10 with previously placed stents underwent diagnostic cath but did not require additional PCI. 64-slice MDCT angiography was performed (Siemens Sensation) followed by PET imaging (Siemens ECAT HR+) with 13mCi 18-FDG. PET imaging was done 3 hours after FDG injection. Myocardial uptake of FDG was minimized by a dietary intervention and beta blockade. Images were coregistered, SUVs were obtained at the locations of interest, and target to background ratios (T/B) were calculated.
Results
: Inflammation, measured as FDG activity (T/B), in the proximal coronary segments was significantly greater in patients presenting with ACS than with stable coronary disease (2.31 ± 0.62 vs. 1.84 ± 0.53, p = 0.0004). Similarly, aortic root inflammation was significantly greater in ACS patients presenting with ACS than in patients not presenting with ACS (3.61 ± 1.27 vs 2.52 ± 0.68, p = 0.028). A strong correlation was also observed between aortic root and proximal coronary inflammation in all patients (r = 0.76). Finally, a gradient of glycolytic activity (likely due to inflammation) was observed, as the left main T/B were significantly greater than the proximal vessels (2.38 ± 0.59 vs 1.77 ± 0.40, p < 0.001) in all patients.
Conclusion:
This preliminary investigation demonstrates that metabolic activity - a surrogate for inflammation - is higher in patients with ACS and that a gradient of inflammatory activity is seen within the coronary vasculature. With further advances in methodology and technology, coronary PET imaging may prove useful for assessment of risk and response to therapy.
