JNM: FDG-PET shows vascular inflammation in healthy people

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Using FDG-PET, researchers found increased vascular inflammation in healthy individuals without hyperlipidemia but with elevated high-sensitivity C-reactive protein. However, what it means prognostically still needs to be determined, according to a study in this month's Journal of Nuclear Medicine.

Because catheter angiography does not provide information about plaque inflammation and vulnerability, researchers said that "new imaging techniques that can demonstrate the dynamic biologic activity within atherosclerotic plaques are critically needed for further risk stratification and early prevention of acute cardiovascular events."

Hye Jin Yoo, MD, from the Korea University College of Medicine in Seoul, South Korea, and colleagues had previously shown that patients with impaired glucose tolerance or type 2 diabetes had higher uptake of FDG-PET, representing inflammation, compared with healthy subjects.

In this study, they chose to examine the association of vascular inflammation in the carotid arterial wall of healthy subjects stratified by levels of high-sensitivity C-reactive protein (hsCRP) and low-density lipoprotein cholesterol (LDL-C).

They enlisted 120 healthy subjects to undergo FDG-PET imaging and used the target-to-background ratio (TBR) as a measure of inflammation.

Researchers found that subjects with high levels of hsCRP ( > 2 mg/L) and low levels of LDL-C ( <130 mg/dL) had a significantly higher TBR than those with low hsCRP and low LDL-C levels or low hsCRP and high LDL-C levels.

These results persisted even though there were no significant differences in patients' carotid intima-media thickness.

The maximum TBR values had the strongest positive correlation with hsCRP level among the various cardiovascular risk factors. However, other emerging inflammatory markers such as lipoprotein-associated phospholipase A2 or monocyte chemoattractant protein-1 were not coherently associated with TBR values.

Multiple stepwise regression analyses showed that hsCRP and diastolic blood pressure were independent decisive factors for maximum TBR, whereas age, diastolic blood pressure and LDL-C were factors that determined the maximum intima-media thickness.

"Although LDL-C is the basis of current guidelines for risk stratification of cardiovascular disease (CVD), approximately 40 percent of deaths from CVD occur in patients with low cholesterol levels," the researchers wrote. "Therefore, there has been growing interest in novel biomarkers that can provide information about the unexplained portion of cardiovascular risk in the conventional risk stratification system. hsCRP is a representative inflammatory biomarker that independently predicts future cardiovascular events and can enhance risk stratification, regardless of the LDL-C level."

They concluded that in healthy individuals, vascular inflammation—as measured by FDG-PET—was increased in those with elevated hsCRP but no hyperlipidemia. However, they called for further studies to "determine the clinical roles of FDG-PET and hsCRP in prognostic and therapeutic implications for cardiovascular events."