Imaging May Detect Suspicious Coronary Plaque Early

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Imaging May Detect Suspicious Coronary Plaque Early

Researchers from the University of Edinburgh  have discovered that using a noninvasive imaging system may be able to spot coronary atherosclerotic plaques that are at high risk for rupture, potentially allowing for earlier involvement in order to prevent any adverse clinical events.

According to Nikhil Joshi, MD, of the University of Edinburgh in Scotland, and peers, on positron emission tomography (PET) and CT images, there was an increased uptake of the radioactive tracer 18F-sodium fluoride (18F-NaF) in ruptured plaques amongst patients with severe myocardial infarction and in plaques with high-risk features, such as more positive remodeling, increased microcalcification, and larger necrotic cores; among patients with stable angina.

Additionally, in a small sample of ruptured carotid plaques, all displayed increased uptake of18F-NaF, which "was associated with histological evidence of active calcification, macrophage infiltration, apoptosis, and necrosis," they reported online in the journal, The Lancet.

"18F-NaF PET-CT is the first noninvasive imaging method to identify and localize ruptured and high-risk coronary plaque," they wrote, citing that the next phase is to reveal that increased 18F-NaF has the ability to predict adverse clinical events.

"If the results prove confirmatory then this technique has the potential to fundamentally alter the way we treat coronary artery disease: moving us away from the current framework based on lesion severity and ischemia to one focused on plaque metabolism and inflammation. It could, for example, permit the identification of the vulnerable patient with single or multiple high-risk or silently ruptured plaques, providing an opportunity to treat and modify their risk to prevent future adverse cardiovascular events,”the researchers note.

Determining which plaques are at risk for rupture has proven to be a difficult task, and as of today no noninvasive imaging techniques have been  able to circumvent this issue.

In this recent study, Joshi and colleagues assessed atherosclerotic plaques using PET-CT with two different radioactive tracers: 18F-NaF, which has been utilized for the past 3 decades for bone imaging, and 18F-fluorodeoxyglucose (18F-FDG), the current noninvasive gold standard.

The study involved 40 patients with acute MI and 40 with stable angina who received elective invasive coronary angiography. All patients received PET-CT, invasive coronary angiography, CT coronary angiography, and CT calcium scoring.

Moreover, the researchers also examined carotid plaque samples from nine patients undergoing carotid endarterectomy for symptomatic carotid artery disease.

Of the patients with acute MI, 18F-NaF uptake was 34% higher in the culprit ruptured plaque as opposed to nonculprit plaques (P<0.0001). Almost all of the patients (93%) had increased 18F-NaF in their culprit plaque.

A similar difference in uptake between culprit and nonculprit plaques was not apparent when 18F-FDG was introduced and used (P=0.34).

Of the patients with stable angina, 45% had plaques with increased 18F-NaF uptake. From those plaques, msot were non-obstructive on coronary angiography and had more high-risk features on intravascular ultrasound as opposed to plaques without uptake of the tracer.

“These findings suggest that we are close to being able to detect when rupture is about to occur,” Gregory Thomas, MD, MPH, of Long Beach Memorial Medical Center in California, and Réka Haraszti, MD, of the University of Massachusetts Medical School in Worcester, wrote in a separate editorial.

"Just because a plaque at risk for rupture can be identified does not mean that we know what to do with this information. Numerous questions remain and prospective trials are needed to explore the association between areas of high 18F-NaF uptake and the frequency and timing of rupture and whether rupture results in clinical events. Nevertheless, Joshi and colleagues and earlier pioneers have identified a new and hopefully fruitful frontier in nuclear cardiology and atherosclerotic coronary imaging,” they added.


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