PET-CT Identifies Ruptured and High-Risk Coronary Plaque

Scientists have discovered that the tracer ¹⁸F-sodium fluoride (¹⁸F-NaF) used with positron emission tomography-computed tomography (PET-CT) imaging technology is the first noninvasive imaging modality to identify and localize ruptured and high-risk coronary plaque.

The University of Edinburgh (Scotland, UK) is leading the heart disease study with the help of a Biograph mCT PET-CT system developed by Siemens Healthcare (Erlangen, Germany). The new study’s findings were published October 2013 in the Lancet. Currently there is no noninvasive way of finding high-risk plaques at risk of rupturing and causing a heart attack. The imaging technology is providing new clues into clinical research into early diagnosis of the disorder.

In the prospective clinical trial, patients with myocardial infarction and stable angina underwent ¹⁸F-NaF and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET-CT and invasive coronary angiography. ¹⁸F-NaF uptake was compared with histology in carotid endarterectomy specimens from patients with symptomatic carotid disease, and with intravascular ultrasound in patients with stable angina. The primary endpoint was the comparison of ¹⁸F-fluoride tissue-to-background ratios of culprit and non-culprit coronary plaques of patients with acute myocardial infarction.

In 93% (37) of patients with myocardial infarction, the highest coronary ¹⁸F-NaF uptake was seen in the culprit plaque. By contrast, coronary ¹⁸F-fluorodeoxyglucose (FDG) uptake was typically concealed by myocardial uptake and where discernible, there were no differences between culprit and non-culprit plaques. Marked ¹⁸F-NaF uptake occurred at the site of all carotid plaque ruptures and was linked with histologic evidence of active calcification, macrophage infiltration, apoptosis, and necrosis. Forty-five percent (18) of patients with stable angina had plaques with focal ¹⁸F-NaF uptake that were associated with more high-risk features on intravascular ultrasound than those without uptake.

The plaque areas in the blood vessels were easily identifiable by using the Biograph mCT scanner. In the patients with angina, advanced notice that they had high-risk plaques and a heart attack may be impending. These patients could then be targeted with aggressive therapy to avoid future events.

“Being able to identify dangerous fatty plaques likely to cause a heart attack is something that conventional heart tests can’t do. This research suggests that PET-CT scanning may provide an answer, identifying ‘ticking time bomb’ patients at risk of a heart attack,” said Prof. Peter Weissberg, medical director at the British Heart Foundation (BHF; London, UK). “Nearly 20 years of BHF-funded research has led us to this point. We now need to confirm these findings, and then understand how best to use new tests like this in the clinic to benefit heart patients.”

BHF clinical lecturer and cardiologist Dr. Marc Dweck, who led the research at the University of Edinburgh, stated: “We have developed what we hope is a way to ‘light up’ plaques on the brink of rupturing and causing a heart attack. If we could know how close a person is to having a heart attack, we could step in with medication or surgery before the damage is done. This is a first step towards that goal. The next stage is to confirm these findings in larger studies to establish first that this technique can truly predict heart attacks and secondly that treatment can help patients avoid these events.”

“Siemens Healthcare is delighted that the Biograph mCT is aiding ground-breaking research into the UK’s biggest killer—heart disease,” remarked Lawrence Foulsham, business manager, molecular imaging at Siemens Healthcare. “The condition is a clinical priority for the UK; therefore advancements in this field are incredibly important. We have a long-standing partnership with the Clinical Research Imaging Center at the University of Edinburgh and look forward to assisting them with further clinical research insights into the future.”

The Clinical Research Imaging Center at the University of Edinburgh installed the Biograph mCT in 2010.

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