ACC: FDG PET a sensitive, specific choice for myocardial imaging

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ATLANTA -- Rob Beanlands, MD, director of the National Cardiac PET Centre and the Molecular Function and Imaging Program at the University of Ottawa Heart Institute, sought to convince physicians that PET FDG is among the best choices in imagining modalities for the assessment of myocardial viability, during an imaging symposium at the 59th annual American College of Cardiology (ACC) conference on March 15.

FDG PET is a simple technique and can be performed on almost any patient, noted Beanlands. “[The modality] can be used if the patient cannot stress, has medical devices or renal failure.”

In addition, FDG PET is associated with a low risk for radiation exposure and an overall low risk of complications. There has been no mortality ever reported for FDG PET imaging, Beanlands said.

Compared to FDG testing 10 to 15 years ago, today the test can be completed in 20 to 30 minutes, as opposed to hours and it can identify high-risk patients, a feature in which Beanlands considered to be one of the most crucial.

“FDG PET detects cell integrity and is very sensitive for viability,” he explained. “It does this by defining cell metabolism and hibernation as opposed to having a focus on scar and contractile reserve.”

Beanlands also explained the process in which FDG undergoes in the body.  “[FDG] goes into the cell alongside glucose, undergoes conversion and becomes trapped in the cell, allowing for the evaluation of normal glucose metabolism as well as the metabolism in viable cells that are ischemic or hibernating. The classic pattern is one of reduced perfusion in the anterior wall with maintained FDG uptake, indicative of myocardial hibernation,” he said.

Citing systematic reviews conducted in the past, Beanlands noted that PET was found to be the most specific test but FDG PET was more sensitive, more so  than MRI and thallium SPECT.

“When you biopsy the myocardium, it is laden with glycogen stores, so it is still actually picking up and storing glucose. Hence, they can attract FDG,” he said.

In addition, when there is viable myocardium found by FDG PET, those patients who do not undergo revascularization are at a significantly increased risk compared to those that do not undergo revascularization. And when there is no viability found with PET, there is no improvement in outcomes with revascularization, Beanlands said.

Citing a recent study that compared the outcomes of patients who underwent FDG PET imaging with those who did not, Beanlands said that a significant beneficial trend was noted in those who underwent FDG PET compared to standard care.  However, guidelines and protocols must be followed, he noted.

Noting that there are newer techniques that can be combined with PET, including CT and CT angiography, Beanlands said, “I think we need to work to integrate the imaging modalities in using all of them to help us address the questions as best we can.”

In terms of what is needed in the future for FDG PET, he cited appropriate patient selection, better standardization and better comparative effectiveness research of this  imaging method to examine the  impact it has on patient outcomes, quality of life and of costs.