FDG PET/CT Imaging for Stroke Risk Stratification in Patients without Atrial Fibrillation

Atrial fibrillation (AF) is a well-known risk factor for ischemic stroke, but it may not be the only one. Atrial cardiomyopathy (AC) might also contribute to stroke, whether in the presence of AF or not. An improved understanding of AC would help with stroke risk stratification, particularly in patients without AF.

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In a recent issue of the Journal of Nuclear Cardiology, a team of researchers at Beijing Chaoyang Hospital explored the potential of atrial ¹⁸F-fluorodeoxyglucose (FDG) imaging with PET/CT for detecting diseased atrial substrate associated with AC. Their study revealed, in a non-AF population, an association between atrial FDG activity and a history of ischemic stroke and AC—suggesting a means of identifying stroke risk in these patients.

In the same issue, Shady Abohashem, MD, Wesam Aldosoky, MD, and Michael T. Osborne, MD, all researchers in the Cardiovascular Imaging Research Center in the Department of Radiology at Massachusetts General Hospital, published an editorial in the Journal of Nuclear Cardiology considering the strengths and limitations of the study.

Below, Dr. Abohashem discusses the study and some of the broader work surrounding it.

Q. What has motivated recent research into additional risk factors for stroke?

Abohashem: Stroke remains a leading cause of death and disability worldwide, with a substantial disease and economic burden. Despite continuous developments, the current risk stratification schemes have resulted in varying treatment recommendations and confusion among clinicians. Hence, improved risk stratification is critical to efficiently identifying high- versus low-risk populations. This, in turn, will shed light on stroke pathogenesis, help reduce unnecessary use of anticoagulation, and ultimately enable the development of effective preventive, diagnostic and prognostic tools.

Q. What is atrial cardiomyopathy? What can it tell us about a patient's risk for stroke?

Abohashem: Atrial cardiomyopathy is a state of atria with abnormal size and function, such as chamber dilation, impaired myocyte function, and fibrosis. AC has been linked to a hypercoagulable state that precipitates thrombus formation and embolic stroke. Despite the established link between AC and atrial fibrillation, AC has been associated with embolic stroke in patients without AF. Approximately 63% of patients with cryptogenic stroke have an increased prevalence of AC markers, which was also present in nearly 45% of patients with embolic stroke of unspecific source (ESUS), suggesting that AC could be an underlying mechanism of ESUS.

Q. What more needs to be done before FDG PET/CT imaging can be implemented clinically for the assessment of stroke risk in patients without AF?

Abohashem: The current study highlights the promise of leveraging FDG PET/CT imaging to assess atrial activity in stroke risk assessment among non-AF patients. However, its clinical implementation necessitates further work. First, validating the current findings in large prospective studies within a diverse population without AF or atherosclerotic disease. Second, evaluating the predictive and prognostic utilities of atrial FDG uptake in ischemic stroke as compared to other imaging parameters and clinical biomarkers and whether adding it to these markers would improve overall stroke risk prediction.

Q. Can you describe your own, related work with PET/CT imaging?

Abohashem: We have an ongoing project aims to assess the arterial and atrial ⁶⁸Ga-DOTATATE uptakes on PET/CT imaging (⁶⁸Ga-DOTATATE is a radiotracer for atherosclerotic inflammation that is specific to inflammatory cells' surface expression of somatostatin receptors) and the risk of cardiovascular diseases including ischemic strokes. These investigations could open new avenues for studying the efficacy of imaging-guided interventions and prevention, among stroke patients, particularly those with no AF.

Q. What about your recent research otherwise?

Abohashem: My work is focused on leveraging advanced multimodality imaging (i.e., FDG PET/CT and MRI) to better understand the mind-heart connection, uncovering the underlying mechanisms linking psychosocial/environmental stressors to heart attacks and ischemic strokes. Our recent work has shown increased FDG uptake in the bone marrow and spleen (as a surrogate for leukopoietic immune activity) and arteries (as a surrogate for atherosclerotic inflammation) in people exposed to high air and noise pollution, respectively, which in turn contributed to their associated risk of heart disease and ischemic stroke. A very recent study of our group published in JAMA Open, demonstrated in 1256 consecutive subjects with acute ischemic stroke underwent MRI, a significant link between low socioeconomic status, initial stroke severity, and long-term disability.

Learn more about the Cardiovascular Imaging Research Center

Learn more about research in the Department of Radiology