Cardiac FDG–PET/MRI Assessment of Myocardial Injury in COVID-19

Quick Takes

  • Myocardial inflammation based on focal FDG uptake was identified in only a small proportion of participants after COVID-19 diagnosis.
  • Focal FDG uptake on PET was associated with higher cardiac MRI regional native T1, T2, and ECV values, worse measures of myocardial systolic function, and elevated inflammatory blood markers.
  • However, in all PET-positive participants, FDG uptake, LVEF, and inflammatory blood markers resolved or improved at follow-up, suggesting that these abnormalities improve over short-term follow-up.

Study Questions:

What are the myocardial metabolic changes early after recovery from coronavirus disease 2019 (COVID-19) using fluorodeoxyglucose (FDG)-positron emission tomography (PET), and association of these changes to abnormalities in cardiac magnetic resonance imaging (MRI)-based function and tissue characterization measures and inflammatory blood markers?

Methods:

The investigators conducted a prospective cohort study at a single-center tertiary referral hospital system. A volunteer sample of adult patients within 3 months of a diagnosis of COVID-19 who responded to a mail invitation were recruited for cardiac PET/MRI and blood biomarker evaluation between November 2020 and June 2021. Demographic characteristics, cardiac and inflammatory blood markers, and fasting combined cardiac 18F-FDG PET/MRI imaging were obtained. Myocardial inflammation as determined by focal FDG uptake on PET was ascertained. All patients with focal FDG uptake at baseline returned for repeated PET/MRI and blood marker assessment 2 months later. Comparisons between groups were made by independent-sample t test for continuous variables with normal distribution, Wilcoxon rank sum test for continuous variables with non-normal distribution, and Fisher exact test for categorical variables.

Results:

Of 47 included patients, 24 (51%) were female, and the mean (standard deviation [SD]) age was 43 (13) years. The mean (SD) interval between COVID-19 diagnosis and PET/MRI was 67 (16) days. Most patients recovered at home during the acute infection (40 [85%]). Eight patients (17%) had focal FDG uptake on PET consistent with myocardial inflammation. Compared with those without FDG uptake, patients with focal FDG uptake had higher regional T2, T1, and extracellular volume (ECV) (colocalizing with focal FDG uptake), higher prevalence of late gadolinium enhancement (6 of 8 [75%] vs. 9 of 39 [23%], p = 0.009), lower left ventricular ejection fraction (LVEF) (mean [SD], 55% [4%] vs. 62% [5%], p < 0.001), worse global longitudinal and circumferential strain (mean [SD], -16% [2%] vs. -17% [2%], p = 0.02 and -18% [2%] vs. -20% [2%], p = 0.047, respectively), and higher systemic inflammatory blood markers including interleukin-6, interleukin-8, and high-sensitivity C-reactive protein. Among patients with focal FDG uptake, PET/MRI, and inflammatory blood markers resolved or improved at follow-up, performed a mean (SD) of 52 (17) days after baseline PET/MRI.

Conclusions:

The authors concluded that among patients recently recovered from COVID-19, myocardial inflammation was identified on PET in a small proportion of patients, and was associated with cardiac MRI abnormalities and elevated inflammatory blood markers at baseline, and improved at follow-up.

Perspective:

This study reports that myocardial inflammation based on focal FDG uptake was identified in only a small proportion of participants imaged approximately 2 months after COVID-19 diagnosis. Of note, focal FDG uptake on PET was associated with higher cardiac MRI regional native T1, T2, and ECV values, worse measures of myocardial systolic function, and elevated inflammatory blood markers. However, in all PET-positive participants, FDG uptake, LVEF, and inflammatory blood markers resolved or improved at follow-up, suggesting that these abnormalities were not related to pre-existing cardiovascular disease. These imaging findings are generally consistent with an imaging phenotype with good prognosis, but does highlight the importance of studies examining the longer-term effects of COVID-19 on the heart.

Keywords: ACC COVID-19 Podcast, Biomarkers, COVID-19, COVID-19 Testing, C-Reactive Protein, Diagnostic Imaging, Fluorodeoxyglucose F18, Gadolinium, Heart Failure, Inflammation, Interleukin-6, Interleukin-8, Magnetic Resonance Imaging, Phenotype, Positron-Emission Tomography, Primary Prevention, Stroke Volume, Ventricular Function, Left


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