We aimed to evaluate the prognostic value of FDG pericardial uptake using FDG-PET/CT in patients admitted for acute pericarditis with pericardial effusion

Acute pericarditis (AP) in developed countries is mostly caused by viral infections. Relapses occur in up to 15% to 30% of patients and may be associated with more frequent hospitalization, lower quality of life and steroid-dependency.

Relapsing pericarditis is often ascribed to an auto-inflammatory process. Since increased glucose metabolism is a hallmark of inflammation, positron emission tomography (PET) with the radiolabeled glucose analog [18F]-2-deoxy-2-fluoro-d-glucose (FDG) may be used to assess pericardial inflammation.

In selected cases, such as malignant pericardial involvement or tuberculous pericarditis, the possibility to use integrated imaging modalities such as Positron Emission Tomography/Computed Tomography (PET/CT) appears a valuable tool in analyzing the pericardial disease.

FDG-PET/CT

In this monocentric retrospective cohort study, all patients admitted for idiopathic acute pericarditis with pericardial effusion from January 2009 to December 2016 who underwent an FDG-PET/CT at diagnosis were considered.

Pericardial FDG uptake was measured by generating a volume of interest to calculate the maximal standardized uptake value. The primary outcome was the pericarditis relapse rate during follow-up.

FDG-PET/CT was performed 23 [7-99] days after diagnosis in 39 patients (52 [18-83] years, 43.6% of women) admitted for acute pericarditis with pericardial effusion. During a median follow-up period of 7.6 [2.4-77.2] months, 7 (17.9%) patients suffered pericarditis relapse that occurred 3.8 [1.6-14.6] months after FDG-PET CT.

In the multivariable analysis, pericardial FDG uptake at diagnosis (OR: 16.6; 95% confidence interval [CI]: 1.25 to 220.8; p?=?0.033) was independently associated with pericarditis relapse. Eventually, patients with pericardial FDG uptake at diagnosis had a higher recurrence rate during follow up (p?=?0.047).

In acute pericarditis with pericardial effusion, increased FDG-PET/CT pericardial uptake is associated with a higher risk for relapse.