Nuclear imaging studies in patients with an indeterminate diagnosis of infective endocarditis: A retrospective analysis of a case series.

Abstract

Objectives: To determine the role of nuclear imaging (NI) in evaluating inconclusive cases with suspicion of infective endocarditis (IE).

Methods: Consecutive patients with an indeterminate diagnosis of IE who underwent labelled leucocyte scintigraphy (LS) or ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) between 2018 and 2021 at 2 reference hospitals in Rio de Janeiro were retrospectively analysed. Subsequent confirmed or rejected diagnoses of IE were evaluated, in addition to clinical and imaging data. Kappa coefficient was used to compared the diagnostic agreement between echocardiographic and NI findings, with a p-value <0.05 considered statistically significant.

Results: A total of 85 NI scans (28 FDG-PET/CT, 57 LS) from 76 patients were evaluated, of whom 48 (63.2 %) underwent only LS, 19 (25 %) only FDG-PET/CT, and 9 (11.8 %) both studies. Average age was 63.8 years (SD ± 18.5) and 51.3 % were women. Prosthetic valves were present in 15.8 % of cases, and intracardiac devices in 10.5 %. Among the 76 patients, 18 (23.7 %) had NI findings suggestive of IE. A total of 28 patients (36.8 %) were ultimately diagnosed with IE, 28.6 % of whom had confirmed infections by NI scans. Echocardiographic results had a low level of agreement with NI findings in those diagnosed with IE (kappa = -0.44).

Conclusions: Nuclear imaging contributed to the diagnosis of IE in approximately 30 % of subsequently confirmed cases, which were initially classified as inconclusive by echocardiography. The low level of agreement between these methods underscores their complementary role in the diagnosis of IE, particularly in indeterminate cases.