Absence of infective endocarditis relapse when end-of-treatment fluorodeoxyglucose positron emission tomography/computed tomography is negative

AIMS: In non-operated infective endocarditis (IE), relapse may impair the outcome of the disease. The aim of the study was to evaluate the relationship between end-of-treatment (EOT) fluorodeoxyglucose positron emission tomography/computed tomography FDG-PET/CT results and relapse in non-operated IE either on native or prosthetic valve. METHODS AND RESULTS: We included 62 patients who underwent an EOT FDG-PET/CT for non-operated IE performed between 30 and 180 days of antibiotic therapy initiation. Qualitative valve assessment categorized initial and EOT FDG-PET/CT as negative or positive. Quantitative analyses were also conducted. Clinical data from medical charts were collected, including endocarditis team decision for IE diagnosis and relapse. Forty-one (66%) patients were male with a median age of 68 years (57; 80) and 42 (68%) had prosthetic valve IE. End-of-treatment FDG-PET/CT was negative in 29 and positive in 33 patients. The proportion of positive scans decreased significantly compared with initial FDG-PET/CT (53% vs. 77%, respectively, P < 0.0001). All relapses (n = 7, 11%) occurred in patients with a positive EOT FDG-PET/CT with a median delay after EOT FDG-PET/CT of 10 days (0; 45). The relapse rate was significantly lower in negative (0/29) than in positive (7/33) EOT FDG-PET/CT (P = 0.01). CONCLUSION: In this series of 62 patients with non-operated IE who underwent EOT FDG-PET/CT, those with a negative scan (almost half of the study population) did not develop IE relapse after a median follow-up of 10 months. These findings need to be confirmed by prospective and larger studies.