Use of 18F-FDG PET/CT in infective endocarditis: a nationwide cohort study from the NIDUS Registry

Background 18F-FDG PET/CT is recommended by ESC guidelines in selected cases of infective endocarditis (IE), particularly in patients with prosthetic valves and inconclusive echocardiography, and for the detection of extracardiac foci. However, its nationwide use and diagnostic contribution remain unclear. Purpose We aimed to characterise the use of PET-CT in a national cohort of patients with IE. Methods Using the nationwide National Danish Endocarditis Studies registry (NIDUS), we included patients with a first IE episode between 2016 and 2021. Patients were stratified according to whether they underwent PET/CT during admission. Results Among 3,551 included patients, 2,378 (67%) underwent PET/CT. The median time from diagnosis to PET/CT was 6 days (IQR 2-10). Compared with no PET/CT, patients with PET/CT were slightly younger (median 73.5 vs 74.0 years, p=0.004) and more often male (69.5% vs 65.8%, p<0.03). PET/CT use did not differ significantly between patients classified as definite and possible IE (79.6% vs. 20.4%, p=0.89). Patients undergoing PET/CT more often had a history of valve prosthesis (28.7% vs. 21.8%, p<0.001) and congenital heart disease (5.5% vs. 3.5%, p=0.008), whereas there was no difference in the frequency of cardiac implantable electronic devices (CIED) (22.0% vs. 22.3%, p=0.77). Staphylococcus aureus and culture-negative IE were less frequent, whereas Streptococcus spp. Were more frequent among patients undergoing PET/CT (all p<0.001). Regarding clinical presentation, fever (63.3% vs. 55.9%, p<0.001) and splinter haemorrhages (5.1% vs. 3.3%, p=0.02) were more frequent among patients undergoing PET/CT. Prosthetic valve involvement (24.1% vs. 18.7%) was more frequent among patients undergoing PET/CT, whereas native valve involvement was slightly less frequent (64.3% vs. 68.7%). Isolated CIED-IE was similar in both groups (10.0% vs. 11.0%). In-hospital mortality was lower among patients who underwent PET/CT (10.5% vs 31.0%, p<0.001), which in part may be explained by survivor bias. Among 2,363 evaluable PET/CT scans, 295 (12.5%) were contributory to the diagnosis or management. Extracardiac PET/CT findings were identified in 59.3% of patients. Among these extracardiac foci, pulmonary involvement was less frequent in contributory than in non-contributory scans (12.5% vs. 19.7%, p=0.005), whereas other extracardiac findings, such as upper gastrointestinal, lower gastrointestinal, dental/oral, and miscellaneous sites, were similarly distributed between groups without significant differences. Conclusion In this nationwide cohort of patients with IE, PET/CT was performed in a high proportion of patients, particularly among those with prosthetic valves. However, only approximately one in eight scans were contributory. Future studies are needed to clarify the clinical contribution and optimal use of PET/CT in all versus selected patients with IE.