FDG-PET CT for the evaluation of native valve endocarditis

645 Objectives: Infective endocarditis (IE) is associated with significant morbidity and mortality. Clinical presentation is highly variable, making the diagnosis of IE challenging. IE is usually diagnosed using the modified Duke criteria, however limitations associated with blood cultures and echocardiography reduce the diagnostic accuracy of the modified Duke criteria with approximately one third of patients investigated for IE classified as possible IE. F-18 Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is an extremely useful technique for evaluation of prosthetic valve IE but there is very limited and conflicting data on its role in native valve IE (NVE). The purpose of this retrospective study is to assess the role of FDG-PET/CT and its inclusion in the modified Duke criteria for the evaluation of patients with suspected NVE. Methods: 3D time-of-flight FDG PET/CT images in patients following myocardial suppression preparation with suspected NVE were retrospectively reviewed independently by two experienced physicians blinded to all clinical information. Abnormal focal increased FDG uptake greater than surrounding blood pool activity in the cardiac valve plane were considered positive for IE by visual analysis. The gold standard consisted of surgical findings, when available, or the modified Duke criteria. Results: 54 subjects were included, 31 (57%) with a diagnosis of NVE. A final diagnosis of NVE was established in 21/31 (67.7%) subjects by surgical cultures and 10/31 (32.3%) using the modified Duke criteria. FDG-PET/CT correctly identified 21/31 (67.7%) subjects with no false positive studies, yielding a sensitivity and specificity of 68% (95%CI: 49-83%) and 100% (95%CI: 85-100%), respectively. Positive and negative predictive values were 100% (95%CI: 84-100%) and 70% (95%CI: 51-84%), respectively. Interobserver agreement was substantial with κ = 0.65 (95%CI 0.45-0.86). Of the 10 false negative studies, 6 had incomplete myocardial suppression and 4 had complete suppression. After excluding subjects (17 patients, 31.5%) with incomplete myocardial suppression, sensitivity and specificity were 80% (95%CI: 56-94%) and 100% (95%CI: 80-100%) with positive and negative predictive values of 100% (95%CI: 79-100%) and 81% (95%CI: 58-95%), respectively. The sensitivity and specificity of the modified Duke criteria were 48% and 74%. 18 subjects (33.3%) were classified as Possible IE with the modified Duke criteria; 13 (72.2%) of which had a final diagnosis of IE based on the gold standard. Positive and negative predictive values of PET were 100% (95%CI: 84-100%) and 70% (95%CI: 51-84%), respectively. Modifying the Duke criteria to include FDG-PET positivity as a major criterion increased sensitivity to 77% without affecting specificity and led to the correct reclassification of 8/18 (44.4%) subjects from Possible IE to Definite IE. Conclusions: The addition of a positive FDG-PET/CT as a major criterion in the modified Duke Criteria improved performance of the criteria for the diagnosis of NVE, particularly in those subjects with possible IE. Optimal myocardial suppression techniques and PET/CT devices are crucial in this patient population.