Multimodal Imaging in Mycobacterium Chimaera Cardiovascular Infections: The Mayo Clinic Experience

Abstract

Objective: To review the salient features of multimodality cardiovascular imaging in patients with disseminated Mycobacterium chimaera (MC) infections after exposure to contaminated heater-cooler units during cardiopulmonary bypass. Patients and Methods: Twelve patients with confirmed MC infection were retrospectively identified after a review from January 1, 2010, to April 30, 2021. The electronic medical records were examined with a focus on transthoracic echocardiography, transesophageal echocardiography, cardiac computed tomography (CT), cardiac magnetic resonance imaging, and positron emission tomography-CT. Results: Three (27.3%) patients had diagnostic findings of endocarditis on transthoracic echocardiography, with most patients having nonspecific abnormalities including elevated prosthetic valve gradients or prosthetic leaflet thickening. Transesophageal echocardiography identified 4 (36.7%) patients with vegetations and 3 (27.3%) with aortic root abscess or pseudoaneurysm, with more common findings such as mild aortic root or prosthetic leaflet thickening. Six (50%) patients underwent cardiac CT imaging, which found aortic root pseudoaneurysms or abscesses, prosthetic ring dehiscence, and leaflet thickening. Three (25%) patients underwent cardiac magnetic resonance imaging demonstrating prosthetic valve vegetations, leaflet thickening, and abnormal myocardial delayed enhancement in a noncoronary distribution, suggesting myocarditis. Ten (83%) patients underwent positron emission tomography-CT, 4 (40%) had an abnormal fluorodeoxyglucose uptake around the cardiac prosthetic material, and 7 (70%) had a fluorodeoxyglucose uptake in other organs, suggesting concomitant multiorgan involvement. Conclusion: Multimodality cardiovascular imaging is central to the management of patients with disseminated MC and can help establish a preliminary diagnosis while awaiting confirmatory microbiological data, potentially reducing the time to diagnosis. Imaging findings are subtle and atypical, not always meeting classically modified Duke’s criteria for infectious endocarditis. Clinicians should have a high index of suspicion for the disease and a low threshold for repeat imaging when initial testing is equivocal.