Multimodality Imaging In Mycobacterium Chimaera Cardiovascular Infections

Introduction: Mycobacterium Chimaera (MC) infections following cardiovascular surgery are challenging to diagnose given their insidious presentation. We therefore reviewed the various imaging modalities used to diagnose these infections at Mayo Clinic. Methods: Cases from 01/01/2010-06/01/2020 were identified using electronic medical records. Demographics and clinical history were collected. Imaging studies, including transthoracic echocardiogram (TTE), transesophageal echocardiogram (TEE), positron emission tomography / computed tomography (PET/CT), cardiac CT (CCT), and cardiac magnetic resonance (CMR) were reviewed. Results: A total of 7 patients (85.7% male) were found. 6 underwent aortic valve replacement and 1 received an aortic composite valve conduit. Surgical dates ranged from 01/2010-12/2018. Mean age at presentation was 63.3 years. Mean time from surgery to symptom onset was 28.0 months. All patients underwent TTE and TEE; prosthetic valve endocarditis was identified in 6 cases between both, while CMR established the diagnosis in 1 case. TTE showed prosthetic valve obstruction in 2 cases and an anterior pseudoaneurysm in 1 case. TEE findings included thickened prosthesis and/or vegetations (n=5), thickened posterior root (n=4), and root abscess (n=3). Among the 3 patients who underwent PET/CT, 2 demonstrated increased fluorodeoxyglucose (FDG) uptake around the aortic prosthesis; in addition, 1 had elevated FDG uptake in the myocardium suggesting myocarditis. 1 patient did not have aortic prosthesis FDG uptake. In the 2 patients who had CCT, 1 showed a pseudoaneurysm that prompted suspicion for endocarditis, and the other revealed a fluid collection adjacent to the aortic valve conduit. 2 patients underwent CMR; 1 had aortic prosthesis thickening and patchy areas of myocardial delayed enhancement suspicious for myocarditis, whereas the other showed vegetation and an aortic root abscess. Conclusion: TTE plus TEE successfully identified MC prosthetic valve endocarditis in most cases with TEE having higher specificity. Advanced imaging techniques are helpful to support the diagnosis and assess for myocardial and/or aortic involvement. Combining these modalities is therefore crucial in unveiling this elusive organism.