Mitral annular fibrous band—a unique morphological variant of a rare congenital mitral valve anomaly: a case report

BACKGROUND: Left atrial bands are rare and can be associated with mitral valve dysfunction, heart failure, and stroke. Most cases are identified on autopsy, and the demonstration in vivo is very uncommon. Various anatomical configurations have been reported. This description of a mitral annular fibrous band contributes to the literature as the first reported case to traverse the supravalvular mitral inflow region, without involving the left atrium. CASE SUMMARY: A 59-year-old man with a history of metastatic duodenal carcinoma was admitted with a 2-week history of fever and rigors. Inflammatory markers were elevated and blood cultures positive for Enterococcus feacium. Transoesophageal echocardiography performed to investigate for infective endocarditis revealed a 2.3 cm long, thin fibrous band attached to the posterior mitral annulus and extending to the base of the middle scallop of the anterior mitral valve leaflet causing localized tethering, but no valve dysfunction. The band was felt to represent a bystander anatomic variant unrelated to the sepsis, which was most likely gastrointestinal in origin. The patient responded well to intravenous antibiotics. CONCLUSIONS: The presence of an abnormal intracardiac structure in the setting of occult infection should always raise the suspicion of infective endocarditis. Using detailed 2D multiplanar and 3D transoesophageal echocardiography, we were able to identify the anomalous band and exclude any overt infective vegetations attached to the band or the leaflets. Once identified, treatment options range from conservative management to surgical resection and mitral valve surgery if concomitant valvular dysfunction is demonstrated.