Challenging diagnosis of a coronary arteriovenous malformation: a case report.

BACKGROUND: Accurately distinguishing between coronary arteriovenous malformations (CAVMs) and fistulas is challenging. We encountered a case of preoperatively undiagnosed CAVM. CASE PRESENTATION: We report the case of a 45-year-old woman diagnosed with cardiac enlargement during a routine health examination. Transthoracic echocardiography showed normal left ventricular systolic function with an ejection fraction of 68%, normal valve function, and a well-defined mass adjacent to the posterior and inferior cardiac walls of the left ventricle. Transesophageal echocardiography revealed a solid mass with a partial honeycomb structure adjacent to the posterior cardiac wall of the left ventricle. A contrast-enhanced computed tomography (CT) scan revealed a solid mass (115 × 79 × 30 mm) with heterogeneous enhancement adhering to the posterior wall and arterial inflow into the mass. Angiography of the right coronary artery revealed mild contrast agent pooling in the venous phase, suggesting the presence of a nutrient vessel in the mass. Cytological examination and histopathological diagnosis after CT-guided needle biopsy revealed Class III tumor with no malignant findings. Considering the challenges in diagnosis with the current tests and the potential risk of cardiac tamponade caused by repeated biopsies, we adopted a policy that tumorectomy should be performed to elucidate the diagnosis. Additional surgical procedures could then be conducted if the intraoperative diagnosis showed a malignant tumor. Intraoperative findings showed that the mass was firmly adherent to the heart between the inferior and lateral walls of the left ventricle. The intraoperative diagnosis of the tumor showed no malignancy. Planned tumorectomy was performed after careful dissection of tumor adhesion. Part of the left marginal vein of the coronary sinus that could not be dissected from the adhesions was resected. Immunohistochemical studies demonstrated CD31+ vascular endothelium, suggesting that the mass was an arteriovenous malformation. The patient's postoperative course was uneventful, without any signs of recurrence. CONCLUSION: This case highlights the difficulty of diagnosing CAVM preoperatively and shows that when tumor imaging is ambiguous, CAVM should be considered and early surgical exploration is crucial.