A 40-year-old man was admitted with necrotising fasciitis of the right thigh. Further workup to evaluate for an infectious source revealed an incidental finding of persistent left superior vena cava via transesophageal echocardiography. This finding was confirmed by cardiac MRI. During his hospitalisation, he also developed altered mental status which was found to be secondary to systemic emboli by a head MRI. The primary source of infection was likely his dental abscesses. He underwent intravenous antibiotic therapy for a total of 6 weeks and was then referred to a specialised vascular centre for further management of his congenital anomaly.