Images in cardiovascular medicine: Concomitant persistent left superior vena cava and agenesis of right superior vena cava: a rare congenital anomaly.

A 21-year-old white male athlete was admitted for syncope. ECG and telemetry showed sinus arrhythmia and sinus bradycardia; at this time, he was asymptomatic. A chest radiograph showed unremarkable findings (Figure 1). During his transthoracic echocardiogram, a massive coronary sinus (area, 3.9 cm) was identified (Figure 2). Because of suspicion of a persistent left superior vena cava (PLSVC), an agitated saline (“bubble”) study was immediately performed. After injection of agitated saline through his left antecubital vein, the dilated coronary sinus was opacified before the right atrium and ventricle, consistent with PLSVC (Figure 3 and Movie I in the online-only Data Supplement). PLSVC, a congenital anomaly of the thoracic venous system, is present in 0.4% of the general population.1 When the left superior cardinal vein fails to regress to form the ligament of Marshall, a persistent left-sided vasculature