RESUMEN
This report describes a 61-year-old female with an anomalous drainage of the right superior vena cava into the left atrium. The patient presented progressively severe dyspnea and precordial pain on exertion, lightheadedness, easy fatiguability and a constant decline in her performance but normal cardiac and pulmonary findings. Following a suspicious lung perfusion scan, diagnosis was assessed by echocardiography and confirmed by cardiac catheterization and nuclear magnetic resonance imaging. This anomaly leading to a right to left shunt appears to be a rare congenital cardiac malformation, particularly if diagnosed in the adult. The calculated shunt volume at rest was approximately 15% of the total body circulation. Although the functional relevance appears questionable, exercise of the upper limbs caused a significant decrease in systemic O2-saturation.