[Clinical case of the month. An unusual presentation of superior vena cava syndrome].

We report the case of a 48-year-old man who was admitted to our emergency department because of a superior vena caval syndrome from which the symptoms occurred only during exercise. His past history included an episode of lower limb deep venous thrombosis. Because an atrio-ventricular partial block was fortuitously evidenced, the patient was submitted to a pacemaker insertion. A few years later, the patient suffered from rapid dyspnea on exercise, associated with facial cyanosis and systemic hypotension. The exploration by phlebography evidenced that the inferior vena cava was completely obstructed. Therefore the venous return from the lower part of the body to right heart was obtained through hypertrophy of the vena azygos. In addition, the presence of cardiac pacing electrodes induced a stenosis at the level of the superior vena cava, just before its entrance into the right atrium. Such a venous network accounted for the occurrence of a chronic superior vena caval syndrome associated with peripheral arterial hypotension during exercise. Treatment consisted of a superior vena caval percutaneous transluminal balloon angioplasty followed by a Wallstent insertion. This procedure led to a correction of all hemodynamic abnormalities responsible for reported pathophysiological limitations to stress.