Lung scanning after massive pulmonary embolism in thoracic surgery: reverse flow phenomena

After thoracotomy, the pulmonary circulation on the operated side is definitely reduced for several weeks. All lung scans carried out during this post-operative period thus show marked asymmetry between the two lungs. The pulmonary blood flow is then much greater in the healthy lung compared with the operated lung where hypoventilation increases vascular resistance. When pulmonary embolism occurs, two abnormalities are noted: amputation of part of the lung field on the healthy side and, paradoxically, normal activity on operated side. After treatment with Urokinase (3 cases) the previous findings were restored. The embolic area disappeared and the operated lung became less marked. Under heparin therapy (2 cases) the phenomenon was more prolonged in time. This inversion of the vascular distribution for which the term of reverse flow has been proposed, shows the purely functional character of certain changes in pulmonary scans