The role of contrast echocardiography in the differential diagnosis of platypnea

The commonest cause of platypnea is right-to-left shunting through a previously unrecognized atrial septal defect; the shunting usually appears after lung resection for a carcinoma and is exacerbated by the upright position. So far, only 13 such cases have been reported, but this syndrome is receiving increasing recognition. We have reviewed all cases reported in the literature. Physical examination, chest roentgenogram and EKG were nonspecific and were not of diagnostic value. Arterial blood gases revealed hypoxia in recumbent position in 9 cases and orthodeoxia (drop in arterial PO₂ of ≥9 torr) in 10 cases. Right-to-left shunt was confirmed using inhalation of 100% oxygen in 7 cases. Contrast echocardiography was done in 8 cases and revealed interatrial shunting in all; increase in the shunt in the upright position was documented in 7 cases. Cardiac catheterization confirmed the diagnosis in all, although 2 patients required repeated studies before the diagnosis was made. Nine patients underwent surgical repair of the atrial septal defect; there were two deaths due to noncardiac causes, and the other 7 had relief of symptoms. In patients who did not undergo surgery, symptoms persisted. Platypnea secondary to interatrial right-to-left shunting is a disabling condition, but is easily diagnosed and is amenable to surgical repair. The diagnosis can be made by different techniques; contrast echocardiography is the best approach, since it is sensitive, specific, and noninvasive. Cardiac catheterization should be done if surgical repair is planned.