Hemodynamic and Ventilatory Effects of Exercise in the Upright Position in Patients with Left-to-right Shunts.

THE behavior of the pulmonary vascular resistance during exercise in patients with ventricular septal defect or patent ductus arteriosus influences the magnitude and direction of tlhe shunt of blood across the defect and also may provide clues concerning the genesis of the pulmonary hypertension often seen in large defects. In previous studies,1' 2 pulmonary artery wedge pressure had not been determined, so that the possible influence of high left ventricular filling pressure on elevation of pulmonary artery pressure during exercise could not be evaluated. Experience in this laboratory suggested that pulmonary artery wedge pressure might rise during exercise, since patients with very large left-to-right shunts through ventricular septal defects generallv showed higher wedge pressure than patients with small shunts. Nadas3 reported the same experience. These considerations led us to stuidy pulmonary and systemic hemodynamics in such patients during exercise. The upright position was used to make the exercise comparable to that usuallv attempted by man. Besides determining wedge pressure, we attempted to evaluate the role of intrapleural pressure and to investigate the possibility of pulmonary venous oxygen unsaturation during exercise in patients with right-to-left shunts, since this would cause erroneous calculations of pulmonary blood flow by the Fick method if full saturation were assumed.