Haemodynamic effects of exercise in isolated pulmonary stenosis before and after surgery.

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Abstract
Seventeen patients with pulmonary stenosis and an intact ventricular septum were studied before and after operation. Nine patients had an intact atrial septum and 8 had an intera-trial shunt. A low cardiac output during exercise in relation to the O2 uptake persisted after operation. The ventricular end-diastolic pressure decreased considerably, the duration of systole shortened, and a rise in right ventricular stroke volume at rest and during exercise was demonstrated in those patients with interatrial shunts. The tendency for low cardiac output during exercise after operation may be due to a peripheral circulation adaptation, from early childhood, which increased the ability to extract and utilize O2. Once so adapted there may be no necessity to increase cardiac output to meet the demand for O2 transport. The importance of a persisting small left ventricle is discussed. The physical working capacity increased appreciably only in those with a right-to-left shunt before operation. This was attributed to the increased arterial O2 saturation during exercise, due to the diminished right-to-left shunt at the atrial level after operation. The considerably reduced right ventricular end-diastolic pressure was apparently responsible for the decreased right-to-left shunt. In patients without an interatrial shunt, physical working capacity was generally normal before and after operation. The normal working capacity in the presence of reduced stroke volume during exercise was possible because of the widened arteriovenous O2 difference.