Effect of exercise in pulmonary stenosis with intact ventricular septum.

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Abstract
Patients with pulmonary stenosis of varying degrees were studied at rest and during exercise. The physical working capacity was below the average for normal subjects, particularly in patients with a severe stenosis (Group I calculated area of the right ventricular outflow tract of less than 0.33 cm2m2 body surface area). In most of these Group I subjects the physical working capacity was low in relation to total amount of hemoglobin and also to heart volume, but in a few it was in the normal range. The cardiac output in relation to O2 uptake, and the stroke volume in relation to blood volume and heart volume, were below the normal, and the increase in right ventricular systolic pressure during exercise in relation to increase in cardiac output was the highest. In less severe stenosis, conditions more or less approached the normal state. In the whole group studied the working capacity was fairly closely correlated with the stroke volume, but less closely with the right ventricular outflow area or the right ventricular systolic pressure at rest. In stenosis the obstruction was more or less compensated by a high right ventricular systolic pressure. Maximal right ventricular systolic pressures of 220 and 240 mm Hg were recorded at rest and during exercise, respectively. The systolic pressure rise is insufficient to give a normal stroke volume in most patients with a high grade stenosis, particularly during exercise. A prolonged duration of systole was observed in most of the pulmonary stenosis patients and helped to compensate for the impeded ejection of the right ventricular stroke volume. A high right ventricular filling pressure, increasing during work, was also regarded as a compensatory mechanism and a prerequisite for the ventricle to maintain a normal stroke volume. A conspicuous increase in the heart volume, probably due to an increased residual volume of the right ventricle and the enlarged right atrium, was found among the patients with severe stenosis. In most of the patients the heart volume was normal or only slightly increased in relation to the total amount of hemoglobin.