The Natural History of Isolated Ventricular Septal Defect

Abstract

Forty patients with isolated ventricular septal defect were studied physiologically two or more times before they underwent surgical treatment. Utilizing baselines obtained by heart catheterizations of normal infants and children, we grouped patients with ventricular septal defect according to the magnitude of the total pulmonary resistance, pulmonary blood flow, and pulmonary arterial pressure, and according to changes in these values over time. The patients with small defects (less than 1 cm. per M.² of body surface area) were easily separable on the basis of physiologic findings. Patients with large ventricular septal defects (greater than 1 cm. per M.² of body surface area) exhibited one of three possible initial responses to the stress of high pulsatile pulmonary flow and increased pulmonary artery pressure: (1) normal regression of total pulmonary resistance; (2) delayed fall in total pulmonary resistance; (3) failure of the total pulmonary resistance to decrease with age. These physiologic responses were thought to be related to normal maturation, delayed maturation, or failure of maturation of the pulmonary vascular bed. It was observed that a subsequent increase in total pulmonary resistance could be superimposed on any of the three initial responses at any time. Clinical evidence and catheterization data suggested that the relative size of the ventricular septal defect had decreased in five patients. The variability of the physiologic courses, the importance of the pulmonary vascular bed in determining these responses, and our lack of understanding of the etiology of the pulmonary vascular changes were noted. The indications for, and timing of surgical intervention in patients with isolated ventricular septal defects, are discussed in light of the above findings.