Effect of size of ventricular septal defect and age on pulmonary hemodynamics at sea level

In 1,265 patients with isolated ventricular septal defects (Natural History Study of congenital heart defects, 1977), older children and adults were classified into those with and without pulmonary hypertension. To ascertain why relatively distinct pulmonary hypertensive and normotensive groups consisted of older children and adults, we reexamined the sea level cardiac catheterization data of 829 patients according to defect size (using the Gorlin formula) and patient age. In patients < 2 years of age, the average pulmonary vascular resistance was not significantly elevated and was not dependent on defect size. Pulmonary hypertension was due to increased blood flow, except for the 2.7% of patients with Eisenmenger-like physiology. For those > 2 years of age, both pulmonary arterial pressure and resistance were higher (p < 0.05) in patients with defect sizes of > 0.5 cm2/m2 than in those with smaller defects, and the Eisenmenger-like physiology was more common in older patients (17.4% in patients aged > 10 years). The group with distinctly higher pressure after 4 years of age reflected higher pulmonary vascular resistances in those in whom large defects persisted. However, 84% of patients aged > 4 years who underwent cardiac catheterization had smaller defects (< 0.5 cm2/m2), accounting for the group observed with low pressure.