1970 Volume 102 Issue 4 Pages 403-412
In normal postnatal development, physiological regression of the muscular coat is accomplished to the major part in the first 6 months. Thereafter, the medial thickness still continues slowly to diminish and practically attains the level of normal adults in 4 years. With the present histometrical method, the medial thickness at an arterial radius of 100 μ was estimated at 9.8 μ immediately after birth, was reduced to 6.8 μ in 6 months, to 6.5 μ in a year and to 5.9 μ in 4 years, while the value for normal adults was 5.4 μ.
In patients with ventricular septal defect (VSD), physiological medial regression does not take place, and the muscular coat retains or increases its neonatal thickness. The medial thickness is correlated with pulmonary blood pressure level and can be expressed by an exponential function of blood pressure. Pulmonary hypertension in VSD is correlated with the dimension of septal defect. Medial hypertorphy in VSD is probably associated with increased vascular resistance of pulmonary circulation.
