Description

The isovolumic relaxation time is the time between closure of the aortic valve and opening of the mitral valve and is prolonged in the fetus and immature neonate. It has also been shown to decrease in neonates with a significant PDA due to early pressure related valve closure/opening. Other potential effects of volume / pressure loading of the left heart include mitral valve regurgitation and stretching of the inter-atrial septum leading to increase in the size of the atrial septal defect.