ABSTRACT
L -► R Shunt Initially blood flows from the high pressure L heart, through the defect, to the lower pressure R heart. This presents the lungs with an increased volume load which, if substantial, may lead to pulmonary edema. At first, pulmonary arteriolar constriction protects the lungs. This increases the pressure in the pulmonary artery and R ventricle, causing R ventricular hypertrophy and ulti mately cardiac dilatation and failure.
