Dextro-transposition of the great arteries pathophysiology


 * Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; ; Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
In dextro-TGA, the pulmonary and the systemic circuits are in parallel circulation, rather than in series, which is incompatible with life if there is no mixing of the two systems.

Pathophysiology



 * In a normal heart, oxygen-depleted (blue) blood is pumped from the right heart, through the pulmonary artery, to the lungs where it is oxygenated. The oxygen-rich red blood then returns to the left heart, via the pulmonary veins, and is pumped through the aorta to the rest of the body, including the heart muscle itself.
 * With d-TGA, blue blood from the right heart is pumped immediately through the aorta and circulated to the body and the heart itself, bypassing the lungs altogether, while the left heart pumps red blood continuously back into the lungs through the pulmonary artery.
 * In effect, two separate "circular" (parallel) circulatory systems are created, rather than the "figure 8" (in series) circulation of a normal cardio-pulmonary system.
 * In d-TGA, the pulmonary and the systemic circuits are in parallel circulation, rather than in series, which is incompatible with life if there is no mixing of the two systems. Therefore, in most cases, a complex d-TGA is the one that allows survival due to the presence of other heart defects like patent foramen ovale (PFO) for mixing blood between the two systems. Other possible mixing sites include a PDA or a VSD.
 * The course of TGA is determined by the degree of hypoxia, and the ability of each ventricle to sustain an increased work load in the presence of reduced coronary arterial oxygenation. It is also important the nature of associate heart defects, and the status of the pulmonary vascular circulation.
 * The pulmonic flow is increased in those cases with transposition and large VSD or large PDA without obstruction to left ventricular outflow. In these cases, pulmonary vascular obstruction develops by 1 to 2 years of age.

Acknowledgements and Initial Contributors to Page
Leida Perez, M.D.