Final answer:
Transposition of the great arteries is a congenital heart defect where the aorta and pulmonary artery are reversed, leading to circulation of oxygen-poor blood in the systemic circuit. Hemodynamic changes include increased right ventricular and pulmonary artery pressure, requiring corrective surgery. A patent ductus arteriosus can temporarily assist with blood mixing until surgery can be performed.
Step-by-step explanation:
Transposition of the great arteries (TGA) is a congenital heart defect where the two main arteries leaving the heart, the aorta and the pulmonary artery, are switched from their normal position, or transposed. This means the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle. As a result, oxygen-poor blood circulates within the systemic circuit and oxygen-rich blood circulates within the pulmonary circuit, which is not compatible with life unless there is some mixing between the two circuits, such as through a patent ductus arteriosus (PDA) or a septal defect.
The hemodynamic changes involve increased pressure within the right ventricle and pulmonary artery due to pumping against the systemic resistance. Blood that would normally go to the body is instead circulated back to the lungs leading to symptoms such as dyspnea, tachycardia, and poor weight gain in infants. Without intervention, this condition can lead to congestive heart failure. Treatments typically involve surgical procedures aimed at correcting the defect, such as the arterial switch operation or, in emergency, keeping the PDA open using medication until surgery is possible.