Select the right-to-left shunt

Select the right-to-left shunt

• A. Transposition Of The Great Vessels
• B. Ventricular Septal Defect
• C. Patent Ductus Arteriosus
• D. Atrial Septal Defect

Answer: (A)

Right-to-left shunt means deoxygenated blood bypasses the lungs and enters the systemic circulation, causing cyanosis. In transposition of the great vessels, the aorta comes off the right ventricle and the pulmonary artery off the left ventricle, creating two parallel circuits instead of one closed loop. For life, mixing between circuits must occur through an ASD, VSD, or PDA. When deoxygenated blood from the right-sided circulation crosses into the left-sided pathway and then into the systemic circulation, the shunt direction is right-to-left, leading to systemic cyanosis. Other defects like VSD or ASD typically produce left-to-right shunts under normal pressures, and a patent ductus arteriosus usually causes left-to-right flow as well unless there is reversal from pulmonary hypertension. Thus, the right-to-left mixing in the context of transposition of the great vessels best explains the question.

Right-to-left shunt means deoxygenated blood bypasses the lungs and enters the systemic circulation, causing cyanosis. In transposition of the great vessels, the aorta comes off the right ventricle and the pulmonary artery off the left ventricle, creating two parallel circuits instead of one closed loop. For life, mixing between circuits must occur through an ASD, VSD, or PDA. When deoxygenated blood from the right-sided circulation crosses into the left-sided pathway and then into the systemic circulation, the shunt direction is right-to-left, leading to systemic cyanosis. Other defects like VSD or ASD typically produce left-to-right shunts under normal pressures, and a patent ductus arteriosus usually causes left-to-right flow as well unless there is reversal from pulmonary hypertension. Thus, the right-to-left mixing in the context of transposition of the great vessels best explains the question.