Atrial septal defect allows movement of blood from which chamber to which chamber?

Atrial septal defect allows movement of blood from which chamber to which chamber?

• A. From left ventricle to right ventricle
• B. From right atrium to left atrium
• C. From left atrium to right atrium
• D. From right ventricle to left ventricle

Answer: (C)

An atrial septal defect creates a left-to-right shunt because the pressure in the left atrium is higher than in the right atrium. Blood moves from the left atrium into the right atrium through the opening in the atrial septum. This increases blood flow to the right heart and into the pulmonary circulation. Over time it can enlarge the right-sided chambers and, if pulmonary pressures rise, the direction of flow can reverse, but the usual pattern is movement from left atrium to right atrium.

An atrial septal defect creates a left-to-right shunt because the pressure in the left atrium is higher than in the right atrium. Blood moves from the left atrium into the right atrium through the opening in the atrial septum. This increases blood flow to the right heart and into the pulmonary circulation. Over time it can enlarge the right-sided chambers and, if pulmonary pressures rise, the direction of flow can reverse, but the usual pattern is movement from left atrium to right atrium.