What is an atrial septal defect?

An atrial septal defect is indeed defined as a hole in the wall (septum) that separates the left and right atria of the heart. This congenital condition allows blood to flow abnormally between the two atria, which can lead to various complications such as increased blood flow to the lungs and potential heart enlargement over time. The presence of a hole disrupts normal blood circulation and may require medical intervention depending on its size and the symptoms it causes.

The other choices identify different cardiac conditions or abnormalities that do not describe an atrial septal defect. For instance, a thickening of the artery walls pertains to conditions like atherosclerosis, while arrhythmias refer to irregular heartbeats, and swelling of the heart tissue can be indicative of an inflammatory condition or cardiomyopathy. Each of these has its own distinct implications for heart health, but they are separate from the structural defect represented by an atrial septal defect.