Final answer:
Small cardiac lesions are typically unrestrictive, meaning they do not significantly hinder heart function. These lesions do not have a defining tendency to close on their own and are not exclusive to atrial septal defects.
Step-by-step explanation:
A characteristic of small cardiac lesions is that they are usually unrestrictive lesions. This means that they do not significantly affect the normal blood flow through the heart or its function. Unlike large lesions which can obstruct blood flow and affect heart function, small cardiac lesions often go unnoticed and may not produce any symptoms. In many cases, these small lesions do not hinder the performance of the heart chambers or valves significantly enough to require treatment. It is also worth noting that small cardiac lesions are not exclusive to atrial septal defects and can be associated with various cardiac conditions. While it is possible for some cardiac lesions to close on their own over time, this is not a defining characteristic of small cardiac lesions.