Final answer:
The inability of heart valves to close properly is called insufficiency, which can lead to regurgitation and is a form of valvular heart disease. Stenosis specifies valve rigidity and is different from insufficiency.
Step-by-step explanation:
The inability of heart valves to close properly is known as insufficiency. Valve insufficiency leads to regurgitation, which is the backward flow of blood due to improper closing of the valve. This is a type of valvular heart disease that can be either a congenital condition or acquired due to other disease processes or trauma.
In contrast, stenosis refers to valves becoming rigid and potentially calcified, affecting the heart's ability to pump blood effectively. Commissurotomy is a surgical procedure to correct stenosis, varices are dilated veins, and coarctation refers to a narrowing of the aorta, none of which describe valve insufficiency.