Final answer:
Aortic valve stenosis is characterized by the narrowing of the aortic semilunar valve, increased resistance to blood flow, and thickening of the myocardium as the heart compensates for the resistance.
Step-by-step explanation:
Aortic valve stenosis is primarily characterized by narrowing of the aortic semilunar valve. This narrowing leads to increased resistance to blood flow, which forces the heart to exert more effort and work harder, resulting in increased afterload. This condition may also lead to thickening of the myocardium (hypertrophy), as the heart muscle compensates for the increased resistance it faces. Over time, the valve may become rigid and even calcify, further affecting blood flow. The correct characterization of aortic valve stenosis encompasses all of these issues, making it clear that the full consequences of the condition are broader than just the narrowing of the valve itself.