What is the most common cause of aortic stenosis (AS)?

The most common cause of aortic stenosis is indeed a degenerative calcified valve. This typically occurs in older adults as a result of age-related wear and tear on the aortic valve. Over time, the valve may become calcified, leading to narrowing (stenosis) that restricts blood flow from the heart into the aorta. This condition is often seen in individuals over the age of 70 and is particularly associated with risk factors such as hypertension and hypercholesterolemia.

While there are other causes of aortic stenosis, they are less common in the general population. Rheumatic fever can lead to stenosis, especially in younger patients who have had previous rheumatic heart disease, but it is now much less common due to advancements in the treatment of streptococcal infections. Infective endocarditis is primarily an infection of the heart valves and does not typically lead to chronic aortic stenosis but may cause acute valvular dysfunction. Congenital conditions, such as a unicuspid or bicuspid aortic valve, do cause aortic stenosis but are more prevalent in a younger cohort compared to age-related degeneration. Therefore, among the options provided, degenerative calcified valve changes are the predominant