Aortic valve stenosis

The aortic valve controls the direction of blood flow from the left ventricle to the aorta. When in good working order, the aortic valve does not impede the flow of blood between these two spaces. Under some circumstances, the aortic valve becomes narrower than normal, impeding the flow of blood. This is known as aortic valve stenosis, or aortic stenosis, often abbreviated as AS. Causes of aortic stenosis include acute rheumatic fever[?], bicuspid aortic valve[?] and congenital anomalies[?]. It is most often diagnosed when it is asymptomatic. It is found on routine examination of the heart. A fairly loud systolic, crescendo-decrescendo murmur is heard loudest at the upper right sternal border, and radiates to the carotid arteries[?]. The murmur increases with squatting, decreases with standing and isometric muscular contraction, which helps distinguish it from hypertrophic obstructive subaortic stenosis[?]. Respiration has no effect on the loudness of the murmur. When symptomatic, aortic stenosis can cause syncope[?], angina and pulmonary edema[?]. More symptoms indicate a worse prognosis. Treatment requires replacement of the diseased valve with either a porcine aortic valve[?] or a cadaveric aortic valve[?], or an prosthetic aortic valve[?].