Aortic Stenosis. Stenosis is defined as a fixed obstruction preventing outflow through a valve. Stenotic lesions of the aortic valve may be either congenital or acquired. Bicuspid valve is associated with a prevalence of approximately 2% and is therefore one of the most common congenital cardiac lesions. Aortic stenosis may also be acquired due to degenerative calcification. The severity of aortic stenosis is characterized by the valve area and mean pressure gradient (Table 142.1).

A low cardiac index can cause underestimation of the severity of aortic stenosis; selected patients benefit from valve replacement for low-output, low-gradient aortic stenosis.

Compensatory changes in response to aortic stenosis include left ventricular hypertrophy. The associated increase in wall thickness and decrease in compliance renders the ventricle preload dependent. Adequate preload is achieved by normovolemia, maintenance of venous return, adequate diastolic filling time, and preservation of sinus rhythm and the associated “atrial kick.” Anesthetic goals for the patient with aortic stenosis therefore include the following: