On the Cusp of Disaster: Distinguish between the Anesthetic Management of Stenotic and Regurgitant Cardiac Valves
George A. Mashour MD, PhD
Theodore A. Alston MD, PhD
The initial approach to the patient with cardiac valve disease involves three basic questions:
Which valve is affected?
Is the lesion stenotic or regurgitant?
What is the severity of stenosis or insufficiency?
This chapter reviews disease of the aortic and mitral valve and provides recommendations for anesthetic management during cardiac surgical repair.
AORTIC VALVE DISEASE
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:
Avoidance of hypovolemia
Avoidance of precipitous decrease in systemic vascular resistance, as may happen during induction of anesthesia
Avoidance of tachycardia, which will decrease diastolic filling time
Maintenance of sinus rhythm and preservation of atrial kick
TABLE 142.1 SEVERITY OF AORTIC STENOSIS CHARACTERIZED BY AREA AND MEAN PRESSURE GRADIENT