A new review article on aortic-valve stenosis comes from Dr. Catherine Otto at the University of Washington School of Medicine in Seattle and Dr. Bernard Prendergast at John Radcliffe Hospital in Oxford, UK.
Valvular aortic stenosis is a progressive disease in which the end stage is characterized by obstruction of left ventricular outflow, resulting in inadequate cardiac output, decreased exercise capacity, heart failure, and death from cardiovascular causes.
•What is the epidemiology of aortic stenosis?
The prevalence of aortic stenosis is only about 0.2% among adults between the ages of 50 and 59 years but increases to 9.8% in octogenarians, with an overall prevalence of 2.8% in adults older than 75 years of age. Although mortality is not increased when aortic stenosis is asymptomatic, the rate of death is more than 50% at 2 years for patients with symptomatic disease unless aortic-valve replacement is performed promptly. A total of 65,000 aortic-valve replacements were performed in the United States in 2010, primarily for aortic stenosis; 70% of these procedures were performed in patients older than 65 years of age, contributing to the high cost of health care in our aging population.
•What clinical factors have been associated with calcific aortic valve disease?
Clinical factors associated with calcific valve disease mirror those associated with coronary atherosclerosis, and coronary artery disease is common among adults with aortic stenosis. Population-based studies have shown associations between calcific valve disease and older age, male sex, elevated serum levels of low-density lipoprotein (LDL) cholesterol and lipoprotein(a), hypertension, smoking, diabetes, and the metabolic syndrome. Specific opulations at increased risk for aortic stenosis include patients with a history of mediastinal irradiation, renal failure, familial hypercholesterolemia, or disorders of calcium metabolism.
Morning Report Questions
Q: Who should undergo an aortic-valve replacement?
A: Clinical outcomes in adults with aortic stenosis are determined primarily by clinical symptoms, the severity of valve obstruction, and the left ventricular response to pressure overload. Assessment of patients and management decisions should take all three of these factors into account. The presence or absence of symptoms is the key element in decision-making. There is robust evidence that aortic-valve replacement prolongs life in patients with symptomatic severe aortic stenosis, regardless of the type or severity of symptoms or the response to medical therapy. However, accurate measures of the severity of stenosis are needed to ensure that valve obstruction — rather than concurrent coronary, pulmonary, or systemic disease or other conditions — is the cause of symptoms. In a patient with typical symptoms, a maximum transvalvular velocity of 4 m per second or greater, in conjunction with calcified immobile valve leaflets, confirms the diagnosis of severe aortic stenosis. Intervention is not needed until symptoms supervene, because the risk of sudden death is less than the risk of intervention, even when valve obstruction is severe. With very severe aortic stenosis, the rate of symptom onset is so high that elective valve replacement may be reasonable in selected cases.
Q: What factors affect choice of valve type for replacement?
A: The primary consideration in the choice of valve type is the risk of reoperation when a bioprosthetic valve is used versus the risk associated with warfarin anticoagulation when a mechanical valve is used. Mechanical valves are appropriate for patients younger than 60 years of age who have no contraindication to anticoagulation, because of the long-term durability of these prostheses. An exception is women of childbearing age, in whom a bioprosthetic valve is preferred, given the risks of anticoagulation and thromboembolism during pregnancy. In patients older than 70 years of age, bioprostheses are favored because valve durability increases with age and the risks of anticoagulation are avoided. In patients between 60 and 70 years of age, the choice of valve is based on patients’ preferences and values after a shared discussion between the patient and the surgeon.