Stages of disease

Pirogov Russian NationalResearch Medical University

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. 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. Currently, there are no medical therapies to prevent or slow the progression of the disease. Instead, improving patient outcomes depends on identifying those at risk for valve disease, accurately measuring the severity of stenosis, managing any concurrent disease, and ensuring the appropriate timing and type of aortic-valve replacement.

STAGES OF DISEASE

The spectrum of aortic stenosis starts with the risk of leaflet changes and progresses from early lesions to valve obstruction, which is initially mild to moderate but eventually becomes severe, without or with clinical symptoms. The severity of aortic stenosis is best characterized by integration of information concerning valve anatomy, hemodynamics, symptoms, and the left ventricular response to pressure overload (

TABLE 1 Disease Stages in Patients with Aortic-Valve Stenosis. and

FIGURE 1 Echocardiographic Evaluation of Aortic-Valve Stenosis.; and, available with the full text of this article at NEJM.org).

Commonly used indexes of the severity of stenosis include the maximum transvalvular velocity and the mean transaortic pressure gradient. These measures remain relatively normal early in the disease course, and symptoms are unusual until the maximum transvalvular velocity is more than four times the normal velocity (i.e., increased to 4.0 m per second). However, patients with concurrent left ventricular systolic dysfunction may have severe valve obstruction with a low velocity and pressure gradient but a small aortic-valve area. Rarely, patients may have severe low-gradient aortic stenosis even with a normal left ventricular ejection fraction.