Diagnosis
����In adults with valvular AS, the obstruction develops gradually, typically
over many years during which the left ventricle (LV) adapts to the systolic
pressure overload with progressive concentric hypertrophy that results
in diastolic dysfunction, reduced coronary reserve, myocardial ischemia,
and eventually, depressed contractility resulting in LV systolic dysfunction.
Ultimately, in some patients, heart failure or sudden death occurs.
Typically, patients with AS are free from cardiovascular symptoms (ie,
angina, syncope, and heart failure) until late in the course of the disease.
������ Once symptoms manifest, the prognosis is poor, with the interval from the onset of
symptoms to the time of death being approximately 2 years in patients with heart failure,
3 years in those with syncope, and 5 years in those with angina.
������ Echocardiography has largely replaced invasive cardiac catheterization as the standard for
quantification of AS.
������ Echocardiographic diagnosis is made by observing a calcified valve with restricted leaflet
opening by two-dimensional (2D) echocardiography with quantification of the peak and
mean AV gradient made by applying the simplified Bernoulli equation (��p = 4v2) to the
maximal velocity recorded through the aortic valve by continuous-wave Doppler.
����Severe stenosis is defined in the guidelines as a peak velocity >4.0 m/s
(corresponding to a peak gradient of 64 mm Hg), a mean gradient
>40 mm Hg, OR valve area <1.0 cm2 when LV systolic function is normal.
������ To account for patient size, the valve area is often indexed to body surface area, ���
with 0.6 cm2/m2 considered to be the threshold for severe AS.
������ An important exception is when the gradient suggests less severe stenosis than the valve
area, most commonly due to low stroke volume, either in dilated ventricles with low
ejection fraction (EF) or small ventricles with normal EF. In this setting, a dobutamine
stress study (maximum stress dose 20 mcg/kg/min), may be helpful. If the maximum jet
velocity rises over 4 m/s with the dobutamine-induced increase in stroke volume while the
aortic valve area (AVA) remains less than 1.0 cm2, then the valve is truly severely stenotic.
On the other hand, if stroke volume increases with little rise in gradient (causing valve
area to increase substantially), then the AS is only mild to moderate in severity, and the
LV dysfunction is due to causes other than AS.
����Other adjunctive testing used in quantifying AS includes transesophageal
echocardiography (TEE), computed tomography (CT) scanning (dynamic
or gated during systole), cardiac magnetic resonance (CMR) and cardiac
catheterization.
����In patients with equivocal symptoms, stress testing, and in particular stress
echocardiography, can be very helpful.
