Abridged Notes
(http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/(Pages)/Aortic_stenosis?OpenDocument )
Aortic stenosis is diagnosed using a number of tests including:
~ Physical examination including listening to the heart with a stethoscope.
~ Chest x-ray.
~ Electrocardiogram (ECG) to monitor the heart rate and pick up any unusual rhythms and to assess thickening of the left ventricle.
~ Echocardiograph (ultrasound scan) of the heart to assess the functioning of the aortic valve and of the left ventricle.
~ Cardiac catheterisation (a slender tube is inserted into a blood vessel of the groin and threaded up to the heart).
~ Left ventriculography, which includes using a dye so that the heart shows up more clearly on x-ray.
~ Coronary arteriography to assess whether there is coronary artery disease in addition to the recognised aortic valve disease
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Detailed Notes: (http://www.emedicine.com/radio/topic46.htm)
Electrocardiography
o In aortic stenosis, ECG usually demonstrates LV hypertrophy; however, in some patients with severe aortic stenosis, LV hypertrophy is absent on ECG, possibly owing to the lack of LV dilatation. Left atrial abnormality is common because the stiff LV increases left atrial afterload and causes the left atrium to dilate.
o In summary, ECG findings demonstrate left atrial abnormality and LV hypertrophy.
• Imaging techniques are described in detail in sections below.
Preferred Examination:
Echocardiography
Echocardiography is the preferred imaging test. Echocardiography is indispensable to the assessment of the extent of LV hypertrophy, systolic ejection performance, and anatomy of the aortic valve.
Doppler interrogation of the aortic valve makes use of the modified Bernoulli equation (gradient = 4 X velocity2) to assess the severity of the stenosis. As blood flows from the body of the LV across the stenotic valve, the flow rate must accelerate for the volume to remain constant. Doppler interrogation of the valve detects this increase in velocity and helps estimate the valvular gradient. In summary, echocardiography may demonstrate the following findings:
• Concentric LV hypertrophy
• Reduced separation of the cusp of the aortic valve
• Mean gradients of greater than 50 mm Hg in patients with severe aortic stenosis on Doppler echocardiography
Chest radiography
Chest radiographs may show several significant findings consistent with aortic stenosis. The aortic valve may appear calcified. With plain images, calcification is best detected on the lateral view. Calcification of the aortic valve is found in almost all adults with hemodynamically significant aortic stenosis.
The LV may be slightly enlarged with a rounded apex, which is a nonspecific finding. The left atrium may be enlarged as well. Visible calcification on plain chest films usually indicates a gradient of 50 mm Hg or more across the valve, which is severe enough to require surgery.
CT scanning
CT scans may exhibit chamber enlargement and calcification of the aortic valve. This calcification is a reliable indicator of severe stenosis, particularly when it is present in a young patient.
Magnetic resonance imaging
Cine MRI can be used to depict the signal void caused by high-velocity jet flow across a narrow valvular orifice associated with the opened valve in aortic stenosis. The signal void is projected into the ascending aorta in systole. Despite the good anatomic detail obtainable by using MRI, echocardiography has superseded MRI because of its improved portability.
Cardiac catheterization and angiography
During catheterization, the transvalvular pressure gradient across the aortic valve is measured, with a catheter in the LV and another in the proximal aorta or femoral artery. A mean pressure gradient of greater than 30 mm Hg usually represents clinically significant aortic stenosis
Routine chest radiography may demonstrate normal or nondiagnostic findings in patients with critical aortic stenosis. Findings include those described below.
• Enlarged cardiac chamber
o The cardiac silhouette is usually normal in size or slightly enlarged on the anteroposterior view. The edge of the LV and the apex may appear rounded, causing a boot-shaped appearance. In the presence of aortic regurgitation or heart failure, substantial cardiomegaly is noted.
o The left atrium may be slightly enlarged in patients with severe aortic stenosis, and radiologic signs of pulmonary venous hypertension may be demonstrated. However, when left atrial enlargement is marked, associated mitral valvular disease should be suspected.
• Valvular calcification
o Calcification of the aortic valve is diagnostic of aortic stenosis.
o This is detected best by using fluoroscopy or CT scans. If seen on plain images, calcification is detected most readily on the lateral view.
o Calcification of the aortic valve is found in almost all adults with hemodynamically significant aortic stenosis.
o The absence of calcium in the region of the aortic valve on careful fluoroscopic examination in a patient older than 35 years essentially excludes severe valvular aortic stenosis. However, in patients older than 65 years with degenerative aortic stenosis, severe calcification of the aortic valve may occur with no or only mild obstruction.
• Dilatation of the aorta
o Poststenotic dilatation of the ascending aorta is a common finding.
o The dilatation is characteristically located in the ascending aorta and increases convexity of the right lateral aspect of the ascending aorta.
o The transverse arch or aortic knob is not enlarged.
o LV hypertrophy and dilatation also occur in this condition and result in enlargement of the heart downward and to the left. The heart is usually not enlarged greatly unless it has begun to decompensate.
• Supravalvular stenosis
o Supravalvular aortic stenosis is a rare condition that is seen as an element of Williams syndrome, which consists of mental and physical retardation, elfin facies, hypercalcemia, and peripheral pulmonary artery stenoses.
o In supravalvular aortic stenosis, a tight hourglass constriction of the ascending aorta is present just cephalic to the valve.
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