Valvular Aortic Stenosis
Definition
Narrowing of the aortic valve orifice.
Etiology
- Degenerative (senile, fibrocalcific) ; mean age 65 to 70
- Congenital (e. g., bicuspid aortic valve)
- Rheumatic fever (inflammatory)
Signs and Symptoms
- Angina pectoris
- Syncope
- Congestive heart failure
Complications
- Results in ventricular pressure overload and hypertrophy
- Increased left ventricular end-diastolic pressure
- Increased left atrial pressure
- Left ventricular systolic dysfunction (late in course)
- Increased pulmonary artery pressures (rare)
- Increased risk of infective endocarditis
- Increased risk of sudden death
Cardiac Auscultation
- Harsh, systolic ejection murmur, crescendo-decrescendo in shape,
best heard at the right upper sternal border, which may radiate
into the carotid arteries - S4 may be heard
- Pulsus parvus et tardus (slow-rising, late-peaking carotid pulse)
Electrocardiogram
- Left ventricular hypertrophy
- Left atrial enlargement
- Atrial fibrillation
Chest X-ray
- Left ventricular hypertrophy
- Left atrial enlargement
- Post-stenotic dilatation of the ascending aorta
Cardiac Catheterization
- Determines peak-to-peak pressure gradient
- Determines mean pressure gradient
- Determines aortic valve area by the Gorlin formula:
AVA (cm2) = (CO ÷ SEP) ÷ (43. 3 x MPG)
Where AVA is the aortic valve area, CO is cardiac output, SEP
the systolic ejection period, 43.3 is the constant, and MPG is the
mean pressure gradient.
Surgical Treatment
- Aortic debridement (rare)
- Aortic balloon valvuloplasty (rare)
- Aortic valve replacement
Bicuspid Aortic Valve
M-Mode
- Thickened aortic valve leaflets
- Eccentric closure line of aortic valve leaflets. The degree of eccentricity can be calculated as:
EI = 1/2 A ÷ a
Where EI is the eccentricity index, A is the internal aortic root diameter at the onset of diastole, and a is the distance from the line of aortic cusp coaptation to the nearest aortic wall at the onset of diastole. - An index ≥ 1.5 indicates a bicuspid aortic valve (74% of patients who have surgically or angiographically proved bicuspid aortic valve). A normal eccentricity index (< 1. 5) does not exclude the presence of a bicuspid aortic valve.
2-D
- Thickened aortic valve leaflets
- Systolic "doming"'
- Diastolic "doming" (aortic valve prolapse)
- Football-shaped opening of the aortic valve best seen in the parasternal short-axis view of the aortic valve
Degenerative/Rheumatic (Inflammatory)
M-Mode
- Increased thickness of aortic valve leaflets
- Decreased excursion of aortic valve leaflets (< 15 mm)
- Absence of systolic flutter of the aortic valve leaflets
- Left ventricular hypertrophy
- Left atrial enlargement
2-D
- Increased thickness of aortic valve leaflets
- Decreased excursion of aortic valve leaflets (< 15 mm)
- Post-stenotic dilatation of the ascending aorta
- Left ventricular hypertrophy
- Increased left ventricular mass
- Decreased left ventricular systolic function (late in course)
- Left atrial enlargement
Doppler
- Determine peak aortic velocity
- Determine maximum instantaneous pressure gradient
- Determine mean transvalvular pressure gradient
- Determine aortic valve area (continuity equation)
- Determine velocity ratio
Important to Note
- The aortic valve should be examined from several windows (e.g. apical, right parasternal, suprasternal, supraclavicular, subcostal, left parasternal) with CW Doppler to confirm that the ultrasound beam is parallel to flow; this ensures that the highest velocity across the aortic valve is obtained.
- Catheterization measures the peak-to-peak gradient, while Doppler determines the maximum instantaneous pressure gradient.
- To confirm the Doppler results, compare the mean gradient and aortic valve area with the Catheterization findings. They should be nearly equal.
- Evaluate left ventricular systolic function because it has a direct effect on the peak velocity of the aortic valve.
- When aortic regurgitation is 3+ or 4+ determine the aortic valve area. Significant AR increases the velocity across the aortic valve, causing stenosis to be overestimated.
- Be careful not to confuse mitral regurgitation with the aortic stenosis jet. Mitral regurgitation is longer in duration because there is no flow during the Isovolumic contraction or Isovolumic relaxation period through the aortic valve. In addition, mitral regurgitation usually has a greater velocity than aortic stenosis because the pressure gradient between the left ventricle and aorta is less than that between the left ventricle and left atrium.
- An asymmetric triangular contour with an early peaking of the jet usually indicates mild aortic stenosis.
- Symmetric and rounded velocity contour with a late peaking jet velocity (peak > 50% of total ejection time) is usually seen in severe aortic stenosis.
- To evaluate whether a bicuspid aortic valve is present, use the parasternal short-axis view of the aortic valve and evaluate the valve in systole. A "raphe" (an underdeveloped aortic cusp) may give the appearance of three leaflets in diastole
- It may be difficult to differentiate a bicuspid aortic valve from an acquired aortic stenosis. Aortic stenosis due to a bicuspid aortic valve usually becomes symptomatic at age 20 to 50, while calcific aortic stenosis occurs in the elderly.