Saturday, November 23, 2013

AORTIC STENOSIS


General Considerations 
  • Most often as result of degeneration of bicuspid aortic valve
  • Less commonly rheumatic heart disease or secondary to degeneration of a tricuspid aortic valve in person > 65 
Location
  • Supravalvular
    • Uncommon
    • Associated with William’s Syndrome
      • Hypercalcemia
      • Elfin facies
      • Pulmonary stenoses
      • Hypoplasia of aorta
      • Stenoses in
        • Renal, celiac, superior mesenteric arteries
  • Valvular
    • Most common
    • Either congenital (from a bicuspid aortic valve) or acquired
      • Bicuspid aortic valve is the most common congenital cardiac anomaly
        • 0.5 –2%
  • Subvalvular
    • Associated with
      • Hypoplastic left heart syndrome
      • Idiopathic Hypertrophic Subaortic Stenosis
      • Hypertrophic cardiomyopathy
      • Subaortic fibrous membrane 
Types
  • Congenital aortic stenosis (more common)
    • Most frequent congenital heart disease associated with intra-uterine growth retardation (IUGR)
      • Subvalvular (30%)
      • Valvular (70%)
        • Degeneration of bicuspid valve
      • Supravalvular
  • Acquired aortic stenosis
    • Rheumatic valvulitis
      • Almost invariably associated with mitral valve disease
    • Fibrocalcific senile aortic stenosis
      • Degenerative 
Clinical Findings
  • Asymptomatic for many years
  • Classical triad
    • Angina
    • Syncope
    • Shortness of breath (heart failure)
  • Systolic ejection murmur
  • Carotid pulsus parvus et tardus
  • Diminished aortic component of 2nd heart sound
  • Sudden death in severe stenosis after exercise
    • Diminished flow in coronary arteries causes ventricular dysrhythmias and fibrillation
    • Decompensation leads to left ventricular dilatation and pulmonary venous congestion
Imaging Findings 
  • In older children or young adults
    • Prominent ascending aorta
      • Poststenotic dilatation of ascending aorta
        • Due to turbulent flow
    • Left ventricular heart configuration
      • Normal-sized or enlarged left ventricle
      • Concentric hypertrophy of left ventricle produces a relatively small left ventricular chamber with thick walls
    • Heart size is frequently normal
  • In adults >30 years
    • Prominent ascending aorta
      • Poststenotic dilatation of ascending aorta
        • Due to turbulent flow
    • Calcification of aortic valve (best seen on RAO)
      • In females, usually indicates hemodynamically significant aortic stenosis
      • Calcification of the valve usually indicates a gradient across valve of > 50mm Hg
      • Calcification begins in bicuspid and rheumatic valve in 4th decade but not until > 65 in tricuspid
      • DDx
        • Calcification of aortic annulus in elderly
        • Calcified coronary artery ostium (thickened cusp echoes only in diastole)
    • Normal to enlarged left ventricle
Echocardiographic findings
  • Thickened and calcified aortic valve with multiple dense cusp echoes throughout cardiac cycle (right > non-coronary > left coronary cusp)
  • Decreased separation of leaflets in systole with reduced opening orifice (13-14 mm = mild AS; 8-12 mm = moderate AS; <8 mm = severe AS)
  • ± Doming in systole
  • Dilated aortic root
  • Increased thickness of LV wall (= concentric LV hypertrophy)
  • Hyperdynamic contraction of LV (in compensated state)
  • Decreased mitral EF slope (reduced LV compliance)
  • LA enlargement
  • Increased aortic valve gradient (Doppler)
  • Decreased aortic valve area (unreliable)
Angiographic findings
 
  • Simultaneous LV and aortic pressures recordings yield valve gradients from left heart catheterization
  • Angiographic technique uses standard RAO left ventriculogram and an aortogram using a 40° LAO projection
  • A non-calcified, bicuspid valve reveals thickening and doming of the valve leaflets in systole
  • A jet of non-opacified blood is visible through stenotic valve
    • Congenitally bicuspid valves still usually have three aortic sinuses with one large non-coronary sinus equal in size to the other two
    • Calcification begins in the bicuspid and rheumatic valve in the 4th decade but not until >65 in tricuspid
    • In rheumatic disease, the aortic valve commissures usually fuse whereas they do not in the degenerated tricuspid valve
 Differentiating Causes of Aortic Stenosis
Etiology/Findings
Calcification
Other clues
Congenital Bicuspid Valve
30’s
Jet effect on aortogram
Degeneration of Tricuspid Valve
> 65
Coronary artery ca++
Commissures don’t fuse
Rheumatic dz in Tricuspid Valve
30’s here; teens in 3rd
world countries
MS or MR almost always present;
commissures fuse
 
Valve areas
 
Normal
Mild
Severe
Critical
2.6-3.5cm2
1.3-1.7
1.0
0.5
 
 
Aortic Stenosis. Frontal radiograph on left demonstrates isolated enlargement of the ascending aorta
(white arrow). The left ventricle is enlarged (red arrow) and the heart is mildly enlarged overall. The lateral view on the right demonstrates calcifications in the region of the aortic valve leaflets (circle). generally, the aortic valve lies above a line drawn from the carina to the junction of the diaphragm with the anterior chest wall. The mitral valve lies below the line.
             
 

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