• Clinical science

Aortic valve stenosis

Abstract

Aortic stenosis (AS) is a valvular heart disease characterized by narrowing of the aortic valve. As a result, the outflow of blood from the left ventricle into the aorta is obstructed. This leads to chronic and progressive excess load on the left ventricle and potentially left ventricular failure. The patient may remain asymptomatic for long periods of time; for this reason, AS is often detected late, i.e., when it first becomes symptomatic (dyspnea on exertion, angina pectoris, or syncope). Auscultation reveals a harsh, crescendo-decrescendo murmur in systole that radiates to the carotids, and pulses are delayed with diminished carotid upstrokes. Echocardiography is the gold standard for diagnosis. Patients with asymptomatic aortic stenosis are treated conservatively. Symptomatic patients or those with severe aortic valve stenosis require valve replacement.

Epidemiology

  • Most common valvular heart disease in industrialized countries
  • Prevalence:
    • Increases with age
    • May reach up to 12.4% among individuals ≥ 75 years

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Classification

By location of obstruction

  • Valvular: most common
  • Supravalvular
  • Subvalvular

By degree of severity

Grade Mean systolic pressure gradient Valve area Symptoms
normal 2-4 mmHg 3-4 cm2
Mild < 25 mm Hg > 1.5 cm2 asymptomatic
Moderate 25–40 mm Hg 1–1.5 cm2 mostly asymptomatic
Severe > 40 mm Hg < 1.0 cm2 possibly asymptomatic
Very severe > 70 mm Hg < 0.6 cm2 symptomatic

By etiology

  • Congenital:
    • Bicuspid aortic valve: Caused by a fusion of two of the three aortic-valve leaflets in utero
      • Most common congenital heart defect, 3:1 predominance
      • Predisposes the valve to dystrophic calcification and degeneration
      • Patients present with symptoms of aortic stenosis earlier than in regular aortic valve calcification
  • Acquired
    • Calcific aortic stenosis: most common cause of aortic stenosis
      • Characterized by calcification and fibrosis of aortic valve leaflets that occur at an increasing rate as patients age (prevalence is 65% in those aged 75–84 years)
      • Similar pathophysiology to atherosclerosis (see generic risk factors for development of arteriosclerosis)
    • Rheumatic fever is a rare cause of AS in developed countries, but continues to remain a significant cause in developing countries.

References:[3][4][5]

Pathophysiology

References:[3][6]

Clinical features

  • The disease may remain asymptomatic for years (particularly with mild or moderate stenosis).
  • Symptoms typically present on exertion, unless AS is severe
  • Dyspnea
  • Angina pectoris
  • Dizziness and syncope
  • Small blood pressure amplitude, decreased pulse pressure
  • Cardiac exam (see cardiovascular examination)
    • Delayed and weak pulse (Pulsus parvus et tardus)
    • Palpable systolic thrill over the bifurcation of the carotids and the aorta
    • Harsh crescendo-decrescendo (diamond-shaped), late systolic ejection murmur that radiates bilaterally to the carotids
      • Best heard in the 2nd right intercostal space
      • Hand grip decreases the intensity of the murmur.
      • Valsalva and standing from squatting decreases or does not change the intensity of the murmur (in contrast to hypertrophic cardiomyopathy).
    • Soft S2 and the aortic component (A2) may be delayed (paradoxical splitting)
    • S4 is best heard at the apex.
    • Sustained point of maximal impulse (PMI)
    • Early systolic ejection click
    • Frequently associated with aortic regurgitation (see diagnosis of aortic regurgitation)
  • Additional signs specific to infants: wheezing and difficulty feeding

SAD (syncope, angina, dyspnea)

Without definite treatment (surgery), more than 50% of the symptomatic patients with severe aortic stenosis will die within the first 2 years of diagnosis!

References:[3][7][4]

Diagnostics

  • ECG
    • Nonspecific for AS
    • Signs of left ventricular hypertrophy (e.g., left axis deviation, positive Sokolow-Lyon index)
  • Chest x-ray
    • Findings of left ventricular hypertrophy, such as left ventricular enlargement and rounded heart apex, usually only in decompensated aortic stenosis, and possibly left atrial enlargement as well
    • Narrowing of retrocardiac space (lateral view)
    • Calcification of aortic valve: signs of more severe disease
  • Echocardiography
    • Transthoracic (TTE) or transesophageal (TEE): preferred primary test and noninvasive gold standard
      • Findings include concentric hypertrophy, narrowing of the opening of the aortic valve, and increased mean pressure gradient across the aortic valve. Concentric hypertrophy occurs in high-pressure states and eccentric hypertrophy occurs in high-volume states.
      • Also utilized to determine the severity of stenosis by parameters such as the mean gradient and cross-sectional area of the opening of the valve
  • Left-heart catheterization
    • Definitive diagnostic test
    • Indication: inconclusive echocardiogram
    • Risk of cerebral embolization

References:[3][8][9]

Treatment

  • Conservative management: regular follow-ups indicated for asymptomatic patients with mild aortic stenosis
  • Surgical (see heart valve prostheses)
    • Indications
      • Symptomatic patients
      • Asymptomatic patients with severe AS and either significantly ↓ LV EF or those undergoing cardiac surgery
    • Aortic valve replacement (AVR): 3 possible approaches
      • Surgical AVR: patients with low surgical risk.
      • Transcatheter AVR (TAVR): patients with high surgical risk or contraindication
      • Catheter balloon valvuloplasty: children without AV calcification

The presence of exertional symptoms (dyspnea on exertion, angina pectoris, syncope) is an indication for surgery!
References:[7]

Prognosis

  • Asymptomatic patients: The mortality rate is < 1% in a given year.
  • Symptomatic patients: The mortality rate in the first 2 years is > 50%.

References:[7]

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  • 2. Osnabrugge RLJ, Mylotte D, Head SJ, et al. Aortic stenosis in the elderly: disease prevalence and number of candidates for transcatheter aortic valve replacement: A meta-analysis and modeling study. J Am Coll Cardiol. 2013; 62(11): pp. 1002–1012. doi: 10.1016/j.jacc.2013.05.015.
  • 3. Kasper DL, Fauci AS, Hauser SL, Longo DL, Lameson JL, Loscalzo J. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill Education; 2015.
  • 4. Crawford MH. Current Diagnosis and Treatment: Cardiology. Lange; 2013.
  • 5. Stritzke J, Linsel-nitschke P, Markus MR, et al. Association between degenerative aortic valve disease and long-term exposure to cardiovascular risk factors: results of the longitudinal population-based KORA/MONICA survey. Eur Heart J. 2009; 30(16): pp. 2044–2053. doi: 10.1093/eurheartj/ehp287.
  • 6. Otto CM. Clinical manifestations and diagnosis of aortic stenosis in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-aortic-stenosis-in-adults. Last updated October 24, 2016. Accessed October 4, 2017.
  • 7. Ren X. Aortic Stenosis. In: Aortic Stenosis. New York, NY: WebMD. http://emedicine.medscape.com/article/150638. Updated December 11, 2016. Accessed February 26, 2017.
  • 8. Saikrishnan N, Kumar G, Sawaya FJ, Lerakis S, Yoganathan AP. Accurate assessment of aortic stenosis: a review of diagnostic modalities and hemodynamics. Circulation. 2014; 129(2): pp. 244–253. doi: 10.1161/CIRCULATIONAHA.113.002310.
  • 9. Cary T, Pearce J. Aortic Stenosis: Pathophysiology, Diagnosis, and Medical Management of Nonsurgical Patients. https://www.ncbi.nlm.nih.gov/pubmed/23547127. Updated February 13, 2017. Accessed March 21, 2018.
last updated 11/11/2018
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