Aortic valve stenosis

Aortic valve 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 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 noninvasive gold standard for diagnosis. Patients with mild asymptomatic aortic stenosis are treated conservatively with monitoring and medical management of related conditions (e.g, hypertension). Symptomatic patients, or those with severe aortic valve stenosis, require immediate aortic valve replacement (AVR) as definitive treatment. Options for valve replacement include surgical AVR or transcatheter AVR (TAVR) for patients with high operative risk. Patients with severe AS have a high risk of developing acute complications such as heart failure and cardiogenic shock, which are challenging to manage and often require critical care interventions and expedited surgery or TAVR.

• Most common valvular heart disease in industrialized countries
• Frequently associated with aortic regurgitation
• Prevalence ^[1]
  • Increases with age
  • May reach up to 12.4% among individuals ≥ 75 years

Epidemiological data refers to the US, unless otherwise specified.

The most common etiologies of valvular aortic stenosis include:

• Aortic valve sclerosis: calcification and fibrosis of aortic valve leaflets ^[2]
  • Most common cause of aortic stenosis
  • Occurs at an increasing rate as patients age (prevalence is 35% in those aged 75–85 years) ^[3]
  • Similar pathophysiology to atherosclerosis (see risk factors for atherosclerosis)
• Bicuspid aortic valve (BAV): fusion of two of the three aortic-valve leaflets in utero ^[2]
  • Most common congenital heart valve malformation , predominantly affects males (3:1) ^[4]
  • Predisposes the valve to dystrophic calcification and degeneration
  • Patients present with symptoms of aortic stenosis earlier than in regular aortic valve calcification. ^[2][4]
  • Congenital aortic stenosis is rare and usually features a unicuspid or bicuspid valve. ^[3]
• Rheumatic fever ^[3]
  • Rare cause of AS in high-income countries due to consistent use of antibiotics for the treatment of streptococcal pharyngitis
  • Still remains a significant cause of AS in lower-income countries, where antibiotics may be less readily available
  • Stenosis is caused by commissural fusion. ^[3]

• Narrowed opening area of the aortic valve during systole → obstruction of blood flow from left ventricle (LV) → increased LV pressure → left ventricular concentric hypertrophy, which leads to:
  • Increased LV oxygen demand
  • Impaired ventricular filling during diastole → left heart failure
  • Reduced coronary flow reserve
• Initially, cardiac output (CO) can be maintained (see “Compensation mechanisms” in “Congestive heart failure”)
• Later, the decreased distensibility of the left ventricle reduces cardiac output and may then cause backflow into the pulmonary veins and capillaries → higher afterload (pulmonic pressure) on the right heart → right heart failure

References:^[5][6]

Aortic stenosis may remain asymptomatic for years, particularly with mild or moderate stenosis. Symptoms usually start to develop when the disease progresses to severe AS, and may present at rest or on exertion.

• Signs and symptoms
  • Dyspnea (typically exertional)
  • Angina pectoris
  • Dizziness and syncope
  • Additional signs specific to infants: wheezing and difficulty feeding
• Physical examination
  • Small blood pressure amplitude, decreased pulse pressure
  • Weak and delayed distal pulse ; (pulsus parvus et tardus) ^[2]
  • Palpable systolic thrill over the bifurcation of the carotids and the aorta ^[2]
  • See cardiovascular examination for further details.
• Auscultation
  • Harsh crescendo-decrescendo (diamond-shaped), late systolic ejection murmur that radiates bilaterally to the carotids
    • Best heard in the 2^nd right intercostal space
    • Handgrip 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).
    • See auscultation in valvular defects for comparison with other valvular heart diseases.
  • Soft S2
  • S4 is best heard at the apex.
  • Early systolic ejection click

To remember the three major symptoms of aortic valve stenosis, think: SAD (syncope, angina, dyspnea).

References:^[5][7]

American Heart Association (AHA)/American College of Cardiology (ACC) staging system ^[8]

• Used to monitor disease progression and determine the need for intervention
• Based on echocardiographic criteria of valve anatomy and hemodynamics
  • Aortic valve area (AVA): the opening area of the aortic valve measured during systole and an important factor in the evaluation of severity of aortic valve stenosis
  • Transaortic velocity: the maximum velocity of blood flow measured across the aortic valve during systole; inversely related to the aortic valve area
  • Mean aortic pressure gradient: the difference in pressure between the left ventricle and the ascending aorta during systole
    • Pressures normally equilibrate relatively rapidly when the valve opens.
    • Valvular stenosis limits the increase in aortic pressure while increasing the LV pressure, leading to a higher gradient.

Initial evaluation

Echocardiography ^[8]

• Indication: Assessment of aortic valve structure, function, and stenosis severity, left ventricle and other heart valves (see valvular heart diseases)
  • TTE: recommended primary test; and noninvasive gold standard used to confirm diagnosis and determine AS severity ^[8]
  • TEE: second-line modality for confirmation of TTE findings or operative planning ^[9]
• Supportive findings
  • Calcification and narrowing of the aortic valve
  • Increased mean aortic pressure gradient and transvalvular velocity
  • Signs of cardiac remodeling, e.g., concentric hypertrophy

Other

• Laboratory studies: usually nonspecific and therefore not routinely indicated; however, they can be useful for the evaluation of other possible etiologies.
  • BNP/NT-proBNP ^[3][10]
  • Troponin T/I ^[10][11][12]
• ECG ^[2][3]
  • ECG signs of LVH (e.g., positive Sokolow-Lyon index)
  • Nonspecific ST-segment and T-wave abnormalities
• Chest x-ray: Used to assess for pulmonary edema or other causes of dyspnea. ^[2]
  • Visible calcifications within the aortic valve may indicate more severe disease. ^[3]
  • Narrowing of retrocardiac space (lateral view)
  • Signs of cardiac remodeling and associated heart failure: x-ray signs of LVH, pulmonary congestion, poststenotic dilation of the aorta

Additional evaluation ^[8]

Low-dose dobutamine stress testing

• Indication: stage D AS with LVEF < 50% to determine the true anatomic severity of the stenosis
• Typical findings
  • Severe AS: valve area, transaortic velocity, and mean aortic pressure gradient stay fixed.
  • Moderate AS: valve area will increase as the stroke volume increases in response to dobutamine.

Exercise stress testing

• Indication: stage C1 AS and stage C2 AS to provoke possible exertional symptoms
• Findings:
  • Typical symptoms, e.g., angina, excessive dyspnea, or dizziness
  • Arrhythmia or ST-segment depression
  • Hypotension or insufficient rise in blood pressure (< 20 mm Hg)
• Interpretation: Exertional findings indicate stage D AS.

Exercise stress testing is contraindicated in patients with severe symptomatic AS (stage D).

Cardiac catheterization

• Diagnostic hemodynamic cardiac catheterization: an accurate diagnostic test for the evaluation of aortic valve area, cardiac output, and mean aortic pressure gradient.
  • Consider in symptomatic patients with inconclusive noninvasive testing or discrepancy between symptoms and noninvasive testing. ^[13]
  • Findings: similar to echocardiographic findings
• Coronary angiography
  • Indication: Preoperative cardiac risk stratification for patients with angina, reduced LVEF, signs of ischemia, or other CAD risk factors
  • Findings: signs of CAD (e.g., coronary stenosis)
• Complications: See “Complications” in cardiac catheterization.

Advanced imaging ^[8][14][15]

Consider the following noninvasive imaging options in the perioperative assessment of patients with severe AS, along with expert consultation. ^[8][14]

• Cardiac CT
  • Used in select patients to rule out concomitant CAD if pretest probability is low
  • Can quantify valve calcification
  • Useful for specific measurements required prior to TAVR
• Cardiac MRI
  • Provides precise information on anatomy and hemodynamics
  • Can be helpful in evaluating severity of AS but is not always available

• See valvular heart diseases for an overview of other cardiac valvulopathies.
• See differential diagnoses of syncope and causes of syncope.
• See differential diagnoses of chest pain.
• See differential diagnosis of dyspnea.

General principles ^[8]

• Aortic valve stenosis is a progressive condition and definitive management requires valve replacement.
• Urgency of valve repair/replacement depends on staging.
  • Symptomatic and/or severe AS: aortic valve replacement usually indicated
  • Asymptomatic or mild-moderate AS: management of medical comorbidities and monitoring echocardiography; some may benefit from early valve replacement ^[16]
• Management of acute complications requires individualized and specialized care.

Medical management

Management of medical comorbidities ^[8]

All patients should be screened and treated for other cardiac risk factors.

• Hypertension: Follow standard hypertension guidelines; medication should be carefully titrated to avoid hypotension.
  • ACE-inhibitors may be beneficial in the prevention of cardiac remodeling. ^[17][18][19]
  • Beta blockers are preferable in patients with concurrent coronary artery disease.
  • Diuretics should be avoided if the left ventricle is small.
• Hyperlipidemia: Statins are not useful in preventing AS progression.
• Diabetes mellitus: See “Treatment” in diabetes mellitus. ^{[20][21][22][23]}
• Atrial fibrillation: See “Management of acute complications” below.

Management of acute complications ^{[3][8][16][24]}

Prompt critical care specialist consultation and rapid surgical referral are recommended. Patients should receive AVR as soon as possible.

• Acute decompensated heart failure: e.g., flash pulmonary edema
  • Use diuretics with caution.
  • Consider vasodilators, e.g., nitroprusside , in severely decompensated patients (stage D AS). ^[25]
  • See also “Management of acute heart failure”.

Afterload reduction (e.g., with vasodilators or diuretics) in severe AS may reduce cardiac output enough to compromise systemic and myocardial perfusion. Careful titration is recommended with specialist guidance.

• Cardiogenic shock
  • Fluid management: requires very careful balance and extreme caution
  • Inotropes and vasopressors: use with caution as effects are difficult to predict
  • Consider bridging devices such as IABP or percutaneous balloon valvuloplasty early. ^[26]

Severe AS compromises coronary perfusion (due to high LV pressure and low pressure in the aortic root). Avoid hypotension as it can cause cardiac ischemia.

• Atrial fibrillation: Maintain sinus rhythm as much as possible.
  • First-line: prompt electrical cardioversion or chemical cardioversion.
  • Second-line: initiate rate control.
  • See management of atrial fibrillation with RVR.

Monitoring and prophylactic antibiotics ^[8]

• Echocardiography
  • Regular follow-up imaging is indicated for asymptomatic patients with:
    • Mild stage B AS: every 3–5 years
    • Moderate stage B AS: every 1–2 years
    • Any stage C AS: every 6–12 month
  • On-demand imaging is indicated for patients with:
    • Any change in signs or symptoms
    • Conditions that have high hemodynamic/metabolic demands
• Prophylactic antibiotics
  • Rheumatic heart disease: should receive secondary prophylaxis, e.g., penicillin G benzathine or sulfadiazine (see “Prevention” in rheumatic fever for more details). ^[27]
  • Dental procedures: consider prophylaxis for infective endocarditis for at-risk patients (e.g., after aortic valve replacement)

Aortic valve replacement (AVR) and repair

Indications

• Symptomatic patients with severe, high-gradient AS (stage D AS)
• Asymptomatic patients with severe AS and:
  • Significantly ↓ LVEF (stage C2 AS)
  • Undergoing cardiac surgery for other indications (stage C AS or stage D AS)
• AVR can also be beneficial for certain patients with moderate (stage B AS) to severe (stage D AS) with specific characteristics.

The presence of exertional symptoms (dyspnea on exertion, angina pectoris, syncope) is an indication for surgery.

Procedure

All patients being considered for TAVR or high-risk surgical AVR should be treated by members of a heart valve team. ^[8]

• Surgical AVR
  • Recommended for patients with: ^[8]
    • Low to moderate surgical risk
    • Higher surgical risk AND severe multivessel coronary artery disease
• Transcatheter AVR (TAVR)
  • Recommended for patients with high or prohibitive surgical risk and predicted survival of > 12 months ^[8][14]
  • Reasonable alternative for patients with intermediate surgical risk ^[8]
  • Emergency TAVR may be considered in certain patient groups. ^[28][29][30]
• Percutaneous balloon valvuloplasty
  • Indicated in children, adolescents, and young adults without AV calcification ^[8]
  • Can consider as a bridging intervention in high-risk patients with stage D AS but overall benefit is questionable. ^[8][31]

Complications of aortic valve replacement ^[32][33][34]

• Vascular complications, thromboembolism/stroke
• Major bleeding
• Renal failure
• Arrhythmias: atrioventricular block, atrial fibrillation
• Aortic regurgitation/paravalvular leak
• Infection: endocarditis

Antithrombotic therapy after aortic valve replacement

NOACs should be avoided in patients with mechanical valves.

• Asymptomatic patients: Mortality rate is < 1% in a given year. ^[20]
• Symptomatic patients: Mortality rate in the first 2 years is > 50% if left untreated. ^[35]