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]

Aortic valve sclerosis occurs without aortic stenosis in its early stages, but can progress to aortic stenosis once signs of LVOT obstruction begin to occur. ^[5]

• 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:^[6][7]

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:^[6][8]

American Heart Association (AHA)/American College of Cardiology (ACC) staging system ^[9][10]

• 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.
• The term critical aortic stenosis is commonly used to describe severe AS and/or decompensated AS, however, there is a lack of consensus on the defining parameters. ^[11][12]

Initial evaluation

Echocardiography ^[9]

• 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 ^[9]
  • TEE: second-line modality for confirmation of TTE findings or operative planning ^[13]
• 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][14]
  • Troponin T/I ^[14][15][16]
• 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 ^[9]

Low-dose dobutamine stress testing

• Indication: stage D AS with LVEF < 50% to determine the true anatomic severity of the stenosis
• Typical findings (in response to dobutamine)
  • Severe AS: The AVA remains fixed, resulting in an increase in transaortic velocity and mean aortic pressure gradient.
  • Moderate AS: The AVA increases as the stroke volume increases.

Exercise stress testing

• Indication: stage C1 AS and stage C2 AS to assess physiological changes with exercise
• Findings: exertional symptoms, e.g., angina, excessive dyspnea, dizziness, or syncope
• Interpretation: Exertional findings indicate stage D AS.

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

Cardiac catheterization

• Diagnostic cardiac catheterization: an accurate diagnostic test for the evaluation of aortic valve area, cardiac output, and mean aortic pressure gradient (not routinely indicated) ^[9][17]
  • Consider in symptomatic patients with inconclusive noninvasive testing or discrepancy between symptoms and noninvasive testing. ^[18]
  • Findings: similar to echocardiographic findings
• Coronary angiography
  • Indications in patients undergoing:
    • Valve surgery: preoperative cardiac risk stratification for patients with angina, reduced LVEF, signs of ischemia, or other CAD risk factors
    • TAVR: intermediate to high risk of CAD
  • Findings: signs of CAD (e.g., coronary stenosis)
• Complications: See “Complications” in cardiac catheterization.

Advanced imaging ^[9][19]

Consider the following noninvasive imaging options in the perioperative assessment of patients with severe AS, along with expert consultation.

• 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 valvulopathies.
• See “Differential diagnoses of syncope” and “Causes of syncope.”
• See “Differential diagnoses of chest pain.”
• See “Differential diagnosis of dyspnea.”

AS is a progressive condition that is definitively treated with aortic valve replacement or repair, the urgency of which depends on disease severity (see “Staging aortic valve stenosis”).

Approach ^[9]

• Symptomatic and/or severe AS: Aortic valve replacement or repair is usually indicated.
• Asymptomatic or mild-to-moderate AS: usually treated conservatively; consider early aortic valve replacement in select patients. ^[20]
• All patients
  • Provide supportive care: e.g., manage comorbidities (e.g., hypertension, diabetes), monitor progression with serial echocardiography, provide IE prophylaxis for at-risk patients.
  • Manage critical complications of AS (e.g., acute heart failure) with individualized critical care focusing on acute stabilization and expedited surgical treatment.
  • Consult cardiology and/or cardiothoracic surgery.

Supportive care

Managing comorbidities ^[9][10]

Screen and treat all patients for ASCVD risk factors (see “ASCVD prevention”). ^[9]

• Hypertension: Follow standard hypertension guidelines; medication should be carefully titrated to avoid hypotension. See “Hypertension management.”
  • ACE inhibitors may be beneficial in the prevention of cardiac remodeling. ^[21][22][23]
  • Beta blockers are preferable in patients with concurrent coronary artery disease. ^[10]
  • Diuretics should be avoided if the left ventricle is small.
• Hyperlipidemia
  • See “Lipid disorders” screening and treatment recommendations.
  • Statins are unlikely to directly prevent AS progression.
• Diabetes mellitus: See “Diabetes management.” ^{[24][25][26][27]}

Echocardiographic monitoring ^[28]

• 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 months
• On-demand imaging is indicated for patients with:
  • Any change in signs or symptoms
  • Conditions that have high hemodynamic/metabolic demands

Prophylactic antibiotics ^[28]

• Rheumatic heart disease: Patients should receive secondary prophylaxis, e.g., penicillin G benzathine or sulfadiazine (see “Prevention” in “Rheumatic fever” for more details). ^[29]
• Dental procedures: Consider prophylaxis for infective endocarditis for at-risk patients (e.g., after aortic valve replacement).
• Nondental procedures (e.g., EGD, TEE, colonoscopy): Antibiotic prophylaxis is not recommended.

Aortic valve replacement (AVR) and repair ^[9]

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

The choice of valve type and procedure approach involves shared decision-making based on multiple factors (e.g., anticoagulation risks, age, life expectancy). Refer candidates to a specialized heart valve team. ^[9]

• Surgical AVR (SAVR) is recommended for patients with:
  • Age < 65 years
  • Life expectancy > 20 years
  • Low to moderate surgical risk
• Transcatheter AVR (TAVR)
  • Recommended for patients with:
    • Age > 80 years
    • Life expectancy < 10 years
    • High or prohibitive surgical risk and predicted survival of > 12 months ^[9]
  • Emergency TAVR may be considered in certain patient groups. ^[30][31][32]
• Percutaneous balloon valvuloplasty ^[9]
  • May be used in children, adolescents, and young adults
  • Limited role in older patients
  • Can consider as a bridging intervention in high-risk patients with stage D AS but overall benefit is questionable. ^[9]

Complications of aortic valve replacement ^[33][34][35]

• 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

The safety and efficacy of DOACs in patients with mechanical valves have not been assessed and their use is not recommended. ^[9]

Dabigatran results in more thrombotic events and bleeding complications in patients with valvulopathy than warfarin. ^[9]

Critical complications of AS

The following can rapidly lead to decompensation and circulatory collapse in patients with severe AS:

• Cardiogenic shock
• Acute heart failure (AHF)
• Atrial fibrillation with RVR

Management ^[36]

Focus on acute stabilization while expediting definitive surgical treatment.

• Consult cardiology and cardiothoracic surgery immediately.
• Tailor stabilization to the physiological constraints of severe AS (e.g., fixed LVOT obstruction, preload dependence); see “Hemodynamic stabilization in severe AS” for details.
• For details on the standard management of each complication, see:
  • “Management of cardiogenic shock”
  • “Management of AHF”
  • “Management of Afib with RVR”

Do not delay surgical treatment of patients with AS and cardiogenic shock, rapid A-fib, and AHF.

Hemodynamic stabilization in severe AS ^[36]

Manage hemodynamically unstable patients with severe AS in consultation with a specialist while awaiting definitive surgical treatment.

• General principles
  • Maintain preload as much as possible.
  • Avoid iatrogenic hypotension.
  • Maintain normal heart rate and sinus rhythm as much as possible.
  • Consider cardiac POCUS to help guide resuscitation.
• Hypervolemia: Use diuretics with caution.
• Flash pulmonary edema: Use nitrates and positive pressure ventilation with caution.
• Hypovolemia: Consider judicious fluid challenges while regularly reassessing fluid responsiveness.
• Persistent hypotension
  • Consider judicious inoconstrictor drugs at the lowest effective dose.
  • Consider bridging with mechanical circulatory support or percutaneous balloon valvuloplasty if definitive surgery is delayed. ^[36][37]
• Unstable bradycardia: Consider dobutamine to increase heart rate and contractility without increasing afterload.
• Unstable tachycardia
  • Electrical cardioversion is preferred in most cases.
  • Use rate control medications and other negative inotropes with caution.

Severe AS is a preload-dependent condition. Ensure adequate volume repletion prior to positive pressure ventilation to prevent circulatory collapse. ^[38]

Titrate diuretics and negative inotropic medications very carefully in severe AS as these can worsen cardiogenic shock and myocardial ischemia.

We list the most important complications. The selection is not exhaustive.

The following applies to unstable patients with aortic stenosis:

• Perform ABCDE assessment.
• Start continuous cardiac monitoring and pulse oximetry.
• If unclear, confirm the diagnosis and aortic stenosis staging with bedside TTE.
• Identify and treat critical complications of AS.
• Consult cardiology and cardiothoracic surgery for definitive management.
• If necessary, begin hemodynamic stabilization for severe AS under specialist guidance while awaiting definitive treatment.
• Initiate emergency preoperative evaluation.
• Transfer to OR or ICU.

• Asymptomatic patients: Mortality rate is < 1% in a given year. ^[24]
• Symptomatic patients: Mortality rate in the first 2 years is > 50% if left untreated. ^[39]