Aortic Stenosis: Causes, Symptoms, and Pathophysiology

• Aortic stenosis (AS) is the narrowing of the aortic valve opening, obstructing blood flow from the left ventricle to the aorta during systole.
• AS increases afterload on the left ventricle, potentially leading to left ventricular hypertrophy, heart failure, and reduced cardiac output.
• The most common cause of AS in older adults is calcific degeneration of the aortic valve leaflets.
• In younger individuals, AS is often caused by congenital valve abnormalities, such as a bicuspid aortic valve.
• Rheumatic heart disease can also cause AS, often in conjunction with mitral valve disease.

Symptoms

• Many patients with AS are asymptomatic for a long period.
• Symptoms typically develop gradually as the stenosis worsens.
• Common symptoms include dyspnea (shortness of breath), angina (chest pain), and syncope (fainting).
• Heart failure symptoms, such as fatigue and edema, may occur as the condition progresses.
• Some patients may experience sudden cardiac death, although this is rare.

Diagnosis

• Physical examination findings suggestive of AS include a systolic ejection murmur, best heard at the right upper sternal border, that radiates to the neck.
• The intensity of the murmur does not always correlate with the severity of the stenosis.
• An echocardiogram is the primary diagnostic tool for AS, providing information about valve morphology, leaflet mobility, and the severity of the stenosis.
• Doppler echocardiography is used to measure the pressure gradient across the aortic valve, peak aortic jet velocity, and valve area.
• Cardiac catheterization may be performed to assess the severity of AS and evaluate for concomitant coronary artery disease, particularly in patients being considered for intervention.
• Computed tomography (CT) angiography can be used to assess the aortic valve and aorta, especially when echocardiography is inconclusive.

Severity

• AS is typically classified as mild, moderate, or severe based on the aortic valve area, mean pressure gradient, and peak aortic jet velocity.
• Severe AS is generally defined as an aortic valve area of ≤1.0 cm², a mean pressure gradient of ≥40 mmHg, or a peak aortic jet velocity of ≥4.0 m/s.
• Asymptomatic patients with severe AS should be monitored closely for the development of symptoms.

Treatment

• There is no effective medical therapy to treat AS.
• Statins have not been shown to slow the progression of AS.
• The main treatment for severe symptomatic AS is aortic valve replacement (AVR).
• AVR can be performed surgically (SAVR) or transcatheter (TAVR).
• SAVR involves open-heart surgery to remove the diseased valve and replace it with a mechanical or bioprosthetic valve.
• TAVR is a less invasive procedure in which a new valve is deployed within the existing aortic valve using a catheter.
• The choice between SAVR and TAVR depends on factors such as the patient's age, overall health, risk profile, and anatomical considerations.
• Balloon aortic valvuloplasty (BAV) is a palliative procedure that can be used to temporarily relieve symptoms in patients who are not candidates for AVR.
• BAV involves inflating a balloon catheter within the aortic valve to stretch the valve open.
• BAV is associated with a high rate of restenosis (re-narrowing of the valve) and is not considered a definitive treatment for AS.

Aortic Valve Replacement (AVR)

• AVR is the definitive treatment for severe symptomatic AS.
• The decision to proceed with AVR should be based on a careful assessment of the patient's symptoms, severity of AS, overall health, and risk profile.
• Both surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) are effective treatment options for severe AS.

Surgical Aortic Valve Replacement (SAVR)

• SAVR involves open-heart surgery to replace the diseased aortic valve with a new valve.
• During SAVR, the patient is placed on cardiopulmonary bypass, and the heart is stopped.
• The surgeon makes an incision in the aorta to access the aortic valve, removes the diseased valve, and sutures a new valve in its place.
• The new valve can be either a mechanical valve or a bioprosthetic valve.
• Mechanical valves are durable and long-lasting but require lifelong anticoagulation with warfarin to prevent blood clots.
• Bioprosthetic valves are made from animal tissue (e.g., porcine or bovine) and do not require lifelong anticoagulation in most cases.
• Bioprosthetic valves have a limited lifespan and may need to be replaced after 10-20 years.
• SAVR is generally recommended for younger patients with a low surgical risk and no other significant comorbidities.

Transcatheter Aortic Valve Replacement (TAVR)

• TAVR is a less invasive procedure that involves deploying a new aortic valve within the existing valve using a catheter.
• TAVR is typically performed through a small incision in the groin (femoral artery approach) or through a small incision in the chest (transapical or subclavian approach).
• The catheter is advanced to the aortic valve, and the new valve is deployed, pushing the existing valve leaflets aside.
• TAVR is generally recommended for older patients with a high surgical risk or significant comorbidities.
• TAVR has been shown to be as effective as SAVR in selected patients with severe AS.
• Complications of TAVR can include stroke, bleeding, vascular complications, and paravalvular leak (leakage of blood around the new valve).

Management of Asymptomatic AS

• Asymptomatic patients with mild to moderate AS do not require specific treatment but should be monitored regularly for the development of symptoms or progression of AS.
• Asymptomatic patients with severe AS should be monitored closely for the development of symptoms.
• Exercise stress testing may be considered in asymptomatic patients with severe AS to assess their functional capacity and identify those at higher risk of developing symptoms.
• Patients with asymptomatic AS should be educated about the symptoms of AS and advised to seek medical attention if they develop any new or worsening symptoms.

Prognosis

• The prognosis of AS depends on the severity of the stenosis and the presence of symptoms.
• Asymptomatic patients with mild to moderate AS generally have a good prognosis.
• Symptomatic patients with severe AS have a poor prognosis if left untreated.
• AVR significantly improves survival and quality of life in patients with severe symptomatic AS.
• The long-term outcomes of AVR depend on factors such as the patient's age, overall health, and the type of valve used.