A bicuspid aortic valve is a common congenital heart defect where the aortic valve has only two leaflets instead of three. Approximately 1-2% of the population is born with a bicuspid aortic valve. Most people with a bicuspid valve live normal lives without any symptoms. However, some complications can arise later in life that may necessitate valve replacement surgery.
Symptoms of a bicuspid aortic valve
Many people with bicuspid valves do not experience any symptoms initially. The following symptoms may develop over time:
- Shortness of breath, especially with exertion
- Fatigue or tiredness
- Chest pain or tightness
- Palpitations or irregular heartbeat
- Fainting or lightheadedness
These symptoms occur because the abnormal bicuspid valve does not open and close properly. This results in improper blood flow from the heart to the rest of the body. Symptoms typically present between ages 30-60 as the valve function deteriorates.
Complications of a bicuspid aortic valve
Several complications can arise with a bicuspid aortic valve that may necessitate surgical intervention:
Aortic Stenosis
Aortic stenosis refers to narrowing of the aortic valve opening. This limits blood flow from the left ventricle into the aorta and is the most common complication of a bicuspid valve. Stenosis usually progresses gradually over years. Severe aortic stenosis causes strain on the heart and significantly limits function. Surgery is required once stenosis becomes severe.
Aortic Regurgitation
Aortic regurgitation, also called aortic insufficiency, occurs when the aortic valve does not close properly. This allows blood to leak backwards into the left ventricle. The extra volume load on the heart eventually leads to left ventricular dysfunction and heart failure. Surgery is necessary once regurgitation becomes severe.
Aortic Dilatation
Many patients with a bicuspid valve develop dilatation (widening) of the aorta. The risk of dissection (aortic wall rupture) also increases. Therefore, the aorta needs regular monitoring with echocardiograms and possible surgical intervention if dilatation is progressing.
Endocarditis
Abnormal turbulence in blood flow from a stenotic or regurgitant bicuspid valve predisposes to bacterial endocarditis (infection of the heart valve). Endocarditis often requires both antibiotics and valve surgery for treatment.
Sudden Cardiac Death
Rarely, some individuals may experience a sudden cardiac arrhythmia and death. Careful monitoring for any arrhythmias is warranted.
Diagnosis of a bicuspid aortic valve
The bicuspid aortic valve is often discovered coincidentally when imaging the heart for other reasons. Other times, a heart murmur heard on physical exam raises suspicion. Diagnosis is made definitively using the following imaging modalities:
- Echocardiogram – This ultrasound of the heart allows direct visualization of the bicuspid aortic valve. It can also assess the valve function and any complications like stenosis, regurgitation, or aortic dilatation. Echocardiography provides all the necessary information to determine whether valve surgery may be indicated.
- MRI/CT scan – These additional imaging modalities can give more detail if needed about the valve structure, aortic dimensions, and anatomy.
Indications for surgery
The American College of Cardiology and American Heart Association guidelines recommend surgery for a bicuspid aortic valve when any of the following are present:
- Severe aortic stenosis (aortic valve area less than 1.0 cm2)
- Severe aortic regurgitation and left ventricular dilatation (end systolic dimension over 50 mm)
- Moderate aortic stenosis and regurgitation when undergoing coronary artery bypass or aortic surgery
- Aortic dilatation with maximum ascending aorta dimension over 5.5 cm
- Symptomatic aortic stenosis with exertional symptoms like chest pain, syncope, or heart failure
The development of any of these signs indicates the bicuspid valve has progressed to a severe dysfunction requiring intervention.
Types of surgery
Two main options exist for surgery to replace a damaged bicuspid aortic valve:
Mechanical aortic valve replacement
This involves excising the diseased native valve and implanting an artificial mechanical valve prosthesis. Mechanical valves are very durable and do not wear out. However, patients require lifelong anticoagulation (blood thinners) to prevent clot formation on the valve.
Bioprosthetic valve replacement
This involves implanting a tissue valve from an animal (either porcine or bovine). Bioprosthetic valves do not require anticoagulation. However, they only last 10-15 years before needing replacement. Bioprosthetic valve replacement is generally reserved for patients over the age of 65 when the need for reoperation is lower.
The choice between mechanical and bioprosthetic valve must balance the risks of lifetime anticoagulation versus higher reoperation rates. The patient’s age, activity level, and medical conditions play a role in selecting the optimal replacement valve.
Transcatheter aortic valve replacement (TAVR)
TAVR is a minimally invasive option for high-risk patients who are not candidates for traditional open-heart surgery. The artificial valve is delivered via a catheter through the femoral artery or directly through the left ventricle. TAVR valves are only approved for use in patients with trileaflet aortic stenosis, not bicuspid valves, due to higher complication risks.
Risks and complications of surgery
Aortic valve replacement surgery is a major procedure with several possible perioperative complications:
- Bleeding – requiring transfusion or reoperation
- Stroke
- Heart rhythm disturbances like atrial fibrillation
- Infection
- Renal failure
- Prolonged mechanical ventilation
- Death (2-4% risk)
Risk assessment using algorithms like the Society of Thoracic Surgeons (STS) Risk Calculator help weigh the expected risks against benefits for an individual patient.
Outcomes and survival after bicuspid valve replacement
For patients undergoing isolated aortic valve replacement, the expected 15-year survival rates are:
Age | 15-year survival |
---|---|
65 | 60% |
70 | 50% |
75 | 40% |
80 | 30% |
Younger patients have better long-term prognosis. Concurrent coronary artery bypass grafting (CABG) surgery decreases 10-year survival by 5-10%. After recovery from surgery, most patients achieve markedly improved function and quality of life thanks to the well-functioning replacement valve.
Follow up after aortic valve replacement
All patients with a prosthetic heart valve require lifelong cardiology follow up on an annual basis. Evaluation includes:
- Physical exam
- Echocardiogram to evaluate valve function
- Periodic CT scans to monitor aortic dilatation if present preoperatively
- Monitoring anticoagulation levels for patients on blood thinners
- Assessing for any signs of valve deterioration or complications
Bioprosthetic valves and mechanical valves carry unique risks that mandate surveillance. Prosthetic valves deteriorate over time and may eventually require redo valve surgery.
Conclusion
Bicuspid aortic valves commonly require replacement during adult life. Surgery is indicated for severe valve stenosis or regurgitation, aortic enlargement, or the development of symptoms. Mechanical and bioprosthetic valves carry different tradeoffs for considerations. Aortic valve surgery is highly effective for relieving symptoms and improving survival, but lifelong monitoring for complications is mandatory.