Congenital Aortic Stenosis
Congenital aortic stenosis refers to a narrowed aortic valve with varying degrees of obstruction. Usually the valve is bicuspid, but other variations exist. Aortic stenosis is a spectrum in which the degree of obstruction ranges from mild to severe. Patients with mild aortic stenosis have no symptoms and do not require an intervention. Greater degrees of aortic stenosis can result in symptoms such as shortness of breath on exertion, chest pain, dizziness, or fainting. The most severe cases present in the newborn period, where there is critical obstruction and inadequate cardiac output which requires emergency intervention. Patients with symptoms from aortic stenosis, and most patients with asymptomatic severe obstruction, require treatment to relieve valve obstruction.
Congenital aortic stenosis differs from calcified aortic stenosis in the older patient because the valve is more pliable in the former and often amenable to balloon valvuloplasty. Patient with a calcified aortic valve are much less likely to benefit from valvuloplasty. Successful balloon valvuloplasty or surgical valvotomy can result in effective palliation and delay the need for aortic valve replacement for years. However, when the aortic valve is calcified, successful long term relief of obstruction with a valvuloplasty is rarely achieved and aortic valve replacement is generally necessary.
Both balloon and surgical valvuloplasty produce a leak in the aortic valve, referred to as aortic regurgitation. In many of these patients, there is combined aortic stenosis and aortic regurgitation but of a degree that does not require valve replacement. These patient must be followed to determine the optimal timing of future valve replacement.
When aortic valve replacement does become necessary, the choice of valve needs to be individualized for each patient. Whereas a mechanical aortic valve has the lowest incidence of reoperation on the aortic valve, it requires lifelong anticoagulation and lifestyle modifications to prevent bleeding. In a woman of childbearing age, it also complicates management of a future pregnancy. For these reasons, many patients opt for a bioprosthetic valve despite the need for future reoperation. However, with the development of transaortic valve replacement (TAVR), it is feasible that a TAVR valve inserted inside a failing bioprosthetic valve will extend the time to reoperation. Aortic stenosis is also associated with dilatation of the aorta. Those with significant dilatation may require replacement of the aorta at the time of aortic valve replacement.
The Ross procedure is an operation that has been performed extensively by our congenital heart surgeons to replace the aortic valve in children and in some young adults. The operation consists of replacing the diseased aortic valve with the patient's own pulmonary valve (known as a pulmonary autograft) and replacing the pulmonary valve with a human cadaver valve (known as a homograft).
The rationale for doing the Ross operation is to provide patients with a long-term solution to aortic valve replacement while avoiding the need for anticoagulation. This is particularly important in children and adolescents, and in women who wish to become pregnant since anticoagulation increases the risk of pregnancy. The Ross procedure is also preferred in patients who have narrowing of the left ventricle just below the aorta valve (known as LVOT obstruction).
The Ross operation is an alternative to conventional aortic valve replacement, but it is a more complicated procedure and should be done by a cardiac surgeon with significant expertise in performing this operation. As a two-valve operation, it has the drawback that there may be future dysfunction of two cardiac valves, the pulmonary autograft and the pulmonary homograft.
Despite this, long term studies have demonstrated satisfactory function of the patient's pulmonary valve in the aortic position. Careful pre-operative selection is important to identify which patients stand to benefit most from the Ross operation. In general, patients who have aortic stenosis as their main problem are usually the best candidates. In some patients, the Ross procedure may include reinforcement of the pulmonary autograft to reduce the risk of late aortic dilatation which may lead to aortic regurgitation.
In addition to these issues, there may be leakage or narrowing of the new pulmonary valve over time which is usually treated with a “valve-in-valve” catheter procedure which does not require surgery.