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 (or pulmonary autograft) is an operation that has been used extensively for aortic valve replacement in children. The operation consists of transferring the patient's own pulmonary valve and root into the aortic position, replacing the pulmonary valve with a pulmonary homograft (human cadaver valve), and reimplanting the coronary arteries. The operation has also been performed in young adults, particularly in women who wish to become pregnant, but the enthusiasm for this operation has waned over the years.
The Ross operation is a more complicated procedure than a conventional aortic valve replacement. Its major drawback is the potential for subsequent dysfunction of both the neo-aortic valve and the pulmonary homograft. Despite initial enthusiasm for the long-term function of the patient's pulmonary valve in the aortic position, premature development of aortic regurgitation, particularly in patients who had a bicuspid aortic valve, is not uncommon. In addition, the incidence of pulmonary homograft dysfunction by either stenosis or regurgitation is not insignificant and represents another cause for reintervention. Finally, dilatation of the neo-aortic root is common, may contribute to the development of aortic regurgitation, and may reach proportions that require replacement. For all of these reasons and the likelihood that TAVR can be used inside a deteriorating bioprosthetic valve, the Ross procedure is rarely offered in our adult congenital population.