Pediatric Valvar Aortic Stenosis Treatment & Management

The main goal is to preserve the native aortic valve and ventricular function for as long as possible before aortic valve replacement is necessary.

Neonates with critical aortic stenosis and low cardiac output require resuscitation and institution of prostaglandin E₁ at a dose of 0.01-0.1 mcg/kg/min. Establishing patency of the ductus arteriosus can restore adequate systemic blood flow and the perfusion of vital organs.

Ongoing treatment in patients with aortic valve stenosis aims to preserve ventricular function and allow the left ventricle to function with only mild to moderate obstruction. If ventricular dysfunction is detected in patients with significant aortic stenosis, medical therapy should be used only for stabilization; such patients are likely to benefit from interventions to reduce the degree of stenosis.

Patients with significant aortic valve insufficiency in combination with mild to moderate stenosis may be carefully treated with afterload reduction and/or diuretic therapy, although hypotension may occur. Patients with small aortic valve areas have a limited capacity for increased cardiac output with activity and may develop syncope or ischemic chest pain with exercise.

Inotropic drugs, such as dopamine, dobutamine, and epinephrine, may be indicated in cases of reduced cardiac output in the presence of decreased left ventricular systolic function. With critical aortic stenosis, avoid drugs that cause significant vasodilation, because they may cause significant hypotension in the presence of a small, cross-sectional aortic valve area. Patients with increased work of breathing and pulmonary edema benefit from intubation, positive pressure ventilation, and diuretic therapy.

Early reports of transcatheter balloon dilation in the 1980s were encouraging, although morbidity related to aortic valve insufficiency and femoral artery compromise were considered limitations of the procedure. With the advent of improved catheter technology, percutaneous balloon valvuloplasty has become the procedure of choice in most centers for severe congenital aortic valve stenosis and can be safely performed with virtually no mortality and with minimal morbidity.

Balloon aortic valvuloplasty is a good initial treatment in most pediatric patients with aortic valve stenosis.^[3] Patients with severely dysplastic valves may have a less favorable result with balloon aortic valvuloplasty, whereas surgical valve reconstruction might be more advantageous.

The overall goal, especially in neonates and infants, is to sufficiently relieve the aortic valve obstruction without development of significant valve insufficiency, thereby resulting in normalization of left ventricular systolic function.

Achievement of this goal typically entails performing a conservative balloon valvuloplasty, reducing the peak-to-peak systolic gradient by 50%. Balloon diameters are usually 80-100% of the aortic valve anulus dimension. In critically ill patients in whom the ductus arteriosus is not patent, surgical backup or circulatory support in the form of an extracorporeal membrane oxygenator (ECMO) should be available.

Neonates with critical aortic stenosis who are maintained on prostaglandin E₁ should be sedated and intubated before the procedure is begun, to help maintain hemodynamic stability during the catheterization procedure.

Catheter techniques

Several catheter techniques have been described over the past 20 years, with each having its own advantages and disadvantages. No consensus regarding which approach is optimal in the neonate with critical aortic valve stenosis has been reached. The techniques include retrograde catheterization via the femoral artery,^[4] the right subscapular artery,^[5] the umbilical artery, or the right carotid artery,^[6] as well as antegrade transvenous catheterization through the atrial septum.

The advantages of a transvenous, subscapular artery, carotid artery, or umbilical artery approach include preservation of the femoral arteries for later intervention and reduced risk of femoral arterial occlusion, which may still occur despite the availability of very low profile balloon dilation catheters. However, crossing the aortic valve in neonates via the umbilical artery can be quite challenging.

The transvenous antegrade approach can also be difficult, especially in the presence of a small, hypertrophied left ventricle. This approach can result in injury to the mitral valve apparatus.

Crossing the aortic valve in a retrograde manner via the right carotid artery is technically easier, although a surgical cutdown and repair of the vessel are necessary. This particular procedure can be performed at the bedside with the aid of continuous transesophageal echocardiographic guidance, which offers the following advantages^[7] :

• Provides continuous hemodynamic assessment preintervention and postintervention
• Avoids fluoroscopy exposure
• Eliminates the need for repeated angiography to assess for aortic valve insufficiency
• Eliminates the need to transport a sick neonate to and from the catheterization laboratory

Sheaths as small as 3F can be used for femoral arterial access in neonates or infants in whom umbilical vessels are closed.

Although surgical aortic valvotomy (transventricular without cardiopulmonary bypass or open valvotomy with cardiopulmonary bypass) was once believed to carry an extremely high risk of morbidity and mortality, it is now considered to be relatively safe and effective. However, the procedure has largely been displaced by balloon aortic valvuloplasty during cardiac catheterization. (Indeed, data from the Pediatric Cardiac Care Quality Assurance Consortium have shown a marked decline in surgical aortic valvotomy as balloon aortic valvuloplasty has become more widely used.)

Occasionally, a significantly unstable neonatal patient who has a small aortic anulus or who requires attention to other associated lesions may be referred for surgical aortic valvotomy.

Turley et al reported good results with surgical aortic valvotomy, although advances in catheter and balloon technology have made it possible to perform balloon aortic valvuloplasty during cardiac catheterization, even in small preterm infants.^[8]

McCrindle et al reported that the early and intermediate results following either surgical valvotomy or catheter balloon valvuloplasty were similar, although the likelihood of important aortic valve insufficiency after balloon valvuloplasty and the likelihood of residual stenosis after surgical valvotomy are increased.^[9]

Patients who require enlargement of an aortic anulus, resection of subaortic stenosis, or repair of supravalvar aortic stenosis or who have a small left ventricle are candidates for surgical aortic valvotomy in addition to other indicated procedures.

The surgical replacement of an aortic valve is primarily reserved for patients in whom balloon valvuloplasty or surgical valvotomy has failed and in whom severe stenosis exists or significant aortic valve insufficiency has developed in association with left ventricular dilation or deterioration of left ventricular systolic function. The 3 options for aortic valve replacement are a mechanical prosthetic valve, a bioprosthetic valve, or the Ross procedure.

Mechanical prosthetic aortic valves are highly dependable and long lasting but require anticoagulation to prevent thromboembolic complications. Anticoagulation necessitates that the patient avoid collision sports and other activities that may result in significant bleeding. Warfarin adds significant complexity to the management of pregnancy, but the issues that arise are not insurmountable.

Delaying surgical valve replacement as long as possible to allow maximum growth of children without compromising ventricular function is an important goal of presurgical management. Such delay allows insertion of the largest possible prosthetic valve and reduces the need for valve replacement solely because of patient growth.

Bioprosthetic aortic valve replacement includes various bioprosthetic materials (bovine pericardial, porcine, and cadaveric homografts) that generally do not last as long as mechanical prosthetic valves. Bioprosthetic valves may be used in patients with contraindications to mechanical valves, in women contemplating pregnancy in the near future, in patients who want to pursue collision sports or other activities with a high risk of trauma, and in patients who may be unable to receive or comply with anticoagulation therapy.

The Ross procedure (pulmonary autograft) or autotransplantation of a pulmonary valve to the aortic position is favored by some surgeons because of the potential for growth of the pulmonary autograft valve through childhood. Such growth has been documented, as has adequate performance of a pulmonary valve in the aortic position. In addition, this procedure avoids the need for anticoagulation and serious sport restrictions, especially in active, injury-prone children.

Problems with this procedure in children include development of early stenosis or insufficiency of a pulmonary homograft placed in the pulmonary position. This can necessitate multiple interventional catheterizations or surgical reoperations during childhood to alleviate the obstruction or insufficiency of the homograft. The availability of catheter-based percutaneous pulmonary valve placement (Melody valve) should limit the need for multiple surgical conduit replacements. Significant enlargement of the neoaortic root, especially within the sinuses, may occur, and aortic insufficiency occasionally develops.

The choice of an aortic valve for aortic valve replacement may be more complicated in female patients contemplating pregnancy.

The choice of a mechanical valve, a bioprosthetic valve, or a Ross procedure should be reviewed at length for all patients, particularly those contemplating valve replacement.

Teratogenic effects of warfarin, management issues of anticoagulation during pregnancy, and need for reoperation, as well as durability of various valve options, should be reviewed at length.

Activity limitations depend on the degree of severity of aortic valve stenosis and, in older children, the results noted on exercise stress testing. Strenuous isometric sports should be avoided; specific recommendations regarding sports participation have been published by the American Heart Association.

Consult a pediatric cardiologist and a pediatric cardiac surgeon, as needed.

Patients with dysmorphic features may require a genetic evaluation. Genetic counseling with regard to the risk of left ventricular outflow tract obstruction in the mother’s subsequent pregnancies also may be indicated. A neonatologist may be consulted to assist with management of critically ill neonates, especially those born prematurely.