Indications for balloon aortic valvotomy parallel those previously adhered to for surgical valvotomy. Some centers have relaxed their clinical indications because of the perception that the risk-to-benefit ratio of a percutaneous procedure is probably superior to that of surgery. Currently, in our program, the indications for balloon valvotomy in patients with congenital valvar aortic stenosis are (a) peak systolic gradient greater than 65 mm Hg in an asymptomatic child; (b) peak systolic gradient of 45 to 65 mm Hg in a child with electrocardiographic evidence of myocardial ischemia (at rest or during exercise) or with symptoms attributable to myocardial ischemia; and (c) the presence of critical aortic stenosis in an infant with low cardiac output, regardless of gradient.

Contraindications to balloon valvotomy include (a) mild to moderate aortic valve stenosis (peak systolic gradient <45 mm Hg) in an asymptomatic child, (b) the presence of associated severe aortic regurgitation (of sufficient severity to warrant valve repair or replacement), (c) important hypoplasia of the aortic valve annulus (e.g., <5 mm in a newborn), and (d) aortic valve calcification (rare in childhood).

The procedure is most often performed using a retrograde transarterial approach. In newborns, we often use a transumbilical arterial approach (10), to spare the newborn femoral artery. Once arterial access is obtained, the stenotic valve is crossed in retrograde fashion. A soft-tipped wire must be used in newborns to avoid perforating an aortic valve cusp. A balloon is utilized with an inflated diameter of 90% to 100% of the diameter of the valve annulus. In children in whom concern exists for femoral artery injury, a double-balloon technique can be used to avoid the larger catheter required with single-balloon dilation (Fig. 83.1). Throughout the procedure, left ventricular (LV) pressure is monitored by an antegrade catheter placed across the foramen ovale or through a transseptal puncture. Patients are fully heparinized. The balloon (or balloons, in the case of a double-balloon technique) is inflated briefly by hand, with care taken to observe the waist of the stenotic valve near the midportion of the balloon. After dilation, repeat hemodynamic measurements are obtained, and an aortic root angiogram is performed to document the presence and severity of any aortic regurgitation that may have been produced.

The largest study describing the acute outcome after balloon dilation in children with congenital aortic stenosis was reported by the Valvuloplasty and Angioplasty of Congenital Anomalies (VACA) Registry (9) in 1990. The VACA Registry reported information from 204 children whose short-term data were submitted to the registry after balloon dilation procedures performed between 1982 and 1986. The registry made no attempt to standardize the dilation procedure. The patients ranged in age from newborn to young adult, with a mean age of 10.1 years. All had congenital valvar aortic stenosis of moderate to severe degree. Balloon dilation acutely decreased the peak systolic gradient from 77 to 30 mm Hg (i.e., mild), with a 10% incidence of increased aortic valve regurgitation. In our experience, less satisfactory gradient relief typically indicates either a suboptimal technical procedure or the presence of more complex LV outflow tract disease (i.e., annulus hypoplasia, subvalvular stenosis, or calcific stenosis).

The longer-term results of aortic valve balloon dilation for congenital aortic valve stenosis indicate that, as with surgical valvotomy, the procedure is palliative. Several studies (11,12,13) have shown satisfactory gradient relief for a period of 2 to 5 years, and longer-term benefits can be expected in some patients. Shim et al. (14) noted that successful balloon aortic valvuloplasty was effective in decreasing LV mass in children with isolated aortic stenosis. In this small study, the decrease in LV mass was gradual and was not statistically significant until the second year.

Neonates with critical aortic stenosis constitute a high-risk subgroup that deserves special mention (Fig. 83.2). Newborns with critical aortic stenosis present with severe LV dysfunction and shock, and they must be resuscitated with prostaglandin E₁ and inotropic support. As with older children, balloon dilation is an effective palliative therapy in newborns with critical aortic stenosis (10,15,16,17) (Fig. 83.3). Egito et al. (16) described the results of balloon dilation in 33 neonates ranging in age from 1 to 33 days. The procedure was performed from the
umbilical artery in 11, from the femoral artery in 20, and antegrade across a patent foramen ovale in 2 children. A second valve procedure was required in 12 children during the follow-up period, underscoring the palliative nature of this procedure. Mosca et al. (18) compared the results of neonatal balloon dilation with those of surgical valvotomy for critical aortic stenosis and found no significant difference between the procedures in the degree of gradient reduction, aortic regurgitation, or patient survival.

Beyond the newborn period, balloon aortic valvotomy is a relatively safe procedure. Immediate complications include aortic valve regurgitation, iliofemoral artery injury, hemorrhage, ventricular arrhythmia, endocarditis, valve leaflet or ventricular perforation, injury to the anterior mitral leaflet, and, rarely, death. Death has been exceedingly uncommon outside the newborn period. In the VACA Registry (9), aortic regurgitation reportedly occurred in only 10% of the children studied. More recent experience suggests that balloon dilation produces new aortic insufficiency in 25% to 30% of patients, and it is typically mild. Severe aortic insufficiency occurs in approximately 5% of patients after the procedure. Aortic insufficiency may relate to a balloon-to-annulus ratio that exceeds 1.0 (9) or to valve morphology (6). Injury to the iliofemoral artery most frequently occurs in infants younger than 12 months of age. For this reason, we prefer the transumbilical route whenever possible for balloon dilation in newborns with critical aortic stenosis (10).

Complications are substantially more frequent and more severe in neonates. The mortality in newborns with critical aortic stenosis is substantial and ranges from 10% to 20% (16,18). Other important complications in the newborn include LV perforation with wire or catheter, severe aortic insufficiency (at times owing to inadvertent valve leaflet perforation and subsequent dilation), arrhythmia, hemorrhage, sepsis, and endocarditis. To avoid sepsis or endocarditis, vancomycin is administered to all patients undergoing transumbilical dilation procedures.