Congenital aortic stenosis is an obstructive heart defect that causes a pathological slowing of blood flow from the left ventricle to the aorta, due to narrowing at the level of the aortic valve (valvular stenosis), below it (subaortic), or above it (supravalvular). It is a relatively common malformation, accounting for about 3–6% of all congenital heart diseases, with an estimated incidence of 4–6 cases per 10,000 live births.
The most frequent form is valvular aortic stenosis, in which the obstruction is caused by commissural fusion or leaflet dysplasia. Unlike degenerative forms seen in adulthood, congenital stenosis has a completely different anatomical and pathophysiological substrate, with potential for progression over time and significant implications for left ventricular development and systemic homeostasis.
The less common non-valvular forms include:
Depending on the severity of the obstruction and the adaptation of the left ventricle, congenital aortic stenosis may be mildly symptomatic for many years or present in a critical form at birth, with neonatal heart failure and systemic hypoperfusion. Critical forms, especially in newborns, may mimic septic shock and require urgent intervention to ensure survival.
Aortic stenosis may occur as an isolated malformation or in association with other congenital anomalies, particularly coarctation of the aorta, bicuspid aortic valve, mitral valve dysplasia, or ventricular septal defects. Early diagnosis and serial echocardiographic monitoring are essential to identify cases at risk of progression.
Treatment depends on the site of obstruction, the severity of the pressure gradient, and the presence of clinical signs. Options include percutaneous balloon valvuloplasty, surgical commissurotomy, or valve replacement in severe cases. Subaortic or supravalvular forms instead require targeted surgical approaches. Prognosis is generally favorable in mild cases, but critical or progressive forms can lead to significant morbidity if not promptly treated.
Congenital aortic stenosis results from abnormal development of the aortic valve or its adjacent structures during cardiac morphogenesis. Between the fifth and eighth week of gestation, the conotruncal portion of the embryonic heart divides to form the right and left outflow tracts, and the endocardial cushions contribute to the formation of the semilunar valves. Errors in this process lead to the formation of a bicuspid aortic valve, abnormal commissural fusion, or leaflet dysplasia, resulting in reduced systolic opening and obstruction to blood flow.
Subaortic stenosis typically originates from a fibrous membrane or muscular thickening in the left ventricular outflow tract. This structure may develop secondarily to chronic blood turbulence or derive from a localized embryonic anomaly. Supravalvular stenosis is generally associated with defects of the ascending aortic wall, often in a syndromic context such as Williams-Beuren syndrome, in which mutations in the ELN (elastin) gene cause abnormal structure of the vascular extracellular matrix.
In many cases, congenital aortic stenosis presents as an isolated lesion, but it can also be part of complex conditions involving an abnormal mitral valve, aortic coarctation, or ventricular septal defect. Notably, the bicuspid aortic valve is a very frequent anomaly, with a prevalence of up to 1–2% in the general population, and may represent the anatomical substrate of progressive aortic stenosis in childhood or adolescence.
In addition to direct causes, several risk factors have been identified that increase the likelihood of developing congenital aortic stenosis. The most relevant include:
From a pathogenetic perspective, the presence of a dysplastic or fused aortic valve creates a mechanical obstacle to systolic outflow from the left ventricle to the aorta. Blood is ejected through a narrowed orifice, resulting in a high-velocity jet and an increased transvalvular pressure gradient. This condition induces concentric left ventricular hypertrophy as an adaptive response to chronic pressure overload.
Progressive hypertrophy reduces ventricular compliance and alters diastolic filling, with increased left atrial pressures and risk of pulmonary congestion. In neonates with critical stenosis, the valvular orifice may be so narrowed that effective systemic output is impaired. In such cases, circulation is temporarily maintained by a patent ductus arteriosus, allowing retrograde flow of oxygenated blood from the lungs to the systemic circulation.
Ductus closure leads to acute circulatory collapse, with reduced systemic perfusion, lactic acidosis, and signs of multiorgan failure. These newborns may present with a clinical picture resembling septic shock, but the absence of infection and the transient response to prostaglandins point to a diagnosis of critical obstructive heart disease. In less severe cases, stenosis may initially be silent but progress over time, leading to left ventricular dysfunction, arrhythmias, and pressure-induced myocardial ischemia.
If left untreated, congenital aortic stenosis may evolve toward heart failure, secondary valvular insufficiency, and risk of sudden death, especially in the presence of severe hypertrophy, exertional syncope, or complex ventricular arrhythmias. Early identification and correction of the obstruction are therefore crucial for long-term prognosis.
The clinical picture of congenital aortic stenosis is determined by a combination of the severity of the obstruction, the patient’s age, and the ability of the left ventricle to adapt to pressure overload. In mild or moderate forms, the disease may remain clinically silent for years, being discovered incidentally during a pediatric or sports examination. Conversely, in severe or critical forms, especially in neonates, symptoms may appear early with signs of systemic hypoperfusion, left-sided heart failure, and hemodynamic collapse.
In neonates with critical aortic stenosis, the perinatal history is often normal until the closure of the ductus arteriosus, which marks the onset of symptoms. The condition may present with:
This clinical picture, highly suggestive of critical aortic stenosis, requires pharmacological maintenance of ductal patency via continuous infusion of prostaglandins (PGE1) and urgent echocardiography to confirm the diagnosis. Without treatment, the course is rapidly fatal.
In stable neonates or infants with severe but non-critical stenosis, symptoms may be less dramatic but still indicative of hemodynamic compromise, including:
In older children and adolescents, aortic stenosis may present with progressive symptoms related to diastolic dysfunction or subendocardial ischemia due to concentric left ventricular hypertrophy. The most frequent clinical signs include:
On physical examination, one of the most characteristic findings is a systolic ejection murmur, heard at the second right intercostal space with radiation to the neck and sometimes the back. The second heart sound may be diminished or paradoxically split in severe cases. In neonates with critical stenosis, peripheral pulses may be weak or absent, systemic blood pressure is reduced, and hepatomegaly may be present due to passive venous congestion. In older children, a sustained apical impulse may be noted, indicating left ventricular hypertrophy, and a bounding carotid pulse in cases with associated aortic regurgitation.
The intensity of the murmur is not always directly proportional to the severity of the stenosis: in cases with a severely narrowed orifice and low output, the murmur may paradoxically soften, which is a warning sign. Likewise, the absence of symptoms in early life does not exclude the possibility of significant progression during adolescence or adulthood, highlighting the importance of regular echocardiographic monitoring even in asymptomatic patients.
In the presence of a bicuspid aortic valve, stenosis may be associated with progressive aortic regurgitation and ascending aortic dilatation, increasing the long-term risk of dissection or rupture. This makes early diagnosis, patient education about warning signs, and the restriction of high-intensity physical activity in untreated individuals all the more essential.
The diagnosis of congenital aortic stenosis must be timely and accurate, as severe forms, especially in neonates, can mimic non-cardiac emergencies and rapidly lead to hemodynamic instability. Clinical suspicion arises in the presence of a systolic ejection murmur, unexplained hypotension, signs of systemic hypoperfusion, or exertional syncope. In the neonatal period, the condition may remain unrecognized until ductal closure, at which point critical symptoms emerge.
Pulse oximetry may reveal a difference between pre- and post-ductal oxygen saturation in neonates with reversed ductal flow.
The electrocardiogram shows signs of left ventricular hypertrophy, with prominent R waves in lateral leads and deep S waves in V1. Left axis deviation may also be present.
Chest X-ray may be normal or reveal a globular cardiac silhouette with increased pulmonary vascular markings in the presence of heart failure.
The key examination is transthoracic echocardiography, which allows for accurate assessment of:
The pressure gradient is quantified using the modified Bernoulli equation, by which stenosis is classified as:
Cardiac magnetic resonance imaging (MRI) is indicated in older children and adolescents to assess valve morphology, aortic anatomy, and left ventricular function.
Multislice computed tomography (CT) is useful in suspected supravalvular stenosis or for surgical planning.
Cardiac catheterization is now reserved for preoperative evaluation or balloon valvuloplasty, as it is an invasive technique no longer required solely for diagnosis.
The therapeutic strategy in congenital aortic stenosis depends on three main factors: severity of the pressure gradient, presence of symptoms, and progression on echocardiographic monitoring. Patients with mild, asymptomatic stenosis do not require immediate treatment but should be periodically monitored with clinical and instrumental evaluations every 6–12 months.
Treatment is indicated in all cases with:
Percutaneous balloon aortic valvuloplasty is the first-line procedure in neonates and infants with isolated, non-dysplastic valvular stenosis. It involves dilating the valve orifice using a balloon catheter introduced via the femoral artery and guided into the aortic position. It is an effective technique in most cases, providing good relief of obstruction and reducing the gradient to non-significant levels.
Surgical valve intervention is indicated in cases with severely dysplastic valves, stenosis associated with complex mitral lesions, or failure of balloon valvuloplasty. Options include surgical commissurotomy, valvuloplasty with leaflet repair, and, in more severe cases, valve replacement with mechanical, biological, or homograft prostheses. In pediatric patients, the Ross procedure is a valid solution in selected cases: it involves replacing the aortic valve with the patient’s own pulmonary valve, which in turn is replaced with a homograft conduit.
Subaortic forms require surgical excision of the fibrous membrane or muscular ridge. In supravalvular stenosis, treatment is almost always surgical, involving enlargement of the aortic tract with a patch or complete reconstruction of the ascending aorta.
The prognosis is favorable in most patients treated early and monitored appropriately. However, there remains a risk of chronic aortic regurgitation, early valve calcification, and the need for reintervention over time, particularly in those who underwent valvuloplasty during the neonatal period. Regular cardiology follow-up, with assessment of ventricular function, degree of regurgitation, and ascending aorta dimensions, is essential to prevent long-term complications, including left ventricular dysfunction, ventricular arrhythmias, and sudden cardiac death.
Although congenital aortic stenosis can be successfully treated in most cases, it may evolve into significant complications either in the absence of treatment or during post-procedural follow-up. The complications depend on the initial severity of the lesion, the treatment method used, and the presence of associated anomalies.
In untreated patients or those with progressive stenosis, the main complication is left ventricular dysfunction secondary to chronic pressure overload. Initially adaptive concentric hypertrophy may evolve into myocardial fibrosis, reduced diastolic compliance, and heart failure with preserved ejection fraction. In more advanced cases, ventricular dilation and overt systolic dysfunction may occur.
One of the most feared complications, especially in young individuals with severe untreated stenosis, is sudden cardiac death, typically due to malignant ventricular arrhythmias or pressure-induced myocardial ischemia. This risk is particularly high in patients with exertional syncope, documented arrhythmias, or marked left ventricular hypertrophy on echocardiogram or ECG.
After percutaneous valvuloplasty, the most frequent complication is residual aortic regurgitation, which may initially be mild but tends to progress over time. Untreated severe regurgitation may lead to left ventricular dilation, systolic dysfunction, and worsening symptoms. In such cases, valve replacement during adolescence or adulthood may be necessary.
Other complications of valvuloplasty include: re-stenosis due to progressive leaflet thickening or scar retraction in about 20–30% of cases, vascular injury or embolization during percutaneous access (rarer in experienced centers), and rare but serious events such as aortic perforation or cardiac tamponade.
In patients undergoing surgical valve replacement, complications include degeneration of biological prostheses over time, early valve calcification, and thrombosis or endocarditis in those with mechanical prostheses. The Ross procedure, while offering the advantages of a native valve anatomy and growth potential, may be complicated by issues affecting both the neo-aorta and the homograft pulmonary conduit.
An additional long-term complication is ascending aortic dilatation, especially in patients with a bicuspid aortic valve. This condition carries an increased risk of aortic dissection or rupture, even at a young age, and requires regular radiologic monitoring with early surgical intervention if critical diameter thresholds are exceeded or rapid progression is observed.
Finally, in patients who undergo multiple procedures or have ventricular dysfunction, atrial or ventricular arrhythmias, exercise intolerance, and need for chronic medical therapy may occur. For this reason, a structured lifelong cardiology follow-up is essential, with periodic assessment of ventricular function, the treated valve, and the ascending aorta, in order to prevent and manage complications early.