OVERVIEW: What every practitioner needs to know
Are you sure your patient has aortic stenosis? What are the typical findings for this disease?
Aortic stenosis can be classified into two broad categories: congenital versus acquired. In pediatrics, congenital aortic stenosis is much more common than acquired aortic stenosis. Congenital aortic stenosis is further subclassified based on the level of stenosis, namely valvar, subvalvar, and supravalvar aortic stenosis.The level of stenosis is important to identify because it has implications for the natural history and associated anomalies. This chapter is limited to congenital valvar aortic stenosis.
Most children are asymptomatic. When symptoms are present, easy fatigability is the most common symptom. The most common presenting physical sign is a heart murmur. Less commonly, exertional angina is present but this is typically only seen with severe obstruction. Syncope ispossible but also requires severe obstruction.
What other disease/condition shares some of these symptoms?
In the neonate or infant, pulmonary stenosis can mimic aortic stenosis. Any cardiac pathologic condition causing a systolic murmur (e.g., mitral regurgitation, tricuspud regurgitation) can be confused with aortic stenosis to less experienced clinicians. However, murmurs due to regurgitation are holosystolic, in contrast to the basilar ejection-type murmur characteristic of aortic stenosis.
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What caused this disease to develop at this time?
The true incidence of valvular aortic stenosis is unknown, since most cases are associated with bicuspid aortic valve (BAV). The prevalence of BAV (with and without valve dysfunction) is estimated to be approximately 1%-2% of the general population and is often not included in overall incidence estimates of congenital heart disease.
Aortic stenosis is associated with certain genetic syndromes such as Turner syndrome, Marfan syndrome, and Jacobsen syndrome. The only known predisposing factor for the development of nonsyndromic valvar aortic stenosis is a positive family history (an affected first-degree family member). The inheritance pattern of nonsyndromic aortic stenosis is often multifactorial, but autosomal dominant inheritance has been described.
No disease-causing genes have been identified. There are no environmental or teratogenic factors that have been proved to cause aortic stenosis.
Aortic stenosis with a congenitally abnormal aortic valve is also associated with annular and ascending aorta dilatation and probably risk of acute aortic dissection. Pathologically, this manifests as cystic medial necrosis, resulting in weakening of the wall of the aorta.
What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?
Electrocardiography will demonstrate abnormal findings of left ventricular hypertrophy in up to 30% of children with significant stenosis, but may be normal in children with less severe disease.
There are no laboratory studies specific to the diagnosis of significant aortic stenosis. In critical neonatal aortic stenosis, a chemistry panel and blood gas analysis might show metabolic acidosis, as it may with many critically ill babies. However, for most cases of aortic stenosis, routine laboratory test results are normal and therefore have no diagnostic value.
Would imaging studies be helpful? If so, which ones?
Transthoracic echocardiography (See Figure 1 and Figure 2) is the gold standard test for the diagnosis of aortic stenosis. Parents and siblings of children with aortic stenosis should receive screening echocardiograms even if asymptomatic because of the familial nature if this disease. This is particularly important when it is associated with aortic dilatation.
Figure 1.
Still from 2D image from an echocardiogram in a newborn with bicuspid aortic valve and moderate aortic valve stenosis.
Figure 2.
Still image from echocardiogram in infant with aortic valve stenosis, showing the bicuspid valve “en face” (R = right coronary cusp, L = left coronary cusp, N = noncoronary cusp).
Chest radiographs are nonspecific, especially in infants and younger children, but are often readily available and inexpensive, and can serve as a screening test for a neonate or infant with heart disease. Aortic dilatation may be noted in the older child.
Confirming the diagnosis
Clinical decision algorithms exist for heart murmur evaluation. The strength of the decision tree relies heavily on the clinical skills of the diagnosing physician. Heart murmurs should first be identified as systolic or diastolic. If the murmur is systolic, they should be further classified as pansystolic or ejection.
Aortic stenosis will present with a systolic ejection murmur. Murmur grade and pitch will help differentiate it from an innocent murmur. Often aortic stenosis and pulmonary stenosis are difficult to distinguish by auscultation alone. The presence of a persistent early systolic ejection click is helpful in localizing obstruction to the aortic valve level.
If you are able to confirm that the patient has aortic stenosis, what treatment should be initiated?
Intervention for aortic stenosis is planned based on the severity of the stenosis, symptoms, and/or the presence of left ventricular dysfunction. The initial gradient at diagnosis seems predictive of the need for intervention (echo mean gradient <25 mm Hg from left ventricle to aorta required intervention in only 20% of cases in one review).
On diagnosis, an immediate referral to a pediatric cardiologist should be made. Medical therapies are not warranted, and subacute bacterial endocarditis (SBE) prophylaxis is no longer recommended for isolated aortic stenosis.
The mainstay of therapy is expectant management, and the general rule for all types of aortic stenosis (subvalvar, valvar, and supravalvar) is one of progression.
Table I gives treatment options for valvar aortic stenosis.
Table I.
| Treatment | Details | Advantages | Disadvantages |
|---|---|---|---|
| Expectant management | If mild to moderate stenosis, exercise restrictions and clinical follow-up | N/A | N/A |
| Balloon valvuloplasty | Initial treatment of choice | Nonsurgical (usually <24 h in hospital) | Risks include aortic regurgitation (see below) |
| Surgery (mechanical valve) | Durable | Needs anticoagulation, No growth potential | |
| Surgery (bioprosthetic valve) | Avoids need for anticoagulation | Not as durable, poor growth potential | |
|
Surgery (Ross procedure) |
Avoids need for anticoagulation, Neoaortic valve grows with child | Universal pulmonary homograft dysfunction (need for reoperation) |
What are the adverse effects associated with each treatment option?
Balloon Valvuloplasty:
Acutely, intimal tears can result, as can other risks typical of invasive cardiac catheterization such as cardiac perforation, tamponade, thrombus formation, stroke, or death.
Aortic Valve Replacement:
Mechanical valve: adverse effects related to anticoagulation
Bioprosthesis: inevitable valve dysfunction/lack of durability and need for reoperation
Ross procedure (autograft of the patient’s native pulmonary valve in the aortic position): need for reoperation (lifelong right ventricle to pulmonary artery conduit replacements, which typically last less than 1 decade)
What are the possible outcomes of aortic stenosis?
Prognosis depends on the treatment chosen (Table II).
Table II.
| Treatment | Counseling/Prognosis |
|---|---|
| Expectant | Possible progressive stenosis; only 2% of patients with bicuspid aortic valve experience valve dysfunction |
| Balloon Valvuloplasty | Depending on results of procedure, if there is less than moderate aortic regurgitation, this is definitive therapy with excellent prognosis |
| Mechanical aortic valve replacement | Very durable, but limited activity because of anticoagulation |
| Bioprosthetic aortic valve replacement | Anticoagulation not necessary, but will need repeated valve replacements and RV-PA conduit replacements due to decreased valve durability and conduit dysfunction |
| Ross procedure | Similar need for reoperations as bioprosthetic aortic valves. Also some evidence of mid-term arrhythmia (PMID 18498822) |
RV-PA = right ventricle-pulmonary artery
What causes this disease and how frequent is it?
Epidemiology
BAV is the most common congenital heart defect. True incidence is unknown because it is clinically silent, but it is estimated to be present in 1%-2% of the general population. However, of all patients with BAV, only 2% will progress to valve dysfunction, either stenosis or regurgitation.
Aortic stenosis composes 3%-8% of all congenital heart disease. There is no seasonal variation. Approximately 10% of aortic stenosis presents in infancy with signs and symptoms of congestive heart failure. The remainder of cases are typically diagnosed incidentally during routine physical examination.
Males have aortic valve stenosis more often than do females (male to female ratio ~4:1). Subaortic stenosis had a female predilection in one study.
Ascending aorta dilatation that is associated with BAV and aortic stenosis may have a common genetic cause. The exact causal link between aortic stenosis and abnormalities of the aortic wall is poorly understood at this time.
BAV is also associated with other congenital heart defects, including other left-sided obstructive lesions such as aortic coarctation and mitral valve anomalies and supravalvar mitral ring, as well as ventricular septal defects.
Recent genetic linkage analysis suggests that some types of hypoplastic left heart syndrome and BAV are genetically related. No disease-causing gene has been identified. Inheritance has been described as sporadic, multifactorial, and autosomal dominant in different cases. Abnormalities in bone morphogenetic protein signaling may be involved in the pathogenesis.
Environmental factors are not known to be predisposing factors.
How do these pathogens/genes/exposures cause the disease?
No disease-causing genes or exposures have been specifically identified, although syndromes such as Turner syndrome, Marfan syndrome, and Jacobsen syndrome have been associated with BAV.
Bone morphogenetic protein (BMP) signaling has been implicated in semilunar valve development. Therefore, abnormal signaling may be involved in the pathogenesis. Deficiency of fibrillin-1 protein, which is normally present in the aortic wall, is noted in patients with BAV and ascending aorta dilatation.
Other clinical manifestations that might help with diagnosis and management
Infants with severe aortic stenosis are diagnosed and managed somewhat differently than an older child with aortic stenosis. Since they often present in heart failure, medical therapy to augment ventricular contractility and help with diuresis in the case of left ventricular dysfunction is often instituted.
Critical aortic stenosis can be diagnosed in fetal life and is identified by reversal of flow in the fetal transverse aortic arch (there is not enough antegrade flow out of the left ventricle to perfuse the ascending aorta and coronary arteries). These patients have a ductal dependent lesion by definition, and prostaglandin E1 infusion should be initiated after birth until a definitive procedure, such as balloon valvuloplasty, can occur.
In infants and children with severe aortic stenosis, care should be taken not to institute excessive afterload reduction in the setting of a fixed left ventricular outflow tract obstruction, since this may reduce coronary driving pressure and predispose to ischemia and arrhythmia.
Are additional laboratory studies available; even some that are not widely available?
No additional laboratory studies are particularly helpful for this diagnosis.
How can aortic stenosis be prevented?
No primary prevention or prophylaxis is available at this time for aortic stenosis. Behavioral factors are not immediately relevant, as behavior does not cause this disease. However, activity restrictions are typically recommended for moderate to severe aortic stenosis, and competitive sports are discouraged for severe aortic stenosis.
Genetic studies have shown a 13%-15% recurrence risk of aortic stenosis in a fetus if the mother is affected, a 5% risk if the father is affected, and a 2% risk if one sibling is affected.
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