Lesions that produce obstruction to ventricular outflow such as pulmonary stenosis (PS), aortic stenosis (AS), and coarctation of the aorta (COA) are discussed in this chapter.
Pulmonary Stenosis
Prevalence
Isolated PS occurs in 8% to 12% of all congenital heart defects (CHDs). PS is often associated with other CHDs, such as tetralogy of Fallot (TOF), single ventricle, and others.
Pathology
- 1.
PS may be valvular, subvalvular (infundibular), supravalvular, or within the RV cavity (i.e., “double-chambered RV”).
- 2.
In valvular PS, the pulmonary valve is thickened, with fused or absent commissures and a small orifice ( Fig. 13-1 , A ). Although the RV is usually normal in size, it is hypoplastic in infants with critical PS (with a nearly atretic valve). Dysplastic valves (consisting of thickened, irregular, immobile tissue and a variably small pulmonary valve annulus) are frequently seen with Noonan’s syndrome.
FIGURE 13-1
Anatomic types of pulmonary stenoses (PSs). A, Valvular stenosis. B, Infundibular stenosis. C, Supravalvular PS (or stenosis of the main pulmonary artery [PA]). Abnormalities are indicated by arrows. AO, aorta; LV, left ventricle; RA, right atrium; RV, right ventricle.
- 3.
Isolated infundibular PS is rare; it is usually associated with a large ventricular septal defect (VSD), as seen in TOF (see Fig. 13-1 , B ).
- 4.
Aberrant hypertrophied muscular bands (running between the ventricular septum and the anterior wall) divide the right ventricular (RV) cavity into a proximal high-pressure chamber and a distal low-pressure chamber (double-chambered RV). A “dimple” in the ordinarily smooth RV surface is found during surgery (see Chapter 15 ).
- 5.
Supravalvular PS (or stenosis of the pulmonary arteries), isolated or in association with other CHDs, occurs in 2% to 3% of all patients with CHD. The stenosis may be single, involving the main pulmonary artery (PA) (see Fig. 13-1 ) or either of its branches, or multiple, involving both the main and several smaller peripheral PA branches (not shown). Commonly associated defects are pulmonary valve stenosis, VSD, and TOF. Peripheral PA stenosis is often seen in association with congenital syndromes; such as Williams syndrome, Noonan’s syndrome, Alagille syndrome, Ehlers-Danlos syndrome, and Silver-Russell syndrome or congenital rubella syndrome. PA stenosis is discussed further in Chapter 15 .
Clinical Manifestations
History
- 1.
Children with mild PS are completely asymptomatic. Exertional dyspnea and easy fatigability may be present in patients with moderately severe cases. Heart failure or exertional chest pain may develop in severe cases.
- 2.
Newborns with critical PS may present with poor feeding, tachypnea, and cyanosis.
Physical Examination ( Fig. 13-2 )
- 1.
Most patients are acyanotic and well developed. Newborns with critical PS are cyanotic and tachypneic.
FIGURE 13-2
Cardiac findings of pulmonary valve stenosis. Abnormal sounds are shown in black. Dots represent areas with systolic thrill. EC, ejection click.
- 2.
A right ventricular tap and a systolic thrill may be present at the upper left sternal border (and occasionally in the suprasternal notch).
- 3.
A systolic ejection click is present at the upper left sternal border only with valvular stenosis. The S2 may split widely, and the P2 may be diminished in intensity. An ejection-type systolic murmur (grade 2–5 of 6) is best audible at the upper left sternal border, and it transmits well to the back, too. The louder and longer the murmur, the more severe the stenosis is.
- 4.
Hepatomegaly may be present if congestive heart failure (CHF) develops.
- 5.
In newborns with critical PS, cyanosis may be present (caused by a right-to-left atrial shunt), and signs of CHF with hepatomegaly and peripheral vasoconstriction may be found.
- 6.
In patients with peripheral PA stenosis, a midsystolic murmur in the pulmonary valve area is well transmitted to the axillae and back. Occasionally, a continuous murmur is audible over the involved lung field.
Electrocardiography
- 1.
The electrocardiogram (ECG) findings are normal in mild cases.
- 2.
Right-axis deviation (RAD) and right ventricular hypertrophy (RVH) are present in moderate PS.
- 3.
Right atrial hypertrophy (RAH) and RVH with “strain” may be seen in severe PS.
- 4.
Neonates with critical PS may show left ventricular hypertrophy (LVH) because of a hypoplastic RV and relatively large left ventricle (LV).
Radiography
- 1.
Heart size is usually normal, but the main PA segment may be prominent with valvular stenosis (caused by poststenotic dilatation) ( Fig. 13-3 ). Cardiomegaly is present only if CHF develops.
FIGURE 13-3
Posteroanterior view of chest radiograph in pulmonary valve stenosis. Note a marked poststenotic dilatation (arrow) and normal pulmonary vascularity.
(Courtesy Dr. Ewell Clarke, San Antonio, TX.)
- 2.
Pulmonary vascular markings are usually normal but may decrease with severe PS.
- 3.
In neonates with critical PS, lung fields are oligemic with a varying degree of cardiomegaly.
Echocardiography
- 1.
Two-dimensional echocardiography in the parasternal short-axis view (see Fig. 5-2 ) shows thick pulmonary valve cusps with restricted systolic motion (doming). The subcostal long-axis view (see Fig. 5-5 ) may show similar findings. The size of the pulmonary valve annulus can be estimated. The main PA is often dilated (poststenotic dilatation).
- 2.
The Doppler study can estimate the pressure gradient across the stenotic valve by the simplified Bernoulli equation. Multiple echocardiographic views, including parasternal short-axis and subcostal long-axis views, should be used to obtain the maximum flow velocity. The instantaneous pressure gradient estimated by Doppler echo is slightly greater than the peak-to-peak systolic pressure gradient obtained by cardiac catheterization. The severity of PS (by Doppler gradient) may be classified as follows.
- a.
Mild: A pressure gradient less than 35 to 40 mm Hg (or RV systolic pressure <50% of the LV pressure).
- b.
Moderate: A valve pressure gradient of 40 to 70 mm Hg (or RV pressure 50%–75% of the LV pressure).
- c.
Severe: A pressure gradient greater than 70 mm Hg (or RV pressure ≥75% LV pressure).
- a.
- 3.
Dysplastic valves are characterized by a noticeably thickened and immobile leaflet and hypoplasia of the pulmonary valve annulus.
- 4.
In neonates, Doppler pressure gradient may underestimate the severity of PS because the PA pressure may be higher than normal, especially in those with PDA with a left-to-right shunt.
Natural History
- 1.
The severity of stenosis is usually not progressive in mild PS. For example, more than 95% of patients with an initial Doppler gradient less than 25 mm Hg did not need operation over a 25-year period. The majority of the patients with mild PS (<35 mm Hg) do well without intervention.
- 2.
In moderate or severe PS, the severity tends to progress with age.
- 3.
CHF may develop in patients with severe stenosis. Sudden death is possible in patients with severe stenosis during heavy physical activities.
- 4.
Without appropriate management, most neonates with critical PS die (see Management).
Management
Medical
- 1.
Newborns with critical PS and cyanosis require emergency treatment to reduce mortality.
- a.
These babies may temporarily improve with prostaglandin E 1 infusion, which reopens the ductus arteriosus, and other supportive measures.
- b.
Balloon valvuloplasty is the procedure of choice in critically ill neonates. Immediate reduction in pressure gradient can be achieved in more than 90% of these neonates.
- c.
Some of these infants are not able to maintain effective forward flow through the pulmonary valve because of noncompliant or hypoplastic RV. Some of them may need one of the following: (1) a prolonged prostaglandin (PG) infusion (for 3 weeks), (2) ductal stenting, or (3) systemic-to-pulmonary shunt surgery.
- d.
In neonates, complications of the balloon procedure are more common than in older patients, with a mortality rate of up to 3%, a major complication rate of 3.5%, and a minor complication rate of 15%.
- e.
About 15% of the patients require reintervention (either repeat valvuloplasty or surgery for infundibular stenosis or dysplastic valve) at a later time.
- f.
Even dysplastic valves appear to mature after the balloon procedure.
- a.
- 2.
Balloon valvuloplasty is the procedure of choice for the valvular stenosis at all ages.
- a.
Indications for the balloon procedure may include the following.
- 1)
A resting pressure gradient of greater than 40 mm Hg with the patient sedated in the catheterization laboratory.
- 2)
If the catheterization gradient is 30 to 39 mm Hg, the balloon procedure may be reasonable.
- 3)
Symptoms attributable to PS with a catheterization gradient greater than 30 mm Hg. The symptoms may include angina, syncope or presyncope, and exertional dyspnea.
- 4)
The procedure is useful and reasonable in patients with dysplastic pulmonary valve, as commonly seen in Noonan’s syndrome. It has a lower success rate with the valvuloplasty (65%). If balloon valvuloplasty is unsuccessful, surgery is indicated.
- 1)
- b.
Results: The balloon procedure carries an extremely low risk, is painless, is less costly than surgery, and shortens hospital stay.
- 1)
A good outcome is achieved in 85% of patients with valvular stenosis. Restenosis after balloon dilatation is extremely rare.
- 2)
Pulmonary regurgitation (PR) after balloon dilatation is common, occurring in 10% to 40% of patients. PR is usually well tolerated, although rarely some of these patients may become candidates for pulmonary valve implantation. Therefore, a balloon smaller than previously recommended (i.e., 120%–140% of the annulus) may be preferable.
- 3)
After relief of severe PS (either by balloon or surgery), a hypertrophied dynamic infundibulum may cause a persistent pressure gradient, with rare occurrences of fatal outcome (“suicidal right ventricle”). Propranolol may be given to reduce hyperdynamic infundibular obstruction. The reduction of this gradient occurs gradually over weeks.
- 1)
- a.
- 3.
Restriction of activity is not necessary in children with this condition except in cases of severe PS (Doppler gradient >70 mm Hg).
Surgical
Indications and Timing
- 1.
Surgical valvotomy should be limited to patients with more complex lesions or those in whom balloon procedure is contraindicated or failed.
- 2.
Other types of obstructions (e.g., infundibular stenosis, anomalous RV muscle bundle) with significant pressure gradients require surgery on an elective basis.
- 3.
If balloon valvuloplasty is unsuccessful or unavailable, infants with critical PS and CHF require surgery on an urgent basis.
Procedure
- 1.
Through a midsternal incision, pulmonary valvotomy is performed for pulmonary valve stenosis under cardiopulmonary bypass. The approach is through the PA. Neonates with critical PS may require a transventricular valvotomy or the insertion of a transannular patch (or both) while receiving prostaglandin E 1 infusion. If severe infundibular hypoplasia is present, a systemic-to-PA shunt is also performed.
- 2.
Dysplastic valves often require complete excision of the valves. Simple valvotomy may be ineffective.
- 3.
Infundibular stenosis requires resection of the infundibular muscle and patch widening of the right ventricular outflow tract.
- 4.
Stenosis at the main PA level requires patch widening of the narrow portion.
- 5.
Anomalous muscle bundles require surgical resection.
Mortality
Surgical mortality occurs in fewer than 1% of older children. The rate is about 10% in critically ill infants.
Aortic Stenosis
Prevalence
Left ventricular outflow tract obstruction (LVOTO), which includes stenosis at, below, or above the aortic valve, represents up to 10% of all CHDs. Valvular AS is the most frequent (71%) followed by subvalvular stenosis (23%) and supravalvular stenosis (6%). Aortic valve stenosis occurs more often in males (male-to-female ratio of 4:1).
Pathology
- 1.
Stenosis may be at the valvular, subvalvular, or supravalvular level ( Fig. 13-4 ).
FIGURE 13-4
Anatomic types of aortic stenoses. A, Normal. B, Valvular stenosis. C, Supravalvular stenosis. D, Discrete subaortic stenosis. E, Idiopathic hypertrophic subaortic stenosis (this condition is discussed in Chapter 18 ).
- 2.
Valvular AS may be caused by a bicuspid aortic valve, a unicuspid aortic valve, or stenosis of the tricuspid (or tricommissural) aortic valve (see Fig. 13-4 , B ). A bicuspid aortic valve with a fused commissure and an eccentric orifice accounts for the most common form of aortic valve stenosis (75%) ( Fig. 13-5 , B ). Less common is the unicuspid valve with one lateral attachment (see Fig. 13-5 , A ). A valve that has three unseparated cusps with a stenotic central orifice is the least common form (see Fig. 13-5 , C ). Many bicuspid aortic valves are nonobstructive during childhood and become stenotic in adult life because of calcification of the valve.
FIGURE 13-5
Anatomic types of aortic valve stenoses. Top row is the side view, and bottom row is the view as seen in surgery during aortotomy. A, Unicuspid aortic valve. B, Bicuspid aortic valve. C, Stenosis of a tricuspid aortic valve.
(From Goor DA, Lillehei CW: Congenital Malformations of the Heart. New York, Grune & Stratton, 1975.)
- 3.
Symptomatic neonates with so-called critical neonatal aortic valve stenosis have primitive, myxomatous valve tissue, with a pinhole opening. The aortic valve ring and ascending aorta are almost always hypoplastic. Hypoplasia of the mitral valve, LV cavity, or LVOT and a VSD are also frequently found, often requiring one-ventricular repair (Norwood operation followed by Fontan operation).
- 4.
Supravalvular AS is an annular constriction at the upper margin of the sinus of Valsalva (see Fig. 13-4 , C ). Occasionally, the ascending aorta is diffusely hypoplastic. This is often associated with Williams syndrome (which includes mental retardation, characteristic facies, and multiple PA stenosis).
- 5.
Subvalvular (subaortic) stenosis may be in the form of a discrete narrowing or a long tunnel-like fibromuscular narrowing of the LVOT.
- a.
Discrete stenosis occurs more often than tunnel stenosis and accounts for about 10% of all AS cases. It may be simple membranous ridge or collar (more common) or fibromuscular ridge with or without membrane. Some subaortic stenosis is believed to develop as the result of turbulence in an abnormally shaped LVOT, which causes endocardial injury and subsequent proliferation and fibrosis.
- 1)
Two thirds of the patients have associated cardiac lesions, such as VSD, patent ductus arteriosus (PDA), or COA.
- 2)
In one third of the patients, the stenosis is isolated; familial isolated subaortic membrane has been reported.
- 3)
In some patients, there is history of surgical intervention, such as membranous VSD closure or PA banding (9 months to 8 years before the development of the membrane).
- 1)
- b.
Tunnel-like subaortic stenosis is often associated with hypoplasia of the ascending aorta and aortic valve ring, as well as thickened aortic valve leaflets. It is usually associated with other LV anomalies, including Shone complex (comprising supramitral ring, parachute mitral valve, subaortic stenosis, and COA).
- c.
Another type of subvalvular stenosis is idiopathic hypertrophic subaortic stenosis (see Fig. 13-4 , E ), a primary disorder of the heart muscle (discussed in Chapter 18 ).
- a.
Clinical Manifestations
History
- 1.
Neonates with critical or severe stenosis of the aortic valve may develop signs of hypoperfusion or respiratory distress caused by pulmonary edema within days to weeks after birth.
- 2.
Most children with mild to moderate AS are asymptomatic. Occasionally, exercise intolerance may be present.
- 3.
Exertional chest pain, easy fatigability, or syncope may occur in a child with severe degree of obstruction.
Physical Examination ( Fig. 13-6 )
- 1.
Infants and children with AS are acyanotic and are normally developed.
FIGURE 13-6
Cardiac findings of aortic valve stenosis. Abnormal sounds are indicated in black. Systolic thrill may be present in areas with dots. EC, ejection click.
- 2.
Except for neonates with critical AS, blood pressure is normal in most patients, but a narrow pulse pressure is present in severe AS. Patients with supravalvular AS may have a higher systolic pressure in the right arm than in the left (caused by the jet of stenosis directed into the innominate artery, the so-called Coanda effect).
- 3.
A systolic thrill may be palpable at the upper right sternal border, in the suprasternal notch, or over the carotid arteries.
- 4.
An ejection click may be heard with valvular AS. The S2 splits either normally or a bit narrowly. The S2 may split paradoxically in severe AS (see Fig. 13-6 ). A harsh, grade 2 to 4 of 6, midsystolic murmur is best heard at the second right or left intercostal space, with good transmission to the neck and apex. A high-pitched, early diastolic decrescendo murmur, which results from aortic regurgitation (AR), may be audible in patients with bicuspid aortic valve and in those with discrete subvalvular stenosis.
- 5.
Peculiar “elfin facies,” mental retardation, and friendly “cocktail party” personalities may be associated with supravalvular AS (e.g., Williams syndrome).
- 6.
Newborns with critical AS may develop signs of reduced peripheral perfusion (with weak and thready pulses, pale cool skin, and slow capillary refill) triggered by ductal constriction. The clinical picture may mimic overwhelming sepsis with low cardiac output. The heart murmur may be absent or faint but becomes louder when CHF improves.
Electrocardiography
In mild cases, the ECG is normal. LVH with or without strain pattern may be present in severe cases ( Fig. 13-7 ). Correlation of the severity of AS and the ECG abnormalities is relatively poor.
Radiography
- 1.
The heart size is usually normal in children, but a dilated ascending aorta or a prominent aortic knob may be seen occasionally in valvular AS, resulting from poststenotic dilatation.
- 2.
Significant cardiomegaly does not develop unless CHF occurs later in life or if AR becomes substantial.
- 3.
Newborns with critical AS show generalized cardiomegaly with pulmonary venous congestion.
Echocardiography
- 1.
Valvular AS
- a.
In the parasternal short-axis view of the two-dimensional (2D) echocardiogram, normal aortic valves are tricuspid, with three cusps of approximately equal size. In diastole, the normal aortic cusp margins form a Y pattern ( Fig. 13-8 ). In systole, a bicuspid aortic valve appears as a noncircular (i.e., football-shaped) orifice (see Fig. 13-8 ). Stenosis of the tricuspid aortic valve appears as a heavy Y pattern in diastole and as a small, centrally located orifice in systole, with three thickened commissures distinctly visible. A unicommissural aortic valve, which is seen often in infants with critical AS, is seen as a circular orifice positioned eccentrically within the aortic root and without visible distinct cusps.
- a.
