The normal right ventricle (RV) has three components: the inlet (including tricuspid valve, chordae tendineae, and papillary muscles), the trabeculated apical portion, and the infundibulum or outflow tract. Under typical conditions, the right heart receives the systemic venous return and pumps to the low-impedance pulmonary vascular bed.1
In the absence of a shunt lesion, the RV has identical output to the left ventricle but pumps at one-sixth of the left ventricular pressure. Right-sided congenital heart disease involving the tricuspid valve, RV outflow tract, or RV chamber itself can disrupt the normal hemodynamics. Valve regurgitation leads to volume overload and compensatory right heart chamber dilation. Obstruction of flow through the outflow tract results in high RV pressure and compensatory hypertrophy of the myocardium. Because of ventricular interdependence (related to the shared interventricular septum and constraining pericardium, among other factors), pressure or volume overload of the RV can impact the function and morphology of the left ventricle.1
Obstruction of blood flow out of the RV can occur proximal to the pulmonic valve, at the pulmonic valve, or distal to the pulmonic valve. These lesions may occur in isolation or in combination. It is important to identify the location and nature of the obstruction, which in some cases may require multiple imaging modalities.2
After percutaneous or surgical relief of pulmonary valve obstruction, pulmonary regurgitation (PR) is the most common complication and requires close surveillance for adverse impact on the RV.
DOUBLE-CHAMBERED RIGHT VENTRICLE
A double-chambered right ventricle (DCRV
) is defined as obstruction of blood flow at or within the sub-infundibular ventricle. It consists of a high-pressure proximal chamber and a low-pressure distal chamber.
DCRV is a rare congenital anomaly seen in approximately 0.5% to 2.0% of all congenital heart disease cases.3
Some cases of DCRV
may be secondary, related to compensatory muscular hypertrophy from a pressure-loading lesion, and therefore the true incidence of primary DCRV
(muscular hypertrophy with no clear other cause) may be lower.4
To date, there is no genetic mutation that has been associated with DCRV
PATHOGENESIS AND ASSOCIATED DEFECTS
The obstruction in DCRV
can be due to thickened trabeculations, anomalous muscle tissue, or an aberrant and hypertrophied moderator band (ie, septomarginal trabeculation).3
Fibromuscular thickening of the infundibulum alone is often referred to as subvalvular pulmonic stenosis (PS). This may be a form of DCRV
or secondary to pressure overload of the RV, as described earlier. DCRV
is commonly associated with other congenital heart defects. Isolated DCRV
is almost always associated with a membranous ventricular septal defect, often small. In addition, DCRV
is associated with tetralogy of Fallot, Ebstein anomaly, and double outlet RV.5
Adults with DCRV
can present with dyspnea, syncope, angina, and exertional intolerance. On examination, a holosystolic murmur is present along the lower left sternal border. Given the RV hypertrophy, an RV heave may be appreciable as well as a thrill.
Differential Diagnosis: Other causes of intraventricular obstruction to blood flow include muscle hypertrophy at the infundibulum, which can occur in PS as well as hypertrophic cardiomyopathy.
MANAGEMENT: DOUBLE-CHAMBERED RIGHT VENTRICLE
Indications for intervention on DCRV
include (a) moderate or greater obstruction (defined as peak velocity >3 m/s by Doppler echocardiography) with symptoms of heart failure, (b) exercise intolerance, or (c) severe asymptomatic obstruction (peak velocity >4 m/s by Doppler echocardiography).8
Medical therapy has not been demonstrated to be beneficial. Although balloon valvotomy has been reported, its efficacy in most patients is yet to be established.9
Surgical repair typically involves a transatrial or transventricular approach. Postoperatively, clinicians must be wary of conduction system disease, particularly right bundle branch block as the right bundle branch runs in the septomarginal trabecula and moderator band. Surgical resection by an experienced congenital surgeon tends to be definitive with excellent long-term results.10
VALVULAR PULMONARY STENOSIS
Valvular PS is a common congenital anomaly. Mild-to-moderate cases may be diagnosed for the first time in adulthood when a murmur is auscultated. Additionally, severe PS treated during childhood has excellent long-term survival, and therefore many adult patients born with PS now require long-term follow-up.12
Three types of valvular PS occur: dome-type, dysplastic, and unicuspid/bicuspid pulmonic valves (Table 108.1
Valvular PS makes up almost 90% of congenital RV outflow tract abnormalities.14
The dome-type valve is the most common type of congenital pulmonic valve abnormality. Although there is no identified genetic abnormality, there does appear to be a chance of inheritance (<5%). Pulmonary valve dysplasia is commonly associated with Noonan syndrome and chromosome 12 mutation, with an autosomal dominant inheritance with variable penetrance.15
Unicuspid, bicuspid, or quadricuspid pulmonic valves are rare, and bicuspid valves may be associated with tetralogy of Fallot. Any of the valve morphologies may also have associated pulmonic regurgitation, though stenosis is more typical.
CLINICAL PRESENTATION: VALVULAR PULMONARY STENOSIS
Ongoing pressure overload to the RV can cause hypertrophy and fibrosis, which may cause right-sided diastolic and
eventually systolic dysfunction. Thus, patients with PS can present with right-sided heart failure or exertional symptoms (eg, dyspnea, syncope, chest pain) related to inadequate pulmonary blood flow with exertion and possibly RV ischemia. Examination findings depend on the severity of the stenosis. In severe disease, a prominent “A” wave in the jugular venous pulse is common. An RV heave is commonly present on cardiac palpation. Heart sounds are notable for an ejection click that decreases in intensity with inspiration and as PS progresses, and may no longer be audible as it moves closer to S1. Wide splitting of S2 will reflect the prolonged pulmonic ejection time. A right-sided S4 is expected in those with a prominent “A” wave in the jugular venous pressure. The systolic ejection murmur peak moves later in systole as severity progresses. Cyanosis can be observed when significant PS occurs in the setting of atrial septal defect or patent foramen ovale, related to high right atrial pressure and right-to-left atrial shunting.
TABLE 108.1 Types of Pulmonary Valve Stenosis
Pulmonary Artery Dilation
Narrow, “fish mouth”-like opening without proper raphe or commissures. Has preserved leaflet motion. Does not tend to have significant calcification.
Common, particularly of the main and left pulmonary artery
Exuberantly thickened leaflets with limited mobility
Possible, though more commonly associated with hypoplastic pulmonary annulus and proximal pulmonary trunk
Genetic syndromes, particularly Noonan
Unicuspid or bicuspid
May be thickened with reduced mobility
Tetralogy of Fallot, transposition of the great arteries
Differential Diagnosis: Other causes of RV outflow tract obstruction should be considered.
DIAGNOSIS: VALVULAR PULMONARY STENOSIS
ECG in advanced disease (RV systolic pressure >60 mm Hg) will demonstrate RV hypertrophy, right atrial enlargement, and right axis deviation. Chest x-ray often reveals findings of preferential flow into the left pulmonary artery (PA) including increased vascular fullness in the left lung and dilation of main and left PAs (often referred to as “witch’s nose,” Figure 108.2
). These findings are more common in dome-type valvular PS compared to valve dysplasia.
When PS is identified, it is critical to assess the severity of obstruction; this is typically done by Doppler echocardiography. PS is considered mild when the peak gradient is <36 mm Hg, moderate with peak gradient 36 to 64 mm Hg, and severe with peak gradient >64 mm Hg or mean gradient >35 mm Hg in the setting of normal RV function. In addition to quantifying the degree of stenosis, assessment of the degree of regurgitation (if present) is necessary, as this has therapeutic implications (see below).
FIGURE 108.2 Chest x-ray in pulmonic stenosis. Chest radiography highlighting multiple features seen in patients with congenital pulmonic stenosis. There is evidence of right atrial and right ventricular enlargement. In addition, the main and left pulmonary arteries are enlarged. Note the absence of an enlarged left atrium or left ventricle, as well as relatively radiolucent lung fields.
Transthoracic echocardiography is usually sufficient to define the morphology and severity of PS. Doppler echocardiography has been demonstrated to have good correlation with invasive hemodynamic assessment for the majority of patients.16
In addition to assessing the pulmonary valve itself, PA dilation is often present and should be described. The RV peak systolic pressure can be estimated with continuous-wave Doppler of the tricuspid regurgitation jet. The PR jet (using the end-PR velocity) is used to estimate PA diastolic pressure. Patients with elevated RV systolic pressure often exhibit systolic ventricular
septal flattening and RV hypertrophy (Figure 108.3A-D
). Because isolated PS is a pressure-loading lesion, the ventricle does not tend to dilate, and, therefore, functional tricuspid regurgitation is not expected. Transesophageal echocardiography does not offer clear advantages over transthoracic echocardiography for evaluation of the pulmonic valve in most patients.
Cardiac computed tomography (CT) and MRI
are typically not required in the evaluation of PS, but can be used to clarify valve morphology if transthoracic echocardiographic imaging is limited. Cardiac CT angiography is commonly used to assess the coronary artery anatomy prior to planned surgical or transcatheter intervention. This is particularly important if transcatheter pulmonary valve-in-valve replacement is planned, as compression can occur if a coronary artery lies too close to the valve landing zone.
In patients with very severe PS and/or significant PR, echocardiographic Doppler evaluation may be less accurate than catheterization.17
In these cases, invasive hemodynamic assessment with right heart catheterization can be beneficial to assess the RV pressure, degree of PS, and any branch PA stenosis. Angiography at the time of right heart catheterization can be used to assess RV size, function, and PA anatomy.
Transthoracic echocardiographic findings in pulmonic stenosis. (A)
Modified parasternal short-axis view in a patient with dome-type pulmonic stenosis demonstrates mild cusp thickening. (B)
Note the typical doming (arrows) of the cusps in this systolic frame from the same patient. (C)
Continuous-wave Doppler through the pulmonic valve demonstrates findings consistent with moderate-severe pulmonic valve stenosis with a peak velocity of nearly 4 m/s, suggesting a peak gradient ≥60 mm Hg. (D)
Hepatic vein pulsed-wave Doppler consistent with a noncompliant RV as suggested by a large atrial reversal (red asterisk). PA, pulmonary artery; RVOT
, right ventricular outflow tract.
MANAGEMENT: VALVULAR PULMONARY STENOSIS
Medical Therapy and Surveillance
Patients with mild PS do not tend to have progression of valve disease. For these patients, follow-up every 3 to 5 years with examination, ECG
, echocardiogram, and selective exercise testing is reasonable.8
Moderate PS has a variable course, with some patients exhibiting progression and some patients demonstrating stable valve gradients over time. Follow-up every 1 to 2 years with the same cardiac testing is appropriate. Patients with severe PS should be considered for transcatheter or surgical intervention, as described next.
Percutaneous or Surgical Intervention
Since the 1980s, the treatment of choice for isolated PS has been percutaneous balloon valvuloplasty. Symptomatic patients with moderate or severe PS should be referred for percutaneous balloon valvuloplasty.8
Other indications for balloon valvuloplasty are cyanosis related to atrial-level shunt and severe PS in the asymptomatic patient.8
Patients who should be considered for primary surgical intervention include those with greater than moderate PR, a hypoplastic pulmonary annulus, subvalvular PS, or supravalvular PS. Traditionally, dysplastic pulmonic valves do not respond as well to percutaneous intervention as the more common dome-shaped pulmonary valves, but balloon valvuloplasty may still be appropriate as first-line therapy in select patients. Surgical intervention is recommended for those patients in whom balloon valvuloplasty failed to resolve symptoms/obstruction or for those who need other interventions such as tricuspid valve repair, surgical therapies for atrial arrhythmias, shunt closure, or left-sided interventions. Surgical management of PS can involve balloon valvuloplasty, valvotomy, or pulmonic valve replacement.8
SPECIAL CONSIDERATIONS: PREGNANCY
In patients who are pregnant, isolated PS tends to be well tolerated, even if severe. The mother tends to do very well, though the neonates tend to have higher rates of premature delivery and perinatal mortality (4.1%).18
Percutaneous balloon valvuloplasty during pregnancy can reduce neonatal risk.
SUPRAVALVULAR PULMONARY STENOSIS
Supravalvular PS involves narrowing of the main or branch PA. It can occur in isolation, in association with RV outflow tract stenosis, or in the setting of a genetic abnormality associated with multiple other cardiac defects. In those with prior surgery, it can also occur at sites of prior interventions (eg, PA banding; Blalock-Thomas-Taussig, Potts, or Waterston shunts; or Jatene arterial switch/post-Lecompte maneuver).19
Native peripheral PA stenosis occurs infrequently in congenital heart disease, and the incidence of postsurgical peripheral PA stenosis is not well defined.20
PATHOGENESIS AND ASSOCIATED DEFECTS
Native isolated peripheral PA stenosis is commonly seen either at the main PA bifurcation or in the left PA at the site of the closed ductus arteriosus. Postsurgical peripheral PA stenosis occurs as a complication of scarring at takedown sites of prior palliative shunts or surgical corrective procedures.
Isolated peripheral PA stenosis is frequently associated with ventricular septal defect. There are multiple genetic syndromes associated with peripheral PA stenosis including Alagille syndrome, Keutel syndrome, Williams syndrome, LEOPARD syndrome, Noonan syndrome, and congenital rubella. Peripheral PA stenosis can also occur in the setting of tetralogy of Fallot.
CLINICAL PRESENTATION: SUPRAVALVULAR PULMONARY STENOSIS
Patients with peripheral PA stenosis present similarly to valvular PS with dyspnea on exertion, right-sided heart failure, and exertional light-headedness. Examination may demonstrate a systolic or even continuous murmur. There will also be evidence of RV hypertension on examination, similar to findings in valvular PS.
DIAGNOSIS: SUPRAVALVULAR PULMONARY STENOSIS
ECG has no specific findings other than RV hypertrophy. Chest x-ray may show a relatively small vascular pedicle as well as increased lucency in the lung fields if the stenosis is unilateral. Transthoracic echocardiography may raise suspicion for increased pressures in the main PA, though two-dimensional (2D) visualization of the PAs can be challenging, especially in adult patients. Parasternal imaging with color flow and continuous-wave Doppler is the most helpful for identifying peripheral PA stenosis on echocardiography. Cross-sectional imaging with CT or MRI
is generally required in the evaluation of peripheral PA stenosis.21
In addition, direct measurement of pressure gradients in the catheterization lab can be very helpful to simultaneously assess the severity of stenosis and identify its precise location with pulmonary angiography (Figure 108.4
FIGURE 108.4 Right ventricular angiography in supravalvular pulmonic stenosis. Lateral view from right ventricular (RV) angiography in a 50-year-old male with tetralogy of Fallot status post repair. He had a bicuspid pulmonic valve with severe stenosis along with severe supravalvular stenosis of the main pulmonary artery (PA) just distal to the pulmonic valve.
MANAGEMENT: SUPRAVALVULAR PULMONARY STENOSIS
Intervention of peripheral PA stenosis is warranted for any symptomatic patient, those with decreased pulmonary blood flow, or those with significantly elevated RV pressures on echocardiography or catheterization. Those patients with PA stenoses that are not significant should continue to be monitored every 3 to 5 years with interval cross-sectional imaging in addition to ECG
, chest x-ray, transthoracic echocardiography, and exercise testing. In a patient with severe obstruction, percutaneous peripheral intervention is the first step. Percutaneous balloon angioplasty, sometimes with stent placement, is commonly performed for branch PA stenosis. After percutaneous intervention, patients require close follow-up; up to a quarter will require repeat intervention for recurrent stenosis.8
PULMONARY ATRESIA WITH INTACT VENTRICULAR SEPTUM
Pulmonary atresia with intact ventricular septum is characterized by complete obstruction of flow through the RV outflow tract, often with RV and tricuspid valve hypoplasia. Pulmonary atresia with intact ventricular septum is rare, estimated to occur in 4 to 5 per 100,000 live births,22
and has no known genetic or gender association.23
Pulmonary atresia with intact ventricular septum is primarily defined by complete obstruction of flow through the RV outflow tract. Membranous atresia, related to atretic pulmonary valve and small annulus, occurs in 75% of cases, whereas the remaining 25% have muscular atresia, or obliteration of the muscular infundibulum.22
RV hypoplasia is present in the majority of cases, though there are a wide variety of RV morphologies possible.24
Most commonly, all three portions of the normal RV are present with relative hypoplasia of each. About one-third of cases are characterized by overgrowth of the trabecular RV (termed a “ bipartite” ventricle with only inlet and infundibulum) and a minority of cases are “unipartite” with muscular obliteration of the trabecular and infundibular portions.22
At the other end of the spectrum, significant RV dilation can occur, in one series representing 4% of cases, and is usually associated with severe tricuspid regurgitation.22
RV hypoplasia is generally associated with a small tricuspid annulus and dysplastic tricuspid valve with abnormal papillary muscles and chordal attachments.24
RV dilation is typically associated with tricuspid regurgitation. Ebstein-like malformation of the tricuspid valve has been estimated to occur in approximately 10% of cases.22
Abnormalities of the coronary circulation are common in pulmonary atresia with intact ventricular septum and can contribute to morbidity and mortality in some patients.23
Suprasystemic RV pressure pushes blood from the RV into vascular channels, consisting of intertrabecular spaces with thick, fibroelastic walls.24
In some cases, these channels form major fistulous connections and communicate with the epicardial coronary circulation.23
In the most severe form, epicardial coronary blood flow is at least partially dependent on flow from the RV to the coronary, termed “RV-dependent coronary circulation.”25
Stenosis or atresia of the proximal coronary artery is occasionally observed in these patients and, when present, leads to chronically deoxygenated coronary blood supply from the RV, in some cases contributing to long-term biventricular dysfunction.25
Additionally, surgical RV decompression in a patient with RV-dependent coronary circulation can result in peri- or postoperative myocardial infarction because of abrupt decrease in coronary perfusion.25
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