Right ventricular outflow tract obstruction
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Overview
Right ventricular outflow tract (RVOT) and pulmonary artery obstruction correspond to 25 % of all congenital heart defects. The right ventricular outflow tract obstruction includes the stenosis or narrowing of the pulmonary valve, the tissue above the valve (supravalvar) and below it(subvalvar). Congenital subvalvar and supravalvar right ventricular outflow tract stenosis usually occurs with other cardiac defects such as Ventricular Septal Defect (VSD) or Tetralogy of Fallot, and depending on those defects and the severity of the obstruction, the timing and type of surgery will vary from patient to patient.
If an RVOT obstruction is present and the ventricular septum is intact, usually the right ventricle will adapt better raising pressure effectively in the absence of shunting. This may result in sufficient pulmonary blood flow to allow the patient to stay asymptomatic longer.
Pulmonary stenosis is one of the most common RVOT obstructions. The oxygen-depleted blood is coming from the body to the heart through th superior and inferior vena cava, arriving into the right atrium, right ventricle, passing through the RVOT and pulmonary valve to the pulmonary artery and lungs to pick up oxygen. Normally the pulmonary valve has three leaflets. These leaflets can be malformed due to congenital defects, producing pulmonary valve narrowing (stenotic) or leaky (insufficient). If the pulmonary valve is tight (stenosis), the right side of the heart needs to work harder to push blood through the valve to the lungs. The stenosis, insufficiency or both can be mild to severe. Therefore the symptoms will depend upon the grades of pulmonary stenosis.
Usually therapy is directed to increase pulmonary blood flow and decompressing the right ventricle (RV) and it will depend on the severity and location of the defect. According to the anatomic features of the pulmonary valve stenosis, the physician may use balloon dilatation (a minimally invasive transvenous procedure) to dilate the obstruction during cardiac catheterization, but if the pulmonary artery is the structure involved, stenting (insertion of a small tube) within the narrowed region can be done following balloon angioplasty. Standard treatment of right ventricular outflow tract or pulmonary artery obstruction involves open chest surgery. [1]
Normal Pulmonary Valve Anatomy
The pulmonic valve or pulmonary valve is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. Similar to the aortic valve, the pulmonic valve opens in ventricular systole, when the pressure in the right ventricle rises above the pressure in the pulmonary artery. At the end of ventricular systole, when the pressure in the right ventricle falls rapidly, the pressure in the pulmonary artery will close the pulmonic valve.
The closure of the pulmonary valve contributes the P2 component of the second heart sound (S2). The right heart is a low-pressure system, so the P2 component of the second heart sound is usually softer than the A2 component of the second heart sound. However, it is physiologically normal in some young people to hear both components separated during inspiration.
Pulmonary Valve Stenosis
Demographics and Epidemiology
- Generally, pulmonary valve stenosis is a congenital defect narrowing of the pulmonary valve (the semilunar valve that separates the right ventricule from the pulmonary artery), but occasionally, it could also be presented in adults as a complication of another illness.
- It's one of the more common heart birth defects, and most cases are mild. If the pulmonary valve stenosis is moderate to severe, it will cause serious symptoms, requiring surgery which is highly successful.
- It occurs in about 1 of 10 children, and females are slightly more likely to be affected than males.
Anatomy
- Typically the valve is domed shaped with fused commissures.
- If the foramen ovale is patent, then right to left shunting can occur at the atrial level.
- If there is pulmonary atresia with an intact ventricular septum then these patients die soon after birth.
Etiology
- Congenital pulmonic stenosis is most common.
- Rheumatic involvement is rare, is usually part of multivalvular involvement, rarely leads to serious deformity.
- Carcinoid plaques can be present in the carcinoid syndrome. These result in constriction of the pulmonic valve ring, retraction and fusion of the valve cusps.
Diagnosis
Clinical Symptoms
- Symptoms develop in only approximately 25% of patients because progression of the disease is rare.
- With a gradient of > 75 mm Hg symptoms include fatigability, DOE, angina, syncope and central cyanosis if there is a right-to-left shunt through a patent foramen ovale (PFO).
- Chest pain
- Syncope
- Congestive heart failure
- Dyspnea
- Fatigue
- Fluid retention
- Cough
- Cough with pink frothy sputum
- Cardiomegaly
Physical examination
- A systolic murmur is often heard in the neonate.
- A small percentage of patients have Noonan's syndrome
- Small stature, retarded, triangle-faced shape, webbed neck, ptosis, hypertelorism, low set ears, and pectus.
- Noonan syndrome is familial.
- If the lesion is severe (>75 mm Hg) then there is a giant a wave secondary to the reduced compliance of the RV.
- There is a loud systolic ejection murmur loudest in the second left intercostal space and peaking in late systole.
- In severe forms, the pulmonic component of the second heart sound may be missing.
Electrocardiogram
- RVH with an R wave in lead V1 of 10 mm and an inverted T wave.
Chest X Ray
- CXR shows post stenotic dilation of the PA.
Echocardiography
- Echocardiography shows thickened and domed leaflets.
- Pulmonic Stenosis 1
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- Pulmonic Stenosis 2
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- Pulmonic Stenosis 3
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Cardiac Catheterization
Right ventriculographic images show pulmonary stenosis.
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Pulmonary Subvalvular Stenosis
Anatomy
- There is hypertrophy of the infundibular muscle causing obstruction.
- The isolated form is rare, more commonly develops in response to an underlying VSD.
Clinical Features
- Similar to valvar pulmonic stenosis.
- No ejection click in contrast to valvar pulmonic stenosis.
- No poststenotic dilation of the pulmonary artery in contrast to valvar pulmonic stenosis.
Pulmonary Supravalvular Stenosis
Anatomy
1. Also called peripheral pulmonary stenosis.
2. May have one or many stenoses of the PA or its branches.
3. Infrequently occurs as an isolated lesion, more commonly occurs as part of Tetralogy of Fallot.
Clinical Features
1. The murmur is most prominent at the upper left sternal border, axillae, and the posterior lung fields.
Differential Diagnosis
1. ASD: Also has a systolic ejection murmur, wide fixed split S2, EKG showing RVH. In ASD the split of the S2 is fixed, there is no ejection click.
2. Small VSD: Amyl nitrate increases venous return and increases the murmur of PS, in VSD the murmur becomes softer.
3. Mild left-sided outflow obstruction: With valsalva the murmur of AS becomes softer after about 5 beats, with PS it becomes softer within 3 beats.
4. Acyanotic or pink tetralogy of Fallot: with amyl nitrate and increased venous return the murmur of PS increases, and the murmur of tetralogy decreases because of peripheraldilation and an increase in right to left shunting.
Indications for Invasive Studies
1. Cardiac catheterization is indicated:
a) In supravalvular or subvalvular stenoses to define the anatomy prior to surgical correction.
b) In the presence of cyanosis to define the anatomy.
General Management
1. The gradients often increase in patients with moderate to severe PS, but patients with mild PS remain stable.
2. Prognosis in patients with PS who have reached adulthood without RV failure or symptoms is reported to be good with minimal risk of endocarditis, RV failure or death.
3. in patients with severe stenoses, there is impaired exercise tolerance and changes in the RV myocardium.
4. Surgery is indicated in patients with fatigability, DOE, cyanosis or CHF.
5. Surgery is recommended in the absence of symptoms if the gradient is greater than 75 mm Hg, and is also preferred if the gradient is as low as 50 to 60 mm Hg.
6. For those with gradients less than 50 mm Hg, then follow-up is recommended.
7. Long-term results of pulmonary valvuloplasty are not yet available, but short term results appear to be excellent.
a) Restenosis is likely is the residual gradient is greater than 30 mm Hg.
b) 79% of these patients have residual pulmonic regurgitation.
c) Following these procedures there is a soft residual systolic murmur, a diastolic murmur of pulmonic insufficiency, and some regression of the EKG criteria of RVH.
Pulmonary Valve Atresia
Pulmonary atresia is a congenital malformation of the pulmonary valve in which the valve orifice fails to develop. Atresia means "no opening". The valve is completely closed thereby obstructing the outflow of blood from the heart to the lungs.
Oxygen-poor blood travels directly from the right atrium to the left side of the heart through a shunt (patent foramen ovale or any other type of atrial septal defect). This oxygen-poor blood is then pumped through the aorta to the rest of the body, making fingers, toes, and lips appear blue or cyanotic.
Babies with this type of cyanotic congenital heart disease survive only for the first few days of life while the normal fetal shunts (patent ductus arteriousus, patent foramen ovale) between left and right circulations remain patent. Without an operation in that period to open the pulmonary valve or to make a shunt between the aorta and the pulmonary arteries, the condition is fatal.
The type of surgery recommended depends on the size of the right ventricle and the pulmonary artery. If they are normal in size and the right ventricle is able to pump blood, open heart surgery can be performed to make blood flow through the heart in a normal pattern. If the right ventricle is small and unable to act as a pump, doctors may perform an operation called the Fontan procedure. In this procedure, the right atrium is connected directly to the pulmonary artery. Many children with Pulmonary Atresia will go on to lead 'normal' lives.
Clinical Symptoms
Symptoms are noted shortly after birth. The most common presentation is a newborn who becomes cyanotic (blue) in the transitional first day of life when the placenta (maternal source of oxygen) is removed. Cyanosis is related to the presence of other defects that allow blood to mix, such as a patent ductus arteriosus, patent foramen ovale, etc. Other symptoms may include rapid breathing, lethargy, irritability, etc.
Types of Pulmonary Atresia
With intact ventricular septum: complex cardiac lesion characterized by one of two patterns of pathophysiology.
Type I disease
In this particular type, there is a combination of pulmonary valvular atresia, competent tricuspid valve, and an intact ventricular septum. As a consequence a right ventricular hypertrophy and chamber obliteration with suprasystemic pressures is developed, which force blood through the myocardial sinusoids that feed the right ventricle into the coronary circulation.
Type II disease
This type consist of proximal pulmonary arterial atresia , an intact ventricular septum, but the tricuspid valve is incompetence allowing retrograde flow of blood into the right atrium and across an atrial septal defect. TTherefore, the right ventricle is either normal or dilated.
Survival has improved due to a combination of the early treatment with Prostaglandin PGE1 (to prevent the PDA from closing) and advances in cardiac surgery (creating shunts between the aorta and the pulmonary artery that may help increase blood flow to the lungs). A more complete repair will depends on the size of the pulmonary artery and right ventricle.
General Management
Patient should be treated in the intensive care unit (ICU) or special care nursery once symptoms are noted. The patient will need oxygen, and possibly even a ventilator, to assist his/her breathing. Intravenous (IV) medications may be given to help the heart and lungs function more efficiently.
A cardiac catheterization procedure can be used as a diagnostic procedure, as well as initial treatment procedure as balloon atrial septostomy to improve mixing oxygenated blood and unoxygenated blood between the right and left atria.
Atrial Septostomy: a special catheter with a balloon in the tip is used to create an opening in the atrial septum. The catheter is guided through the foramen ovale to the left atrium (LA). Once the ballon is in the LA is inflated and then pulled back opening a bigger hole between the right atrium and the LA to mix blood.
If the hospital does not have a catheterization lab with skill physician to perform the ballon atrial septostomy, an intravenous medication called prostaglandin is administered to keep the ductus arteriousus from closing.
Those intervention will only allow time to stabilize the baby, because surgery is the definitive treatment to improve blood flow to the lungs
Stenosis of Pulmonary Arterial Segment
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Carcinoid Tumor in the Right Ventricular Outflow Tract
- Carcinoid Tumor in the Right Ventricular Outflow Tract 1
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- Carcinoid Tumor in the Right Ventricular Outflow Tract 2
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- Carcinoid Tumor in the Right Ventricular Outflow Tract 3
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Sources
- Giuliani et al, Cardiology: Fundamentals and Practice, Second Edition, Mosby Year Book, Boston, 1991, pp. 1687-1692.
References
- ↑ Surgery for congenital heart defects. J.Stark and M. de leval. Grune & Stratton.
Acknowledgements
The content on this page was first contributed by Dr. Leida Perez