You are in: eMedicine Specialties > Radiology > CARDIAC Pulmonic StenosisArticle Last Updated: Sep 19, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Vibhuti N Singh, MD, MPH, FACC, FSCAI, Director, Suncoast Cardiovascular Center; Chair, Cardiology Division and Cath Labs, Department of Medicine, Bayfront Medical Center; Clinical Assistant Professor, Division of Cardiology, University of South Florida College of Medicine Vibhuti N Singh is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, and Florida Medical Association Coauthor(s): Sherif Wassef, MD, MS, FRCS, Consulting Staff, Department of Vascular and Interventional Radiology, Hahnemann University Hospital Editors: Justin D Pearlman, MD, PhD, ME, MA, Director of Dartmouth Advanced Imaging Center, Professor of Medicine, Professor of Radiology, Adjunct Professor, Thayer Bioengineering and Computer Science, Dartmouth-Hitchcock Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David S Levey, MD, PhD, Orthopedic/Spine MRI TeleRadiologist, Radsource, LLC; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Clinical Assistant Professor of Radiology, University of Washington Medical School Author and Editor Disclosure Synonyms and related keywords: pulmonic stenosis, pulmonary valve stenosis, pulmonary stenosis, pulmonary valvular stenosis, PS, right ventricular outflow obstruction, isolated right ventricular obstruction, valvular stenosis, infundibular stenosis, supravalvular stenosis INTRODUCTIONSection 2 of 12
  BackgroundThe term pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis) is used to refer to the 2 types of right ventricular outflow obstruction—namely, valvular stenosis and infundibular stenosis. Valvular pulmonary stenosis commonly occurs as an isolated lesion. Occasionally, supravalvular stenosis may occur. The most common cause of valvular PS is congenital. Rheumatic inflammation of the pulmonic valve is uncommon. Rheumatic pulmonary valve disease usually involves other valves; it rarely leads to serious pulmonic valvular deformity. One study from New Mexico reported a high incidence of significant pulmonic valve involvement secondary to rheumatic fever. Such involvement may occur in association with the pulmonary hypertension that occurs at high altitudes and the increase in stress that such hypertension places on the pulmonic valve. In patients with malignant carcinoid, carcinoid plaques, not unlike those affecting the tricuspid valve, may involve the outflow tract of the right ventricle. The plaques result in constriction of the pulmonic valve ring, retraction and fusion of the valve cusps, and either PS or the combination of PS and pulmonic regurgitation. Obstruction in the region of the pulmonic valve may be extrinsic to the valve apparatus and may be produced by cardiac tumors or by aneurysm of the sinus of Valsalva. Congenital PS is usually treated by balloon dilation; it sometimes requires surgical valvotomy. If there is severe hypoxia (PaO2 <30 mm Hg), then it may be necessary to create a systemic-to-pulmonary shunt; prostaglandin may be required to maintain patent ductus.1, 2, 3, 4 PathophysiologyValvular pulmonic stenosis is the most common form of isolated right ventricular obstruction; it occurs in about 7% of patients with congenital heart disease. The pulmonic valve lesion is often accompanied by hypertrophy of the septal and parietal bands, with narrowing of the right ventricular infundibulum; such hypertrophy is especially prevalent in severe cases of PS. In the severest forms, fused cusps of varying thickness and rigidity form a fibrous dome. Pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis) typically occurs in the fetal heart during the first 8 weeks of pregnancy. Pulmonic valve dysplasia, which is especially common in patients with Noonan syndrome, produces obstruction in the absence of adherent leaflets. The leaflets are thickened, rigid, and myxomatous; and they are restricted in their lateral movement by tissue pads within the pulmonic valve sinuses. In valvular PS, the pulmonary valve leaflets are thickened and domed during systole; the configuration returns to normal during diastole. Poststenotic dilatation of the main pulmonary trunk and sometimes of the left pulmonary artery is usual. In dysplastic PS, the leaflets of the dysplastic pulmonic valve are not fused anatomically; rather, they are thickened and immobile; thus, on angiography, the appearance of the valve changes little during the cardiac cycle. A small annulus and narrow sinuses of Valsalva commonly accompany valve dysplasia. With either type of valve, systolic narrowing of the right ventricular infundibulum usually is associated with moderate or severe obstruction.5, 6 FrequencyUnited StatesValvular pulmonic stenosis results from fusion of the valve cusps during mid to late intrauterine development. This is the most common form of isolated right ventricular obstruction; it occurs in about 7% of patients with congenital heart disease. InternationalInternationally, the incidence of pulmonic stenosis is the same as that in the United States. Mortality/Morbidity
RaceNo particular racial predilection has been reported for pulmonic stenosis. SexNo clear sex dominance has been described for pulmonic stenosis. AgeIf not detected at birth, pulmonic stenosis is usually diagnosed by 3 years of age; patients present with dyspnea and fatigue. AnatomyValvular pulmonic stenosis, which results from fusion of the valve cusps during mid to late intrauterine development, is the most common form of isolated right ventricular obstruction; it occurs in about 7% of patients with congenital heart disease. Hypertrophy of the septal and parietal bands, with narrowing the right ventricular infundibulum, often accompanies the pulmonic valve lesion, especially if it is severe. In the severest cases, fused cusps of varying thickness and rigidity form a fibrous dome. Pulmonic valve dysplasia is especially common in patients with Noonan syndrome. Although the leaflets are not adherent, obstruction occurs nevertheless, owing to the fact that the leaflets are thickened, rigid, and myxomatous and that their lateral movement is limited by tissue pads within the pulmonic valve sinuses. Clinical DetailsNatural history Mild and moderate valvular pulmonic stenoses (PS, pulmonary stenosis, pulmonary valve stenosis) have a generally favorable course. Although severe PS may lead to right heart failure, arrhythmias, and early death, most children with repaired pulmonary valves or mild to moderate disease lead full, healthy lives. In some patients with mild PS, the disease may progress, and the patient will require intervention later; other patients do well and never require intervention. In serial hemodynamic studies conducted over 4- to 8-year intervals, pressure gradients remained unchanged in three fourths of patients. Of the remaining patients, equal percentages experienced increased or decreased obstruction. Significant increases in the pressure gradient may occur, especially in children with a gradient in excess of 50 mm Hg at initial examination.7 General physical examination findings The physical findings often suggest the severity of obstruction. Right ventricular hypertrophy reduces compliance of that chamber, and a forceful right atrial contraction is necessary to augment right ventricular filling. Prominent a waves in the jugular venous pulse, a fourth heart sound, and, occasionally, presystolic pulsations of the liver reflect vigorous atrial contraction and suggest the presence of severe stenosis. Cardiomegaly and a right ventricular parasternal lift accompany moderate or severe obstruction. A systolic thrill is palpable along the upper left sternal border in all but the mildest forms of stenosis. The first heart sound is normal; it is followed by a systolic ejection sound at the upper left sternal edge, which is produced by sudden opening of the stenotic valve. An ejection sound is not heard in patients with pulmonic valve dysplasia. The ejection sound typically is louder during expiration; when it is inaudible or occurs less than 0.08 seconds after the onset of the Q wave on ECG, severe obstruction is suggested. The right ventricular ejection is prolonged in patients with moderate or severe stenosis; in such patients, the sound of pulmonic valve closure is delayed and soft. On auscultation, the characteristic feature of valvular PS is a harsh, diamond-shaped systolic ejection murmur heard best at the upper left sternal border. With more severe valvular obstruction, the systolic murmur becomes louder, and its crescendo occurs later in systole, such that it obscures the aortic component of the second sound; these signs occur as a result of prolongation of right ventricular systole. The holosystolic decrescendo murmur of tricuspid regurgitation may accompany severe PS, especially in the presence of congestive heart failure. Cyanosis, which reflects venoarterial shunting through a patent foramen ovale, is absent in cases of mild stenosis; it is infrequent in cases of moderate obstruction. Cyanosis may not be apparent in patients with severe obstruction if the atrial septum is intact. Presentation in infants and neonates The clinical presentation and course of circulation in a newborn with PS depends on the severity of obstruction and on the degree of development of the following structures: the right ventricle and its outflow tract; the tricuspid valve; and the pulmonary arterial tree. The greater the degree of pulmonic valve stenosis, the more closely the manifestations resemble those observed in cases of pulmonary atresia in which the ventricular septum is intact. Severe PS is characterized by cyanosis; the cyanosis is the result of right-to-left shunting through the foramen ovale, as well as cardiomegaly and diminished pulmonary blood flow in the absence of persistent patency of the ductus arteriosus. Hypoxemia and metabolic acidemia, rather than right ventricular failure, are the main clinical disturbances in symptomatic neonates. These symptoms may be alleviated temporarily with an infusion of prostaglandin E1, which allows the patent ductus arteriosus to be maintained. Babies with these conditions may usually be distinguished from those with tetralogy of Fallot or tricuspid or pulmonary atresia on the basis of radiographic and ECG evidence. In typical cases of tetralogy, there is no radiographic evidence of cardiomegaly. For infants with tricuspid and pulmonary atresia, ECGs show a preponderance of left ventricular forces, in contrast to the right ventricular hypertrophy usually observed in patients with critical PS who are without right ventricular hypoplasia. Combined 2-dimensional ECG and continuous-wave Doppler examination may be used to characterize the anatomic valve abnormality and its severity. MRI may be performed in utero; although there are no reports of harm resulting from the use of MRI in utero, there is insufficient date to guarantee that there are no harmful effects. These techniques have essentially eliminated the need for cardiac catheterization and angiographic studies to establish a precise diagnosis. Presentation in children In cases of PS in which the cardiac output is normal, PS is considered mild if the valve gradient is less than 25 mm Hg; PS is considered moderate if the gradient is 25-49 mm Hg; PS is considered severe if the gradient is 50-79 mm Hg; PS is considered critical if the gradient is 80 mm Hg or higher. Most patients with mild PS are asymptomatic; for these patients, the condition is discovered during routine examination. The severity of stenosis may increase with time. Progression may be relative. Progression may reflect disproportional physical growth of the patient, or it may reflect infundibular narrowing, which occurs as a result of progressive hypertrophy of the right ventricular outflow tract or fibrosis of the valve cusps. Symptoms, when present, vary from mild exertional dyspnea and mild cyanosis to signs and symptoms of heart failure, depending on the degree of obstruction and the level of myocardial compensation. Exertional fatigue, syncope, and chest pain are related to an inability to augment pulmonary blood flow during exercise in some patients with moderate or severe obstruction. Preferred ExaminationEchocardiography Reliable localization of the site of obstruction and an assessment of its severity are possible with combined continuous-wave or pulsed-wave Doppler and 2-dimensional echocardiography. The 2-dimensional echocardiogram usually shows prominent pulmonary valve echoes with restricted systolic motion, as well as poststenotic dilation of the main pulmonary artery and its branches. Electrocardiography Electrocardiography (ECG) may be helpful in assessing the degree of obstruction to right ventricular output. In mild cases, the ECG often appears normal, whereas moderate and severe stenoses are associated with right-axis deviation and right ventricular hypertrophy. In patients with severe stenosis who are 2-20 years of age, right ventricular pressure may be estimated by multiplying the height of the R wave in lead V4R or V1 by 5. A tall QR wave in the right precordial leads with T-wave inversion, together with ST-segment suppression (right ventricular strain), reflects severe stenosis. When a regular sinus rhythm is observed in lead V1 (20% of patients), right ventricular pressures are lower than those in cases in which there is a pure R wave of equal amplitude. High-amplitude P waves in leads II and V1 indicate right atrial enlargement; such findings are associated with severe stenosis. Limitations of TechniquesThere are very few limitations of these techniques. A good-quality ECG may be unobtainable in obese patients or in patients in whom the acoustic windows are poor. DIFFERENTIALSSection 3 of 12
Pulmonary Hypertension Tetralogy of Fallot Tricuspid Atresia Tricuspid Valve Disease RADIOGRAPHSection 4 of 12
FindingsIn some patients with pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis), no recognizable abnormality is noted. In patients who have normal peripheral pulmonary vascularity, the characteristic findings of valvular stenosis are right ventricular enlargement and prominence of the main and left pulmonary arteries. The right atrium is sometimes enlarged. Isolated infundibular stenosis is rare. The heart may be of normal size, but it is enlarged in about one half of patients. The enlargement is right-sided and results in a rounded right, lower cardiac contour in the frontal projection. The apex may be elevated and blunted. The most characteristic finding is enlargement of the main pulmonary artery, which results in convexity of the left, upper cardiac margin below the aortic knob. This enlargement of the main pulmonary artery is caused by poststenotic dilatation. The dilatation involves the main pulmonary artery and the left pulmonary artery, producing a prominent arterial silhouette of the left hilum. The change in the left pulmonary artery may be best seen in the lateral projection as it arches over the left bronchus. The right pulmonary artery may be dilated, but this vessel is hidden by mediastinal opacity. Therefore, in patients with PS, the hilar vessels appear to be of different sizes; by contrast, in patients with pulmonary hypertension, the hilar vessels appear to be of the same size. This is a helpful sign in the differential diagnosis. Poststenotic dilatation occurs in valvular stenosis; by contrast, in infundibular and supravalvular stenosis, the pulmonary artery is not prominent, and radiographic findings indicative of cardiovascular disease may be absent. The large, main arterial change is associated with the normal size of the vessels in the lungs and in the right hilum.8, 9 Degree of ConfidenceThe degree of confidence is moderate in pulmonic stenosis. False Positives/NegativesThe results of a radiographic examination are nonspecific in pulmonic stenosis. CT SCANSection 5 of 12
FindingsCT of the heart usually requires modification of the standard CT techniques used for investigating other parts of the body. Degree of ConfidenceThe degree of confidence is moderate in pulmonic stenosis. The x-ray exposure, the need for contrast medium, and an inability to image in multiple planes limit the usefulness of CT in the evaluation of congenital heart disease. False Positives/NegativesThe rates of false positive and false negative findings are low in pulmonic stenosis. MRISection 6 of 12
FindingsSeveral factors make MRI especially useful for establishing a cardiovascular diagnosis. First, a high natural contrast exists between the blood pool and the cardiovascular structures because of the lack of signal from flowing blood with the spin-echo MRI technique and because of the brightness of blood with the gradient-echo (cine MRI) technique. When the spin-echo technique is used, blood appears black on images; therefore, internal structures of the heart may be visualized within the signal void of the cardiac chambers. Cardiac imaging usually requires some form of physiologic gating of the imaging sequence. The gating with MRI requires the use of a nonferromagnetic physiologic signal-sensing circuit. An electronically isolated ECG electrode lead circuit that contains little metal has been used for repetitive synchronization (ie, ECG gating) of pulse sequences to fixed segments of the cardiac cycle. ECG gating is used prospectively for some sequences (spin-echo) or retrospectively for others (cine gradient-echo). MRI may be used to determine whether valvular stenosis and regurgitation are present. This is done by using cine MRI to depict the signal void caused by a high-velocity jet flow across a narrow valvular orifice associated with the opened valve in stenosis. In cases of pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis), the high-velocity jet produces a signal void that is projected into the pulmonary artery in systole. The volumes of shunts, valvular function, and pressure gradients across valves and conduits may be estimated by use of velocity-encoded cine MRI (velocity-flow mapping). However, these capabilities are not employed as widely as they might be, owing to the fact that echocardiography and Doppler techniques are used for many of these purposes. Consequently, the current clinical role of MRI is to supplement the information acquired by means of echocardiography. Because MRI defines the right ventricular myocardium, it may be the preferred technique for the accurate determination of right ventricular function. MRI has shown reasonable accuracy in measuring right ventricular end-diastolic, end-systolic, and stroke volumes, as well as the ejection fraction.10, 11 Degree of ConfidenceThe degree of confidence is high in pulmonic stenosis. False Positives/NegativesThe rates of false positive and false negative findings are low in pulmonic stenosis. ULTRASOUNDSection 7 of 12
FindingsReliable localization of the site of obstruction and assessment of its severity are possible with combined continuous-wave or pulsed-wave Doppler and 2-dimensional echocardiography. The 2-dimensional echocardiogram usually shows prominent pulmonary valve echoes with restricted systolic motion, as well as poststenotic dilation of the main pulmonary artery and its branches. In contrast to these findings in classic valvular PS, patients with a dysplastic valve have thickened and immobile leaflets with hypoplasia of the pulmonary valve annulus and absent poststenotic dilatation of the pulmonary artery. Parasternal and subcostal views are required to detect most accurately maximal blood flow velocity in the pulmonary artery. This velocity is converted to a pressure difference across the valve by using a modified Bernoulli equation: pressure difference (in mm Hg) = 4 X the squared peak Doppler velocity (in meters per second). A semiquantitative estimation of pulmonary and tricuspid regurgitation can be obtained. The peak systolic velocity of the tricuspid regurgitant jet provides a reliable indirect measurement of the severity of obstruction because the reverse gradient between the right ventricle and right atrium allows the derivation of the ventricular peak systolic pressure. One may assume a value for right atrial pressure, or look at inferior vena cava collapse during sniff, using 5 mm Hg if it clearly narrows, 10 if partial narrowing, 15 if no narrowing; or the right atrial pressure can be estimated from vertical distance from midright atrium to pulsation level in jugular veins, converted from centimeters of water to millimeters of mercury.12, 13 Degree of ConfidenceThe degree of confidence is high in pulmonic stenosis. False Positives/NegativesThe rate of false findings is low in pulmonic stenosis. NUCLEAR MEDICINESection 8 of 12
FindingsRadionuclide studies (for example, multiple gated acquisition [MUGA] scans) may be used to assess right ventricular function and left ventricular function in patients with pulmonic stenosis and dyspnea. Degree of ConfidenceNuclear medicine studies are nonspecific in pulmonic stenosis. False Positives/NegativesThe rates of false positive and false negative findings are low in pulmonic stenosis. ANGIOGRAPHYSection 9 of 12
FindingsAngiocardiography may show enlargement of the right atrium and ventricle. It usually provides a superb demonstration of the actual site and degree of pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis), along with the poststenotic dilatation of the pulmonary artery. Cardiac catheterization and angiocardiography are now used only rarely to establish or preclude other diagnostic possibilities. The usual indication for cardiac catheterization is to provide definitive therapy for the lesion. However, cardiac catheterization may also be used to localize the site of obstruction, to evaluate its severity, and to document the coexistence of additional cardiac malformations. The resting cardiac output usually is normal, even in cases of severe stenosis; in most children, cardiac output increases with exercise. Right ventricular dysfunction occurs especially when venoarterial shunting is significant and produces systemic arterial desaturation. During hemodynamic evaluation of patients with critical stenosis, care must be taken to avoid dangerously occluding the stenotic valve opening with the cardiac catheter. In PS, the valve gradient is usually obtained by means of a catheter pull-back maneuver from the pulmonary artery to the right ventricle, although multilumen catheters are available for simultaneous pressure recordings. In typical cases of valvular PS, the angiographic appearance differs from that of a dysplastic valve. In PS, the valve is thickened and domed during systole; the configuration returns to normal in diastole. Poststenotic dilatation of the main pulmonary trunk and sometimes of the left pulmonary artery are usual. Although the leaflets of the dysplastic valve are not fused anatomically, they are thickened and immobile; thus, on angiography, the valve appears to change little during the cardiac cycle. In addition, a small annulus and narrow sinuses of Valsalva are common accompaniments of valve dysplasia. With either type of valve, systolic narrowing of the right ventricular infundibulum usually is associated with moderate or severe obstruction.14 Degree of ConfidenceThe degree of confidence is high in pulmonic stenosis. False Positives/NegativesThe rates of false positive and false negative findings are low in pulmonic stenosis. INTERVENTIONSection 10 of 12
General considerations Percutaneous valvuloplasty is appropriate in most patients. In some patients, surgical relief may be accomplished at an extremely low risk. The valve is approached through an incision in the pulmonary arterial trunk; resection of the infundibular muscle, if necessary, may be accomplished through the pulmonic valve. A repeat operation or subsequent balloon valvuloplasty is seldom required. In patients with a dysplastic valve in whom transcatheter valvuloplasty is ineffective, the thickened valve tissue is removed; a patch is often required to widen the annulus and the proximal main pulmonary artery. In children with mild pulmonic stenosis (PS, pulmonary stenosis, pulmonary valve stenosis), prophylaxis against infective endocarditis is recommended; these patients need not restrict their physical activities. After the stenosis is relieved, cardiac performance (as judged on the basis of exercise testing) improves in children in whom postoperative resolution of right ventricular hypertrophy is expected. In adults, by contrast, myocardial fibrosis may account for a lack of improvement.15, 16, 17, 18, 19, 20 Percutaneous transluminal balloon valvuloplasty Percutaneous transluminal balloon valvuloplasty is the initial procedure of choice for patients with typical PS and moderate to severe degrees of obstruction. This approach provides palliative improvement; the likelihood is great that the improvement will prove permanent. Balloon valvuloplasty Balloon dilatation of the pulmonary valve is the therapeutic procedure of choice for PS; however, a pulmonary valvotomy and systemic-to-pulmonary arterial shunt may be necessary in infants in whom the right ventricular cavity is underdeveloped. In these patients, success has been achieved with a modification of balloon valvuloplasty. In the modified procedure, initial predilation is achieved by use of a coronary dilatation catheter, which facilitates the introduction of a definitive balloon catheter. Transcatheter balloon valvuloplasty may be expected to reduce but not abolish the pressure difference in neonates with mobile doming valves. Sustained relief of the severe obstruction is usual, as is good growth of the right ventricle. This approach is less effective in patients with dysplastic valves. It is contraindicated if valve dysplasia is associated with annular hypoplasia. Cardiac catheterization and angiocardiography Cardiac catheterization and angiocardiography are now used only rarely to establish or preclude other possible diagnoses. The usual indication for cardiac catheterization is to provide definitive therapy for the lesion. However, cardiac catheterization may also be used to localize the site of obstruction, to evaluate its severity, and to document the coexistence of additional cardiac malformations. Medical/Legal Pitfalls
Special Concerns
FURTHER READINGSection 11 of 12
ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease). REFERENCESSection 12 of 12
Article Last Updated: Sep 19, 2008 |
