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| REVIEW ARTICLE |
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| Year : 2018 | Volume
: 7
| Issue : 4 | Page : 154-160 |
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Isolated infundibular pulmonary stenosis
Sita Ram Mittal DM,
Department of Cardiology, Mittal Hospital and Research Centre, Ajmer, Rajasthan, India
| Date of Web Publication | 15-Oct-2018 |
Correspondence Address:
Dr. Sita Ram Mittal
XI/101, Brahmpuri, Ajmer - 305 001, Rajasthan
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/JCPC.JCPC_18_18
A case of isolated infundibular pulmonary stenosis is reported and literature is reviewed. Infundibular pulmonary stenosis is usually a part of tetralogy of Fallot or is associated with ventricular septal defect. Isolated infundibular pulmonary stenosis is rare. Patients may be asymptomatic in spite of significant stenosis. Dyspnea, chest pain, and presyncope or syncope on effort are common symptoms in significant obstruction. Ejection systolic murmur is best audible in the left 3rd intercostal space and increases on inspiration. Additional murmur of tricuspid regurgitation may appear if there is right ventricular failure. Absence of pulmonary valvular click and normal intensity and splitting of the second sound differentiate it from pulmonary valve stenosis. Electrocardiogram shows right ventricular overload. Two-dimensional (2D) echocardiography shows right ventricular hypertrophy with narrowing of infundibulum, normal pulmonary valve, main pulmonary artery, and branch pulmonary arteries. Right ventricle and right atrium may dilate if there is right-sided failure with significant tricuspid regurgitation. Doppler evaluation reveals systolic gradient in the region of infundibulum with no additional gradient at the level of pulmonary valve, main pulmonary artery, or branch pulmonary arteries. Tricuspid regurgitation may be present. 2D echocardiography with Doppler evaluation also excludes other lesions. Angiography is usually not required. Surgery is safe and effective in relieving obstruction. Stent implantation is safe and effective in highly selected patients with discretely narrow circumferential stenotic segment and near-normal-sized peristenotic segment between the pulmonary and tricuspid valves. Keywords: Congenital heart disease, echocardiography, ejection systolic murmur, electrocardiography, right ventricular hypertrophy, right ventricular outflow obstruction, sudden death
How to cite this article:
Mittal SR. Isolated infundibular pulmonary stenosis. J Clin Prev Cardiol 2018;7:154-60 |
| Introduction | |  |
Isolated infundibular pulmonary stenosis is a rare congenital disorder with obstruction to right ventricular outflow at the level of infundibulum. Thorough clinical examination and echocardiography help in confirming the diagnosis and excluding other diseases.
| Case Report | | |
A 6-year-old female child was referred for evaluation of a systolic murmur along the left sternal border. The child was asymptomatic. Murmur was detected at the age of 3 months. Electrocardiogram revealed right-axis deviation with right ventricular hypertrophy [Figure 1]. On echocardiography, the left ventricle was normal. The right atrium and right ventricle were moderately dilated [Figure 2]a. M-mode echocardiogram from parasternal long-axis view related increased thickness (12.9 mm) of right ventricular outflow tract (RVOT) free wall [Figure 2]b. Short-axis view revealed systolic narrowing of RVOT [Figure 2]c. Color Doppler evaluation [Figure 2]d revealed turbulence and gradient across RVOT [Figure 2]e. There was severe tricuspid regurgitation [Figure 3]a with calculated right ventricular systolic pressure of 172.4 mmHg [Figure 3]b. There were no other lesions. Findings were diagnostic of isolated infundibular pulmonary stenosis. | Figure 1: Electrocardiogram showing right-axis deviation and right ventricular hypertrophy
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 | Figure 2: (a) Subcostal four-chamber view showing dilated right atrium and right ventricle, LA = Left atrium, LV = Left ventricle. (b) M-mode echocardiogram from parasternal long-axis view showing thickening of right ventricular anterior wall and normal interventricular septum and left ventricle. (c) Short-axis view showing systolic obliteration of the right ventricular outflow tract (arrow). Ao = Aorta, RA = Right atrium, PA = Main pulmonary artery. (d) Color Doppler evaluation showing turbulence (arrow) across the right ventricular outflow tract. Ao = Aorta, LA = Left atrium, RA = Right atrium, MPA = Main pulmonary artery. (e) Doppler evaluation showing gradient across the right ventricular outflow tract
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 | Figure 3: (a) Color Doppler evaluation in apical four-chamber view showing severe tricuspid regurgitation. (b) Continuous wave Doppler evaluation of tricuspid regurgitation jet showing right ventricular systolic pressure of 172.4 mmHg
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| Review of Literature | | |
Introduction
Right ventricular infundibulum refers to the area of RVOT between the right ventricular cavity and pulmonary valve [Figure 4]a and [Figure 4]b. Infundibular pulmonary stenosis refers to obstruction in this region. It is usually a part of tetralogy of Fallot or is associated with ventricular septal defect (VSD). Isolated infundibular pulmonary stenosis is diagnosed when there is no additional obstruction at the level of pulmonary valve, main pulmonary artery, or its branches, and there are no associated lesions such as VSD or tetralogy of Fallot. It is very rare.[1],[2],[3] There are only isolated case reports.[2],[4],[5],[6] | Figure 4: Diagrammatic representation of infundibulum (I) of right ventricle. (a) In frontal view (b) in short-axis view at the level of aortic root. SVC = Superior vena cava, IVC = Inferior vena cava, RA = Right atrium, TV = Tricuspid valve, RV = Right ventricle, PV = Pulmonary valve, MPA = Main pulmonary artery, RPA = Right pulmonary artery, LPA = Left pulmonary artery, LA = Left atrium, ICS = Intercostal space
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Pathology
Infundibular pulmonary stenosis can be due to the following:[3]
- Fibrous or muscular band in the infundibulum [Figure 5]a
- Diffuse muscular thickening of the infundibulum [Figure 5]b.
 | Figure 5: (a) Diagrammatic representation of fibromuscular band (marked*) producing infundibular obstruction. (b) Diagrammatic representation of diffuse muscular thickening (marked*) producing infundibular obstruction
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Some workers have observed that morphogenetic regularities of compensatory or adaptive reactions in isolated infundibular stenosis are similar to those observed in hypertrophic cardiomyopathy.[7] These authors have suggested that abnormalities in the structure of the hypertrophic myocardium in isolated stenosis of the right ventricular infundibulum are a result of fundamental error in the cardiac morphogenesis and not a reflection of the degree of cardiac hypertrophy.
Other associated congenital anomalies reported in literature
There are isolated case reports of other congenital anomalies associated with isolated infundibular pulmonary stenosis. These include single coronary artery,[8] calcific aortic stenosis,[9] persistent left superior vena cava draining in coronary sinus,[10],[11] main pulmonary artery aneurysm,[12] and left ventricular apical hypoplasia with aortic valve stenosis.[13]
Hemodynamics
Right ventricle hypertrophy is an attempt to push blood against the infundibular obstruction. In mild-to-moderate obstruction, there are no other hemodynamic changes. Hypertrophied right ventricle can push blood across the obstruction at rest and even during sternous exercise without significant increase in its end-diastolic pressure [Figure 6]a. In severe obstruction, there is significant right ventricular hypertrophy. This results in decreased compliance of right ventricle and increase in its end-diastolic pressure [Figure 6]b. The right atrium has to contract forcefully to push blood into the hypertrophied right ventricle. This results in elevated right atrial pressure. Gradually, the right atrium dilates. | Figure 6: Hemodynamics in (a) mild infundibular stenosis (b) severe infundibular stenosis
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Initially, the hypertrophied right ventricle can maintain cardiac output at rest in spite of significant infundibular stenosis. At this stage, pulmonary artery pressure remains normal. However, during exertion, the requirement of cardiac output increases and right ventricle fails to maintain the desired cardiac output. This results in presyncope or syncope on effort. Inadequate cardiac output along with increased oxygen demand of the hypertrophied right ventricle results in angina on effort.
Gradually, the compensatory mechanisms fail and right ventricle starts dilating. Dilatation of the right ventricle and tricuspid annulus results in noncooptation of tricuspid leaflets and tricuspid regurgitation ensues. This results in further dilatation of the right atrium and increased systemic venous congestion. Flow across infundibulum declines and pulmonary artery pressure is reduced. Increased pressure and dilatation of the right atrium favors stretching of foramen ovale, resulting in right-to-left shunt at atrial level. It results in cyanosis.
Symptoms
Infundibular pulmonary stenosis is present since birth.[3] Many patients are asymptomatic[7],[14] because the hypertrophied right ventricle can maintain adequate flow across the obstruction. Patients with severe stenosis may also be asymptomatic.[2],[14]
Others may have dyspnea, chest pain, and palpitation on effort.[4],[14] Some patients may complain of epigastric pain.[3] This is because of exercise-induced right ventricular failure and hepatic congestion. When the right ventricle fails to maintain adequate cardiac output during effort, patients may develop presyncope or syncope on efforts.[3],[14] Patients with severe stenosis are at risk of sudden death[2] even when asymptomatic. A history of squatting goes against the diagnosis of isolated infundibular pulmonary stenosis and suggests a diagnosis of acyanotic tetralogy of Fallot.
Signs
Growth and development are usually normal.[3] Patients with mild-to-moderate obstruction have an ejection systolic murmur due to turbulent flow across narrowed infundibulum during systole [Figure 7]. Murmur is best audible in the left third intercostal space.[1] It increases on inspiration because of inspiratory increase in right ventricular stroke volume. There is no pulmonary valvular click[15] [Figure 7]. Splitting of the second sound is normal with normal intensity of pulmonary component [Figure 7]. Systolic thrill is present over the left third intercostal space.[4] Jugular venous pulse is normal [Figure 8]a. | Figure 7: Auscultatory findings in isolated infundibular pulmonary stenosis. ESM = Ejection systolic mumur, S1 = First heart sound, A2 = Aortic component of the second heart sound, P2 = Pulmonary component of the second heart sound
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 | Figure 8: Jugular venous pulse waves in (a) mild infundibular pulmonary stenosis. (b) Severe infundibular pulmonary stenosis. (c) Severe infundibular pulmonary stenosis with tricuspid regurgitation. A = Atrial contraction, x = Atrial relaxation, c = Closure of tricuspid valve, x' = Right ventricular contraction, v = Right atrial filling, y = Opening of tricuspid valve and emptying of the right atrium
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With increasing obstruction, left parasternal heave appears due to increased systolic pressure of the right ventricle. It is below the left third intercostal space.[15] The length of murmur increases. Jugular venous pulse may show prominent “a” wave due to forceful contraction of the right atrium against hypertrophied right ventricle [Figure 8]b. Transmission of forceful right atrial contraction to inferior vena cava and hepatic veins may produce presystolic hepatic pulsations even in the absence of right ventricular failure.
Development of tricuspid regurgitation produces another systolic murmur along the left lower sternal border [Figure 9]. This murmur also increases on inspiration. Identification of two separate murmurs may be difficult. Location of thrill helps in identifying the site of lesion. Prominent “V” wave in jugular venous pulse [Figure 8]c gives clue to the presence of tricuspid regurgitation. | Figure 9: Auscultatory findings in infundibular pulmonary stenosis with tricuspid regurgitation
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Signs of systemic venous congestion (pulsatile engorgement of neck veins, pulsatile enlargement of liver, and dependent pitting edema) suggest right ventricular failure. With onset of right ventricular failure and tricuspid incompetence, forward flow through the infundibular stenosis declines. The intensity of thrill and murmur may reduce.[3] Cyanosis may appear due to right-to-left shunt across stretched patent foramen ovale.
Investigations
Electrocardiogram
Right-axis deviation and right ventricular hypertrophy are common findings.
Skiagram of chest
It does not show any diagnostic finding. Cardiac size and contour are normal. Absence of prominence of main pulmonary artery supports the possibility of infundibular stenosis over pulmonary valve stenosis. Pulmonary vascularity is normal. The right atrium may become prominent with gross tricuspid regurgitation.
Two-dimensional echocardiography with Doppler evaluation
The diagnostic short-axis view at the level of aortic root is most informative. It confirms isolated obstruction at the level of right ventricular infundibulum [Figure 10]. There is turbulence across RVOT. Pulmonary valve, main pulmonary artery, and its branches are normal with no additional gradient at any other level. The right ventricle is hypertrophied. In advanced stage, the right atrium and right ventricle may be dilated with the presence of tricuspid regurgitation. Dilatation and diminished inspiratory collapse of inferior vena cava suggest right ventricular failure with systemic venous congestion. Rarely, some patients may have dilatation of the RVOT between infundibular stenosis and pulmonary valve due to jet effect of turbulent flow coming across infundibulum.[16] Echocardiography also excludes other lesions. | Figure 10: Diagrammatic representation of two-dimensional and color Doppler findings in short-axis view at the level of aortic root in isolated infundibular pulmonary stenosis. LA = Left atrium, RA = Right atrium, TV = Tricuspid valve, RV = Right ventricle, I = Infundibulum, T = Turbulent flow, PV = Pulmonary valve, MPA = Main pulmonary artery, RPA = Right pulmonary artery, LPA = Left pulmonary artery, Ao = Aorta
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Right ventricular angiography
It does not provide any additional useful information and is usually not indicated. It shows infundibular narrowing. There is no doming of pulmonary valve. Main pulmonary artery, its branches, and peripheral pulmonary arteries are normal. The right atrium and right ventricle may be dilated with the presence of tricuspid regurgitation. Overenthusiastic attempt to pass the catheter across tight obstruction is not safe and should be avoided.
Cardiac magnetic resonance imaging
It allows three-dimensional (3D) information about cardiac morphology.[6] It may be useful if details of infundibular region are not clear on echocardiography.
Differential diagnosis
Atrial septal defect
It produces hyperdynamic pulsations in the left parasternal region with systolic murmur in the left second intercostal space due to increased volume of blood flowing through normal pulmonary valve [Figure 11]. However, there is no thrill. There is wide and fixed splitting of the second heart sound with loud pulmonary component [Figure 11]. Electrocardiogram shows incomplete right bundle branch block. Skiagram shows dilatation of the right atrium and pulmonary plethora. Echocardiography with Doppler evaluation confirms the diagnosis. | Figure 11: Diagrammatic representation of hemodynamics and auscultatory findings in atrial septal defect
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Supracristal ventricular septal defect (subpulmonic ventricular septal defect)
Systolic murmur and thrill are best in the left second intercostal space [Figure 12]a. Murmur radiates upward toward the left clavicle, suprasternal notch, and left side of the neck.[17] Left ventricular enlargement on clinical examination, expiratory increase in systolic murmur, and biventricular enlargement on electrocardiogram support the possibility of VSD. 2D echocardiography with Doppler evaluation shows subpulmonic VSD with normal thickness of infundibulation [Figure 12]b. | Figure 12: Diagrammatic representation of (a) Auscultatory findings in supracrystal ventricular septal defect. (b) Echocardiographic findings in short-axis view at the level of left ventricular outflow tract, T = Turbulent flow
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Acyanotic tetralogy of Fallot
History of squatting on effort, appearance of cyanosis on effort, quite precordium, absence of thrill, single second sound, and concave pulmonary artery segment on skiagram of chest support the possibility of acyanotic tetralogy of Fallot. Electrocardiogram does not show classical right ventricular hypertrophy. Echocardiography confirms overriding of aorta in addition to infundibular pulmonary stenosis.
Subinfundibular obstruction (double-chambered right ventricle)
Fibromuscular bands in the right ventricular cavity separate a proximal sinus chamber (high-pressure chamber) from a distal infundibular chamber (low-pressure chamber) [Figure 13]. Patients are asymptomatic.[1] Right ventricular impulse is unimpressive and confined to subxiphord area.[15] Systolic thrill and murmur are present over the left lower sternal border in the 4th and 5th intercostal spaces[15] [Figure 13]. There is no ejection click.[15] Electrocardiogram (ECG) does not show significant right ventricular hypertrophy in spite of long murmur.[15] 2D echocardiography and color flow imaging show the site of obstruction in the right ventricular cavity and separate infundibular chamber. This anomaly usually co-exists with a VSD.[15] | Figure 13: Pathology and auscultatory findings in subinfundibular obstruction (double-chambered right ventricle). FMB = Fibromuscular band in right ventricular cavity, T = Turbulent flow
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Pulmonary valvular stenosis
Thrill and murmur best over the left 2nd intercostal space, presence of pulmonary valvular click, wide splitting of the second sound with feeble pulmonary component [Figure 14]a support the possibility of pulmonary valvular stenosis. Skiagram of chest shows prominence of main pulmonary artery due to poststenotic dilatation. Echocardiography shows thick and doming pulmonary valve with gradient across pulmonary valve [Figure 14]b. | Figure 14: Diagrammatic representation of (a) Pathology and auscultatory findings in pulmonary valve stenosis. (b) Echocardiography findings in short-axis view at the level of aortic root, T = Turbulent flow
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Supravalvular pulmonary stenosis (stenosis involving main pulmonary trunk or its bifurcation)
Splitting of the second sound and intensity of pulmonary component are normal[15] [Figure 15]a. Murmur is usually best audible in the left second intercostal space and radiates laterally over lung fields and toward the right second intercostal space [Figure 15]a. Electrocardiogram shows right ventricular hypertrophy. Skiagram of chest is usually normal. Echocardiography (parasternal short-axis view) shows turbulence and gradient in the main pulmonary artery or at its bifurcation [Figure 15]b. | Figure 15: Diagrammatic representation of (a) Pathology and auscultatory findings of supravalvular pulmonary stenosis. (b) Echocardiography findings in short-axis view at the level of aortic root, T = Turbulent flow
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Infundibular stenosis with pulmonary valve stenosis
Infundibular stenosis may be an independent pathology or may occur due to infundibular hypertrophy secondary to valvular pulmonary stenosis.[1],[15] Clinical examination, electrocardiogram, and skiagram of chest do not help in identifying simultaneous obstruction at these two sites. Echocardiography can be helpful. Detecting two separate levels of gradient may be difficult. Turbulence starting in infundibular region with thickening and doming of pulmonary valve can give a clue. Magnetic resonance imaging may be required for clear delineation of pathology.
Infundibular stenosis with ventricular septal defect
Clinical diagnosis is difficult. Echocardiography is helpful. VSD may close leaving behind the isolated infundibular pulmonary stenosis.[18]
Tricuspid regurgitation
It also produces a systolic murmur that increases on inspiration. The murmur is best audible along the left lower sternal border. Usually, it is secondary to pulmonary artery hypertension which produces systolic pulsations in the left second intercostal space, pulmonary vascular click that increases on inspiration, and loud pulmonary component of the second sound. Usually, there is no thrill. Jugular venous pulse shows prominent “V” wave with sharp “Y” descent.
Other conditions causing right ventricular outflow tract obstruction
Protrusion of right sinus of Valsalva into RVOT, aneurysm of ventricular septum, cyst of interventricular septum,[19] and intra- or extra-cardiac mass lesions in the RVOT, for example, sarcoma can also produce findings resembling infundibular pulmonary stenosis. Echocardiography is useful in identifying these conditions. Magnetic resonance imaging is more informative.
Natural history/prognosis
Most of the patients are asymptomatic and may reach adulthood,[2],[4],[5],[10],[11],[14] middle age,[6],[8] or rarely even old age.[9] Severity of stenosis can increase with age. In the absence of other lesions, prognosis depends on the severity of obstruction and right ventricular function. Patients with mild-to-moderate stenosis have normal life span except the risk of infective endocarditis.[3] Infective endocarditis can occur at the site of infundibular stenosis or may involve pulmonary valve[20] damaged by the jet effect. Patients with severe stenosis are at a risk of sudden death any time throughout their lives[2],[3] even if they are asymptomatic. Risk is more in patients with right ventricular failure and/or episodes of paroxysmal dyspnea or palpitation.
Management
Patients with mild-to-moderate infundibular stenosis are asymptomatic and do not require treatment. Patients with severe stenosis should be treated even if asymptomatic as they are prone to sudden death. Surgery is safe and effective.[4],[9],[14],[16],[21] DDD pacing (right atrium sensed and left ventricle paced) has been shown to acutely decrease gradient across obstruction.[22] However, it does not have any role in long-term management.
Stent implantation is safe and effective in discretely narrow circumferential stenotic segment with near-normal-sized peristenotic segment between the pulmonary and tricuspid valves so that stent with desirable length could be deployed optimally without interfering with the pulmonary or tricuspid valve function.[23],[24] In young children, there is possibility of future mismatch due to growing infundibular dimension.[24] Intimal hyperplasia and subsequent intraluminal narrowing are infrequent.[24] Vigilant follow-up is necessary to exclude possible late-stent compression or fracture due to hypertrophied and hypercontractile infundibulum.[24]
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15]
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