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Ventricular Septal Defect: Evaluation and Management
img Dr. Munesh Tomar MD (Ped) DNB Fellowship(Ped Card)
Consultant, Deptt of Pediatric Cardiology
Escorts Heart Institute and research Centre,Okhla Road,
New Delhi 10025
Phone: 09871897833
Fax : 91-11-26825013
Email: muneshtomar@yahoo.co.in

Ventricular Septal Defect (VSD) is the most common form of congenital heart disease, if bicuspid aortic valve is excluded. It is a defect in the ventricular septum which separates the two ventricles and can occur in any part of ventricular septum. Roger H provided the first clinical description of VSD in 1879.

PREVALENCE:
Isolated VSD accounts for approximately 20 % of all congenital heart defects with reported prevalence of 0.3 – 3.3 per 1000 live births 2-5. VSD is more common among preterm infants and stillborns as compared to term infants. The prevalence of VSD is lower in adults due to spontaneous closure of many defects. VSD’s are most common congenital cardiac lesion found in association with various chromosomal syndromes including trisomy 13, trisomy 18, trisomy 21 and others 6.
EMBRYOLOGY:
Ventricular septal defect results from a delay in closure of the interventricular septum beyond the first 7 weeks of intrauterine life. The reason for this delayed or incomplete closure is still unknown. The normal development of interventricular septum depends upon the endocardial cushions, conotruncal ridges, growth of tissues at the crest of interventricular septum and muscular septum. VSD occurs as a result of maldevelopment of one or more of these structures.

ANATOMICAL CONSIDERATIONS:
Ventricular Septal Defects can be present in any part of interventricular septum and are hence classified according to their anatomical location.( Figure 1).

A. Perimembranous VSD : These are the most common type of ventricular septal defects and account for approximately 80 % of the VSD’s. They involve the membranous part of ventricular septum which lies in the outflow tract of the left ventricle immediately beneath the aortic valve. They usually extend into muscular, inlet or outlet portion of ventricular septum. B. Inlet VSD : These VSD account for 5 to 8 % of all the VSD's. They are located posteriorly and inferior to perimembranous portion of ventricular septum.
C. Subarterial VSD or Doubly committed VSD or Subpulmonary VSD : These VSD account for 5 to 7 % of all the VSD’s. They are located just beneath the pulmonary valve.
D. Muscular VSD : These VSD account for 5 to 20 % of all the VSD’s and are further subclassified depending on their location in the muscular septum.
i) Central : Located in the mid-muscular part of the ventricular septum with multiple apparent channels on right ventricular side and single defect on the left ventricular side.
ii) Apical : Located in the apical part of the ventricular septum with multiple apparent channels on right ventricular side and single defect on the left ventricular side.
iii) Swiss Cheese : Multiple muscular defects in the ventricular septum.
Fig 1 : Anatomical Position of various types of VSD's

PHYSIOLOGY
Defect in the ventricular septum results in communication between the systemic circulation and the pulmonary circulation or left to right shunt. The magnitude of left to right shunt is determined by a) size of the defect and b) Pulmonary vascular resistance. VSD’s can be divided into three categories : small, moderate and large based on both the size of defect and pulmonary vascular resistance. Small defects limit the magnitude of left to right shunt and restrict pressure elevation in the right ventricle. The left to right shunt is small and right ventricle and pulmonary artery pressures are normal in such patients. Moderate defects offer resistance to pressure but usually little resistance to left to right flow. The left to right shunt is moderate and right ventricle and pulmonary artery pressures are mild/moderately elevated in such patients. Large defects do not offer any resistance to left to right shunt and hence results in large left to right shunt and equalization of pressures in the ventricles. Large left to right shunt results in increased flow in lungs ( Increased Pulmonary blood flow) which leads to increased pulmonary venous return to left atrium causing left atrial and ventricular volume overload. The right ventricular pressures are elevated to the same level as left ventricular pressure resulting in severe pulmonary arterial hypertension. Although as mentioned above large left to right shunt results in over circulation in pulmonary bed , left ventricular volume overload and pulmonary arterial hypertension it needs special mention that if a large VSD is left unattended in the presence of pulmonary arterial hypertension for prolonged duration ( 1 year or more) may result in some irreversible hypertrophy of muscles in the medial wall of pulmonary arterioles . This can progress further to reach a stage when the shunt reverses to right to left and render the patient inoperable.

CLINICAL PRESENTATION
The clinical presentation of ventricular septal defects is diverse varying from patient with no symptoms to those with manifestations of congestive heart failure (CHF). The wide spectrum of symptoms and physical findings depends in most cases upon three main factors a). The size of defect, b) Magnitude of left to right shunt and c) Degree of pulmonary arterial hypertension . However presence of any acquired conditions resulting from the presence of VSD itself like aortic regurgitation secondary to aortic valve prolapsed , aneurysm of the ventricular septum, acquired left ventricular outflow tract obstruction and right ventricular outflow tract obstruction can produce symptoms out of proportion to those expected from the effective size of defect and magnitude of left to right shunt.
A. Small VSD : These are most commonly not associated with any symptoms. The magnitude of blood shunting from left ventricle to right ventricle is small with no increase in the right ventricular pressure. Most often they are referred because of murmur detected on routine examination for some incidental illness. The murmur of small VSD is most often detected around 2 to 6 weeks of age. The murmur is not heard just after birth and during first few weeks because of high pulmonary vascular resistance present at birth which declines gradually over next 2 to 6 weeks. These usually do not interfere with feeding and normal weight gain. The cardiac examination usually reveals a systolic thrill along the left sternal border . The first heart sound may be masked by presence of a harsh, holosystolic murmur heard grade 4/6 heard best along the left lower sternal border. Second Heart sound (S2) is normally split. Small VSD’s do not produce any diastolic murmur.
B. Moderate Size VSD : Moderate sized VSD’s usually produce murmur between 2 to 6 weeks after birth. The appearance of murmur usually precedes the symptoms such as mild tachypnea, excessive sweating, feeding difficulties, inadequate weight gain and at times frequent episodes of chest infections. Decline in rate of weight gain occurs most commonly between 2 to 4 months. Physical findings in moderate sized VSD’s include increased intensity of precordial impulse , normal first heart sound and narrow split second heart sound with increased intensity of P2. Third heart sound (S3) is present if magnitude of left to right shunt is > 2:1.A harsh pansystolic murmur best heard at lower left sternal border is present. A low pitched mid diastolic rumble occurring due to increased flow across the mitral valve indicates that the shunt is > 2 : 1.
C. Large VSD’s : Large VSD’s usually present around 6 to 8 weeks with symptoms of poor weight gain, frequent respiratory tract infections and excessive sweating as the pulmonary vascular resistance falls by this period. The physical findings include presence of tachypnea, tachycardia and hepatomegaly. The precordial activity is increased with parasternal lift. Second heart sound is narrowly split but split is detectable in most patients. A low pitched ejection systolic murmur grade 3/6 is present along with a mid diastolic rumble. Pulmonary component of second heart sound is accentuated. The above mentioned findings are true for children presenting in early to late infancy but those presenting at a later age with pulmonary vascular obstructive disease usually do not have respiratory complaints but are mildly cyanosed with often clubbing of the fingers. In such patients the systolic murmur is short if at all present , P2 is loud banging with a short early diastolic murmur of pulmonary regurgitation ( Graham Steele’s murmur).
ASSOCIATED CONDITIONS
There are certain associated conditions arising because of VSD itself and these include a) secondary aortic regurgitation b) subaortic obstruction c) right ventricular outflow tract obstruction and d) Ventricular septal aneurysm.
Aortic Regurgitation can occur in both doubly committed VSD and perimembranous VSD’s. In the former it is due to poorly supported right coronary cusp while in the latter due to maldevelopment of aortic commissures. Discrete subaortic obstruction may represent an incidental association or as a result of malaligned septum. This can sometimes result in left ventricular outflow obstruction. Right ventricular outflow obstruction occurs in 3 to 7 % patients and is due to hypertrophy of anomalous muscle bundles. Aneurysm of ventricular septum often occurs in perimembranous VSD’s and is considered responsible for decrease in size or spontaneous closure of these VSD’s

RADIOLOGICAL FEATURES The radiological features are variable in VSD depending upon the magnitude of left to right shunt and degree of pulmonary arterial hypertension. In Small VSD’s the chest roentgenogram is usually normal (Fig 2). Moderate VSD’s are associated with increase in cardiac silhouette , prominent left ventricular contour, left atrial enlargement ( evidenced by uplifting of the air column of the left main bronchus and enhancement of pulmonary vascular markings (Fig 3). Large VSD’s produce marked cardiomegaly, left atrial enlargement, pulmonary plethora, interstitial edema and Kerley B lines ( Fig 4). In older children with large VSD and pulmonary vascular obstructive disease the heart size decreases but enlargement of pulmonary trunk persists and lung fields appear oligaemic ( Fig 5).

Fig 2 CXR of a Small VSD                  Fig 3 CXR of a Moderate VSD

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Fig 4 CXR of a Large VSD, ↑ PBF Fig 5 CXR of a VSD with Eisenmenger
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ELECTROCARDIOGRAPHIC FINDINGS
The Electrocardiogram reflects the hemodynamic and the trace are influenced by the size of defect and pulmonary vascular resistance. In patients with small VSD the ECG is generally normal. However rhythm disturbances such as complete heart block, atrial fibrillation and flutter are reported in small perimembranous VSD’s with septal aneurysms. Moderate sized VSD’s produce broad notched P waves with some degree of left ventricular hypertrophy. Large VSD’s may also manifest evidence of left ventricular hypertrophy alone but mostly there is combined right and left ventricular hypertrophy in the midprecordial leads ( Katz-Wachtel phenomenon). In patients with Eisenmenger syndrome right ventricular hypertrophy is manifested by tall R waves in Lead V1 while the left precordial Q waves are absent suggesting pressure overload of Right ventricle. The QRS axis is generally normal in small and moderate sized VSD’s while right axis deviation occurs in those with large VSD. Left axis deviation of QRS can occur in perimembranous VSD with inlet extension and those with formation of ventricular septal aneurysm. Electrocardiogram provides vital information regarding the hemodynamic of ventricular septal defect and hence remains an important tool in the diagnosis as well as management.
ECHOCARDIOGRAPHY
Trans-thoracic 2-Dimensional colour Doppler echocardiography is the modality of choice to evaluate the size, number and anatomical location of most VSD’s apart from measurement of atrial and ventricular dimensions and estimation of pulmonary artery pressures. The size of defect can be measured accurately from the 2 dimensional images. The size of VSD is measured in relation to the size of aorta. The VSDs are considered as large defect if they are as large as aorta . The VSDs measuring one-third to two-third of the aortic diameter are considered moderate and those less than one-third the size of aorta are considered small. The conventional echocardiographic views like apical 4 chamber view, parasternal long axis view, parasternal short axis view, subcostal sagittal views provide accurate information regarding the specific anatomical location of VSD’s. Apical 4 chamber view are helpful in diagnosing inlet VSD’s, midmuscular and apical muscular defects. Parasternal Long axis view demonstrates the perimembranous defects with or without formation of septal aneurysms. Para-sternal short axis view helps in differentiating perimembranous and outlet VSD’s ( located at 10 -11 o’ clock and 11-12 o’ clock position respectively ) from the doubly committed VSD’s which are located at1-2 o’ clock position. The interventricular pressure gradient estimated by Doppler echocardiography is useful in predicting the Right ventricular pressure and the pulmonary artery pressures. Left atrial and left ventricular dimensions provide information regarding the magnitude of left to right shunt. Echocardiographic evaluation in patients with VSD should be targeted to identify the presence of associated anomalies such as straddling or overriding atrioventricular valves, aortic regurgitation, aortic valve prolapse, ventricular inflow and outflow obstructions. In most clinical situations echocardiography provides enough information to decide on management and type of closure of VSD’s., In some clinical situations such as patients with poor echocardiographic windows trans-esophageal echocardiography may be required for detailed assessment. Intra-operative trans-esophageal and epicardial echocardiography is useful in assessing the adequacy of repair and detection of residual defects. Postoperative echocardiography is helpful in detecting residual lesions and monitoring the pulmonary artery pressures.

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Fig 7 Echocardiographic images of various type of VSD’sCARDIAC CATHETERISATION AND ANGIOGRAPHY
Cardiac catheterization and selective angiography provides definitive hemodynamic and anatomical details of VSD’s. In the past cardiac catheterization and angiography was a standard diagnostic modality but in the last 2 decades non invasive modalities (especially trans-thoracic and trans-esophageal echocardiography) provide excellent information and therefore this modality is reserved for children with ill defined anatomy, associated lesions or those with pulmonary arterial hypertension of unknown reactivity. The most common indication for cardiac catheterization in the present era is to assess the response of pulmonary vascular bed to oxygen and other pulmonary vasodilators like nitric oxide.
Cardiac catheterization is performed to measure the pulmonary blood flow (Qp), systemic blood flow (Qs), pulmonary vascular resistance ( Rp), systemic vascular resistance (Rs), Qp/Qs ratio in order to study the hemodynamic alterations. This requires measurement of oxygen saturations in SVC, IVC, Right atrium, Right ventricle, pulmonary trunk, pulmonary artery branches, aorta and pulmonary veins respectively and pressure measurements of right atrium, pulmonary artery wedge, pulmonary artery and aorta. The calculations are made using the Fick’s Principle. In patients with high pulmonary vascular resistance (patients with large VSD presenting late, no or borderline cardiomegaly, presence of short mid diastolic rumble, high Rp at room air) further investigation to assess the response of pulmonary vasodilators like oxygen and/or nitric oxide is recommended. This requires administration of oxygen in a concentration of 0.95-1.0 with a tight fitting mask for 10 minutes and Nitric oxide at a concentration of 10-80 ppm. Though precise cut off values of pulmonary vascular resistance to ensure safe surgical outcome is uncertain, surgery is generally advised if PVR decreases to 6-8 wood units.m2.
Left ventricular angiography documents the location, size and number of VSD’s. The Long axis oblique view visualizes the conoventricular, midmuscular and apical portions of the ventricular septum. If the long axis oblique view does not clearly delineate the defect four chamber views can be performed. Right Anterior oblique view displays the anterior portion of interventricular septum. Left ventricular angiogram is usually indicated in patients with poor echocardiographic windows and those with multiple VSD’s to assess the accurate size of defects since apical muscular VSD are difficult to be located at the time of surgical correction.
Cardiac catheterization provides us with useful information about the hemodynamic while angiography provides precise anatomical details of ventricular septal defect. Although informative the indications for catheterization are limited in the present era

NATURAL HISTORY
The natural history of ventricular septal defects has been widely studied and reported. Small defects are asymptomatic and rarely need treatment. The spontaneous closure is reported in approximately 40 % cases being much more common with small muscular defects ( approx 80 %). Small VSD is not an indication for surgery and present day recommendations is medical follow up with bacterial endocarditis prophylaxis. Majority of small VSD’s close in the first 2 years of life. Moderate and large VSD’s may close spontaneously but less frequently as compared to small defects. The spontaneous closure rate in such defects is approximately 8-10 %. Significant proportion of children with moderate sized VSD need surgical closure between 1 to 5 years of age. Large VSD may show reduction in size of defect in small proportion of patients but most need early surgical closure. Pulmonary vascular obstructive disease has been reported in such defects as early as second year of life. The outcome of patients with Eisenmenger syndrome is poor both in terms of survival and functional limitation. Aortic regurgitation secondary to prolapse of aortic valve is well reported and tends to be progressive especially in association with doubly committed VSD’s. Patients with moderate and large sized VSD’s occasionally develop significant infundibular pulmonary stenosis which can progress in severity and require surgical intervention.

MANAGEMENT STRATEGIES
A. MEDICAL MANAGEMENT
Children with small VSD are asymptomatic and have excellent long term prognosis and hence should just receive bacterial endocardial prophylaxis. Children with moderate to large sized VSD’s develop symptoms due to congestive heart failure and in such patients a trial of medical therapy is indicated. This usually is needed in patients with left to right shunt > 2 : 1. With improved surgical results in the present era surgery is recommended in early infancy if symptoms donot respond to medical therapy.
The goal of medical therapy in such patients is to a) Relieve symptoms of congestive heart failure b) Reduction in risk of respiratory tract infections and c) To ascertain adequate weight gain.
The treatment of CHF in such patients includes fluid restriction, diuretic therapy, digoxin, angiotensin converting enzyme inhibitors and caloric supplementation. Oxygen should be used judiciously to reduce hypoxemia as excessive oxygenation can rather increase the left to right shunt by reducing the pulmonary vascular resistance. Diuretic therapy includes furosemide ( 1-3 mg/kg/day) and spironolactone can minimize the potassium loss. After-load reduction with captopril ( 0.5 -1.0 mg/kg/dose) is useful in reducing the pulmonary blood flow and systemic resistance. Spironolactone should not be administered if captopril is already being administered due to risk of potassium retention. Caloric supplementation including addition of medium chain triglycerides helps in achieving adequate weight gain. Failure to thrive and non improvement in symptoms due to congestive heart failure are indications for early repair of VSD.
Patients with large VSD developing pulmonary vascular disease are inoperable and require symptomatic therapy and counseling. No specific therapy is available for such patients although some centres use anti-platelet agents like aspirin. Partial exchange transfusion is recommended to relieve symptoms secondary to polycythemia.
B:SURGICAL MANAGEMENT
Surgical Closure of ventricular septal defects is the preferred modality. With improving cardiopulmonary bypass techniques, infants with weight as low as 2 Kg can undergo successful repair. Surgical mortality is 2-3 % for single VSD or VSD with aortic insufficiency and 4-5 % for multiple VSD repair. Pulmonary artery banding is presently done only in children with multiple VSD’s not amenable to surgical closure and in those with straddling atrioventricular valves.
Indications of VSD Closure :A) Moderate to large VSD with uncontrolled CHF , recurrent lower respiratory tract infections or growth failure ( early infancy)
B) Older children with left to right shunt > 2:1
C) Small perimembranous or doubly committed VSD’s with associated aortic insufficiency require early repair to prevent progression of aortic insufficiency.
D) Small VSD with history of Infective endo-carditis.
Majority of Perimembranous and inlet VSD’s are closed vis transatrial approach while doubly commited or subpulmonary VSD are best approached via pulmonary artery under cardiopulmonary bypass. Although majority of VSD’s can be dealt with surgical closure there are still some situations where surgical closure is not feasible and hence pulmonary artery banding is done in those situations.
Indications of Pulmonary Artery (PA) Banding :
A. Multiple VSD’s ie presence of some remote large muscular VSD’s
B. Large VSD with straddling AV Valve
C. Extremely small infants ( Varies from centre to centre).
Disadvantages of PA Banding include early operative mortality, need for two surgeries, subaortic stenosis and technical difficulty involving debanding at time of second surgery.
TRANSCATHETER THERAPY
In the recent years muscular VSD and lately perimembranous VSD have been closed with transcatheter approach. This however can be done in selected cases only. The major advantage of these procedures is no surgical scar, less hospital stay and avoidance of cardiopulmonary bypass. The limitations of the procedure are proper case selection, risk of device embolisation and its feasibility in children > 8-10 Kg in weight. Amplatzer’s muscular and perimembranous VSD devices have been used with good initial results. The procedure is accomplished via femoral approach and in some cases jugular venous approach.
HYBRID APPROACH
Latest development in the management of VSD includes a combined surgical and non surgical approach. This is useful especially in infants with lower weight since transcatheter approach is not feasible in small infants. In this approach sternotomy is done but thereafter VSD Device is deployed via purse string suture on right ventricle. The major advantage of this procedure is avoidance of cardiopulmonary bypass, less blood loss and speedy post operative recovery since it is accomplished on the beating heart. This modality is still not a routine procedure but holds a lot of promise for the future.

Guidelines for management during follow up of children with VSD

Age Indication for Surgery
1.      < 6 mo Uncontrolled CHF , Failure to Thrive
2.      6 – 24 mo Pulmonary Hypertension , Symptoms
3.      2 – 5 yrs Qp/Qs > 2 : 1 , Aortic Regurgitation
4.      > 5 yrs Aortic Regurgitation

SURGICAL RESULTS AND LONG TERM OUTCOME
The surgical results in the present era are gratifying. The mortality in patients with VSD is < than 2-3 %. This is mainly attributable to improved cardiopulmonary bypass technique and post operative care. Immediate complications encountered after Surgical closure of VSD include a) Residual Left to right shunt , b) Non regression of Pulmonary arterial hypertension, c) Ventricular dysfunction and d) AV Block.
Long term results are excellent in patients operated at appropriate time . Post surgery infants show improved growth, weight gain remain symptom free and lead normal lives. Children with large VSD operated late tend to have residual pulmonary arterial hypertension and may not fair well in contrast to those treated at ideal age.Bacterial endocarditis prophylaxis is not recommended after repair if there is no residual defect.

References
1. Roger H. Recherches cliniques sur la communication congenitale des deux coeurs , pars inocclusion du septum interventriculare. Bull Acad Med Paris 1879; 1074, 1187.
2. Ferencz E, Rubin JD, Brenner JI, Neill CA, Perry LW, Hepner SI, Downing JW , McCarter RJ: Congenital Heart Disease: Prevalence at livebirth. Am J Epidemiol 121;31, 1985.
3. Fyler DC: Report OF The New England regional infant cardiac program. Pediatrics 65 (suppl): 375, 1980.
4. Hoffman JIE, Christianson R : Congenital Heart Disease in a cohort of 19,502 births with long term follow -up. Am J Cardiol 42 : 641, 1978.
5. Martin GR, Perry LW, Ferencz C. Increased prevalence of ventricular septal defect: Epidemic or improved diagnosis. Pediatrics 83: 200, 1989.
6. Nora JJ, Fraser FLC. Medical Genetics. Philadelphia:Lea & Febiger, 1974:334.

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