Surgical Indications In Congenital Heart Disease

Anita Khalil

Congenital heart disease can be classified into 2 main groups:

1. Acyanotic
2. Cyanotic

Acyanotic Congenital Heart Disease

Acyanotic heart diseases constitute major chunk of congenital heart defects. Three main groups can be identified:

1. Obstructive left sided lesions - these lesions obstruct the forward blood flow into the systemic circuit. Examples are congenital aortic stenosis, coarctation etc.
2. Large communications or shunt between systemic and pulmonary circulation leading to excessive pulmonary blood flow (e.g.) VSD, ASD, PDA, TAPVC.
3. Intrinsic or extrinsic myocardial diseases (e.g.) cardiomyopathies, pericardial diseases.

The child or infant with acyanotic heart disease manifest with characteristic symptoms of poor feeding, fatigue and dyspnoea and growth failure. Weight gain is usually more affected than height. Heart failure is more common, which presents with respiratory rate more than 60/minute during sleep. Coarctation of aorta which usually precipitates congestive cardiac failure in the first week of life. Primary myocardial disease or aortic stenosis are other causes of left ventricular dysfunction.

After infancy the most common cause of heart failure is increased pulmonary blood flow, which is due to left to right shunts in VSD, PDA or aorto-pulmonary window. Heart failure from any cause may be exaggerated by anaemia. Chest x-ray usually shows cardiomegaly with or without increased pulmonary blood flow. Electrocardiogram must be analysed with a difference. Normal right ventricular dominance in newborn later gradually evolves to the normal pattern. Each anatomical defect shows it's own pattern - cyanotic defects with RVOT obstruction will usually show a right ventricular dominance whereas acyanotic defects apart from ASD and PVOT obstructions (e.g.) Pulmonic stenosis and Eisenmenger's syndromes), will manifest with a left ventricular dominance.

Two dimensional echo-cardiography with colour doppler give the anatomic diagnosis of congenital heart defect though cardiac catheterization and angiographic studies give the definitive diagnosis. In most cases, angiography also provides information of cardiac performance.

Atrial septal Defect (ASD)

These patients are usually asymptomatic. A soft systolic murmur in the parasternal area may be picked up on routine examination, where wide fixed split of second heart sound is usually diagnostic.

Common types of ASDs encountered are of the secundum type and approximately 10% have defects at junction of SVC and RA called sinus venous defects. Cardiac catheterization confirms the diagnosis and clarifies the location of defects. The shunt is qualified as QP/QS and operation is recommended when the defect is large with increased pulmonary flow and the QP/QS is > 1.5. If the echo confirms the diagnosis then cardiac catheterization can be avoided in such cases.

Surgery - Operation is indicated in symptomatic patients irrespective of age.

In asymptomatic patients, the operation is deferred till the patient reaches 5 years of age. All ASDs are usually repaired on cardiopulmonary bypass. The right thoracotomy can be used in females to avoid ugly median scar and recently in ASDs have been repaired by direct suturing.

Ventricular Septal Defect (VSD)

Ventricular septal defect (VSD) is the most common congenital cardiac defect comprising 20-25% of all lesions. VSD can occur as an isolated defect or can be a part of a complex lesion. The various types of VSD depending on the sites are:-

Perimembranous VSD, muscular VSD, and finally outlet and inlet VSDs. VSDs can be small or large.

Spontaneous closure of VSD occurs in around 30% of small VSDs, especially muscular ones. Large defect rarely closes without surgery. Increased pulmonary blood flow may result in pulmonary hypertension by about 12 months of age but rarely becomes irreversible before 2 years of age.

Chest x-ray shows cardiomegaly and increased pulmonary blood flow depending upon the shunt.
ECG is normal in small defects, left ventricular dilatation in moderate to large defects.

2D echocardiogram is diagnostic and reveals the site, size, number of VSDS and other associated lesions. Pulmonary artery pressure and left ventricular function are also assessed. Cardiac catheterization is indicated in symptomatic patients or in those who have a large shunt and QP:QS is > 1.5

Surgery: Indications

1. In children less than 5-6 years - Small VSD with normal pH pressure - surgery is deferred.
2. If in these children - VSDS do not close spontaneously by 8 years - elective surgery is indicated to prevent SBE also, and reversal of shunt.
3. Large VSD with large shunt and increased pulmonary pressure- pulmonary vascular resistance (PVR) is calculated. If PVR is less than 4 Units - surgery is indicated. If PVR is more than 4 units -then response to 100% O2 inhalation is tried. In response to this, if the P.A. pressure goes down - then surgery is indicated.
4. However, if the VSD is large with severe PAH and where the PVR is > 4 units and the PA pressure does not reduce in response to 100% O2 - then only heart lung transplantation can save these patients.

Surgery - Palliative and Corrective

Palliative surgery - Banding of pulmonary artery is done to reduce the pulmonary blood flow in very small children with a large or multiple VSDS.

Corrective surgery - Repair of VSD is undertaken on cardio-pulmonary bypass. Small defects are sutured and large defects are closed by dacron patch.

Mostly the approach to close the VSD should be through the right atrium., because, one should strictly avoid the conduction tissue which usually runs along the postero-inferior margin of VSD, and sutures are placed 2-3 mm away from the inferior edge of the VSD.

If the suturing damages the conduction tissue then, bundle branch block, complete heart block or other forms of arrhythmias may result necessitating permanent pacemaker implantation.

Patent Ductus Arteriosus (PDA)

PDA connects main PA to descending aorta 5-10 mm distal to the origin of left subclavian artery, and it closes spontaneously during 2-3 weeks of life. If it does not close spontaneously, then it has to be closed surgically or by a device.

On examination, there is a typical bounding peripheral pulse and the typical systolo-diastolic "machinery" murmur in the infra-clavicular area is heard. In the premature infants only systolic murmur is heard because of increased pulmonary vascular resistance.

Chest x-ray shows plethoric lung fields and enlarged left ventricle and ECG also documents left ventricular hypertrophy in presence of CCF. Echocardiography reveals LV volume overload with increased pulm-artery flow and confirms the presence of PAN. Cardiac catheterization is only indicated if PDA is part of a complex lesion or if the diagnosis is in doubt. Closure of PDA can be brought about by a (1) Intervention. (2) Surgery.

Intervention

The PDA is closed by an umbrella (Rashkinds') device which is put in the PDA by a catheter. However, recurrence rate is high and device is expensive and beyond reach of most of the poorer section of society.

Surgery

PDA can be closed by left thoracotomy by just ligating or dividing the ductus and suturing both the ends. Complicated PDAs (e.g.) hypertensive, calcified, infected or recanalysed ductus will need cardio-pulmonary bypass for repair.

Coarctation Of Aorta

Coarctation is narrowing of upper portion of descending aorta, the lesion could be localised or diffuse. Coarctation is usually associated with bicuspid aortic valve, PDA, VSD etc. Coarctation leads to absent peripheral pulses which is diagnostic and elevated blood pressure in the upper limbs. Adequate collateral circulation develops around the coarcted segment. The number of collaterals determine the flow in aorta distal to the coarctation. If the coarctation is severe and adequate collateral circulation is not present, then left ventricular failure (LVF) sets in. Coarctation of Aorta is the commonest cause of CCF in infancy. Cyanosis may be present in lower limbs because of shunting of de-oxygenated blood from pulmonary artery to the descending aorta through PDA. Chest x-ray shows left ventricular dilatation with enlarged ascending aorta. Rib notching caused by erosion of inferior margins of the ribs by enlarged tortuous intercostal arteries is characteristic of coarctation. ECG shows LAD and LVH.

2-D echocardiography - reveals a gradient across the coarcted segment and increased pressure in the arch of the aorta. Cardiac catheterization and angiography are essential in all cases of coarctation of aorta to evaluate the extent of narrowness, adequacy of collaterals and the nature of the aorta distal to the coarctation.

Treatment

The therapeutic approach depends on the age and clinical status of the patient.

1. Conservative/medical treatment is advised in infants with CCF.
2. Surgery - is the mainstay of treatment of coarctation.

Interventions- Balloon dilatation of the coarctated segment is also done but recurrence rate is high and the procedure is beyond reach for many because of high cost.

If the coarctation is repaired early, then there is a high incidence of recurrence, and if it is delayed, then hypertension becomes a permanent feature. To avoid both, the coarctation should be repaired by 4-5 years of age. The simplest surgery done is a diamond pattern repair using a dacron material over the coarctation segment, but recurrence is the disadvantage in this method.

The other and more reliable method is resection of coarctation segment and end to end anastomosis of the aorta, and with this procedure recurrence is not seen at all.

Cyanotic Heart Disease

Cyanotic heart disease includes a large number of cardiac lesions which are surgically correctable. They can be prognostically classified in the following manner:

1. Lesions with decreased pulmonary blood flow:
   1. Low risk group
      1. Tetralogy of Fallot.
      2. ASD with pulmonary stenosis and R-L shunt.
      3. Venacaval anomalies to left atrium.
   2. High risk group
      1. tricuspid atresia
      2. Pulmonary atresia
      3. Persistent truncus arteriosus with hypoplastic pulmonary arteries.
2. Lesions with increased pulmonary flow
   1. Low risk group
      1. total anomalous pulmonary venous return with normal pulmonary resistance.
      2. Transposition of great arteries with intact ventricular septum.
      3. Congenital pulmonary arterio-venous fistula.
   2. High risk group
      1. Transposition of great arteries with VSD or PS.
      2. Double outlet right ventricle.
      3. Truncus Arterosis
      4. Complete atrio-ventricular canal defects.
      5. Single Ventricle.

   Basic principles of the surgical management of a few defects will be discussed.

   Tetralogy of Fallot (TOF)

   TOF is a unique combination of right ventricular outflow obstruction with ventricular septal defect which is most of the time dextroposed overriding the septum. Aim of the surgery is to close the VSD with a dacron patch to the right of aorta, accomodating it's dextraposition and also relief of RVOT obstruction.

   Clinical symptomatology esp. cyanotic spells, their severity and frequency are directly related to the severity of RVOT obstruction.

   1. Mild - pulmonary valve stenosis and mild infundibular hypertrophy - least symptomatic with mild cyanosis. Adequate pulmonary valvotomy with resection of hypertrophied infundibulum relieve the RVOT obstruction..
   2. Moderate - a little more severe than the mild group - desaturation leading on to central cyanosis may be a little more - but still does not need corrective surgery during the first year.
   3. Severe - severe narrowing of outflow tract. They may need to be operated during the first few months of life as cyanosis worsens with increasing infundibular obstruction. Complete atresia of the pulmonary valve usually requires operative intervention immediately after birth when the ductus arteriosus closes.

   Treatment

   1. Immediate palliative surgery is required by creating a shunt between left subclavian artery to pulmonary artery (Blalock- Taussig shunt).
   2. Pott's Shunt - The descending aorta is anastomosed to the pulmonary artery.
   3. Waterston's Shunt - Ascending aorta is anastomosed to the right pulmonary artery.

   The above mentioned palliative procedures prolong life and increase exercise tolerance. The basic heart disease remains unaltered. The palliative surgery allows better saturation which facilitates growth and the child is allowed to grow.

   Corrective Surgery - is preferably performed between 2-5 years of age after palliative surgery. Brock's Procedure - consists of closure of ventricular septal defect and resection of infundibular obstruction.

   Major complications include complete heart block, right bundle branch block with or without left anterior hemiblock, residual ventricular septal defect and residual pulmonic stenosis. With suitable anatomy, the operation can be performed at any age.

   Tricuspid Atresia

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   Congenital absence of tricuspid valve is called tricuspid atresia. The right ventricle is hypoplastic and the inflow into the right ventricle is absent. The only exit for the systemic venous blood coming to the right atrium through the inferior and superior vena cava by way of an atrial septal defect or a patent foreman ovale. There is complete mixing of the systemic venous and pulmonary venous blood in the left atrium from where the blood passes to the left ventricle.

   Clinical presentation depends on the state of pulmonary flow which may be diminished or increased. Approximately 90% of tricuspid atresia have diminished pulmonary flow, so the presentation is more or less identical to that of Fallot's tetralogy.

   Clinical features of tricuspid atresia:-

   1. Apical impulse - left ventricular type.
   2. Prominent 'a' waves in jugular veins.
   3. Enlarged liver with pre-systolic pulsation.
   4. Electrocardiogram -LAD (axis - 450) and LVH.
   5. X-ray chest - cardiomegaly (left ventricular) with oligaemic lung fields. Prominent superior vena cava - shadow.
   6. Echo-cardiogram - large single ventricle identified. Atretic tricuspid valve can be seen.

   Treatment

   1. Medical management is the same as that of TOF.
   2. Surgery
      1. Palliative surgery - in severe hypoxia- Blalock - Taussig Shunt to be done. Glenn Shunt - anastomosing superior vena cava to the right pulmonary artery.
      2. Corrective surgery - none since tricuspid valve cannot be reconstructed. Fontan operation: Anastomosis of right atrium with the pulmonary artery bypassing the RV and closing the ASD. In addition a valve is introduced between the right atrium and inferior vena cava so that the blood cannot go backwards into IVC. Ideal time for Fontal operation is 4 years or more.

   Transposition Of Great Vessels (TGA)

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   TGA is that situation when the aorta arises from the right ventricle and the pulmonary artery is from the left ventricle.

   

   Complete TGA Aorta arises from right ventricle and pulmonary artery from left ventricle so both the circulations are completely separate.

   Corrected TGA Left atrium drains into inverted morphologically right ventricle, from which aorta arises. Similarly right atrium drains into morphologically inverted left ventricle from which pulmonary artery arises. So here the route and flow of blood is normal.

   Haemodynamics

   In TGA since systemic and pulmonary circulations are separate, survival depends on the presence of atrial ventricular or aorto-pulmonary communications.

   Complete TGA - with intact ventricular septum.

   • With ventricular septal defect
   • with or without pulmonary stenosis.

   In TGA with intact ventricular septum - survival depends on the mixing available between the two circulations, and here it is the presence of ASD or patent foramen ovale and being small , the mixing is poor leading on to severe hypoxia and acidosis in the newborns. Presence of a large VSD with TGA leads on to good mixing, thereby decreasing the hypoxia and cyanosis but in these cases, increased pulmonary blood flow leads on to early development of pulmonary hypertension and subsequently reversal of shunt.. Clinically, patients of complete TGA with intact ventricular septum are - cyanosed at birth.

   • Extreme tachypnoea
   • Congestive cardiac failure in the Ist week.
   • X-ray chest
   • Cardiomegaly with narrow base and plethoric lung fields. "Egg on side" appearance
   • ECG - RAD with RVH
   • Echo - Cardiogram : parallel ascending aorta being anterior and to right of pulmonary artery which bifurcates lower down.

   TGA with VSD - presents almost a similar picture with cyanosis, tachypnoea and CCF.

   Treatment

   Medical

   1. Treatment of congestive cardiac failure by decongestive measures.
   2. Oxygen inhalation. But to improve oxygenation - balloon atrial septostomy should be done - which is successful till the age of 6-12 weeks.

   Surgical

   1. Jatene's Switch operation Both the pulmonary artery and the aorta are transected. The distal aorta is anastomosed to the proximal pulmonary stump and the distal pulmonary artery to the proximal aortic stump. The coronary arteries are also shifted to the aorta from pulmonary artery..
   2. Atrial Switch Operation (Mustard or Senning) Pulmonary venous blood is re-directed to the right ventricle and systemic venous blood to the left ventricle thus establishing normal route of blood flow. But Jatene's switch operation is preferred to the atrial switch since the latter results in complications later on.
   3. If a VSD is also present, it should be closed at the same time or pulmonary artery banding should be done to protect the pulmonary artery.
   4. If a PDA is present, it should be excised at the same time because pulmonary obstructive disease appears early leading on to pulmonary hypertension.
   5. Patients with TGA should be operated as early as possible, even below the age of 3 months because complications appear fast.

   References

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   1. Approach to diagnosis of Congenital heart disease without recourse to special tests. Nadas AS -Circulation 1972;20:602.,
   2. Spontaneous functional closing of ventricular septal defects - Nadas AS, Scott IP, Hauck AJ and Rudolph AM. New Engl J Med 1961; 264 : 309-314.
   3. The haemodynamics of complete transposition of great vessels. Shaher, RM : British Heart J 1964; 26: 343-348.
   4. Terminology of congenital heart disease - glossary and commentary. Van Praagh R. Circulation 1977; 56: 139-142.
   5. Tricuspid atresia: A re-evaluation and classification. J Thoracic and Cardiovascular surgery 1974; 67:530.
   6. Diseases of cardio-vascular system. In : Essential Pediatrics, 5th Ed. Eds. R. Tandon and S. Shrivastava. Interprint, 2000.

    

   
   
   
   
   
   
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