Cardiac Surgery in the Newborn: Improved Results in the Current Era

 

Andrew C. Fiore, M.D., Professor of Surgery
Saadeh Jureidini, M.D., Professor of Cardiology|
William Keenan, M.D., Professor of Neonatology
Robert G. Johnson, M.D., Professor of Surgery
St. Louis University School of Medicine and Cardinal Glennon
Childrenís Hospital, St. Louis, Missouri

 

In the current era, pediatric cardiovascular surgeons can safely operate on newborns to palliate or completely correct congenital heart defects in babies as small as 1.5Ė2.0 kilograms. The various cardiac anomalies treated can be categorized with respect to their dependency on a patent ductus arteriosus for systemic or pulmonary blood flow. Procedures in the neonate require the combined effort of the pediatric cardiac surgeon and interventional cardiologist. The early results are directly linked to the complexity of the congenital defect, but are generally good so long as the intervention can provide two functional ventricular chambers. Although great strides have been made, continued progress in the treatment of neonates with congenital heart defects remains challenging and requires the collaborative effort between pediatricians, perinatologists, neonatologists, interventional cardiologists, pediatric cardiovascular surgeons and intensive care unit nurses.

Clearly, one of the most significant advances in pediatric cardiac surgery in the last ten years has been the ability of cardiac surgeons to repair congenital heart defects in newborns with low mortality and morbidity. Newborns as small as two kilograms can be safely placed on cardiopulmonary bypass and undergo successful cardiac surgery1. In the current era, we try to avoid palliative procedures and perform complete repair of the congenital heart defect whenever possible. However, this is not always feasible, especially in newborns with single ventricle (univentricular heart).

The focus of this report is to review the common congenital heart defects operated upon in the newborn period. We fully recognize that alternative surgical approaches can be successfully employed for many of these anomalies, but herein we report strategies that have proven to be highly effective in our hands.

Congenital heart disease in the newborn can be broadly categorized by the relationship between the patientís cardiac defect and the patent ductus arteriosus and this categorization yields four distinct groups. First are newborns dependent on a patent ductus arteriosus (PDA) for pulmonary blood flow; second are newborns dependent on the PDA for systemic blood flow; and third are those dependent on the patent ductus for proper mixing of oxygenated blood such as transposition of the great arteries and fourthly are neonates with a non ductal dependent circulation.

For the ductal dependent group, intravenous prostaglandin (E-1) is used as necessary to maintain ductal patency and is the single most important step in supporting these patients to diagnosis and definitive therapy. Nevertheless, all newborns ductal dependent for systemic or pulmonary blood flow require an intervention, surgical or cardiologic to eliminate ductal dependence prior to discharge.

 

I. Pulmonary flow ductal dependence.

Newborns with congenital heart disease who are dependent on the patency of their ductus for pulmonary blood flow present with varying degrees of cyanosis.

A. Critical Pulmonary Valve Stenosis with Intact Ventricular Septum

In general, these babies will present with cyanosis and require initial treatment with a balloon dilatation of their pulmonary valve2. In the unlikely event that balloon dilatation is unsuccessful, then a modified Blalock-Taussig shunt is performed to provide a consistent source of pulmonary blood flow allowing this continuation of the prostaglandins so the baby can be discharged home. The Blalock-Taussig shunt is performed by interposing a Gore-Tex tube graft from the subclavian artery to the ipsi-lateral pulmonary artery through either a sternotomy or lateral thoracotomy incision. In cases of pulmonary atresia with a right ventricle of adequate size, a Blalock-Taussig shunt is inserted first and is followed by operative pulmonary valvotomy usually performed without cardiopulmonary bypass, 5-10 days later. The valvotomy is important as it permits forward flow of blue blood from the right ventricle to the pulmonary arteries. Right ventricular growth is enhanced by permitting the hypoplastic right ventricle to empty through the new opening made in the pulmonary valve. In the future, as the right ventricle grows to an acceptable size, the patient may require further balloon dilatation of the pulmonary valve, coil occlusion of the shunt, and patch enlargement of the right ventricular outflow tract or pulmonary valve replacement. These steps are all directed at maintaining a functional pulmonary ventricle3.

If the patientís right ventricle does not grow sufficiently then, a partial or total caval pulmonary connection will be required. In this procedure, the Blalock-Taussig shunt is removed and the superior vena cava alone is connected to the pulmonary artery (usually from 3- 8 months of age). This constitutes a bi-directional superior caval pulmonary connection or a Glenn shunt and this can be followed at 2-3 years of age by an inferior vena cava to pulmonary artery connection if the childís right ventricle remains severely hypoplastic. Such a total caval-pulmonary connection is also called a Fontan operation for univentricular heart4.

B. Tricuspid Atresia:

Babies with tricuspid atresia usually have a severely hypoplastic right ventricle and by definition have a univentricular heart of the left ventricular type. Patients with tricuspid atresia and normally related pulmonary artery and aorta, in the absence of a ventricular septal defect (VSD) are usually cyanotic shortly after birth, are ductal dependent for pulmonary blood flow and require a modified Blalock-Taussig shunt. If a sufficiently large VSD is present, then these patients will have a consistent source of pulmonary blood through the VSD and then can be discharged. As the VSD closes, however, the patient will become more cyanotic and a Blalock-Taussig shunt is performed if the child is less than three months old. In older children, a staged palliation towards the Fontan operation is performed as described earlier5.

Occasionally, patients with tricuspid atresia and ventricular septal defect are born with transposition of the great arteries. In this situation, the pulmonary artery originates from the left ventricle and the aorta originates from the rudimentary right ventricular chamber. Pulmonary blood flow is excessive and systemic flow is dependent on the size of the ventricular septal defect. Although several surgical options exist for this subgroup, the most conservative initial operation is placement of a narrowing band around their main pulmonary artery to protect their distal pulmonary arteries from damage caused by the excessive pulmonary blood flow. At 3-4 months of age, the band is removed and staged palliation toward the Fontan operation is begun as described earlier.

C. Tetralogy of Fallot

Newborns with tetralogy of Fallot who are mildly cyanotic (oxygen saturation greater than 80%) can be discharged with or without Inderal with a total repair planned electively at 3-5 months of age. Beta blockade relaxes the hypertrophied right ventricle muscle enhancing pulmonary blood flow in some patients. If acute cyanotic spells occur off prostaglandins, or if the baby is prostaglandin dependent for pulmonary blood flow, then a modified Blalock-Taussig shunt is performed. The patient is then discharged and the complete repair again planned electively at 3-5 months of age6.

II. Systemic flow ductal dependence.

These newborns are dependent on their ductus arteriosus for systemic blood flow and unlike the babies who are pulmonary flow dependent, these newborns present with severely decreased cardiac output. This decreased systemic flow is characterized by pallor, diminished peripheral pulses, low urine output, cool extremities and varying degrees of metabolic acidosis. Included are newborns born with left ventricular outflow tract obstruction at various levels.

A. Congenital Valvular Aortic Stenosis

Newborns with critical valvar aortic stenosis in whom the mitral valve and left ventricle are of acceptable size, are treated with balloon aortic valvuloplasty. This has proven to be highly successful and it is unusual for these patients to require operative procedures to further open the stenotic valve in the newborn period7. However, patients with significant hypoplasia of the mitral valve and/or the left ventricle, should not undergo balloon dilatation of the aortic valve, but rather be treated as hypoplastic left heart syndrome and undergo staged palliative reconstruction employing the modified Norwood procedure followed by the total caval pulmonary connection. (Fontan operation; see HLHS) 8

B. Coarctation of the Aorta

Newborns with this condition who are ductal dependent for systemic blood flow are selectively treated. If the coarctation segment is long and/or hypoplasia of the aortic arch coexists, surgical intervention is undertaken9. The recurrence rate for balloon dilatation of aortic coarctation in newborns is significant. However, the procedure will usually allow the baby to be discharged to home for at least 2-3 months before a recurrent coarctation evolves. When recurrence occurs (50-75% cases), the patient will require operation. The aortic coarctation segment is resected and an end-to-end anastomosis performed with absorbable suture, which allows for growth and may decrease the rate of late re-coarctation10.

C. Interrupted Aortic Arch

Most commonly the aortic arch is interrupted between the left common carotid and left subclavian artery with flow to the descending thoracic aorta through the patent ductus. The vast majority of these patients have an associated ventricular septal defect and varying degrees of left ventricular outflow tract obstruction. At operation, the patent ductus is divided and the ascending and descending aorta are joined primarily as in coarctation11. The associated VSD is closed at the same or at a later time depending on the size of the left-to-right shunt and the degree of congestive heart failure preoperatively. The left ventricular outflow tract obstruction is usually addressed when the baby is older, if necessary.

D. Hypoplastic Left Heart Syndrome (HLHS)

Newborns born with this condition have severe hypoplasia of all left heart structures including mitral valve, aortic valve, aortic arch and left ventricle. They are ductal dependent for systemic blood flow. In such children, we employ a staged palliative reconstruction performing a modified Norwood procedure initially, followed by a bi-directional superior caval to pulmonary artery connection (Glenn shunt) at 3-5 months of age. At 2-3 years of age, an inferior vena cava to pulmonary artery connection is performed (Fontan operation).

In the current era, heart transplantation is not a practical option because donor availability is so limited. Non-operative therapy, as an alternative has been discouraging especially when compared to the improved results with staged reconstruction. 12

 

III. Oxygenation ductal dependence.

These are babies who are born with congenital heart disease that requires a patent ductus for adequate mixing of saturated and desaturated blood.

A. Transposition of the Great Vessels (TGV)

In this anomaly, the aorta originates from the right ventricle and the pulmonary artery originates from the left ventricle. This special group of newborns often requires the patent ductus for mixing of blue saturated blood from the right ventricle with red oxygenated blood from the left ventricle. These neonates present with varying degrees of cyanosis depending on their pulmonary vascular resistance and the adequacy of mixing. Sometimes, an atrial septal defect is enlarged (Rashkind balloon septostomy) to enhance mixing. Nitric oxide can also be used to lower pulmonary vascular resistance, enhance pulmonary blood flow and reducing cyanosis. Children with TGV undergo the "arterial switch" operation within 7-30 days after birth. In this operation the two great vessels are transposed to their correct ventricles and the coronary arteries are transferred to the ascending aorta. The atrial septal defect (all patients with TGV) and the ventricular septal defect (30% of patients with TGV) are simultaneously closed transatrially13. This group of infants are among the youngest neonates to be definitively corrected (non staged approach) with their initial operation.

IV. Ductal independence.

These are neonates who are not dependent on a patent ductus but still require urgent operation.

A. Total anomalous pulmonary venous return (TAPVR)

The majority of these infants present with low cardiac output because the left atrium and left ventricle are inadequately filled with blood. This results from an anatomic defect by all four pulmonary veins draining into a collection chamber not connected to the left atrium. Instead of passing through to left ventricle, red blood from this chamber is channeled into the right atrium and blood fills the left ventricle only through an atrial septal defect or a patent foramen ovale. The cardiac output remains low because of poor left ventricular filling. Correction requires an operation to connect the pulmonary venous collection chamber to the left atrium with closure of the atrial septal defect14.

Occasionally, the connection between the pulmonary venous collection chamber and the right atrium is obstructed. These newborns are critically ill at birth and require operation urgently, presenting with particularly severe respiratory distress, pulmonary congestion and low cardiac putput.

B. Truncus Arteriosus

In this anomaly the main pulmonary artery arises from the ascending aorta. These babies are

born with no ductus arteriosus, but all patients in this category must have a ventricular and an atrial septal defect. As pulmonary vascular resistance decreases postnatally, more blood is shunted away from the aorta into the low resistance pulmonary circuit (lungs). These patients develop severe congestive heart failure in the first 7-14 days after birth and can experience coronary insufficiency with sudden death as more blood is shunted away from the aorta and into the lungs.

For these neonates, operation is performed within the first 7-14 days of life and consists of VSD closure and detachment of the main pulmonary artery from the ascending aorta. The main pulmonary artery is connected to the right ventricle by a valved tube15.

C. Anomalous origin of the left main coronary artery from the pulmonary artery.

In this condition, the left main coronary artery arises from the main pulmonary artery and not the ascending aorta. This means that desaturating blue blood perfuses the left main coronary artery supplying the left ventricle and papillary muscles of the mitral valve when the pulmonary pressure and resistance is sufficiently elevated. Over time, as the pulmonary vascular resistance falls, the direction of blood flow changes so that blood from the anomalous coronary flows into the main pulmonary artery following the path of least resistance, and resulting in global myocardial ischemia.

Babies with this condition present with severe low cardiac output state secondary to acute myocardial infarction and varying degrees of mitral insufficiency. Urgent operation may be required to transpose the left main coronary artery to the ascending aorta. Mitral valve repair is rarely but occasionally needed, as may be a short course of ECMO (extra corporeal membrane oxygenation) to support the left ventricle as it recovers from the acute myocardial infarction16.

 

Conclusion:

The enclosed table summarizes the anatomy, presentation and intervention of the neonatal congenital heart defects described in the text. The overall interventional results are quite good, but less optimal results are obtained with specific defects. While the early mortality has significantly improved, in neonates with hypoplastic left heart syndrome (HLHS) it still carries a high risk of early death. The surgical results of interrupted aortic arch repair are generally good but are very dependent on the complexity of the frequently associated lesions. While anomalous pulmonary venous return carries an excellent early prognosis, the subgroup of patients presenting with obstructed total veins have a slightly higher hospital mortality. Clearly, patients with univentricular heart (tricuspid atresia and HLHS) who require staged palliation to a Fontan operation have a worse long-term prognosis than those congenital heart defects which when repaired have separate functional pulmonary and systemic ventricles. Even so, the majority of neonates with univentricular heart enjoy an excellent lifestyle after completion of their staged palliative reconstruction to a Fontan operation.

The encouraging results we, and others, have seen with neonatal congenital heart defects has come through employing the diagnostic and treatment strategies elaborated above. We also note that the success of such strategies requires a dedicated congenital heart surgery team of neonatologists, anesthesiologists, intensivists, heart/lung perfusionists and intensive care unit nurses who are all specialized in the care of newborns with congenital heart defects if optimal results and continued improvement is to occur.

 

 

Anatomy Presentation Type Ductal Patency Initial Intervention Early Mortality (%) Early Prognosis
Pulmonary valve stenosis Cyanosis Pulmonary Angioplasty 1-5 good
Tricuspid atresia Cyanosis Pulmonary BT shunt or Glenn shunt 1-3 good
Tetralogy of Fallot Cyanosis Pulmonary Complete repair or BT shunt 1-3 good
Valvar aortic stenosis CHF

low C.O.

Systemic Balloon dilatation 3-5 good
Coarctation of aorta CHF

low C.O.

Systemic Surgery or balloon dilatation .5-1 good
Interrupted aortic arch CHF

low C.O.

Systemic Surgical repair 5-10 Variable per

other defects

HLHS Cyanosis Systemic Palliative surgical repair 15-20 fair
TGV Cyanosis or normal Mixing Surgical repair 2-4 good
TAPVR Low C.O. Non ductal dependent Surgery 1-5 good; fair if obstructed
AOLCA Low C.O. Non ductal dependent Surgery 1-5 good
Truncus arteriosus Cyanosis or CHF No ductus Surgical repair 3-8 good

C.O., cardiac output; CHF, congestive heart failure; HLHS, hypoplastic left heart syndrome; TGV, transposition of the great vessels; TAPVR, total anomalous pulmonary venous return; AOLCA, anomalous origin of left coronary artery; BT, Blalock-Taussig

 

References

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