A systemic aortopulmonary shunt reduces cyanosis by increasing pulmonary arterial blood flow. Selecting an appropriate shunt size is a critical point during this usually technically simple procedure. A shunt that is too small can cause residual cyanosis, and a shunt that is too large can cause volume load or even the development of congestive heart failure. Shunt types include:

VSD is, by far, the most common congenital heart defect. This defect leads to volume overload in both ventricles. If the defect is large and pulmonary resistance is also low, the patient will develop symptoms of congestive heart failure. Increased flow and pressure in the pulmonary arteries can lead to irreversible damage to pulmonary microcirculation, namely the development of pulmonary vascular disease. Muller and Darmann⁴ first described pulmonary artery banding to reduce flow and pressure (▶Fig. 2.4) in the 1950s. Similar to pulmonary artery shunts, pulmonary artery bands do not grow as the patient does. After a pulmonary artery band is placed, children can become cyanotic again as they grow. If scarring occurs, this can lead to distortion of both pulmonary arterial outflow tracts and pulmonary valves.

Cyanosis generally occurs due to reduced pulmonary blood flow. It can, however, also occur in cases of TGA. If neither PDA nor a septal defect is present, the newborn will die as a result of cyanosis. Blalock and Hanlon described a refined method in 1950: they surgically removed a large portion of the atrial septum in order to create an iatrogenic ASD in newborns with TGA. After the introduction of the Rashkind balloon septostomy, also known as the Rashkind maneuver (▶Fig. 2.5) in 1966,⁵ the Blalock and Hanlon surgical method is seldom used.

A general goal in pediatric cardiac surgery is to correct the congenital heart defect as soon as possible. Biventricular correction, however, is often not possible. If only one functional ventricle is capable of independently sustaining one of the two circulatory systems—either systemic or pulmonary—independently, this is known as “univentricular heart.” The most common forms of a functional univentricular heart occur due to the following defects:

The umbrella term “hypoplastic left heart syndrome” encompasses a broad spectrum of heart defects with varying degrees of expression of the underdevelopment of the left ventricular structures:

The most commonly associated defects are IAA, TAPVR, or an abnormal atrioventricular valve.

In cases of univentricular heart, the main treatment goals are to separate systemic and pulmonary circulation, ensure normal volume load for the functional singular ventricle, and reach normal arterial saturation. Surgical management generally occurs in three steps:

All aforementioned palliative interventions render a thoracotomy necessary. The latter can lead to scarring in the mediastinum and vessels, distortion, or even dissection. Furthermore, gradual therapy always means a minimum of two interventions, and thus an additional burden.

Early correction of congenital heart defects has only become possible with the introduction of open-heart surgery. Temporary interruption of circulation, supported by hypothermia, allows early correction of less complex congenital heart defects. The first complex cardiac surgical interventions—TOF or AVSD—were performed either via cross-circulation (in which one parent was utilized as oxygenator⁶) or cardiopulmonary bypass. In the 1950s and 1960s, however, the two-step treatment with initial palliative and subsequent corrective intervention remained standard for older patients.

Brian Barrat-Boyes and his successor Castañeda completed numerous procedures at Children’s Hospital of Boston using a heart-lung machine in 1972. The introduction of Prostaglandin E1 in the late 1970s made it possible to hold the ductus arteriosus or ductus Botalli open in newborns purely via medication, and thus achieve preoperative stabilization for the early correction of certain congenital heart defects. Optimizing invasive and noninvasive diagnostics also improved the conditions for early surgical correction.

The differences between the right and left ventricle do not develop until shortly after birth. Compared to the left ventricle, the right ventricle is significantly thinner. The left
ventricle rapidly increases in thickness and mass. This is achieved by hyperplasia and hypertrophy of the left ventricular myocytes. The myocytes’ ability to divide is believed to persist only until the third month of life. Developing new myocytes within a growing individual requires the concurrent formation of new coronary arteries by means of angiogenesis. Muscular hypertrophy, e.g., sustained high blood pressure, reduces the ability to form collateral arteries. Cardiac development can be disrupted by the palliative intervention, itself. The best-known examples are a large VSD accompanied by tetralogy of Fallot, which must then be treated using a shunt, and complete atrioventricular canal that must then be treated via pulmonary artery banding. In these cases, the right ventricle is exposed to pressure overload—with the corresponding hypertrophy—and thus assumes a round form rather than a semicircular one.

Early correction, on the other hand, allows the pulmonary vessels to develop normally during the first year of life. Pulmonary resistance is reduced with the involution of the smooth musculature in the arterioles. If pulmonary arterial pressure and flow are not reduced within the first 1-2 years of life, this can begin to contribute to the development of pulmonary hypertonia. Generally speaking, a child is considered inoperable if pulmonary vessel resistance has exceeded threefourths of systemic resistance and remains fixed. From that point onward, the child becomes increasingly cyanotic due to reduced pulmonary blood flow. The initial left-right shunt can convert to a right-left shunt. This phenomenon is known as the Eisenmenger reaction or Eisenmenger syndrome. Palliative interventions are meant to prevent this conversion. Pulmonary bands are placed to maintain pressure well below that of half of systemic pressure.

Indication for surgery—in the sense of large left-right shunts and pulmonary overflow—occurs in infancy for all cases of hemodynamically relevant ventricular septal defects.

The usual route to VSD correction consists of a median sternotomy with subtotal, bilateral thymectomy, longitudinal perdicardiotomy, and removal of the pericardial portion for later use as a VSD patch. VSDs are treated primarily with the assistance of a heart-lung machine and under conditions of mild-to-moderate hypothermia. In addition, the ascending aorta and the superior and inferior hollow veins are cannulated. After stabilizing the flow of the heart-lung machine, the ascending aorta is clamped off. A cardioplegic solution is used to induce cardiac arrest, which is then concluded with the closure of both hollow veins.

For children with pulmonary hypertonia, the PDA is inspected and may be clamped off. During cardiac arrest, a longitudinal incision is made in the right atrium. The fossa ovalis, tricuspid valve, and coronary sinus are then inspected. The type (membranous or muscular) and position of the VSD with respect to the aforementioned structures determine how surgery proceeds:

The arterial switch operation, also known simply as “arterial switch,” is definitively one of the greatest success stories in pediatric cardiac surgery. Before the arterial switch operation was established by Jatene et al. in 1975,⁷ surgical treatment consisted of the choice to perform physiological correction via either a Mustard⁸ or Senning atrial switch operation. The blood from the superior and inferior hollow veins was diverted into the anatomic left ventricle via the mitral valve using a venous baffle (▶Fig. 2.9). This blood was then transported into the lungs so that the blood from the pulmonary veins was pumped into the aorta via the right atrium and right ventricle.

Despite the intermittently increased rate of early mortality for the arterial switch operation, which is generally performed in infancy during the first (5-10) days of life and is thus extremely technically demanding, anatomical correction has established itself due to its significant benefits over the long term.

The arterial switch operation is performed as follows: after a median sternotomy and subtotal bilateral thymectomy (▶Fig. 2.10a) have been performed, a piece of the pericardium is removed (▶Fig. 2.10b) to be used for reconstructing the neopulmonary artery (▶Fig. 2.10e) after the coronary button has been removed (▶Fig. 2.10c and d). It may also be used to close the concurrent ASD. The pulmonary arteries are exposed up to the bifurcation, and the ductus arteriosus is dissected. After being attached to the heart-lung machine via bicaval cannulation, the left atrium is drained via the right superior pulmonary veins using a vent catheter, supported by the superior position of the aortic cannula (nearly in the aortic arch). During a total bypass, the patient is cooled to a state of moderate hypothermia. The blood flow within the pulmonary arteries has to be controlled and the ductus arteriosus doubly suppressed, divided, and overstitched. After cardioplegic cardiac arrest, the aorta is transected approximately 2 cm above the valve, and the commissures are marked with three retaining stitches. At the same time, the aorta is stretched. The area between the aorta and the pulmonary artery is dissected completely. Both coronary buttons are excised, taking care to protect the semilunar valves, and retaining stitches are placed. The defect in the aortic wall is covered using a pericardial patch of the appropriate size (▶Fig. 2.10f). After transection of the pulmonary artery, the pulmonary valve is stretched using three retaining stitches. Then, based on the position of the commissures and the size, position, and anatomy of the coronary button, the pulmonary arterial root is reconstructed and the coronary buttons are sewn into the neoaorta, so that they are neither exposed to tension nor possess too much clearance. The aorta is closed using the Lecompte maneuver,¹⁰ namely displacement of the pulmonary arterial bifurcation ventral to the aorta (▶Fig. 2.10g). If the ASD is closed either directly or with a pericardial patch, the aortic clamp is removed, enabling coronary perfusion. The pulmonary artery is stitched on the beating heart (▶Fig. 2.10h), and the atrium is then closed. The chest cavity is either closed or left open depending on the patient’s hemodynamic and respiratory condition.