Single functioning ventricle

The Hemi-Fontan Procedure

The hemi-Fontan procedure is so named because it diverts roughly half of systemic venous blood flow into the pulmonary circulation. The procedure requires cardiopulmonary bypass. It involves creation of an anastomosis between the side of the SVC and the main pulmonary artery (Fig. 8-57, A). The SVC is not disconnected from the right atrium, but a patch is placed at the SVC inlet to the right atrium to prevent SVC blood flow from entering the heart. The connection may alternatively include arteriotomies in the superior and inferior surfaces of the right pulmonary artery to allow for the connection to the superior vena cava (SVC).⁵⁸⁹

Fig. 8-57 The hemi-Fontan/Bi-Directional Glenn operations. A, The hemi-Fontan operation from the surgeon's point of view (this view is rotated 90 degrees counterclockwise from other figures of congenital heart defects and surgical repairs included in this chapter). A right atrial spiral incision is made, extending from the superior vena cava (SVC) to the surface of the right atrium (RA). B, After incision in the right pulmonary artery (RPA), a vascular confluence is created incorporating the cardiac end of the SVC, the cephalad portion of the RA (the portion nearest the head), and the RPA. C, The confluence is roofed with a patch of polytetrafluoroethylene (PTFE). A second PTFE baffle forms the floor of this confluence and separates the inferior vena cava (IVC) and coronary sinus (CS) blood from the SVC blood, thus diverting IVC and coronary sinus venous return through the atrial septal defect (ASD) to the left atrium. AO, aorta. D, The bidirectional Glenn operation. After transection of the superior vena cava (SVC), the cephalad end (i.e., bringing venous return from the head and upper extremities) is anastomosed to the right pulmonary artery (RPA). The cardiac end of the SVC is oversewn. The azygous (Az) vein is ligated (tied off). Blood flow from the inferior vena cava (IVC) passes through the atrial septal defect (ASD) to the left atrium, and thus contributes to left ventricular preload. AO, aorta.

(From Nichols DG. Critical heart disease in infants and children, ed 2, Philadelphia, 1995, Elsevier, Figs. 39-8 and 39-9.)

The Glenn Anastomosis

The Glenn anastomosis is performed with or without cardiopulmonary bypass. It involves division of the superior vena cava above the heart. The top portion (bringing venous blood from the head and upper extremities) is sewn directly into the top of the main pulmonary artery (on the patient's right side) and the cut end of the SVC that leads to the right atrium is oversewn. If a right and left SVC are present, a bilateral bidirectional Glenn is performed to join each SVC to the corresponding pulmonary artery.⁹³⁵ Occasionally, bilateral SVC's are present and the much smaller SVC can be ligated.⁹³⁵

The Glenn results in the diversion of all superior vena caval venous blood away from the heart and directly into the pulmonary arteries. The bidirectional Glenn immediately relieves overload of the functioning single ventricle, increases ventricular function, and improves the function of the AV valves.⁹³⁵ By directing a significant portion of desaturated systemic venous blood directly into the pulmonary circulation, effective pulmonary blood flow and systemic oxygenation is improved, particularly in young children.

In most centers, the Glenn procedure is performed as a stage 2 palliation technique for hypoplastic left heart syndrome. It follows an initial Norwood palliation, and is performed when the infant is about 4 to 6 months of age. This delayed timing for the second stage has followed reports that earlier performance of cavopulmonary anastomoses (i.e., at less than 4 months of age) resulted in lower arterial oxygen saturation in the early postoperative period and longer length of hospital stay.⁴¹⁰

Postoperative Care After the Glenn or Hemi-Fontan

Potential early postoperative complications of the Glenn and the hemi-Fontan procedures include bleeding, chylothorax, pleural effusion, and superior vena caval obstruction. Arterial oxygen saturation should be near 80% to 85% for infants in room air.^589,935 In the older patient, the arterial oxygen saturation may be lower after the Glenn because the volume of systemic venous return from the upper body that is diverted to the lungs is a smaller portion of total systemic venous return in older than in younger patients.⁹³⁵ Repair of additional lesions, such as pulmonary artery or aortic reconstruction, can add to the complexity of the postoperative course.

Oxygen therapy can be used without restriction following the Glenn procedure. During the immediate postoperative period, the head of the bed should be elevated with the head in a midline position, to enhance blood flow from the superior vena cava into the pulmonary arteries. The face and upper extremities are often edematous and plethoric in appearance during the immediate postoperative period (parents should be informed about this potential change in appearance in advance), but the child's appearance should return to normal within several days.

Small increases in pulmonary vascular resistance can lead to systemic venous hypertension with low cardiac output despite a technically successful procedure.⁴⁷⁶ Pulmonary hypertension can be present and pulmonary vascular resistance can be elevated after cardiopulmonary bypass.^935,942 Treatment for elevated pulmonary vascular resistance can include the use of oxygen, vasodilators, and milrinone. Inhaled nitric oxide has been shown to be beneficial^8,298 in the early postoperative period after Fontan and Glenn procedures.

Patients with elevated pulmonary vascular resistance (greater than 3.5 Wood units) or elevated mean pulmonary artery pressures (greater than 18   mm Hg) have been found to have higher risk for postoperative superior vena caval syndrome, low oxygen saturation (less than 70% to 75%), and death.¹⁷⁴ High SVC pressure with high arterial oxygen saturation may indicate the presence of a large aortopulmonary collateral vessel producing an effective left-to-right shunt.⁵⁹¹ Marked elevations in the SVC pressure result in decreased systemic perfusion.⁸

Initial postoperative SVC pressure may exceed 15   mm Hg, but should fall to 12   mm Hg or less within 2 days.⁵⁹¹ For flow to occur through the Glenn, pulmonary vascular resistance must be low, so anything that causes pulmonary vasoconstriction will reduce blood flow through the Glenn and increase SVC pressure.

A superior vena caval syndrome may develop when SVC pressure is elevated; this syndrome produces upper body edema and plethora.⁹³⁵ Possible causes of superior vena caval syndrome include obstruction at the anastomosis, elevated pulmonary resistance or distortions of the pulmonary arteries with obstruction to flow.⁹³⁵ The elevated SVC pressure can be associated with an elevated transpulmonary gradient (SVC pressure minus intraatrial pressure).⁵⁹¹ Identification of the cause for persistent SVC pressure elevation despite treatment requires a search for anatomic causes⁸ that can generally be treated during cardiac catheterization.

The Glenn anastomosis places cerebral blood flow and cardiopulmonary blood flow in a series, and autoregulatory mechanisms in these two tissue beds respond to changes in acid-base status and carbon dioxide tension in opposite ways.^393,935 Increased alveolar oxygenation will produce pulmonary vasodilation. Factors known to produce pulmonary vasoconstriction (e.g., hypoventilation, acidosis, and reducing alveolar oxygenation) will cause cerebral vasodilation. Recent studies have shown that hypercarbia (maintaining the PaCO₂ approximately 55   mm Hg) after a bidirectional Glenn will increase cardiac output by increasing cerebral blood flow, pulmonary blood flow and systemic arterial oxygenation, without significant elevation in pulmonary vascular resistance.^{98,99,393,935}

Elevated atrial pressures may result from ventricular dysfunction, presence of arrhythmias with loss of AV synchrony, and atrioventricular valve regurgitation. The elevated atrial pressures can cause elevation in the SVC pressure.⁵⁹¹ Heart rhythm disturbances may include sinus node dysfunction, treated with chronotropic medication therapy or temporary pacing.⁹³⁵

Pulmonary management includes weaning positive pressure ventilation to allow spontaneous ventilation as soon as possible. Early extubation is optimal to promote pulmonary blood flow. The arterial PaO₂ should remain greater than 30   mm Hg. Hypercapnia with the PaCO₂ approximately 55   mm Hg (range, 45-55   mm Hg) can increase cardiac output, systemic oxygenation, and pulmonary and cerebral blood flow.

After the bidirectional Glenn procedure the patient does not usually improve in response to inhaled nitric oxide,⁵ but cases of impaired pulmonary circulation after bidirectional Glenn have been treated successfully with inhaled nitric oxide²⁹⁸ and sildenafil⁶⁴⁶ to promote pulmonary vasodilation. Improved pulmonary blood flow results in improved systemic arterial oxygenation and systemic blood flow and decreases the transpulmonary gradient. If there is difficulty in weaning mechanical ventilation, rule out a diaphragm paralysis.

Systemic arterial hypertension is often present postoperatively. Causes can include pain, intracranial hypertension, or catecholamine secretion.⁹³⁵ Treatment may include administration of vasodilators. Caution is required to avoid aggressive lowering of the blood pressure, because it may have a negative affect on cerebral perfusion pressure.⁹³⁵ Irritability is a common postoperative finding and requires provision of comfort measures, analgesics and sedation (see Chapter 5, Sedatives, Analgesics, and Neuromuscular Blockade).

Severe hypoxemia and cyanosis, with low arterial oxygen saturation (less than 70% to 75%), or an arterial PaO₂ of less than 30   mm Hg requires prompt identification and intervention. Such hypoxemia can be caused by pulmonary venous desaturation resulting from pulmonary problems such as atelectasis, elevated diaphragm, pleural effusion, tube obstruction, or pulmonary edema. Increased pulmonary vascular resistance and resulting decrease in pulmonary blood flow can also cause lower arterial oxygen saturation, because less pulmonary venous blood returns to the heart to mix with the systemic venous return from the inferior vena cava.

Persistent low cardiac output with low mixed venous oxygen saturation can lead to worsening hypoxemia and cyanosis, so treatment must focus on improving cardiac output. A hematocrit of at least 40% is maintained to optimize oxygen carrying capacity. A cardiac catheterization procedure may be required for complete assessment, definitive diagnosis, and intervention to treat the cause of the severe hypoxemia and cyanosis. Interventions may include sealing decompressing collateral venous vessels, angioplasty, and possible stenting of a stenotic anastomosis or pulmonary vessel.

Deterioration in arterial oxygen saturation in the weeks to months postoperatively can be caused by opening of veno-venous collaterals (from the superior vena cava into the right atrium or inferior vena cava). Such collaterals will decompress (reduce) the elevated SVC pressure,⁶⁸⁶ but will increase cyanosis. The venous collaterals can be identified by echocardiography with a “bubble study,” injecting agitated saline into an upper extremity and watching for the movement of the saline into the heart. An echocardiogram may also reveal a previously undiagnosed left superior vena cava or a baffle leak (in the intracardiac SVC patch for the hemi-Fontan).⁹³⁵

Persistent elevation of SVC pressure can lead to persistent pleural effusions and interstitial infiltrates if the pulmonary lymphatic vessels cannot drain into the hypertensive central veins.⁵⁹¹ Pleural effusions are managed with diuresis and control of intravascular volume. Drainage is monitored for the development of chylous effusion, a whitish, opaque fluid. The chyle volume is increased, particularly with oral feedings containing fats (see Postoperative Care after Fontan Procedure, Pleural and Pericardial Effusions). Untreated pleural effusions further decrease pulmonary blood flow and arterial oxygen saturation, leading to worsening cyanosis.⁵⁹¹

The bidirectional Glenn for infants has a hospital mortality of 1.8% in the 4-year (2006-2010) report from the Society of Thoracic Surgeons (STS) database, and 2.5% in infants undergoing bilateral bidirectional Glenn. Reported STS mortality for the hemi-Fontan procedure is 3.2%. Survival at 1 year was 96%, and at 5 years was 89% in a recent 10-year analysis,⁷⁷⁷ with preoperative atrioventricular valve regurgitation identified as a risk factor for death or transplant.

Patients undergoing the Glenn procedure in the past may have undergone the original Glenn connection (first reported in 1958), joining the SVC exclusively to the right pulmonary artery. This method is no longer used because it was associated with a high rate of complications, including the development of pulmonary arteriovenous fistulae, pulmonary artery or superior vena caval distortion, loss of continuity between right and left pulmonary arteries, and failure of normal right pulmonary artery development.³⁴² The bidirectional Glenn procedure is not associated with significant occurrence of pulmonary arteriovenous fistulae.⁷²⁶

When pulmonic stenosis or a pulmonary band is present the bidirectional Glenn may be created and an existing systemic-to-pulmonary artery shunt may be left intact to provide additional antegrade pulmonary blood flow. The bidirectional Glenn with additional antegrade pulmonary blood flow may produce a resting arterial oxygen saturation of approximately 90%. This combination may serve as the final surgery if the patient is found to be a suboptimal Fontan candidate.¹³³

If pulmonary arteriovenous malformations develop, desaturated venous blood within the lungs bypasses the pulmonary capillary bed and returns into the pulmonary veins without gas exchange, so hypoxemia and cyanosis worsen.⁸⁸¹ The possible cause for the formation of these vessels is the lack of a “hepatic factor.”⁴⁸⁹ Hepatic factor is a postulated (but not yet identified) substance in hepatic venous blood; if hepatic venous blood does not traverse the pulmonary circulation (i.e., if it bypasses the lungs), patients are more likely to develop pulmonary arteriovenous malformations or fistulae. Completion of the Fontan procedure restores the “hepatic factor” flow through the pulmonary circulation, with potential resolution of pulmonary arteriovenous malformations.⁸⁸¹

With time and growth the relative quantity of systemic venous return from the upper body diminishes, causing the child to become increasingly hypoxemic, cyanotic, and polycythemic.³⁴² As the child grows, oxygen consumption increases and the growth of the lower body results in an increase in the volume of desaturated systemic venous returning to the heart via the inferior vena cava.⁸⁸¹ Once this growth in the lower body occurs, the Glenn anastomosis will not provide sufficient pulmonary blood flow,²⁴¹ and an additional surgical procedure will be needed to improve pulmonary blood flow. Typically, a Fontan-type correction is anticipated. In selected cases, an additional systemic to pulmonary artery shunt will be placed with no progression to the Fontan.

Selected patients will be eligible to have a “one-and-a-half” ventricle repair, with surgical correction of blood flow at the ventricular level and maintenance of the bidirectional Glenn.⁵²² Alternatively, a bi-ventricular repair can be accomplished with takedown of the previously completed Glenn and Fontan procedures.³⁷⁹ Selected patients with unmanageable, severely decreased ventricular function may be referred for cardiac transplantation.

Preoperative Evaluation

Before the Fontan procedure, evaluation includes echocardiogram and cardiac catheterization to assess hemodynamics and suitability for Fontan procedure. Interventional procedures during the catheterization may include closure of aortopulmonary collateral vessels and dilation and possible stenting of narrowed structures including the pulmonary arteries or aorta.

“Ideal” hemodynamic criteria for a Fontan procedure include: low pulmonary vascular resistance (less than 2 Wood units, indexed to body surface area), pulmonary artery mean pressure less than 15   mm Hg, central pulmonary arteries that are large and without distortion, good ventricular function and low pulmonary venous atrial pressure (less than 5   mm Hg).⁵⁸⁹ Mild elevation in pulmonary vascular resistance (greater than 3 Wood units) can prevent a successful Fontan procedure.³⁴² A 24-hour Holter monitor can detect loss of AV synchrony or bradycardia. After cardiac catheterization, patients may have transient complete heart block related to catheter manipulation.⁴⁵²

Fenestrated Fontan

The Fontan procedure produces passive flow of systemic venous blood through the pulmonary circulation. Because no ventricle ejects the flow forward into the lungs,⁹⁴² blood flow requires that pulmonary venous and left atrial pressures and pulmonary vascular resistance remain low. Patients with increased risk factors, including elevated pulmonary pressure or elevated pulmonary vascular resistance or less than optimal ventricular function, may have restricted forward flow through a conventional Fontan, with decreased pulmonary venous return and low cardiac output. These patients may undergo a fenestrated Fontan, first described in 1990.¹⁰⁸ In the fenestrated Fontan, there is a hole (fenestration) placed in the Fontan baffle to allow some inferior vena caval blood flow to enter the pulmonary venous atrium. This creates a right-to-left shunt whenever pressure in the Fontan baffle is elevated. The fenestration allows maintenance of cardiac output despite elevated pulmonary vascular resistance, although the systemic oxygen saturation will be lower than normal (as the result of the right-to-left shunt through the fenestration).

Use of the fenestrated Fontan and use of modified ultrafiltration to control intravascular volume have been shown to decrease the duration and severity of pleural effusions after the Fontan.³⁰⁶ Children with a fenestrated Fontan have been shown to have fewer complications, with less chest tube drainage and shorter length of hospital stay, and they are less likely to need additional postoperative procedures.⁵²³ With a right-to-left shunt, risk for systemic embolization exists. No air can be allowed to enter any intravenous device (see section, Common Clinical Conditions, Hypoxemia) as long as the fenestration is present.

Fenestrations are expected to cause systemic oxygen desaturation, so it is essential that the bedside nurse and receiving team know if such fenestrations were created, so the team will know to expect arterial oxygen desaturation. If the oxygen saturation rises or is higher than postoperative baseline values, the fenestration may have closed or become occluded; this must be promptly reported to the surgical team. Spontaneous fenestration closure may occur immediately after or days after surgery, causing acute deterioration with hypotension, renal failure, and excessive edema, in the presence of normally (fully) saturated blood.⁵⁸⁹ Echocardiographic evaluation for fenestration patency and prompt interventional venous cardiac catheterization may involve balloon dilation or placement of a stent⁵⁵ or an ASD dilation device to reopen the fenestration. Cardiac catheter intervention perforation of the extracardiac conduit with implantation of a covered stent into the Fontan fenestration has been successful for the patient with a failing Fontan caused by closure of the fenestration.⁶¹⁶

Outcomes have improved for both the standard and high-risk Fontan patient with fenestrated Fontan.⁶²¹ By 1 year after surgery, 20% to 40% of fenestrations close spontaneously.⁶⁸⁶ Elective, future fenestration closure is completed with interventional cardiac catheterization and implantation of the Amplatzer device (see Atrial Septal Defect, and Evolve Fig. 8-2 in the Chapter 8 Supplement on the Evolve Website),^389,621 or occlusion device. After fenestration closure, the arterial oxygen saturation is expected to rise.

If there is no fenestration in the Fontan circuit, all IVC blood flow will enter the pulmonary artery and systemic arterial blood should be near fully saturated (i.e., arterial oxygen saturation above 95% and near 100%) following surgery. Excellent outcomes with this procedure have been reported.⁷⁵⁸

Patients with heterotaxy variants may have complex venous anatomy including an interrupted IVC that does not enter the right atrium. Instead, the IVC joins to the azygous venous system and eventually enters the SVC; this anatomy is particularly likely in patients with polysplenia and bilateral left-sidedness.⁵⁹¹ In these patients completion of a bilateral bidirectional Glenn is equivalent to near completion of a Fontan procedure because both the SVC and IVC blood flow will then enter the pulmonary arterial system. The only lower body venous flow not entering the pulmonary circulation is the hepatic blood.⁵⁹¹ This bilateral cavopulmonary anastomosis procedure has been called the Kawashima procedure.

Postoperative Care After Fontan Procedure

Extubation with spontaneous ventilation should be allowed as soon as it is feasible after Fontan surgery because it may improve hemodynamics.⁹³⁵ Systemic venous return is facilitated by the subatmospheric pleural and intrathoracic pressures generated by spontaneous inspiration.⁹⁴² If positive pressure ventilation must be provided, extremely high levels of positive end-expiratory pressure (PEEP) should be avoided because they can impede pulmonary blood flow and contribute to a fall in cardiac output.⁹⁴² A PEEP of 3 to 5   cm H₂O can be used without causing hemodynamic compromise,⁹⁴² and can help improve ventilation-perfusion matching by reducing areas of microatelectasis.⁹³⁵ Positive pressure ventilation can decrease preload to the right and left atria and increase afterload to the pulmonary circulation.⁹⁴² Ventilation goals, however, include extubation with spontaneous ventilation as soon as possible. Non-fenestrated Fontan patients should have arterial saturations above 95%.

Pulmonary pressure and pulmonary vascular resistance can be elevated following cardiopulmonary bypass.^935,942 With even small increases in pulmonary resistance or any impediment to forward flow through the pulmonary vascular bed, the left heart filling will be compromised, leading to lower cardiac output.²⁵³ Treatment with oxygen and or nitric oxide has been successful in promoting pulmonary vasodilation and improving cardiac output.^298,327

After the Fontan operation, low cardiac output is the most common and most severe complication. It is often caused by inadequate flow of blood into the pulmonary circulation that results from hypovolemia and inadequate systemic venous pressure (low right atrial [RA] and left atrial [LA] pressures), elevated pulmonary vascular resistance (low LA and high RA pressures), obstruction at the site of surgery, or pump failure.⁹³⁵ Additional causes include pulmonary artery distortion or hypoplasia, pulmonary venous obstruction, or residual left-to-right shunts (Table 8-34).³⁴² The combination of low cardiac output with a high LA pressure is worrisome and may indicate potential left ventricular dysfunction, significant atrioventricular (AV) valve insufficiency or obstruction, loss of AV synchrony caused by arrhythmias, presence of obstruction to ventricular outflow, or cardiac tamponade.^934,935 Any of these complications must be identified and treated.

Table 8-34 Differential Diagnosis of Low Cardiac Output After Fontan

Reproduced with permission from Wernovsky G, Bove EL: Early bidirectional cavopulmonary shunt in young infants. In Chang AC, Hanley F, Wernovsky G, Wessel DL, editors: Pediatric cardiac intensive care. Baltimore, 2008, Williams & Wilkins, p. 283.

Management of low cardiac output after Fontan is highlighted in Fig. 8-59. Inadequate intravascular volume and low central venous pressure can cause postoperative low cardiac output. Central venous pressure must equal or exceed the pulmonary artery pressure for flow into the pulmonary circulation to occur. A central venous pressure of 12 to 15   mm Hg may be needed to provide that pressure gradient and forward flow.⁷⁵⁰ Treatment of low cardiac output requires both judicious administration of intravenous fluid as well as administration of vasoactive medications (including inotropic agents and vasodilators). Therapy should be modified based on evaluation of the child's systemic perfusion, including assessment of mixed venous oxygen saturation, serum lactate and urine output. Avoid relative hypovolemia, with low central venous pressure and resultant low left atrial pressure.

Fig. 8-59 Management algorithm for low cardiac output after Fontan-type correction of tricuspid atresia or single ventricle. AV, Atrioventricular; CVP, central venous pressure; LAP, left atrial pressure; PA, pulmonary artery; PAP, pulmonary artery pressure; PEEP, positive and expiratory pressure; SVC, superior vena cava; VSD, ventricular septal defect.

(Modified from Okanlami O, et al: Tricuspid atresia and the Fontan operation. In Nichols DG, et al, editors. Critical heart disease in infants and children. St Louis, 1995, Mosby.)

Diuretics, including Lasix and Aldactone (an aldosterone antagonist) are used to treat congestive heart failure,⁸⁸¹ but aggressive diuresis is avoided. Afterload reduction is used to improve cardiac output and decrease single ventricle end-diastolic (filling) pressure,³⁸⁴ as well as decrease elevated systemic vascular resistance.⁵⁸⁹

Management of low cardiac output includes efforts to reduce pulmonary vascular resistance (see section, Common Clinical Conditions, Pulmonary Hypertension). These efforts include administration of supplementary oxygen even if arterial oxygen saturation is adequate.⁵⁹¹ Avoid acidosis, hypoventilation, atelectasis (or other causes of alveolar hypoxia), hypothermia, and agitation. Anemia is treated to support adequate oxygen-carrying capacity and arterial oxygen content. Factors that increase oxygen consumption (fever, pain, agitation, and infection) should be avoided or promptly treated. When cardiac output is optimized and there is a good balance between oxygen delivery and oxygen demand, the mixed venous oxygen saturation will rise. In addition to monitoring and support of the arterial oxyhemoglobin saturation, the PaO₂ must be monitored and maintained above 30   mm Hg (Table 8-35).

Table 8-35 Optimizing Pulmonary and Systemic Blood Flow in Patients with Single Ventricle

A CVP greater than 15 to 18   mm Hg suggests difficulty with passive Fontan flow into the pulmonary capillary bed.⁵⁹¹ Anatomic obstruction in the Fontan systemic venous pathway leads to elevated transpulmonary gradient (CVP minus LAP) with a value above 10   mm Hg suggesting difficulty with passive Fontan flow into the pulmonary circulation.⁵⁹¹ Clinical signs include hepatomegaly, ascites, edema of the head and neck, anasarca, and signs of low cardiac output. The left atrial pressure is derived from the common atrial pressure with typical desired pressure slightly greater than 5   mm Hg (but not a lot higher).

Bleeding is most likely to occur if a coagulopathy existed preoperatively (related to chronic hypoxemia and polycythemia—see section, Common Clinical Conditions, Hypoxemia) or a significant amount of scar tissue (from previous palliative surgical procedures) was dissected. If synthetic polytetrafluoroethylene is used for the surgical correction, platelet adherence to the surface of this material will produce a fall in the child's platelet count immediately after surgery.

Continued cyanosis/hypoxemia may result from pulmonary venous desaturation related to atelectasis, elevated diaphragm, pleural effusions, pneumothorax, hypoventilation, or pulmonary edema (Table 8-36). Excessive cyanosis may be caused by a leak in the intracardiac baffle (or an intentional fenestration). If a fenestration is present within the Fontan circuit, right-to-left shunting with systemic desaturation is expected. Cyanosis may also result from decreased mixed venous oxygen saturation.

Table 8-36 Differential Diagnosis of Cyanosis After the Superior Cavopulmonary Anastomosis and the Fontan Completion

From Marino BS, Spray TL, Greeley WJ. Separating the circulations: cavopulmonary connections (Bidirectional Glenn, hemi-Fontan) and the modified Fontan operation. In Nicholls DG, editor in chief. Critical heart disease in infants, children and adolescents, ed 2, Philadelphia, 2006, Saunders. Table 41-2.

Veno-venous collaterals may develop (from the SVC to the pulmonary venous atrium), but typically take weeks or months to develop after bidirectional Glenn or Fontan procedures. These collaterals increase cyanosis and require assessment and device closure during cardiac catheterization. It is uncommon for current bidirectional Glenn patients to develop pulmonary arteriovenous malformation (AVM) fistulae, which shunt blood flow away from the pulmonary capillaries and produce cyanosis. If these are present preoperatively in the Fontan patients, they will cause persistent cyanosis in the postoperative period. Pulmonary AVMs cannot be closed with coils or devices during cardiac catheterization, and must resolve over time. The cause for development of pulmonary AVMs is suspected to be lack of flow of a “hepatic factor” into the pulmonary circulation; when hepatic venous blood flows through the pulmonary circulation following the Fontan procedure, the problem resolves. Cyanosis and inability to wean from mechanical ventilation can also be related to diaphragm paralysis, with resultant risk for hypoventilation, atelectasis and increased pulmonary resistance.

Chronically cyanotic patients often develop collateral vessels from the systemic to the pulmonary arteries, resulting in increased pulmonary blood flow.⁴³⁴ The collateral vessels can cause ventricular volume overload,⁴³⁴ requiring transcatheter occlusion either before or after the Fontan procedure. Echocardiography with agitated saline contrast can be used to diagnose a right-to-left intrapulmonary or intracardiac shunt in the patient with unexplained cyanosis following a Glenn or Fontan operation.^162,474 The agitated saline can help to detect location of a Fontan leak.⁴⁷⁴

Pleural and pericardial effusions are common postoperative problems requiring prolonged hospitalization.⁹³⁵ The causes are multifactorial.⁵⁷⁷ Elevated systemic venous pressure impedes lymphatic return into the venous circulation.⁵⁹¹ Treatment by evacuation is needed because large fluid collections compress the lung, raising pulmonary vascular resistance,⁵⁸⁹ and significant pericardial effusions can cause tamponade.

An effusion is a chylothorax when milky appearing lymph fluid drains into the chest. Insertion of chest tubes may be necessary if pleural fluid accumulation compromises ventilation and oxygenation. Chylothorax can require initiation of and long-term management with a diet low in long-chain triglycerides,¹³⁸ with Portagen as the infant formula. Because this fluid represents fluid loss from the body the total amount of fluid drained must be considered when evaluating the child's fluid balance. In addition, fat-soluble vitamins may be lost in the lymph fluid so replacement of vitamins A, D, K, and E is often required.¹³⁸ Some children lose large proteins, including coagulation factors and fibrinogen, in this fluid; monitoring of the coagulation panel is advisable. Replacement of intravascular volume may be required with protein, electrolytes, and immunoglobulins.⁹³⁵ Octreotide IV infusion has been used with improvement.¹⁶¹ Thoracic duct ligation may be required for persistent drainage.

Recent factors associated with decreased incidence of effusions include use of fenestrations in the Fontan circuit, use of modified ultrafiltration, and the use of an “adjustable atrial septal defect.”⁹³⁵ Systemic venous congestion can lead to additional complications, including pericardial effusion, ascites, and liver congestion, which may produce liver dysfunction.

After the Fontan procedure, anticoagulation is typically initiated with aspirin, dipyridamole, or Coumadin (once intracardiac catheters and temporary pacing wires are removed). Slower venous blood flow occurs through the Fontan circuit, with passage through prosthetic materials, making patients susceptible to thrombus formation.^591,881 Choice of therapy remains a matter of debate⁵⁷¹ The persistent right-to-left fenestration shunt may also increase risk for thrombus formation and systemic embolization.

Rare complications include the development of plastic bronchitis with the formation of thick, tenacious protein casts within the bronchus.^325,949 These casts cause life threatening obstruction of the airway and can result in pulmonary failure. Management is complex and involves repeated bronchoscopies.⁷⁰⁹

Arrhythmias can be problematic postoperatively. The presence of a normal sinus rhythm is not required for successful function of the Fontan, although the presence of chronic atrial fibrillation is worrisome because it often is associated with severe right atrial dilation and may indicate the presence of a severely restrictive atrial septal defect or left ventricular failure. Temporary or permanent cardiac pacing wires can be used postoperatively to control the cardiac rhythm.

Heart block or junctional tachyarrhythmias (loss of AV synchrony) raise intracardiac pressures, causing increased resistance to atrial filling and resulting in lower ventricular filling volume, additional pulmonary venous congestion, and low cardiac output as effective atrial contractility is lost or the atria contract against a closed AV valve.⁶⁹⁵ Loss of sinus rhythm, with escape rhythms such as junctional ectopic tachycardia, are poorly tolerated.^589,935

Potential arrhythmias, including atrial flutter or fibrillation, primary atrial tachycardia, or accelerated junctional tachycardia, may develop postoperatively.³⁴² Sinus node dysfunction is common after Fontan completion,⁵⁹¹ possibly related to sinus node injury or interruption of sinus node blood supply.⁵⁹¹ Sinus node dysfunction may result from an atrial septal defect; if an atrial septal defect is restrictive preoperatively, it leads to right atrial dilation.³⁴² The atrial arrhythmias may reappear if significant right atrial hypertension develops postoperatively.

Preoperative Holter monitoring to establish baseline rhythm alterations can indicate the need for placement of permanent epicardial wires and a pacemaker generator during the Fontan procedure. Treatment can include temporary or permanent pacing and use of antiarrhythmic drugs. Atrial pacing wires allow for accurate rhythm diagnosis (see section, Common Clinical Conditions, Arrhythmias).⁵⁸⁹

Early perioperative Fontan failure may be related to multiple factors, including myocardial injury or elevated pulmonary vascular resistance.^394,935 If elevated systemic venous pressure and low cardiac output persist despite maximal support, patients are brought to the cardiac catheterization laboratory for evaluation of their hemodynamics and anatomy. Transcatheter interventions have been completed safely in the early postoperative period after the Fontan procedure, including balloon angioplasty, occlusion of residual antegrade pulmonary flow or insertion of stents in narrowed Fontan or arterial structures.⁸³ During interventional cardiac catheterization, an emergent fenestration may be created in the extracardiac Fontan circuit to improve cardiac output.⁶¹⁶ A Fontan “takedown” to a bidirectional cavopulmonary shunt is uncommon, but may be a life-saving measure in the face of severe low cardiac output.⁵⁸⁹

Neurologic and developmental monitoring is required in patients with a single ventricle because risk for unfavorable developmental sequelae is high.⁶⁴⁸ Poor neurologic outcome is particularly likely in children with hypoplastic left heart syndrome who can have cognitive, motor, and neurologic deficits.^554,767 Developmental evaluations are essential, with initiation of an early intervention programs, ongoing assessment and other interventions as needed.

Multiple factors create higher risks for developmental delay, including prolonged hypoxemia, unstable hemodynamics, multiple cardiac catheterizations, congestive heart failure, and a series of surgical procedures.⁶⁴⁸ An increased incidence of preoperative and postoperative periventricular leukomalacia, a nonspecific sign of cerebral white matter injury, has been found among patients who have undergone neonatal open-heart surgery.⁵⁵⁷

Physical activity level is reduced after Fontan procedures.⁵⁹⁶ Single ventricle patients with a Fontan procedure have been reported to have reduced exercise capacity.^682,966 Obesity has the potential to increase pulmonary vascular resistance, as well as lead to other morbidities, and should be prevented in patients after the Fontan procedure.⁵⁹⁶ Ongoing care requires attention to promoting physical activity and healthy heart living.

After the Fontan procedure, most children demonstrate significant symptomatic improvement, although most also demonstrate abnormalities in exercise tolerance. In general the child demonstrates a high heart rate, high ventilation for oxygen consumption, and oxygen desaturation with exercise. Most children have an increase in physiologic dead space and a ventilation/perfusion mismatch, whether or not a Glenn anastomosis was performed before the Fontan procedure.⁹³⁴ Left ventricular ejection fraction often is reduced after the Fontan procedure, and the capacity to increase cardiac output in response to exercise varies from patient to patient. If left ventricular function is extremely poor, cardiac transplantation ultimately may be performed.⁹³⁴

Development of protein losing enteropathy (PLE) after a Fontan is associated with a poor clinical course.³¹¹ The incidence is 4% to 13%.⁷⁵⁶ Elevated systemic venous pressures are thought to contribute to protein-losing enteropathy, a loss of proteins throughout the GI tract,²¹⁷ but the precise cause unknown.⁷⁵⁶ Symptoms include diarrhea, ascites, fatigue, abdominal pain, pleural effusions, shortness of breath, emesis, and peripheral edema.⁷⁵⁶ Fecal alpha₁-antitrypsin is increased (greater than 200   mg/dL) and serum albumin is chronically low (less than 3.9   g/dL).⁷⁵⁶

Interventions include heparin administration, a high protein/low-fat diet, diuretic therapy, medications to improve cardiovascular function (afterload reduction, inotropic support), albumin infusions,^612,756 prednisone,^612,862 octreotide, budesonide,⁸⁴⁹ sildenafil⁷³⁰ and creation of atrial fenestration.⁶¹² After the onset of PLE, survival is 46% to 59%,⁷⁵⁶ with 50% mortality in 5 years.⁶¹²

Monitoring of calcium, serum albumin, and total protein is required for patients with PLE, with intermittent infusions of these substances if needed. Subcutaneous heparin therapy has been shown to provide subjective symptomatic improvement in most patients, but it does not increase the clinical remission or decrease the need for albumin administration.⁷⁵⁶ No cure is known.²¹⁷

The outcomes of the Fontan procedure with the evolving modalities of management require ongoing evaluation. Transcatheter fenestration with creation of an interatrial communication for the Fontan circuit has not prevented protein-losing enteropathy.⁹¹⁴

Postoperative mortality associated with the Fontan procedure reported by centers in the Society of Thoracic Surgeons (2006-2010)⁸²³ database is 1.3% for the extracardiac fenestrated Fontan and 1.2% for the nonfenestrated procedure. The STS database reports postoperative hospital mortality of 1.0% for the fenestrated lateral tunnel.⁸²³ Adults (greater than 18 years old) presenting for Fontan revision/conversion have 8% mortality prior to discharge. Mortality for children with Down syndrome is higher following both the Glenn and Fontan surgery, and the procedures are rarely performed in these children.³³⁹

Results of the Fontan palliation continue to improve. Survival at 20 years after Fontan procedure ranges from 82.6%⁴⁶⁶ to 87%.⁶⁷² The leading causes of death after Fontan are related to thromboembolism, sudden death, and heart failure.⁴⁶⁶ For double inlet left ventricle patients, 78% are reported to be alive at 12 years.⁴⁶⁸ Ten percent of the patients with single left ventricle develop complete heart block.⁴⁵² A 15-year followup of extracardiac Fontan patients had 85% survival at 15 years (including operative deaths), with 92% of long-term survivors free from late heart failure. Three percent of the patients developed extracardiac conduit obstruction, and 3% experienced ventricular failure.³¹⁹ Extracardiac conduit total cavopulmonary connection 10-year survival is reported at 93.6% with low morbidity, no restenosis, and 115/126 in normal sinus rhythm.⁶⁴²

Risk factors for adverse early and late outcomes include preoperative impaired ventricular function and elevated pulmonary vascular resistance.³⁹² Late complications of the Fontan procedure include the development of conduit obstruction; this may cause sudden death if a Glenn anastomosis is not in place. Late arrhythmias, including atrial arrhythmias and complete heart block, also have been reported, requiring antiarrhythmic therapy and potential pacemaker insertion. Although many patients are able to resume normal daily activities without difficulty, others demonstrate persistent signs of systemic venous congestion and low cardiac output.

Late Fontan failure symptoms include those of congestive heart failure, as well as the development of protein losing enteropathy.³⁹⁴ Maintenance of low pulmonary artery pressure and vascular resistance with adequate unobstructed pulmonary blood flow and pulmonary venous return are important for optimal long-term Fontan hemodynamics.⁶⁷⁶ Cardiac catheter intervention dilation of Fontan pathway stenosis can improve hemodynamics, as well as improve or relieve chronic ascites.⁶⁷⁶ For those patients who develop intractable atrial arrhythmias requiring Fontan conversion, the procedure is completed with low mortality and is effective.⁵⁸²

Orthotopic cardiac transplantation remains an option for the patients with single functioning ventricule and may be an option for patients with severe ventricular dysfunction. The long-term morbidity and mortality related to transplant have prevented it from becoming a primary option for surgical management.³⁴²

Interventional Catheterization

Perforation of the pulmonary valve during cardiac catheterization allows some blood flow across the right ventricular outflow tract. Since the 1990s radiofrequency energy has been used in the cardiac catheterization lab to perforate the pulmonary valve and establish antegrade pulmonary blood flow, with anticipation that the flow will stimulate RV growth and allow acute RV decompression. Laser-guided techniques also can be used. After pulmonary valve perforation, balloon dilation is performed. Perforation can be accomplished in 80% of patients with pulmonary atresia and intact ventricular septum.⁶⁶² Complications occur in nearly 15% of patients, however, and can include perforation and tamponade. Mortality is approximately 8%.³⁸⁹

Another intervention that can be performed during cardiac catheterization to improve pulmonary blood flow is placement of a stent within the ductus arteriosus to maintain ductal patency.⁷⁸³ Future potential coarctation (i.e., stenosis or narrowing) of the left pulmonary artery associated with the site of ductus arteriosus stent insertion requires ongoing assessment.¹⁸

The atrial right-to-left shunt often persists despite relief of the RV outflow obstruction because of the combined effects of tricuspid stenosis, annular hypoplasia, and a small, noncompliant RV. The prostaglandin E₁ infusion may be continued for days to weeks to ensure sufficient pulmonary blood flow, arterial oxygen saturation, and oxygen delivery. Postprocedure care includes the guidelines for single ventricle care presented in the section, Single Functioning Ventricle, Overview of Management earlier in this section of the chapter, and Cardiac Catheterization in the last section of this chapter.

If hypoxemia persists, an additional source of pulmonary blood flow can be created with a surgical Blalock-Taussig shunt or a stent placed within the ductus during a cardiac catheterization. A source of additional pulmonary blood flow is required in 33% to 70% of patients.^350,662 Throughout the hospitalization, IV tubing must be kept free of air, because any air entering the systemic venous circulation may ultimately be shunted into the systemic arterial circulation, and may produce a cerebral air embolus.

When successful, these interventional therapies avoid the use of cardiopulmonary bypass in the newborn, and can facilitate later biventricular repair or “one-and-a-half ventricle” repair.³⁵⁰ The long-term results of this approach continue to be analyzed.⁶⁶²

Surgical Palliation to Increase Pulmonary Outflow and Blood Flow

Improved pulmonary blood flow can be achieved by a surgical pulmonary valvotomy. A closed transventricular pulmonary valvotomy does not require use of cardiopulmonary bypass. A curved blade is inserted through a small stab wound in the right ventricular outflow tract; the stab wound is surrounded by purse-string sutures (to prevent bleeding). A similar procedure may be performed using inflow occlusion and a small incision in the pulmonary artery. The valvotomy improves pulmonary blood flow and decompresses the right ventricle. In addition, it enables right ventricular ejection of blood, and so may stimulate growth of the hypoplastic right ventricle.⁶²⁰ Postoperatively, management as for single ventricle physiology is needed (as detailed in the Single Functioning Ventricle, Overview of Management).

Open-heart procedures performed in the newborn include an open pulmonary valvotomy followed by insertion of a patch in the pulmonary outflow tract. The ductus arteriosus can be ligated if systemic arterial saturation is adequate.⁶²⁰ If pulmonary blood flow (and systemic arterial saturation) remains inadequate after the valvotomy, a systemic-to-pulmonary artery shunt is also created. Postoperative complications include progressive right ventricular dysfunction, low cardiac output, and malignant ventricular arrhythmias. Congestive heart failure also may be present, with signs of systemic venous congestion. After any palliative procedure, absolutely no air can be allowed to enter any intravenous system because systemic venous blood continues to be shunted into the systemic arterial circulation.

Patients who have RV outflow reconstruction with creation of a Blalock-Taussig shunt can present with signs of low cardiac output if previously undiagnosed RV coronary sinusoids produce myocardial ischemia. Such low cardiac output is particularly likely if the right ventricular outflow reconstruction produced decompression of the right ventricle in patients with right ventricular-dependent coronary circulation. Signs of myocardial ischemia include ventricular arrhythmias and ECG changes (ST segment depression or elevation and T wave changes) immediately after surgery. An echocardiogram will confirm areas of myocardial dyskinesis or akinesis.⁹³⁶

If pulmonary insufficiency and tricuspid insufficiency are both present postoperatively, an ineffective “circular shunt” can develop. This shunt can develop after pulmonary valvotomy or RV outflow reconstruction that produces pulmonary insufficiency and creation of a systemic to pulmonary shunt. The systemic to pulmonary shunt delivers blood flow from the aorta to the pulmonary circulation; because pulmonary insufficiency is present, some of the shunted blood flows retrograde into the RV. If tricuspid valve regurgitation is also present, some of the blood from the RV is ejected back into the right atrium and then shunts right-to-left into the left atrium, ultimately flowing into the aorta and systemic circulation. This blood can then flow back through the systemic to pulmonary shunt, into the pulmonary artery, and back into the RV to the right atrium, left atrium, and aorta. The net result of this circular shunt is inadequate systemic blood flow. Signs of poor perfusion, including oliguria, metabolic acidosis, and systemic hypotension may develop several days after surgery.⁶⁶² Therapies to decrease this postoperative physiology include increasing pulmonary vascular resistance and lowering systemic vascular resistance. The patient may require narrowing of the shunt or repair of the tricuspid valve.⁹³⁶

“One-and-a-half Ventricle” Repair

If RV development continues to be borderline, and the tricuspid valve is small, a “one-and-a-half ventricle” repair can be completed.⁶²⁰ This consists of a bidirectional Glenn (SVC to right pulmonary artery shunt) anastamosis⁹³⁶ to direct SVC flow directly into the pulmonary circulation. The IVC flow continues to enter the right atrium, and flows through the tricuspid valve, and is ejected by the right ventricle into the pulmonary circulation. A right ventricular outflow enlargement is performed to relieve residual pulmonary stenosis. When the atrial septal defect is closed, total separation of the systemic and pulmonary venous blood and separation of the systemic and pulmonary circulations is achieved.⁶²⁰ If atrial septal defect closure is not tolerated, a restrictive atrial opening may be left with plans for future closure via an interventional cardiac catheterization procedure. Immediately after surgery the atrial defect allows for right-to-left atrial shunting, and systemic arterial desaturation is present (see Single Functioning Ventricle, Overview of Management, Palliative Surgery for Univentricular Heart: The Bidirectional Glenn and Hemi-Fontan Procedure [Cavopulmonary Anastomosis] in this section, and the section, Postoperative Care and Anticoagulation).

Patients treated with an RV outflow tract enlargement procedure combined with a systemic to pulmonary artery shunt for mild to moderate RV hypoplasia require ongoing echocardiographic assessment of RV and tricuspid valve growth. If adequate growth is observed, a cardiac catheterization is performed and the shunt is temporarily occluded to evaluate adequacy of systemic arterial saturation (a sign of adequate pulmonary blood flow and adequate RV output). A temporary balloon may also be inserted to occlude the atrial septal defect to assess the ability of the RV to maintain adequate cardiac output. If the arterial oxygen saturation is maintained during catheterization testing, the shunt may be permanently closed. The catheterization may show need for additional surgery to enlarge the RV outflow tract as the next procedure.⁶²⁰

Biventricular Repair

When the right ventricle and both pulmonary arteries are of adequate size, total correction of the pulmonary atresia can be performed using a median sternotomy incision, cardiopulmonary bypass, and hypothermia in the newborn or after successful staged palliation during infancy. A transannular patch (with or without a cusp) or a conduit is inserted between the right ventricle and pulmonary artery; the use of antibiotic-treated cryopreserved valved pulmonary or aortic homografts currently is preferred over the use of prosthetic conduits. After biventricular repair, the atrial septal defect may be closed, or an atrial defect may be allowed to remain open temporarily to decompress the right heart in the immediate postoperative period; this will produce varying degrees of right-to-left shunting of blood and varying degrees of systemic arterial oxygen desaturation and cyanosis. Later, when flow patterns are established, the ASD may be closed during cardiac catheterization or additional surgery.

Postoperative complications after biventricular repair or “one-and-a-half ventricle” repair include low cardiac output, congestive heart failure, arrhythmias, bleeding, and neurologic complications. Severe congestive heart failure and right ventricular dysfunction (with signs of severe systemic venous congestion, including tachycardia, hepatomegaly, ascites, and pleural effusions) may develop after right ventricular outflow reconstruction. As noted, a small atrial defect may be left in place after any of these procedures, to allow for a right-to-left shunt when residual RV dysfunction is present. It is important to know if a residual ASD is present, because this will cause systemic arterial oxygen desaturation. In addition, if a residual ASD and right-to-left shunt is present, no air can be allowed to enter any intravenous catheter, because it may be shunted into the systemic arterial circulation and may produce a cerebral air embolus.

Ventricular dysfunction and signs of myocardial ischemia, ventricular arrhythmias, or ventricular infarction can develop in patients with RV sinusoids. It is important to monitor for ST-segment changes postoperatively.

Univentricular Repair

If the tricuspid valve and RV continue to be severely hypoplastic, they will be too small to support adequate pulmonary blood flow, and biventricular repair will not be possible. A staged univentricular pathway is planned and a bidirectional cavopulmonary anastomosis is performed with closure of the systemic to pulmonary artery shunt as the second stage. Postoperative evaluation will monitor RV and tricuspid valve status to determine future suitability for RV outflow tract enlargement with a “one-and-a-half- ventricle” repair, or completion of a Fontan procedure (see Single Functioning Ventricle, Overview of Management, Corrective Surgery: The Completion Fontan Procedure).

If the patient has an initial systemic to pulmonary artery palliation (shunt or stenting of the ductus arteriosus) and a univentricular heart pathway is anticipated, cardiac catheterization is performed at 3 to 6 months of age in preparation for the second-stage bidirectional Glenn with takedown of the systemic to pulmonary artery shunt. A total cavopulmonary connection (Fontan procedure) will then be completed.

For children with RV-dependent coronary circulation the Fontan pathway is planned to maintain elevated RV pressure, directing oxygenated (pulmonary venous) blood into the RV then into the coronary arteries via retrograde flow. This may include a lateral tunnel or extracardiac Fontan. The surgical procedure is planned to avoid even temporary RV decompression during cardiopulmonary bypass, because RV decompression can lead to lethal myocardial ischemia.⁶²⁰ The Fontan procedure (with or without a fenestration) joins the inferior vena caval flow to the pulmonary artery, so that systemic venous blood is diverted into the pulmonary arteries; oxygenated pulmonary venous blood must be able to flow through the tricuspid valve and into the RV and then into the coronary circulation (see Single Functioning Ventricle, Overview of Management, Corrective Surgery: The Completion Fontan Procedure).

Perioperative mortality varies widely and by specific procedure. The Society of Thoracic Surgeons, reporting 2006-2010 data, identify 7.1% (modified shunt) to 11.9% (central shunt) overall hospital mortality in neonates undergoing systemic to pulmonary artery shunts.⁸²³ Biventricular repair management strategies and outcomes have been reported, but broad application is limited due to the variability in intracardiac and great vessel anatomy.¹⁸³ The Congenital Heart Surgeon Society database for 408 neonates with pulmonary atresia and intact ventricular septum reports 77% survival at 1 month, 60% survival at 5 years, and 58% survival at 15 years of age. A biventricular repair was reported in 33%, a Fontan in 20%, and a “one-and-a-half ventricle” repair in 5%. Outcomes continue to improve.³⁴

The survivors of pulmonary atresia with intact ventricular septum are now beginning to reach adulthood and they will require lifelong care. Long-term results are affected by the patient's unique hemodynamics and the subsequent interventions. Late survivors can develop arrhythmias, residual right ventricular outflow obstruction, right atrial dilation, tricuspid regurgitation, and pulmonary regurgitation. Some may continue to have cyanosis from residual atrial septal defects or other shunts. The specific potential problems are varied because of the unique forms of palliation performed, possible progression of coronary artery abnormalities, and—for those with the univentricular interventions—all of the potential complications related to the Fontan procedure. These late complications, assessments, and late management options are detailed by Daubeney.²¹⁹ Lifelong, continuous care is required into adulthood by experts in the management of adults with congenital heart disease.⁹²⁷

Some advanced concepts in the care of the child with pulmonary atresia and intact ventricular septum are listed in Box 8-42.

Box 8-42 Advanced Concepts: Pulmonary Atresia with Intact Ventricular Septum (IVS)

• A “circular shunt” can develop after creation of a systemic to pulmonary artery shunt if severe pulmonary and tricuspid insufficiency develop.

Pulmonary insufficiency can result from RV outflow tract reconstruction with a transannular patch or from a percutaneous pulmonary valvotomy. Tricuspid insufficiency can result from right ventricular dysfunction and dilation.

In the presence of both pulmonary and tricuspid regurgitation, blood from the aorta flows through the systemic to pulmonary artery shunt into the pulmonary artery, then flows retrograde (through the insufficient pulmonary valve) into the right ventricle. The blood can then flow retrograde (through the insufficient tricuspid valve) into the right atrium. Blood from the right atrium can flow through the atrial septal defect to the left atrium and into the ventricle and can be ejected into the aorta, to again flow through the systemic to pulmonary shunt.

A circular shunt produces low cardiac output.

• Decreased aortic diastolic pressure, tachycardia, and hypovolemia in the presence of RV sinusoids or RV-dependent coronary circulation will reduce myocardial oxygen delivery and produce myocardial ischemia. Such ischemia can produce ventricular arrhythmias and low cardiac output.

Reduced aortic diastolic pressure decreases coronary perfusion pressure in general. In patients with RV sinusoids it will also increase retrograde flow of systemic venous blood from the right ventricle through the sinusoids.

Tachycardia decreases coronary perfusion time.

Hypovolemia reduces right ventricular end-diastolic pressure and decreases retrograde perfusion through the sinusoids. Patients with RV-dependent coronary circulation have limited antegrade flow from the coronary artery, so anything that reduces RV pressure will reduce the major source of blood flow to the coronary circulation. Decreased aortic diastolic pressure will also reduce what little antegrade flow is present through the coronary circulation

• Signs of myocardial ischemia include ST-segment depression (in leads with upright QRS complex) and T-wave abnormalities. Myocardial infarction can produce ST-segment elevation (in leads with upright QRS complex). These changes require immediate recognition and therapy.

The Norwood Procedure

This operation establishes permanent, unobstructed systemic blood flow from the right ventricle into a reconstructed neo-aorta. This procedure requires cardiopulmonary bypass, altered perfusion (circulatory arrest or regional perfusion), and deep hypothermia.⁸⁸¹ Pulmonary blood flow is provided by a prosthetic shunt from an aortic branch to a pulmonary artery. To eliminate obstruction to pulmonary venous return, the interatrial septum is resected.

The distal main pulmonary artery is transected. The aorta is incised longitudinally from the left subclavian artery, across the arch to the ascending aorta. An anastomosis is created between the trunk of the proximal main pulmonary artery and the ascending aorta and aortic arch. A portion of pulmonary homograft can be used to complete aortic reconstruction and prevent development of stenosis. Pulmonary blood flow is created by insertion of a 3- to 4-mm Gore-Tex systemic-to-pulmonary artery shunt between the innominate artery (or the aorta) and the pulmonary artery. The existing atrial septal defect or patent foramen ovale is enlarged (see Fig. 8-63, A and B).

After the completion of the stage 1 procedure, parallel circulations exist. The right ventricle receives systemic and pulmonary venous blood and ejects that mixed venous blood into the new aorta that was fashioned from the aorta and original pulmonary artery trunk. Pulmonary blood flow occurs through the systemic-to-pulmonary artery shunt. Pulmonary venous return enters the left atrium and flows chiefly into the right atrium, and is mixed with systemic venous blood in the right ventricle.

Several postoperative complications can develop after the Norwood procedure. The same single ventricle circulation guidelines for care are to be followed as during the preoperative period, with targeted arterial oxygen saturation near 80%.

Optimizing systemic oxygen delivery remains crucial. Low cardiac output syndrome is common during the first 24 to 48 postoperative hours,⁹³⁵ and inotropic medications are required. There are many causes of low cardiac output syndrome after intervention for complex neonatal congenital heart disease using cardiopulmonary bypass. Causes of low cardiac output after the Norwood procedure can include residual anatomic lesions such as residual aortic arch obstruction.⁹³⁵ In addition, metabolic demands are increased postoperatively. It is important to note that neonates can develop shock despite the presence of an adequate arterial blood pressure, so close observation is needed to detect signs of poor perfusion (see Shock in Chapter 6).⁵⁶⁸

Inotropic medications are titrated carefully to support cardiac output and systemic perfusion while avoiding a significant increase in systemic vascular resistance that can lead to increased pulmonary blood flow with systemic hypoperfusion and the potential for decreased systemic oxygen delivery. Cardiovascular surgical centers have reported improved survival and neurologic outcome with the routine initiation of mechanical circulatory assistance in the operating room, at the conclusion of the Norwood procedure (see Chapter 7). This practice enables support of cardiovascular function to meet the increased postoperative oxygen requirements.⁸⁸⁷

Continuous close monitoring for adequacy of oxygen delivery versus consumption (demand) is needed and includes the typical monitoring for the complex postoperative patient with additional measurements. Oxygen delivery status can be continually or intermittently evaluated with the use of a catheter in the superior vena cava to measure central venous oxygen saturation (ScvO₂). Goal directed therapy targeting an ScvO₂ of 75% as an indicator of adequate systemic oxygen delivery versus demand has resulted in improved survival after HLHS palliation.^590,880 Continuous ScvO₂ monitoring has also decreased the incidence of sudden circulatory collapse in the postoperative period.⁸⁸² An ScvO₂ saturation below 45% may be associated with ischemic brain injury.⁵⁹⁰ The difference between the arterial and central venous oxygen saturation should also be assessed. A rising arterial venous oxygen saturation difference is a strong indicator of inadequate oxygen delivery, and a difference of 40% to 50% or more indicates severely low cardiac output.^384,935 A rising serum lactate also indicates inadequate systemic oxygen delivery.

Near infrared spectroscopy (NIRS) sensors over the forehead and kidney area on the lower back have been used to identify real-time trends in oxygenation of the brain and somatic tissue. After palliation for HLHS, cerebral saturations greater than 50% and somatic values greater than 60% have predicted better outcomes.⁵⁹⁰ Trends can be continually monitored and response to therapies assessed with good correlation between ScvO₂ saturations and NIRS saturations⁵⁹⁰ for additional details of postoperative care.

Postoperatively, excessive pulmonary blood flow is present if the arterial oxygen saturation is greater than 85% to 88%.⁹³⁵ Although both pulmonary and systemic vascular resistance should be evaluated and optimized, the primary determinant of the pulmonary to systemic flow ratio is the systemic vascular resistance. Successful treatment methods to improve systemic perfusion involve therapies to decrease systemic vascular resistance.

Afterload reduction enhances systemic blood flow and improves systemic oxygen delivery as more blood flows to the systemic circulation (and less to the pulmonary circulation). Milrinone is often used as both a vasodilator and positive inotropic agent (it is an inodilator).

Phenoxybenzamine has been used successfully for prolonged afterload reduction through alpha-adrenergic blockade both post cardiopulmonary bypass and in the postoperative period. Decreasing the systemic vascular resistance can lead to a more balanced single ventricle circulation with a more stable postoperative course and higher systemic oxygen delivery.³⁸² However, use of phenoxybenzamine can lead to sustained, excessive vasodilation and systemic hypoperfusion, requiring the initiation of catecholamines, including norepinephrine to optimize the systemic vascular resistance.⁵⁹¹ When inotropic support is required during the use of phenoxybenzamine with low mixed venous saturation and elevated systemic vascular resistance, epinephrine may be useful.⁵⁹¹ The arterial diastolic pressure should be maintained at greater than 30   mm Hg⁵⁹⁰ to maintain adequate coronary perfusion pressure.

Elevated systemic resistance and arterial blood pressure can result from a residual aortic arch obstruction. Clinical exam and echocardiography can be used to evaluate the reconstruction and detect any obstruction.

Monitor for bleeding. Bleeding may occur at any of the extensive suture lines along the aorta, because these suture lines are exposed to systemic pressure. Post-bypass coagulopathy can also contribute to bleeding. Anemia must be avoided and the hematocrit maintained at least 40% to support adequate oxygen-carrying capacity.

Titrate preload (with volume therapy) to maintain right atrial and right ventricular end-diastolic pressure, and support optimal cardiac output. Typically an initial CVP of 12 to 14   mm Hg is maintained.⁸⁸¹

Monitor for arrhythmias. Sinus tachycardia is the newborn's most efficient mechanism to raise cardiac output, and it is a nonspecific sign of distress. As a result, development of tachycardia should prompt careful assessment of the newborn's airway, oxygenation, ventilation, and perfusion. Malignant arrhythmias including bradycardia, loss of sinus rhythm, or supraventricular tachycardia are not well tolerated and can lead to severe low cardiac output.

Monitor for neurologic complications, including seizures. Closely monitor the neonate's serum ionized calcium and provide supplementation as needed. Absolutely no air can be allowed to enter any intravenous system because it may be shunted into the cerebral circulation, producing a cerebral air embolus (stroke).

Additional support. Elective delayed sternal closure may be used. Methods to minimize oxygen consumption include providing narcotics and sedation and maintenance of normothermia and a neutral thermal environment. For further information about management, see Single Functioning Ventricle, Overview of Management.

Monitor for signs of deterioration. A decrease in pulmonary blood flow may result from hypotension or low systemic vascular resistance. A narrowed shunt can produce increasing cyanosis and development of metabolic acidosis at any time postoperatively. The shunt murmur may change and the diastolic blood pressure may increase. If shunt occlusion is suspected, immediate therapy is indicated, including heparinization to minimize clot progression, elevation of the arterial blood pressure with epinephrine (to enhance shunt flow), and rapid echocardiogram. Elective heparinization to decrease the possibility of prosthetic shunt occlusion may begin after the risk of postoperative bleeding has passed, with eventual transition to anticoagulation with aspirin or low molecular weight heparin. Hypoxemia unresponsive to therapy requires initiation of cardiopulmonary support or ECMO.

The atrial septal defect may become obstructive, leading to pulmonary venous hypertension; this is particularly likely in those patients undergoing the hybrid stage 1 intervention. Signs may develop gradually and include increasing tachypnea, decreasing arterial oxygen saturation, cyanosis, oxygen dependence, poor feeding, and signs of pulmonary venous congestion on chest radiograph. The shunt murmur intensity may decrease.⁵¹⁴ The diagnosis can be made by echocardiography and treatment can include interventional cardiac catheterization to dilate the atrial septum, with possible stent implantation.

Right ventricular dysfunction and tricuspid regurgitation can develop requiring additional inotropic support and initiation of afterload reduction to reduce systemic vascular resistance (ventricular afterload). If treatment does not improve ventricular function, the infant may require an early second-stage bidirectional Glenn procedure, with tricuspid valve plication. Some infants are referred directly for cardiac transplantation.

Nutrition is initially provided parenterally. As the risk for systemic hypoperfusion subsides, enteral feeding begins, increasing gradually to 110 to 130   kcal/kg per day using fortified formula or breast milk.⁸⁸¹ Optimal nutrition is critical for growth after palliation, but may be complicated by the development of poor oral feeding, impaired circulation with mesenteric hypoperfusion, necrotizing enterocolitis, or presence of postoperative recurrent laryngeal nerve injury.^591,935 Necrotizing enterocolitis increases the risk for death.⁴¹² Malnutrition is common,⁴⁶¹ with formula intolerance and prolonged feedings associated with impaired somatic growth until after the second stage surgical procedure.^645,825

Nasogastric or gastrostomy tube feedings may be required. Normal rate of weight gain in infants following Norwood Stage I surgery have been achieved using calorie enhanced formulas with home surveillance monitoring of nutrition and weight gains.⁸⁹¹ Management of these potential challenges is reviewed in the section, Common Clinical Conditions, Altered Nutrition and Potential Gastrointestinal Complications.

Re-coarctations in the aorta are reported in 11% to 37%¹⁷⁰ of patients, and reintervention is most commonly required in the first 6 months after the Norwood procedure.³⁵ Clinical symptoms include decreased femoral pulses and hypertension in the upper extremities. A gradient of 10   mm Hg or more between the blood pressures in the upper and lower extremities (with the higher pressure in the upper extremities) requires assessment by echocardiography. Re-coarctation also leads to high arterial saturation because the obstruction in the aorta increases systemic vascular resistance, so it increases pulmonary blood flow.⁹³⁵ The increased pulmonary blood flow can lead to even further pressure and volume load for the right ventricle, resulting in poor ventricular function and signs of heart failure. Re-coarctation is treated successfully by balloon dilation during interventional cardiac catheterization and possible aortic stent implantation or re-operation.¹⁷⁰

Late complications include progressive congestive heart failure, pulmonary artery distortion, pulmonary vein stenosis and sudden death. The systemic to pulmonary artery shunt (Blalock-Taussig or other) or RV to PA conduit provide the only source for pulmonary blood flow and can progressively narrow at any time, causing increased cyanosis and hypoxemia.

Approximately 5% to 16%^502,812 of immediate survivors of stage 1 Norwood die in the interval between stage 1 and the stage 2 procedures. Multiple risk factors for interstage death include postoperative arrhythmias, decreased ventricular function at discharge,^502,812 and residual or recurrent lesions.

The limited cardiac reserve and chronic hypoxemia and cyanosis in patients with palliated HLHS reduce their tolerance of dehydration, fever, increased metabolic demands, serious respiratory illness, or advancing heart failure. Use of home monitoring protocols have improved interstage survival for surgical^316-318,502 and hybrid stage I²⁹³ palliated HLHS by providing extensive parental education and combinations of home oxygen saturation monitoring, daily weights with digital scales, surveillance for intercurrent illness, and monitoring of oral intake.^318,881,891 National, multicenter quality improvement collaboratives are underway by the Joint Council on Congenital Heart Disease to reduce clinical practice variations and improve long-term outcomes for children with HLHS.⁵⁰²

The Sano Procedure

This first stage intervention for HLHS is identical to the Norwood procedure except that the source for pulmonary blood flow is a 5- to 6-mm graft sewn between the right ventricle and the main pulmonary artery.⁸⁸¹ Insertion of this graft requires a small right ventriculotomy (Fig. 8-63, B).

The described potential advantage of the Sano procedure includes the fact that the right ventricle to pulmonary artery connection avoids the low diastolic pressure that results from the aortic runoff with a systemic to pulmonary artery shunt.⁵¹⁴ The aortic diastolic blood pressure has been found to be higher after the Sano procedure, but there is more variability in pulmonary blood flow.^208,316

Potential postoperative complications include the development of conduit stenosis that produces cyanosis and hypoxemia and requires intervention.⁴⁹⁶ Oxygen therapy should be used for these infants with cyanosis because their shunt to the pulmonary system only occurs during systole, rather than during systole and diastole as following a systemic to pulmonary artery shunt.

Reports have not documented any difference between the Norwood and the Sano procedure when freedom from cardiac transplantation after 12 months⁶⁷⁰ and survival are evaluated.^{53,54,316,317} It may take years to determine the effects of the ventriculotomy and right ventricular to pulmonary artery shunt on right ventricular function and the pulmonary vascular bed.⁵³