Anesthesia Care Provider

Anesthesia care should be provided by an experienced individual who is familiar with children with CHD, the planned operative procedure, and the surgeon’s usual approach. The most important factor that an anesthesiologist can offer a child with CHD is a comprehensive understanding of the anatomic abnormalities, pathophysiology of the cardiac malformation, and how this may be affected by the anesthetic and surgical procedure. Familiarity with the most likely residua and sequelae is essential.¹⁸ Adequate communication among all physicians involved enhances the likelihood of the best possible outcome.

Premedication

The use of premedication to provide sedation and anxiolysis is routine before most surgical procedures because some degree of fear or anxiety is expected. This facilitates parental separation, entry into the operating room, placement of monitors, and induction of anesthesia. The cardiorespiratory effects of premedication in children may be influenced by the underlying systemic disease.^48–52

Commonly used premedications include oral or intravenous benzodiazepines, opioids, and small amounts of hypnotic agents. Drugs such as barbiturates and ketamine are occasionally used. Alternative routes for premedication include intramuscular, intranasal, and rectal methods. Children with hemodynamic decompensation may require little or no premedication. Caution should also be exercised for those with a history of cardiovascular pathology associated with significant increases in pulmonary artery pressure or pulmonary arteriolar resistance because hypoventilation and hypoxemia may be detrimental. Conversely, children susceptible to hypercyanotic episodes or those with catecholamine-induced arrhythmias may benefit from heavy premedication. In selected children (e.g., infants and children with cyanotic heart disease), oxygen saturation monitoring after premedication and the administration of supplemental oxygen is recommended.⁵⁰

Intravenous Access

Secure intravenous access is mandatory for administration of fluids and medications during anesthesia care. In most children with CHD, intravenous access is established after an inhalational induction. In those considered at great risk, such as children with severe outflow tract obstruction, moderate to severe cardiac dysfunction, pulmonary hypertension, or potential for hemodynamic compromise, consideration should be given for placement of intravenous access before induction of anesthesia or very early in the induction. The size of the intravenous catheter should be determined by the anticipated fluid requirements. If peripheral access is poor, central venous access may be necessary, particularly if there is potential for large intravascular volume shifts and to allow monitoring of central venous pressure. Placement of a central venous catheter may be assisted by audio Doppler or two-dimensional ultrasound guidance (see Chapter 48). In the small infant with single-ventricle physiology, central venous cannulation with catheter placement in the superior vena cava may be undesirable in view of concerns about potential vascular complications that may affect pulmonary blood flow or subsequent surgical palliation. In these children, a small catheter or alternative approach (e.g., femoral venous access) should be considered. In children with an existent or potential right-to-left shunt, all air must be removed from intravenous infusion tubing. Air filters may be difficult to use in the operating room because they may restrict the rate at which intravenous fluids or blood may be administered in emergency situations. They may be more useful in the preoperative and postoperative periods.

Emergency Drugs

In view of the potential for hemodynamic instability in some children with CHD that may occur under any circumstance and at any time, drugs for emergency situations should be prepared or immediately available to the anesthesiologist providing care.

Arterial Blood Pressure Assessment

Basic blood pressure monitoring begins with pulse palpation. An automated blood pressure cuff is used in most children. The selection of monitoring site may be influenced by vascular anomalies (e.g., aortic arch pathology, aberrant origin and course of aortic arch vessels) or prior surgical interventions (e.g., Blalock-Taussig shunt, arterial cutdown). Direct systemic blood pressure monitoring by an indwelling arterial catheter may be necessary for beat-to-beat assessment and for blood gas analysis. In children, this is usually accomplished after induction of anesthesia. Arterial cannulation can be achieved percutaneously in most circumstances with a reduced risk of complications (see Chapter 48). Use of the radial arteries is preferable, particularly in the neonate, to minimize catheter-related vascular problems. Ultrasound guidance with Doppler or two-dimensional imaging may facilitate cannulation. The decision regarding the need for invasive monitoring is largely based on the child’s clinical condition and nature of the surgical procedure.

Electrocardiography

An ECG is used to monitor heart rate, cardiac rhythm, and ST-segment analysis. One or multiple leads typically are displayed. Most systems use two leads: standard lead II for arrhythmia monitoring plus inferior ischemia detection and precordial lead V₅ for lateral ischemia detection. Arrhythmias may occur as a result of hypoxia, electrolyte imbalances, acid-base abnormalities, intravascular or intracardiac catheters, and surgical manipulations near or around the thorax. Ischemia may be evident on direct examination of the ECG or ST-segment analysis.⁵³ Although in the adult population this is associated with worsened outcome, the implication for children is unknown.^54,55

Pulse Oximetry

Placement of an oximeter probe is well tolerated, even by uncooperative children, and it is typically one of the earliest monitors applied during induction of anesthesia. Monitoring arterial oxygen saturation is particularly useful in infants, cyanotic children, and those with complex anatomy or significant hemodynamic compromise. In addition to providing continuous assessment of oxygen-hemoglobin saturation and heart rate, the pulse oximeter waveform may indicate the adequacy of peripheral perfusion and cardiac output.^56,57 Other parameters that may be reflected by the Spo₂ include intracardiac or great artery–level shunting and pulmonary blood flow.

Capnography

Capnography can confirm proper endotracheal tube placement, help to assess the adequacy of ventilation, and aid recognition of pathologic conditions such as bronchospasm, airway obstruction, and malignant hyperthermia. In spontaneously breathing, sedated children receiving supplemental oxygen through a nasal cannula, capnography monitors the end-tidal or exhaled carbon dioxide (Petco₂) concentration. A prospective, observational study in children undergoing cardiac catheterization with sedation administered by nonanesthesiologists found that monitored Petco₂ values provided a reasonable estimate of arterial blood CO₂ values.⁵⁸ Although the absolute value for Petco₂ may not be as reliable as in the presence of an endotracheal tube, the capnograph waveform confirms the presence or absence of respirations and air exchange. End-tidal CO₂ monitoring also provides a gross index of pulmonary blood flow. In children with cyanotic heart disease, Petco₂ values may underestimate arterial carbon dioxide tension (Paco₂) measurements due to altered pulmonary blood flow and ventilation/perfusion mismatch.^59,60

Temperature Monitoring

Temperature should be routinely monitored during most procedures. Although temperature swings are usually not profound, some children, particularly small neonates, may become significantly hypothermic because of the large body surface area to body weight ratio and decreased amount of subcutaneous tissue. This may influence oxygen delivery (i.e., increased oxygen consumption) and emergence from anesthesia, cause detrimental changes in hemodynamics, and affect hemostasis.

Urinary Output Measurements

The production of urine is a useful index of the adequacy of renal perfusion and cardiac output. Urine output is usually monitored during cases involving major fluid shifts or blood loss or when the surgical procedure is expected to be prolonged. No specific value for urine output is necessarily predictive of good renal function in the postoperative period.

Transesophageal Echocardiography

Numerous publications have documented the utility of transesophageal echocardiography as a monitoring device in high-risk adults undergoing noncardiac procedures.^61–72 Sporadic reports have demonstrated the utility of this imaging approach in children undergoing noncardiac surgery.^73–78 However, the contribution or application of this modality in the pediatric age group in this particular setting has not been well defined and requires further investigation.

Anesthesia Technique

General anesthesia has the advantages of wide acceptance, ease of application, and relative certainty of effect. It is the appropriate choice for most children undergoing noncardiac surgery. Disadvantages include a greater potential for wide fluctuations in the hemodynamics and a prolonged recovery period. The intravenous route allows for rapid induction of anesthesia. If intravenous access is not available, inhalational induction may be performed. Inhalational anesthetics dilate vascular beds and reduce sympathetic responsiveness. These are desirable goals for most children, even those with heart disease, because adequate myocardial function and a reactive sympathetic nervous system are usual. However, children with ventricular dysfunction may require an increased resting sympathetic tone to maintain systemic perfusion. Potent inhalational agents in this setting may further impair myocardial function, decrease sympathetic tone, and potentially cause cardiovascular decompensation. These children and others with a relatively fixed cardiac output may require a technique that combines several medications (i.e., balanced technique) to achieve anesthesia while minimizing the risk of hemodynamic compromise. A potent opioid, amnestic agent, and muscle relaxant technique minimizes myocardial depression and tends to leave sympathetic responsiveness intact while providing analgesia, amnesia, and immobility.

Regional anesthesia has been safe and effective in children with CHD (see Chapters 41 and 42).^76–79 Advantages of regional anesthesia, such as epidural and spinal techniques, include an effect largely limited to the surgical site, decreased number of systemic medications, a potentially brief recovery period, and usually a more pleasant experience for the child. Use of these techniques, however, may not always be effective. Regional anesthesia retains the potential for hemodynamic compromise, particularly in hypovolemic children or those with a fixed cardiac output. It is also contraindicated in those with coagulation defects. The administration of agents such as local anesthetics, opioids, or other adjuvants (e.g., clonidine) into the caudal space may attenuate the sympathetic outflow associated with surgical manipulation and noxious stimuli and facilitate postoperative pain management.

The choice of technique affects termination of the anesthesia and emergence. Anesthesia performed with fewer agents is inherently simpler and usually easier and more predictable to terminate. The availability of ultra-short-acting opioids (e.g., remifentanil) and other agents (e.g., dexmedetomidine) has avoided the need for postoperative ventilation solely related to residual effects of depressant drugs. Ventricular function and the presence of intracardiac shunts can significantly affect uptake and distribution of inhalational anesthetics and the kinetics of intravenous medications (see Chapter 6).

Inhalational Agents

The use of inhalational anesthetics has been at the forefront of pediatric anesthesia practice for many years.^80,81 Sevoflurane was introduced in the mid-1990s, replacing halothane for induction of anesthesia in many centers. A study on the safety and efficacy of inhaled agents in infants and children with CHD during cardiac surgery demonstrated twice as many episodes of hypotension, moderate bradycardia, and emergent drug use in those who received halothane compared with those who received sevoflurane.⁸² These data and those from other studies that demonstrated the potential benefits of sevoflurane on hemodynamic stability and minimal impact on myocardial performance led to sevoflurane becoming the preferred anesthetic agent for children, particularly those with heart disease.^83–88 Nonetheless, in some jurisdictions and under some conditions, halothane may remain the primary anesthetic for children.

Intravenous Agents

Propofol is one of the most frequently used medications for intravenous sedation and general anesthesia. It has been used in children with CHD in numerous settings.^89–92 The hemodynamic effects of propofol have been investigated in children with normal hearts and in those with cardiovascular disease. An echocardiographic study in infants with normal hearts undergoing elective surgery demonstrated that propofol did not alter heart rate, shortening fraction, rate-corrected velocity of circumferential fiber shortening, or cardiac index after intravenous induction.⁹³ However, this medication decreased arterial blood pressure to a greater extent than thiopental, an effect attributed to a reduction in afterload. A comparison of propofol and ketamine during cardiac catheterization found that propofol caused a transient decrease in mean arterial pressure and mild arterial oxygen desaturation in some children.⁹⁴ In view of the significantly faster recovery, it was concluded that propofol was a practical alternative to ketamine for elective cardiac catheterization in children.

Another investigation in 30 children with CHD undergoing cardiac catheterization demonstrated significant decreases in mean arterial blood pressure and systemic vascular resistance during propofol administration.⁸⁹ No changes in heart rate, mean pulmonary artery pressure, or pulmonary vascular resistance were observed. In children with intracardiac shunts, the net result of propofol was a significant increase in the right-to-left shunt, a decrease in the left-to-right shunt, and decreased pulmonary-to-systemic blood flow ratio, resulting in a statistically significant decrease in the Pao₂ and arterial oxygen saturation (Sao₂), as well as reversal of the shunt direction from left-to-right to right-to-left in two patients. It was also shown that propofol could lead to further hemoglobin desaturation in children with cyanotic heart disease.

The effects of propofol have been examined in children undergoing electrophysiologic testing and radiofrequency catheter ablation for tachyarrhythmias. The drug has no significant effect on sinoatrial or atrioventricular node function or accessory pathway conduction in Wolff-Parkinson-White syndrome.^95,96 However, a study documented that ectopic atrial tachycardia may be suppressed during propofol administration in children.⁹⁷

Collectively, these data suggest that the judicious use of propofol may be a reasonable option in children with adequate cardiovascular reserve who can tolerate mild decreases in myocardial contractility and heart rate and mild to moderate decreases in systemic vascular resistance. The effects of propofol on the direction and magnitude of intracardiac shunts may be an important consideration in children with cyanotic heart disease and may influence the hemodynamic assessment of those undergoing evaluation of pulmonary-to-systemic blood flow ratios in the cardiac catheterization laboratory.

Thiopental, a rapid-acting barbiturate, was used for many years for induction of anesthesia. Several investigations have documented the cardiovascular responses to this agent in the pediatric age group. In children with normal hearts, the cardiac index remains unchanged, although the shortening fraction decreases and alterations in load-independent parameters of contractility occur.⁹³ The myocardial depressant properties of barbiturates are well established, as are its effects on venodilation and blood pooling in the periphery. These data suggest that a subset of children who receive thiopental may be at risk for hemodynamic instability. It has been suggested that thiopental should be used with caution, particularly in those with limited reserve or increased sympathetic tone. Thiopental is not available for use in the United States.

Etomidate, a carboxylated imidazole derivative, has anesthetic and amnestic properties but no analgesic effects. This agent demonstrates favorable qualities over other intravenous drugs due to its lack of effect on hemodynamics.^98,99 This, combined with laboratory and clinical data that support minimal effects on myocardial contractility, makes this drug a particularly desirable agent in critically ill children and in those with limited cardiovascular reserve.¹⁰⁰ Despite these benefits, several undesirable adverse effects are associated with etomidate, including pain on intravenous administration, myoclonic movements that may mimic seizure activity, and inhibition of adrenal steroid synthesis perioperatively.^101,102 Although used primarily as an induction agent, etomidate has been administered for sedation of children during cardiac catheterization and in other settings.^103–105 A concentrated form of this medication is available in Europe but not in the United States.

Ketamine is a dissociative anesthetic agent administered by the intravenous, intramuscular, and oral routes. In view of its sympathomimetic effects that result in an increased heart rate, blood pressure, and cardiac output, this drug has been widely used in children with heart disease, particularly in younger children. The effects of this agent on systemic vascular resistance make it a suitable choice in children with right-to-left shunts because pulmonary blood flow is enhanced. This contrasts with inhalational agents, which by causing systemic vasodilation may decrease pulmonary blood flow in the presence of an intracardiac communication and potentially worsen the degree of cyanosis. In clinical use, however, oxygen saturation typically increases with both agents. Additional favorable properties include intense analgesia at subanesthetic doses and a lack of respiratory depressant effects.

Several investigations have addressed the concern of potential detrimental changes in pulmonary vascular tone resulting from ketamine although no significant effects have been reported on pulmonary arterial pressures and pulmonary vascular resistance at the usual clinical doses.^106–109 Regarding its effect on myocardial performance, in-vitro investigations have shown a direct myocardial depressant effect in animal species and the failing adult human heart. This is considered to be the result of inhibition of L-type voltage-dependent calcium channels in the sarcolemmal membrane and may be a consideration in critically ill infants with severely impaired cardiac reserves. Additional undesirable effects of ketamine include emergence reactions, excessive salivation, vomiting, and increased intracranial pressure.

Dexmedetomidine is a selective α₂-adrenergic agonist agent being increasing used in the pediatric age group. Compared with clonidine, the drug exhibits greater specificity for the α₂-adrenergic receptor over the α₁-adrenergic receptor. Favorable effects of the drug include sedation, anxiolysis, and analgesia. This medication provides hemodynamic stability, although adverse effects have been reported, including bradycardia, hypertension, and hypotension. A study of the hemodynamic effects in children undergoing dexmedetomidine sedation for radiologic imaging demonstrated modest decreases in heart rate and blood pressure. These changes in response to moderate doses were independent of age, required no pharmacologic interventions, and did not result in any adverse events; however, high dose dexmedetomidine can be associated with significant bradycardia.^110,110a In addition, treatment of dexmedetomidine-induced bradycardia with glycopyrrolate (5 μg/kg) has been associated with severe persistent hypertension.^110b

Dexmedetomidine is used as a premedication agent, during diagnostic studies and procedural sedation, to reduce emergence delirium, in the treatment of symptoms associated with opioid withdrawal, and as an adjuvant agent in the operating room and postoperative settings.¹¹¹ In children with CHD, its benefits have been reported during monitored anesthesia care, diagnostic and interventional cardiac catheterization, intraoperative sedation, after cardiac and thoracic surgery, as a primary agent during invasive procedures, and in the treatment of perioperative atrial and junctional tachyarrhythmias.^112–119 This medication has also been used in children with pulmonary hypertension with good results.^120,121

The effects of dexmedetomidine on cardiac electrophysiology have been examined in children; the drug significantly depresses sinus and atrioventricular nodal function.¹²² Other findings included a reduction in the heart rate and increases in arterial blood pressure. Hammer and colleagues concluded that this medication should be considered undesirable for electrophysiologic studies and that it could be associated with adverse effects in patients at risk for bradycardia or atrioventricular block.¹²² In contrast, another study concluded that dexmedetomidine was not associated with any significant or any atypical ECG interval abnormalities, except for a trend toward a decrease in heart rate in children with CHD.¹²³ Until additional data are available, it may be prudent to exercise caution when considering the use of dexmedetomidine in children with conduction abnormalities.

Although the experience suggests an overall safety profile in children with CHD, fragile patients may not tolerate the heart rate and blood pressure fluctuations associated with dexmedetomidine administration. Significant adverse effects have been described that include severe bradycardia progressing to asystole.¹²⁴

Opioids and benzodiazepines are widely used medications in pediatric anesthesia practice. Opioids attenuate the neuroendocrine stress response associated with anesthesia and surgery.^125,126 After repair of CHD, these medications have been shown to blunt the stress response in the pulmonary circulation elicited by airway manipulations.¹²⁷ Morphine administration may be associated with histamine release and hypotension. The synthetic opioids are devoid of these effects and provide excellent hemodynamic stability with minimal changes in heart rate and blood pressure in children with CHD.¹²⁸ The primary concern about opioid administration is their central respiratory depressant effects because their primary cardiovascular manifestations are minimal. Benzodiazepines provide sedation and amnesia during the perioperative period. Midazolam administration may allow a reduction in the inspired concentration of inhalational anesthetic agents, which is a desirable feature in children with labile hemodynamics or in those considered at great risk for the myocardial depressant properties of inhalational anesthetics. Studies of the effects of benzodiazepines in children with CHD are limited.¹²⁹

Neuromuscular blocking drugs facilitate endotracheal intubation and prevent reflex movement during surgery if the anesthetics alone are insufficient. All inhalational anesthetics potentiate the effects of nondepolarizing muscle relaxants. These medications have various onsets and durations of action and diverse hemodynamic effects. The cardiovascular and autonomic effects of muscle relaxants have been characterized mainly in adults with acquired cardiovascular disease^130–133 (see also Chapter 6). Drug selection is based on the need to facilitate endotracheal intubation and surgical relaxation, hemodynamic side effects, and the anticipated duration of surgery.

Anatomy and Pathophysiology

Defects in the interatrial septum, or atrial septal defects (ASDs) (see Fig. 15-1), are among the most common congenital cardiac anomalies (30% to 40% of CHD) in childhood. ASDs occur in 1 of 1500 live births. Based on their location, several types of defects have been identified:

An atrial communication allows mixing of the pulmonary and systemic venous returns. A left-to-right shunt allows pulmonary venous blood to enter the right atrium. The magnitude of shunting correlates with the size of the defect, relative ventricular compliances, and pulmonary artery pressures. A clinically significant defect results in right-sided volume overload. A pulmonary-to-systemic blood flow ratio that exceeds 2 to 1 and the potential detrimental effects of chronic right ventricular volume overload are indications for intervention.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Surgical closure of secundum ASDs in childhood provides excellent results, almost normal long-term survival, and negligible mortality.^186–189 Normal ventricular function should be anticipated after repair of these defects. Rarely, children may demonstrate persistent right ventricular dilation and abnormal ventricular septal motion, but this may not be associated with a functional deficit.¹⁹⁰ Atrial arrhythmias and ventricular dysfunction may occur after late repairs as a result of chronic volume overload. Delayed defect closure may be a risk factor for the rare development of pulmonary hypertension or pulmonary vascular disease later in life due to the abnormally increased pulmonary blood flow.¹⁹¹

Transcatheter approaches are an alternative to surgery for closure of secundum ASDs in selected children, with excellent success rates for relatively small communications (see Chapter 20).^192–194 Complications are rare and may be associated with the intervention or occur at a later time.¹⁹⁵

After surgical closure of ostium primum defects, morbidity manifests primarily as mitral valve dysfunction (e.g., mitral regurgitation) and left ventricular outflow tract obstruction.^196–200 In most children, outcomes are favorable after repair at an early age. After closure of sinus venosus defects, potential problems include pulmonary venous obstruction and loss of sinus node function.^201–203 Repair of coronary sinus defects consists of patch closure of the atrial communication at the mouth of the coronary sinus. This leaves a small right-to-left shunt as deoxygenated blood from the coronary sinus continues to drain directly into the left atrium.²⁰⁴ If a connection between the left superior vena cava and left atrial connection persists, a variety of surgical approaches may allow redirection of the abnormal systemic venous return. For most children with atrial communications, significant postoperative sequelae are unlikely to occur, and outcomes are generally good. In most cases, no major repercussion from the repaired defect should be expected for future anesthesia care.

Anatomy and Pathophysiology

Ventricular septal defects (VSDs) are the most common of all congenital cardiac anomalies, comprising 30% to 60% of CHD (excluding a bicuspid aortic valve) and occurring in 2 to 6 cases per 1000 live births (see Fig. 15-2, A).²⁰⁵ VSDs can be found in isolation or in the context of other structural malformations. Large defects require early attention for symptoms related to congestive heart failure or pulmonary hypertension. VSDs have a greater rate of spontaneous closure in childhood—about 75% closure by 6 months to 1 year.^206,207

Various classification schemes have been proposed for VSDs based on their anatomic location, size, restrictive or nonrestrictive nature, and hemodynamic significance.^208,209 The following scheme categorizes defects as four major morphologic types based on their anatomic location. In some cases, the boundaries of a defect may extend beyond the margin of a particular region of the ventricular septum into another.

The characterization of VSDs based on their size and likely hemodynamic significance is extremely useful when caring for children who have not undergone repair:

The physiologic effects of the communications that allow shunting at the ventricular level are determined by the size of the defect, amount of shunting, and relative pulmonary and systemic vascular resistances. Physiologically, isolated defects may be classified as pressure restrictive (i.e., right ventricular pressure less than left ventricular pressure) or nonrestrictive defects (i.e., equal or near-equal ventricular pressures). Restrictive defects often imply limited flow through the communication. This is frequently the case with small VSDs in which the pressure gradient determines the magnitude of shunting. If the defect is large and nonrestrictive, the amount of flow across the orifice depends on the ratio between the pulmonary and systemic vascular resistances. Reduced pulmonary vascular resistance in the context of a nonrestrictive VSD leads to a large left-to-right shunt, increased pulmonary blood flow, pulmonary hypertension, and increased myocardial work, as evidenced by a volume load to the left heart. Nonrestrictive left-to-right shunts result in pulmonary congestion and abnormal respiratory mechanics characterized by decreased lung compliance, increased airway resistance, and increased work of breathing. Increases in alveolar dead space and alveolar to arterial oxygen gradients are to be expected, as well as increases in minute ventilation and potential oxygen requirements.

An important perioperative consideration for children with defects associated with increased pulmonary blood flow is the pulmonary steal phenomenon, which may result from decreases in pulmonary vascular resistance as left-to-right shunting increases at the expense of systemic blood flow. This requires an appraisal of the factors that may influence pulmonary vascular tone to prevent compromises in systemic perfusion.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Surgical closure of VSDs early in childhood results in excellent outcomes, usually without sequelae.^211–213 Surgical intervention in older children may lead to reduced left ventricular function and increased left ventricular mass.²¹⁴ Small communications, although regarded as hemodynamically insignificant, may not be benign. This has led to ongoing controversy regarding the need for definitive intervention. Several young children with moderate defects remain relatively asymptomatic until later life, when gradual decompensation may ensue related to increased end-diastolic volume and ventricular dilation. In these children, defect closure is indicated if the magnitude of the increase in pulmonary vascular resistance is not prohibitive, which is rarely the case. Severely increased pulmonary vascular resistance (more than 7 Wood units per m²) augments the risks associated with the surgical procedure, and it may not return to normal levels after the intervention.²¹⁵ If postoperative pulmonary hypertension persists, the prognosis is unfavorable, with the potential for eventual right ventricular failure.²¹⁶ Development of Eisenmenger syndrome (i.e., pulmonary vascular obstructive disease and reversal in the direction of the ventricular level shunt) has become rare due to early recognition and management of children with these defects.

Postoperative sequelae after VSD closure include residual or, less commonly, recurrent defects, arrhythmias or other conduction system disturbances, subaortic obstruction, and valvar regurgitation.²¹⁷ Although surgical closure is considered the gold standard, transcatheter closure by device placement is feasible for selected muscular and postoperative residual defects defects.^218,219 Early data demonstrate excellent closure rates with reduced rates of complications²²⁰ (see also Chapter 20). Limited experience and follow-up are available with catheter-based interventions for closure of membranous communications.^221–224

Anatomy and Pathophysiology

Atrioventricular septal defects (AVSDs), also known as atrioventricular canal defects or endocardial cushion defects, result in deficiency of the atrioventricular septum and altered formation of the atrioventricular valves (see Fig. 15-2, B).²²⁵ These rare defects comprise only 4% of CHD cases, although they have a prevalence among patients with Down syndrome of 25%. AVSDs can be classified as follows:

Complete defects are associated with nonrestrictive intracardiac shunting, excessive pulmonary blood flow, congestive heart failure, and systemic right ventricular and pulmonary artery systolic pressures. Without intervention, they may lead to early pulmonary vascular changes. The severity of atrioventricular valve regurgitation also influences the clinical presentation. Partial AVSDs are less likely to be associated with pulmonary overcirculation of sufficient severity to cause significant heart failure symptoms.

Perioperative concerns similar to those previously described in children with nonrestrictive ventricular communications are applicable, but they also are magnified in those with unrepaired complete defects. In children with increased pulmonary vascular resistance and a reactive pulmonary bed, issues such as airway manipulation, light anesthesia, hypoxemia, or hypercarbia may lead to an increase in pulmonary artery pressures to suprasystemic levels.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

The surgical approach for complete defects has evolved from a two-stage intervention (i.e., initial pulmonary artery banding to limit pulmonary blood flow and subsequent complete repair) to a single strategy of primary repair in infancy. For a complete defect, this consists of partition of the common atrioventricular valve, patch closure of the intracardiac communications, and closure of the left-sided valvar cleft. The long-term outlook after repair is generally good, with a small likelihood of residual dysfunction.^226–228

Postoperative problems include left atrioventricular valve regurgitation or stenosis, residual intracardiac shunting, atrioventricular block, and subaortic obstruction.^199,200 Occasionally, pulmonary hypertension persists or develops postoperatively; it is more likely in children with Down syndrome. In the remote past, uncorrected defects resulted in Eisenmenger physiology, accounting for significant late morbidity and early death.²²⁹ Considerations for noncardiac surgery in children after surgical repair include the residual effects of the prior ventricular volume load, the status of the atrioventricular valve, and patency of the left ventricular outflow tract.

Anatomy and Pathophysiology

Pulmonary valve stenosis is the most common pathology among children with right ventricular outflow tract obstruction.²³⁰ Other lesions that result in obstruction to pulmonary blood flow include infundibular stenosis, muscle bundles within the body of the right ventricle, and anatomic alterations in the pulmonary arterial bed. These pathologies may be found in isolation or occur as part of more complex malformations. Such is the case in tetralogy of Fallot (discussed later), in which multiple anatomic levels of right ventricular outflow tract obstruction are typically encountered (see Fig. 15-5).

Although isolated valvar pulmonary stenosis is congenital in most cases, the disease can be progressive. In the uncomplicated or pure variant, an interatrial communication in the form of a PFO or secundum ASD may be identified, and the ventricular septum is intact.

The magnitude of right ventricular outflow tract obstruction is directly related to the degree of valvar narrowing. This imposes an afterload burden on the right ventricle, resulting in right ventricular hypertrophy, decreased ventricular diastolic compliance, and tricuspid regurgitation. In severe cases, the systolic pressure generated by the right ventricle may exceed that of the left ventricle. Cyanosis in children with pulmonary stenosis usually reflects right-to-left interatrial shunting and reduced pulmonary blood flow. It may be associated with severe right ventricular hypertrophy, fibrosis, or ventricular dysfunction.

Most children with mild to moderate valvar stenosis remain asymptomatic, and the pathology is relatively well tolerated chronically. Severe obstruction in older children is frequently associated with limited exercise tolerance. Subendocardial ischemia is a potential risk in children with a hypertensive, hypertrophied right ventricle. Management is directed at maintaining coronary perfusion and an inotropic state of the myocardium.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Percutaneous balloon valvuloplasty is very effective and currently considered the treatment of choice for valvar pulmonary stenosis, replacing surgical valvotomy in most cases. Outcomes are excellent, and long-term issues are rare.^231–233 Dysplastic valves have a less favorable response to catheter-based interventions, and affected children are more likely to require surgery. Indications for repeat intervention include residual right ventricular outflow tract obstruction and progressive pulmonary regurgitation.²³⁴

In children with significant right ventricular hypertrophy undergoing noncardiac surgery, adequate ventricular preload and optimization of volume status are recommended. Further increases in right ventricular afterload should be avoided in those with residual or recurrent outflow tract obstruction.

Anatomy and Pathophysiology

Left ventricular outflow tract obstruction may occur at the level of the aortic valve, supravalvar region, or subvalvar region. It may take place in isolation or as part of complex cardiovascular disease. A bicuspid aortic valve is the most common of all congenital cardiac anomalies, occurring in approximately 2% of the general population.²³⁵ Although it may not necessarily imply valvar stenosis, this abnormality can be associated with progressive obstruction or regurgitation. A bicuspid valve may be found in asymptomatic individuals or within the context of severe left heart obstruction. The prevalence of coexistent defects is relatively large and frequently includes patent ductus arteriosus, VSD, aortic coarctation, and other abnormalities of the aorta and its branches.

Infants with critical aortic stenosis and those with severe obstruction require early intervention in view of ductal dependency, heart failure symptoms, and the degree of ventricular dysfunction. Older children with moderate to severe obstruction may present with decreased exercise tolerance, syncopal episodes, or myocardial ischemia. Impedance to left ventricular ejection in aortic stenosis results in elevation of left ventricular systolic pressure and increased myocardial force. Ventricular hypertrophy is the compensatory response to the increased afterload. Contractile function is normal to increased, but diastolic impairment may occur.

In supravalvar aortic stenosis, the narrowing typically occurs at the sinotubular junction. The coronary arteries arise proximal to the area of obstruction and are subjected to increased systolic pressures equal to that of the left ventricle. The arteriopathy found in many of these children may involve the origin of the coronary arteries or other systemic and pulmonary vessels.²³⁶ This malformation may occur as part of Williams syndrome, which is characterized by elfin facies, mental retardation, idiopathic hypercalcemia, and other features. Several reports have described unexpected complications in these children, including death during anesthesia care.^237–240 Affected children should be considered at increased risk for any procedure.

Subvalvar aortic stenosis may take a variety of forms, including a discrete fibromuscular ridge or membrane, complex tunnel-like obstruction, or hypertrophy of the interventricular septum (i.e., hypertrophic cardiomyopathy). The association of left ventricular obstructive lesions such as a bicuspid aortic valve, subaortic stenosis, aortic coarctation, and mitral valve inflow obstruction (e.g., parachute mitral valve, supravalvar mitral ring) is referred to as the Shone complex.

Hypoplastic left heart syndrome (HLHS) represents an extreme form of left ventricular outflow tract obstruction (see Fig. 15-10). It encompasses a constellation of malformations, affecting left-sided cardiac structures (e.g., mitral and aortic valves, aorta, arch) (see “Single Ventricle”).

Common features of the anomalies that result in obstruction to left ventricular output include a pressure gradient across the involved region, increased left ventricular systolic pressure, increased myocardial force, and left ventricular wall stress. With chronic obstruction, the hypertrophied myocardium is at risk for subendocardial ischemia as a consequence of an imbalance in the ratio of myocardial oxygen supply and demand. Factors such as increases in left ventricular afterload, inadequate hypertrophic remodeling, and decreases in myocardial systolic or diastolic performance may compromise stroke volume and contribute to cardiac dysfunction and heart failure in this setting.²⁴¹ These issues are relevant for children with more than mild obstruction, and they influence anesthesia care during noncardiac surgery or other interventions.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Individuals with a bicuspid aortic valve may remain asymptomatic for many years but are at risk for aortic stenosis or regurgitation and concomitant hemodynamic alterations. Some of those requiring surgical intervention during childhood undergo reoperation for recurrent stenosis or progressive regurgitation in the next 25 years.²⁴² Percutaneous balloon valvuloplasty may be a treatment option for critical or severe aortic valve disease.²⁴³ Surgical alternatives include valvotomy, mechanical or bioprosthetic valve placement, and root replacement with homograft or autograft material. In the Ross operation, the native, diseased root is replaced by a pulmonary autograft, and an extracardiac conduit establishes continuity between the right ventricle and main pulmonary artery.²⁴⁴ Repeat intervention for eventual failure of the right ventricular conduit is anticipated in these children.²⁴⁵ In addition to surveillance of the right ventricular outflow tract, monitoring for aortic root dilation and concomitant regurgitation is an important component of follow-up.^246,247

Management of discrete subaortic stenosis remains a challenge, and the timing of surgery is controversial.²⁴⁸ Postoperative complications include residual or recurrent obstruction and progressive aortic regurgitation. For severe supravalvar obstruction, surgical intervention is recommended, and it results in adequate relief of the obstruction in most cases.²⁴⁹

Myocardial fibrosis and ventricular dysfunction may be a feature of severe aortic outflow obstruction in infancy. Although adequate relief of the obstruction results in significant clinical improvement, abolition of congestive heart failure, and myocardial remodeling in most children, ventricular hypertrophy or dilation persists along with various degrees of systolic or diastolic impairment in many. Other problems include myocardial ischemia, ventricular failure, and risk of sudden death.^250,251 Important concerns related to anesthesia and surgery are the potentially limited left ventricular functional reserve and alterations of the fine balance between myocardial oxygen supply and demand. Maintenance of coronary perfusion and ventricular contractile function is key in the care of these children. Pharmacologic agents with vasoactive and inotropic properties should be readily available during anesthesia care.

Anatomy and Pathophysiology

The ductus arteriosus is a vascular structure connecting the pulmonary trunk and thoracic aorta (see Fig. 15-4). It enables right ventricular output into the descending aorta during fetal life, within the context of typically increased pulmonary vascular resistance. Persistent patent ductus arteriosus (PDA) may be an isolated finding or associated with other forms of heart disease. Prematurity is an important risk factor.

The magnitude and direction of great artery shunting depends on the size of the communication and the pulmonary vascular resistance. In children with moderate or large left-to-right shunts, the physiologic effects are those of increased pulmonary blood flow and left ventricular volume overload.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Children with a tiny or small PDA have a normal life expectancy.²⁵² Those with hemodynamically significant communications eventually develop symptoms related to left ventricular volume overload. In some cases, this predisposes them to moderate or severe pulmonary hypertension. Although unlikely in the current era, in the past, the long-standing, high-pressure, and high-flow states associated with a moderate or large communication resulted in Eisenmenger syndrome in some children.

Ductal closure can be performed by surgical ligation or division. This is the favored approach in preterm infants and those with large communications.²⁵³ Percutaneous catheter occlusion can also be accomplished with a good success rate²⁵⁴ (see also Chapter 20). Video-assisted thoracoscopic surgery has been used for ductal ligation.^255,256 Regardless of the approach, interruption of this vascular structure is rarely associated with long-term issues. Children can expect a normal cardiovascular reserve and should be managed accordingly during future anesthesia care.

Anatomy and Pathophysiology

Coarctation of the aorta is characterized by narrowing of the aortic lumen in the thoracic region. The constriction may be discrete or diffuse. In infants, a long, narrowed aortic segment often is associated with hypoplasia of the transverse arch and aortic isthmus, in which case other structural cardiac malformations may also exist.²⁵⁷ Associated defects include a bicuspid aortic valve, VSD, mitral valve abnormalities, and other types of left-sided obstructive lesions.

Hemodynamic consequences result from obstruction to systemic blood flow and increased left ventricular afterload. During infancy, ventricular dilation and heart failure predominate. In older children, arterial hypertension is found proximal to the region of aortic obstruction, and they have some degree of left ventricular hypertrophy. Ventricular function is usually well preserved. Collateral circulation develops with a long-standing pathologic process.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Symptoms associated with severe aortic arch obstruction or concomitant cardiovascular pathology lead to early intervention in some children.²⁵⁸ Alterations in ventricular systolic function associated with a neonatal presentation usually resolve after relief of the obstruction. Systemic hypertension and a residual gradient that exceeds 25 to 30 mm Hg are regarded as indications for repeat intervention. Various catheter-based and surgical approaches have been applied to the management of this lesion; each has advantages and disadvantages²⁵⁹ (see also Chapter 20).

Repair at an early age is advocated in view of reduced surgical risks for the younger age group, and early repair minimizes late morbidity.²⁶⁰ Long-term issues include systemic hypertension (independent of the hemodynamic result) and residual or recurrent aortic arch obstruction.²⁶¹ Left ventricular hypertrophy may persist in some children after repair, particularly in those undergoing interventions later in childhood. Abnormalities in diastolic ventricular function have been reported after successful repair.²⁶² Catheter techniques (i.e., balloon angioplasty with and without stent implantation) have been effective in relieving the obstruction and normalizing blood pressure.²⁶³ This approach may be used as primary therapy or to address residual or recurrent disease.²⁶⁴ Aortic aneurysms can occur around the area of coarctation or elsewhere in the aorta after surgical intervention or balloon angioplasty. Additional long-term problems result from coexistent defects, such as bicuspid aortic valve and premature development of coronary artery disease. Aortic coarctation has been associated with cerebral aneurysms.

Anatomy and Pathophysiology

Tetralogy of Fallot (TOF) is the most common cyanotic cardiac lesion (see Fig. 15-5).²⁶⁵ This malformation is characterized by right ventricular outflow tract obstruction, an interventricular communication, right ventricular hypertrophy, and aortic override. There is considerable variation in the severity of the disease, accounting for the spectrum of clinical manifestations. The subpulmonary obstruction arises from anterior deviation of the infundibular septum and may have dynamic and fixed components.²⁶⁶ Pulmonary valve stenosis almost invariably exists, and the main pulmonary artery and distal branches often demonstrate various degrees of hypoplasia. The limitation of pulmonary blood flow and magnitude of ventricular level right-to-left shunting account for the degree of cyanosis.

Pressure overload accounts for hypertrophy of the right ventricular myocardium. The large, nonrestrictive VSD and the outflow obstruction result in a right ventricular pressure at systemic levels, and the pulmonary artery systolic pressure is reduced. Increases in the severity of the right ventricular outflow tract obstruction or decreases in systemic vascular resistance exacerbate right-to-left intracardiac shunting and systemic arterial desaturation, increasing the level of cyanosis. These features characterize hypercyanotic episodes or tet spells.

Several TOF variants are recognized, including the “pink” or mild forms at one end of the spectrum, and complex defects, such as pulmonary atresia with diminutive or discontinuous distal branches, at the other. Associated cardiovascular anomalies in children with TOF include an atrial communication, right aortic arch, multiple VSDs, persistent left superior vena cava to the coronary sinus, complete AVSD, and abnormal origin or course of the coronary arteries. Unoperated TOF is associated with the potential for hypercyanotic episodes and ventricular outflow tract obstruction.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

The surgical management of TOF has evolved from a strategy of a staged approach with initial palliation using a systemic-to-pulmonary shunt to a single-stage, definitive repair in infants. Ongoing controversy exists about the favored approach in the neonate or very young infant in need of surgical therapy.^267,268 In selected cases, percutaneous balloon pulmonary valvuloplasty may be performed as a palliative, temporizing measure.²⁶⁹ The definitive repair of TOF, although a successful operation enabling most children to be free of symptoms, may be associated with significant postoperative residua.^270,271 Volume loads may arise from pulmonary regurgitation, residual shunts, and the presence of aortopulmonary collaterals. Ventricular pressure loads, however, may result from residual or recurrent right ventricular outflow tract or obstruction to the pulmonary artery bed. This situation is associated with right ventricular hypertension, myocardial hypertrophy, and reduced ventricular compliance.

Conditions that may require repeat intervention include pulmonary regurgitation of significant severity, residual or recurrent pulmonary outflow tract obstruction, and residual, hemodynamically significant intracardiac shunts. Catheter-based procedures may be effective in the management of obstruction of the pulmonary vasculature, and they have been applied to rehabilitate the vascular tree in cases of significant underdevelopment. Children who have undergone right ventricle–to–pulmonary artery reconstruction by means of placement of an extracardiac conduit eventually develop conduit failure (i.e., stenosis or regurgitation) requiring reoperation.²⁷² Aortic root dilation can lead to increasing degrees of regurgitation and the need for surgical intervention.

In the past, most children underwent definitive repair at an older age, consisting of an extensive right ventriculotomy to facilitate resection of the infundibular obstruction and closure of the VSD. Many were also subjected to procedures that included placement of a large patch that encompassed the subpulmonic region, valve annulus, and supravalvar region (i.e., transannular patch). Although effective in relieving the obstruction, this approach invariably resulted in pulmonary regurgitation, which was reasonably well-tolerated but progressed over time.

On late follow-up, pulmonary regurgitation has been identified as a major cause of morbidity, and it may result in progressive right ventricular dysfunction due to significant volume overload, ventricular arrhythmias with their associated disabilities, and even death. In recognition of the long-term morbidity linked to severe pulmonary regurgitation, the surgical strategy for this defect has undergone reappraisal and modification over the years.²⁷³ A current method uses a transatrial approach for closure of the VSD, minimizing the size of an infundibular incision (if one is required) and avoiding or limiting the size of the transannular patch.^274,275

Although surgical refinements have led to overall improvements in postoperative outcomes, the preoperative evaluation of these children should include inquiries regarding exercise tolerance as an indicator of functional status and an appraisal of right ventricular function, residual pathology, potential rhythm abnormalities, and conduction disturbances. Magnetic resonance imaging is extremely useful in the evaluation of right ventricular systolic function, quantitation of the severity of pulmonary regurgitation, and evaluation of the distal pulmonary vascular bed. Electrophysiologic testing and programmed ventricular stimulation may be indicated to refine antiarrhythmic drug therapy, for ablation of arrhythmia foci, or for implantation of a cardioverter-defibrillator system.

Postoperatively, a subset of children develops a pattern that is characterized by right ventricular diastolic noncompliance, which is known as restrictive right ventricular physiology. It is associated with a reduced likelihood of progressive pulmonary regurgitation and right ventricular dilation. In these children, the right ventricle operates at a greater end-diastolic pressure, and the children demonstrate superior exercise performance in addition to a reduced likelihood of developing ventricular rhythm abnormalities.²⁷⁶

Perioperative goals for the child with pulmonary regurgitation and right ventricular dysfunction include optimizing right ventricular filling, maintaining or supporting right ventricular function, and minimizing factors that may further increase right ventricular work (e.g., increased pulmonary vascular resistance, increased peak inspiratory pressures). Any detrimental factor that may affect the right ventricle may also negatively affect the left ventricle due to ventricular interdependence. In children with restrictive right ventricular physiology, the myocardial supply-to-demand relationship is of particular importance because the stiff, poorly compliant right ventricular myocardium may not tolerate alterations in this balance and may be vulnerable to decreases in subendocardial oxygen delivery.

Anatomy and Pathophysiology

In d-transposition of the great arteries (d-TGA), the aorta arises from the anatomic right ventricle, and the pulmonary artery arises from the left ventricle (see Fig. 15-6). This anomaly accounts for the most common cause of cyanotic heart disease in the neonatal period. Associated defects include VSDs, left ventricular outflow tract obstruction, and coronary artery anomalies.

In d-TGA, the systemic and pulmonary circulations operate in parallel rather than in series, resulting in cyanosis. Mixing at the atrial, ventricular, or ductal level is essential for survival. Initial management in most infants includes prostaglandin E₁ therapy to maintain ductal patency and to enhance intercirculatory mixing. If restrictive, the interatrial communication may require enlargement by balloon atrial septostomy.

Because most neonates with d-TGA are otherwise healthy, the concerns before surgical correction primarily are those associated with diagnostic procedures or interventions in the cardiac catheterization laboratory. Considerations for anesthetic management primarily are related to cyanosis and heart failure, which are more likely to occur in infants with coexistent large VSDs. An inadequate communication for intercirculatory mixing may account for profound hypoxemia, potentially progressing to metabolic acidosis due to compromised tissue oxygenation. Less commonly, increased pulmonary vascular resistance may account for severe cyanosis despite prostaglandin E₁ therapy and an adequate anatomic communication.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Several decades ago, the approach to d-TGA consisted of an atrial baffle (i.e., atrial switch) or redirection procedure (i.e., Mustard or Senning operations). Physiologic correction was accomplished by allowing systemic venous blood to drain into the left ventricle and pulmonary artery while pulmonary venous blood was rerouted through the tricuspid valve into the right ventricle and aorta. The right ventricle remained as the chamber ejecting against systemic afterload. These procedures provided relief of cyanosis and reasonably good survival.²⁷⁷ In the long term, however, this approach led to complications such as sinus node dysfunction and atrial rhythm disturbances.²⁷⁸ Progressive right ventricular dilation, tricuspid (i.e., systemic atrioventricular valve) annular dilation, associated regurgitation, and eventual right ventricular dysfunction or failure were causes of major morbidity.^279–281 In addition to the rhythm abnormalities and conduction defects, this problem was thought to account for sudden death in some individuals later in life. Other problems included progressive obstruction of venous pathways and intracardiac shunting through atrial baffle leaks. Abnormal right and left ventricular responses to exercise have also been documented in these patients.²⁸²

The arterial switch operation (i.e., Jatene procedure) is the standard surgical approach in neonates with d-TGA. The repair establishes a normal, concordant relationship between the ventricles and their respective great arteries, achieving anatomic correction. The procedure involves transection of the arterial trunks above the level of the semilunar valves, anastomotic connections to their appropriate outflows, translocation of the coronary arteries to the neoaortic root, and closure of any intracardiac communications (see Fig. 15-7, A-E). Normal physiology is restored, enabling the left ventricle to function as the systemic pump. This procedure can be performed with good results, and long-term outcomes usually are very favorable.^283–286 Potential postoperative problems include supravalvar pulmonary or aortic obstruction. Neoaortic root dilation and aortic regurgitation may be identified on follow-up. Ventricular function is normal in most cases.²⁸⁷

Anesthetic management of most children after the arterial switch operation should be the same as in those without structural or functional abnormalities. However, there is some concern about coronary complications in these children that may not be evident clinically or identified by routine surveillance methods. Investigations have demonstrated postoperative regional left ventricular wall motion abnormalities, evidence of myocardial perfusion defects, and pathologic changes in the coronary vasculature, suggesting a risk for coronary insufficiency.^288–292

Anatomy and Pathophysiology

Congenitally corrected transposition of the great arteries, also known as l-transposition of the great arteries (l-TGA), is characterized by malposition of the great vessels and ventricular inversion (i.e., atrioventricular and ventriculoarterial discordance). In this anomaly, the right atrium empties into an anatomic left ventricle, which then contracts into the pulmonary trunk. The left atrium opens into an anatomic right ventricle, which ejects into the aorta. The aorta is typically oriented in a leftward and anterior position with respect to the pulmonary artery.

Cyanosis is absent because the circulations are physiologically corrected. The anatomic right ventricle functions as the systemic pump. Associated defects are frequently present and include pulmonary outflow tract obstruction, a ventricular communication, and tricuspid (left-sided) abnormalities. In some individuals, this lesion may remain undetected until the onset of arrhythmias or syncope due to complete atrioventricular block or the effects of concomitant pathology.²⁹³

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Without associated defects, children with corrected transposition may do well for many years. Development of complete atrioventricular block is common with increasing age.²⁹⁴ Selected children, particularly those at a young age or with coexistent defects that maintain left ventricular pressure at systemic levels, may be suitable candidates for a surgical intervention that restores the left ventricle as the systemic chamber.²⁹⁵ This complex repair, known as the double-switch operation or a variation thereof, combines redirection of the systemic and pulmonary venous flows in an atrial baffle procedure with the arterial switch operation. This strategy, however, may not affect mortality compared with conservative management.²⁹⁶

Issues that require long-term surveillance in children with congenitally corrected transposition include right ventricular performance and tricuspid valve competency.²⁹⁷ The overall long-term survival of individuals with this condition is substantially reduced compared with age-matched controls.^298,299

Anatomy and Pathophysiology

Truncus arteriosus is characterized by a single arterial trunk that gives rise to the aorta, pulmonary root, and coronary arteries (see Fig. 15-8). A ventricular communication usually exists underneath the single arterial root or truncal valve. Various anatomic types are identified according to the origin of the pulmonary arteries from the arterial trunk.^300,301 Associated pathology includes a right aortic arch, aortic arch interruption, abnormalities of the truncal valve (e.g., abnormal number of cusps, stenosis, regurgitation), and coronary artery anomalies. Approximately one third of children with truncus arteriosus have DiGeorge syndrome (see Chapter 14).

Clinical features of the neonate with this defect largely depend on the status of the pulmonary vasculature. If the resistance is increased, the infant is well compensated. The normal decrease in pulmonary vascular resistance leads to symptoms related to pulmonary overcirculation and congestive heart failure, accounting for the need for surgical intervention early in life. Truncus arteriosus is one of the structural malformations associated with a significant risk for adverse events before correction, because balancing the pulmonary and vascular resistances may be quite challenging.³⁰² The physiology that characterizes a reduced pulmonary vascular resistance and a significant runoff setting is that of an increased arterial oxygen saturation, reduced diastolic arterial pressures (potentially leading to myocardial ischemia), systemic hypotension, impaired cardiac output, and hypoperfusion of distal beds.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Surgery for truncus arteriosus consists of detaching the main pulmonary artery segment from the truncal root, repairing the ensuing aortic wall defect, closing the VSD to allow left ventricular output through the arterial root, and placing an extracardiac right ventricle–to–pulmonary artery conduit. Alternative approaches to establishing this continuity have been performed without the use of conduits.³⁰³

Neonates undergoing truncus arteriosus repair have excellent survival rates.^304–307 Late complications include conduit failure, residual or recurrent pulmonary artery obstruction, and truncal valve problems. Truncal valve dysfunction may require repair or replacement. The main issues of concern are the status of the right ventricle–to–pulmonary artery conduit and truncal root, consequences related to semilunar valve problems, and biventricular function.

Anatomy and Pathophysiology

The classic findings in Ebstein anomaly for the tricuspid valve include a large sail-like anterior leaflet and apically displaced septal and posterior leaflets.^308,309 This configuration commonly results in an atrialized portion of the right ventricle and tricuspid regurgitation. Some degree of right ventricular dysplasia is common. An interatrial communication is a frequent finding, and it may produce right-to-left shunting and clinical cyanosis. The spectrum of disease ranges from minimal or no symptoms to intractable congestive heart failure.³¹⁰ A neonatal presentation implies a major clinical problem and usually portends a poor prognosis. Symptoms in older children include cyanosis, palpitations, dyspnea, and exercise intolerance. Initial symptoms may be related to supraventricular tachycardia.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Children with Ebstein anomaly may require only conservative management and follow-up. In most cases, however, surgery is indicated for tricuspid regurgitation, closure of interatrial communications, or other associated problems. Procedures to ablate arrhythmias may be indicated. In contrast to adults, children are less likely to require valve replacement.³¹¹ A cavopulmonary or Glenn connection may be performed in some cases as part of a so-called one and a half ventricle approach to limit the right-sided volume load associated with severe tricuspid valve regurgitation.^312,313 One report indicated good functional outcomes and long-term survival after surgery for Ebstein anomaly.³¹⁴ Atrial arrhythmias (including Wolf-Parkinson-White syndrome) are common before and after surgery.

Anatomy and Pathophysiology

Interrupted aortic arch is an uncommon malformation characterized by discontinuity between the ascending and descending thoracic aorta (see Fig. 15-14). Ductal patency is essential for systemic perfusion beyond the area of interruption. This anomaly is classified in terms of the site of interruption. It is type A if it occurs distal to the left subclavian artery, type B if between the left carotid and left subclavian arteries, and type C if between the carotid arteries. Type B interruption is the most common variant, followed in frequency by types A and C.

Interrupted aortic arch is typically associated with a posteriorly malaligned VSD, resulting in subaortic obstruction. Other defects include a right aortic arch, aberrant origin of a subclavian artery, and truncus arteriosus. Many children with this anomaly have DiGeorge syndrome.

Neonatal presentation of interrupted aortic arch is related to ductal closure in the setting of aortic arch obstruction (e.g., congestive heart failure, poor perfusion, cardiovascular collapse, shock) and occasionally to differential cyanosis. Stabilization of the infant and initiation of prostaglandin E₁ therapy is critical. The site of interruption and presence of coexistent anomalies can influence the selection of sites for blood pressure monitoring and pulse oximetry. An adequate response to prostaglandin E₁ therapy implies no significant gradient between the areas proximal and distal to the obstruction and an oxygen saturation differential (i.e., increased values in beds supplied proximal to the interruption, reduced values distally).

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Surgical intervention is necessary for interrupted aortic arch during the first few days of life. The goal is to establish aortic arch continuity and to address coexistent defects. The current approach favors a one-stage repair.^315–317 Survival in uncomplicated cases is excellent.³¹⁸ Problems after repair mainly involve the left ventricular outflow tract.³¹⁹ Reoperation may be required and in some cases may consist of left ventricular outflow tract enlargement (i.e., Konno procedure). Eventual aortic root or valve replacement or a Ross-Konno procedure may be necessary.

Anatomy and Pathophysiology

Congenital anomalies of the coronary arteries include an abnormal origin of one of the main branches, aberrant vascular course, or pathologic communications that involve the coronary circulation.^320,321 The most common anomalies detected during childhood include anomalous origin of the left main coronary artery from the pulmonary artery (ALCAPA), coronary artery–to–pulmonary artery fistulas, and coronary cameral fistulas (i.e., connection between a coronary artery and cardiac chamber). Although rare, anomalous origin of a coronary artery from the incorrect (contralateral) sinus of Valsalva may occur in asymptomatic children and adolescents.³²² In some instances, a major coronary artery courses between the great arteries. This situation may be associated with compromised coronary blood flow and myocardial ischemia during exercise, presumably related to dilation of the arterial roots to accommodate the increased stroke volume.

The clinical presentation varies according to the nature of the anomaly. Infants and young children with ALCAPA may exhibit severe ventricular dysfunction and mitral valve regurgitation, which are largely ischemic in nature. Children with fistulous coronary artery connections may present with a heart murmur or evidence of ventricular volume overload. Significant symptoms may indicate congestive heart failure. Other coronary artery anomalies may manifest as myocardial ischemia, causing exertional syncope or chest pain, and in some cases, arrhythmias may lead to a near-death event.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

After surgical intervention for ALCAPA, most children demonstrate significant recovery of myocardial function. Others continue to exhibit alterations in myocardial performance and may develop dilated cardiomyopathy; if it is severe, they may require cardiac transplantation. A few children reach adulthood without symptoms or any intervention. Coronary artery fistulas resulting in congestive symptoms may be referred for catheter-based or surgical interventions. Anginal complaints, myocardial infarction, and sudden death are risks when an aberrant coronary artery courses between the arterial trunks. The risk is greater when the left coronary artery originates from the right sinus of Valsalva and courses between the aorta and the right ventricular outflow tract. Sudden death is most likely to occur during or immediately after strenuous exercise. The implications of anesthesia for coronary artery anomalies primarily are related to the underlying potential for myocardial ischemia, effects of ventricular volume overload, and ventricular dysfunction.

Anatomy and Pathophysiology

The single-ventricle (i.e., univentricular heart) spectrum encompasses several congenital cardiac defects. They are characterized by abnormalities such as ventricular hypoplasia (i.e., HLHS), atrioventricular valve atresia (i.e., tricuspid atresia), or abnormal atrioventricular connections (i.e., double-inlet left ventricle). Pathologies with two distinct ventricles may also be considered in the functional single-ventricle category due to associated defects that preclude a biventricular circulation (i.e., unbalanced AVSD).

Single-ventricle physiology is characterized by complete mixing of the systemic and pulmonary venous circulations at the atrial or ventricular levels. Aortic or pulmonary outflow tract obstruction is a common feature in these pathologies. An important management strategy early in the palliation pathway involves optimizing the balance between the pulmonary and systemic circulations.

Treatment Options, Residua, Sequelae, and Long-Term Outcomes

Surgical interventions available for children with functional single-ventricle physiology include the following: