Abstract
Coarctation of the aorta is a common form of congenital heart disease. Presentation, evaluation, and treatment of coarctation of the aorta is different in neonates and infants compared with older children. Neonates may present in shock and require prostaglandin E 1 to maintain ductal patentcy until the time of surgical repair. Older children usually present with upper extremity hypertension or murmur. The approach to surgical repair of coarctation in neonates and infants depends on the presence or absence of concomitant defects and the degree of associated arch hypoplasia. For older children, robust collaterals and limited mobility of the aorta may mandate patch repair, interposition graft, or bypass of the coarctation segment. Percutaneous techniques, including angioplasty and stent placement, are often viable options for older children and adolescents with native or recurrent coarctation. Surgical and interventional outcomes have improved over time. Reliable repair may be anticipated with a very low rate of morbidity and mortality, although lifetime follow-up is recommended.
Key Words
Coarctation, Aorta, Neonatal surgery, Angioplasty, Stents, Outcomes
Coarctation of the aorta (CoA) is a heterogenous lesion that generally refers to a congenital narrowing of the thoracic aorta, directly opposite, proximal, or distal to the ductus arteriosus, resulting in a pressure gradient. True coarctation is a distinct, shelf-like thickening or infolding of the aortic media into the lumen of the aorta, although coarctation has also been used to describe a long-segment narrowing, or hypoplasia of a segment of the aorta.
CoA is relatively common. The estimated prevalence is approximately 3 cases per 10,000 live births worldwide. Aortic coarctation is recognized in 5% to 8% of patients with congenital heart disease excluding mitral valve prolapse or related bicuspid aortic valve. The male to female ratio is between 1.27 : 1 and 1.74 : 1.
CoA was first described in 1760 by Morgagni, but it was not until the 1920s that it became recognized as a cause of shortened life span, hypertension, endocarditis, and congestive heart failure (CHF). Of the patients with CoA who survived infancy, mean life expectancy in the presurgical era was only three decades. A pivotal time in the evolution of the treatment of infants with CoA and other aortic arch anomalies was the late 1970s, when prostaglandin E 1 (PGE 1 ) became available to maintain patency of the ductus arteriosus. This drug allowed preoperative stabilization of critically ill neonates presenting with shock.
Surgical repair was pioneered by Crafoord and Gross in the 1940s. In the decades that followed, various surgical and interventional techniques have been developed, leading to dramatically improved patient outcomes.
Anatomy, Embryology, and Classification Systems
An aortic coarctation usually lies in close proximity to the ductus arteriosus or ligamentum arteriosum, commonly just distal to the left subclavian artery ( Fig. 45.1 ). An isolated coarctation is more commonly found in older children. In infants, CoA is commonly associated with hypoplasia of the aortic isthmus and other cardiac anomalies. Aortic hypoplasia is defined as a narrowed external diameter of an aortic segment with a normal aortic media. Proximal and distal transverse arch hypoplasia are defined as 60% and 50%, respectively, of the diameter of the ascending aorta; isthmic hypoplasia is defined as less than 40% of the diameter of the ascending aorta. Some degree of arch hypoplasia is present in most normal neonates.
There are two main embryologic theories to explain the development of coarctation. Some investigators have suggested that ductus smooth muscle tissue migrates into the periductal aorta and subsequently causes constriction after birth as the ductus closes. A second theory to explain the development of CoA cites decreased aortic flow secondary to associated cardiac defects. The flow theory is supported by the fact that constellations of intracardiac anomalies with decreased aortic flow patterns have an increased incidence of CoA and other arch anomalies and that constellations with increased aortic flow (because of decreased pulmonary flow) rarely are associated with CoA. Lymphatic obstruction and related aortic compression is another theory described in Turner syndrome.
Historically coarctations were classified as either adult (postductal) or infantile (preductal). The adult form referred to a discrete narrowing, which was more properly described as juxtaductal in location. The infantile or preductal form was characterized by more diffuse narrowing of an aortic segment in addition to the juxtaductal narrowing. A more modern classification from the Congenital Heart Surgery Nomenclature and Database Project, which guides the surgical approach, recognizes three categories: (1) isolated coarctation, (2) coarctation with ventricular septal defect (VSD), and (3) coarctation with complex intracardiac anomaly.
Associated Defects
Coarctation is often associated with other defects. Bicuspid aortic valve and VSD represent the two most common associated defects, present in 40% to 50% and 25% to 40%, respectively. CoA is also frequently associated with complex heart disease and other left-sided obstructive lesions. For example, Shone’s syndrome describes multilevel left-sided obstruction consisting of CoA, supravalvular mitral stenosis, parachute mitral valve, and subaortic stenosis. Right-sided obstructive lesions such as tetralogy of Fallot, tricuspid atresia, pulmonary stenosis, and atresia are rarely associated with CoA. Intracranial aneurysms represent a potentially life-threatening associated extracardiac abnormality.
CoA has a known association with several chromosomal abnormality syndromes, in particular trisomy 13 and 18, Turner, Noonan, Jacobsen, Williams-Beuren, Ellis-van Creveld, and PHACES syndrome.
Newborns and Infants
Pathophysiology
Among patients with CoA, young age at presentation closely correlates with severity of obstruction and associated defects. This correlation may be explained by the predictable timing and process of ductal closure. When ductal closure causes aortic obstruction, a severe increase in left ventricular (LV) afterload results. LV ejection fraction decreases acutely in response to the higher afterload, because there is no time for compensatory development of muscle hypertrophy. Such increased afterload results in elevated ventricular wall tension, decreased myocardial perfusion pressure, and, in extreme cases, ischemic myocardium.
The increased LV end-diastolic pressure and increased left atrial pressure cause a left-to-right shunt at the foramen ovale and hence increased pulmonary blood flow (Q p ) that leads to clinical heart failure. Pulmonary hypertension occurs secondary to (1) increased Q p and (2) increased pulmonary venous pressures secondary to left atrial hypertension. The volume- and pressure-loaded right ventricle often demonstrates depressed function.
This pattern of CHF is exaggerated in the presence of severe CoA with a large VSD ( Fig. 45.2 ). LV blood is ejected into the right ventricle and pulmonary circulation at systemic pressures, leading to a substantially increased pulmonary-to-systemic blood flow ratio (Q p :Q s ). As the ductus closes, Q s decreases further, and Q p :Q s may become much greater than 1 : 1. Systemic hypoperfusion leads to the oliguria and metabolic acidosis observed in many infants on presentation.
Other associated cardiac lesions may influence the hemodynamic burden. For example, in cases in which the ductus remains patent, the right ventricle is able to support systemic perfusion. In cases of severe coarctation in neonates, “critical coarctation,” adequate systemic cardiac output can be maintained by the right ventricle only across a patent ductus arteriosus. These infants present in profound shock with systemic hypotension, acidosis, and tachypnea (from pulmonary hypertension) when the ductus closes. They emergently require intravenous PGE 1 to open the ductus and restore systemic perfusion. Hypertrophy and volume overload help the right ventricle to maintain adequate cardiac output, especially in the presence of a VSD. Infants with atrioventricular septal defects and coarctation can experience more severe heart failure for equivalent degrees of aortic obstruction than infants without atrioventricular septal defects because of the addition of atrioventricular valve regurgitation to the left-to-right shunting described previously.
Presentation
Infants under 3 months of age with CoA have characteristic presenting signs ( Box 45.1 ). CHF is often present. Poor peripheral perfusion, acidosis, tachypnea, and failure to thrive are common. The physical examination reveals an ejection murmur along the left sternal border and in the left subscapular area. The precordial impulse is prominent and often accompanied by a systolic thrill if the infant has intracardiac defects. Hepatomegaly and a gallop rhythm point to CHF. Femoral pulses are diminished in most, but not all, cases. CoA is difficult to diagnose prenatally due to flow across the ductus arteriosus in utero. Less than 25% of neonates in the United States requiring neonatal surgery for coarctation are diagnosed prenatally. It is a diagnosis that is also frequently missed in the newborn period. Patients are often not referred until they are in shock or renal failure. Less than 30% of infants with physical findings of CoA are referred with the correct diagnosis. Most infants are thought to have other diagnoses despite decreased femoral pulses in 88% of cases because decreased femoral pulse can also be a sign of shock from other causes (such as neonatal sepsis). Conversely, patients may be erroneously suspected of having a coarctation when they are in shock. Even in patients over 1 year of age, the diagnosis is usually delayed despite classic findings of murmur and upper extremity hypertension. In contrast to older children, infants presenting before 5 days of age rarely have upper extremity hypertension due to depressed cardiac output. After 5 days, hypertension becomes more common, and after 15 days the incidence is 86%. Aortic obstruction is the most likely diagnosis when these physical findings are accompanied by a gradient between upper and lower extremity pulses and systolic pressure. However, the absence of such a gradient does not rule out the diagnosis of aortic obstruction, and, in fact, when distal (systemic) perfusion is maintained by a patent ductus arteriosus, the pressures in the lower extremities may be equal to or even higher than those in the upper extremities.
Tachypnea
Cyanosis
Poor perfusion
Difficulty feeding
Failure to thrive
Hepatomegaly
Cardiomegaly
Decreased femoral pulses
Murmur
Metabolic acidosis
Respiratory failure
The absence of a systolic pressure gradient in patients with CoA usually has one of three anatomic or physiologic explanations: (1) The ductus may be patent such that the right ventricle provides flow to the lower body. These patients may have differential cyanosis with lower oxygen saturations recorded from the toe than the preductal hand. (2) LV function may be so poor that systemic hypotension makes it impossible to detect a gradient between upper and lower extremities. (3) Finally, in rare instances the right subclavian artery has an aberrant origin distal to the coarctation, thus eliminating any gradient. The physician should never exclude the diagnosis of CoA solely because of failure to detect a gradient in pulse volume or systolic pressures between upper and lower extremities.
Evaluation
Electrocardiographic (ECG) findings are influenced by the presence of associated intracardiac anomalies and the age at presentation. Infants most commonly show right ventricular hypertrophy and later develop biventricular hypertrophy. A minority of patients have LV hypertrophy alone. ST-segment depression and T-wave inversion in V 5 and V 6 can also be found.
The chest radiograph of infants with CoA is different from that of older patients with isolated CoA. In infancy, cardiomegaly and pulmonary congestion are hallmarks ( Fig. 45.3 ). Two-dimensional echocardiography with Doppler (echo Doppler) is a sensitive and specific diagnostic method for infants with CoA ( Fig. 45.4 ) and associated intracardiac anomalies. In experienced hands, diagnosis of CoA by echo Doppler achieved 95% sensitivity and 99% specificity. Prenatal diagnosis of CoA based on normal fetal aortic arch growth curves has evolved significantly.
The role of cardiac catheterization in CoA continues to develop in light of the greater use of noninvasive diagnostic techniques. Cardiac catheterization and angiography are desirable if echocardiography fails to delineate the anatomy completely or where balloon angioplasty or stent placement offers definitive treatment ( Fig. 45.5 ).
Medical Management
The primary objective in the medical management of neonates with critical CoA is to maintain ductal patency with PGE 1 . It is our practice to administer PGE 1 to every newborn in shock until critical coarctation, interrupted aortic arch, or other ductus-dependent lesions have been excluded.
Although shock and CHF usually improve after PGE 1 administration, some infants will require inotropic support and mechanical ventilation in addition to PGE 1 . Hyperoxia and hypocarbia should be avoided to minimize pulmonary overcirculation.
PGE 1 is given initially in doses of 0.05 mcg/kg/min to 0.1 mcg/kg/min but can be increased gradually to 0.2 mcg/kg/min if it is not effective at the lower dose. Maximal response occurs 15 minutes to 4 hours after the start of the infusion. Side effects and complications of PGE 1 include cutaneous vasodilation, hypotension, rhythm or conduction disturbances, respiratory depression and apnea, fever, jitteriness or seizure activity, increased infection, diarrhea, necrotizing enterocolitis, metabolic derangements, and (rarely) coagulopathy. Many side effects are related to high doses, longer infusion periods, and poorer general medical condition at the start of therapy. McElhinney and coworkers found an elevated risk of necrotizing enterocolitis in neonates whose highest dose of prostaglandin was greater than 0.05 mcg/kg/min. It is common practice to decrease the dose to 0.01 to 0.02 mcg/kg/min as soon as the desired effect has been achieved.
Endotracheal intubation and mechanical ventilation are frequently required in the newborn with critical coarctation because of CHF, shock, and the risk of apnea from PGE 1 therapy. If PGE 1 is begun in the absence of shock and apnea, ventilatory support is not mandatory, provided that resources for intubation are immediately available. In newborns with isolated CoA the expected decrease in the pulmonary vascular resistance from ventilation and PGE 1 does not affect the hemodynamics. Conversely, in those with CoA and VSD, more blood will be shunted left to right as the pulmonary vascular resistance falls. Ventilation must be carefully controlled to help balance Q p :Q s in patients with arch obstruction and left-to-right intracardiac shunt. This requires a ventilation strategy designed to increase pulmonary vascular resistance by lowering the fraction of inspired oxygen (FiO 2 ) to maintain O 2 saturations of approximately 85% and adjusting minute ventilation to achieve a pCO 2 of 40 to 50 mm Hg. Maintaining Q p :Q s as close to 1 : 1 as possible is a necessary strategy for maintaining adequate systemic blood flow. Normal acid-base balance with lactate levels below 2 mmol/L can provide an indication of adequate oxygen delivery. Mixed venous oxygen saturation is not useful as a measure of systemic oxygen delivery if the measurement is obtained from the right atrium in the presence of a significant atrial shunt, which raises right atrial saturation.
Fluid and electrolyte balance should also be optimized before surgery. Severe metabolic acidosis (pH < 7.2) from systemic hypoperfusion is corrected with bicarbonate administration (0.5 to 1 mEq/kg), given slowly. Bicarbonate doses can be repeated until the metabolic acidosis has resolved; however, inability to correct the acidosis with multiple doses of bicarbonate suggests persistent acid production. This could be associated with poor myocardial function or ischemic tissue, such as ischemic bowel. Severe anemia can also contribute to persistent acidosis.
Although it is appropriate to correct dehydration, fluid volume expansion, even in the hypotensive infant with critical coarctation, may be hazardous. Hypotension is usually not caused by hypovolemia in this setting but rather by aortic obstruction, ductus closure, and ventricular failure. During the initial resuscitation in the emergency department, a small fluid bolus (normal saline, 5 mL/kg) may be useful as a therapeutic trial. An additional bolus is justified only if there is a favorable response to the first bolus. Infants with prolonged shock and acidosis who develop fluid loss from capillary leak syndrome may require repeated fluid boluses. Some infants develop systemic vasodilation after PGE 1 and require titrated isotonic fluid administration (5 mL/kg per dose).
Conversely, the newborn with an established diagnosis of CoA and CHF who is responding to PGE 1 therapy should receive fluid restriction (70% to 80% of maintenance requirements) to limit the salt and water load in the face of heart failure. Another scenario involves the newborn who remains hypotensive despite restoration of ductal patency with PGE 1 . Poor ventricular function is the likely cause of persistent hypotension in this setting, and the infant may benefit from inotropic support rather than volume expansion. Low-dose dopamine (5 to 7 mcg/kg/min) may be useful in this situation. With a patent ductus, balanced circulation, and necessary inotropic support the infant should be readily stabilized during the preoperative period. Table 45.1 summarizes preoperative management strategies for infants with critical CoA.
| Drugs |
|
| Ventilation | Controlled ventilation with avoidance of hyperoxia or hypocarbia to maintain balanced circulation (Q p :Q s 1 : 1) |
| Fluid management |
|
| Laboratory studies |
|
| Imaging |
|
Most infants can be adequately stabilized with the measures described herein, and surgery should be delayed for 12 to 24 hours until metabolic derangements have been corrected. Symptomatic infants who are unresponsive to PGE 1 have a high mortality. The options for these patients include emergency repair of CoA with or without cardiopulmonary bypass. Additional diagnoses should be sought if the patient is difficult to stabilize.
Timing of Intervention
The objective of surgical treatment of CoA is relief of aortic obstruction with minimal risk of repeat stenosis. The debate surrounding the ideal age for repair has focused on the issues of operative mortality in infancy, the risk of restenosis, and the likelihood of persistent hypertension after repair. Neonates presenting with CHF should undergo repair as soon as they are metabolically stable. Nonetheless, the optimal surgical technique and whether single- or two-stage repair of associated defects is appropriate are still debated.
Anesthetic Management
A preoperative understanding of concomitant congenital anomalies is critical to the anesthetic management of the infant with CoA. Transthoracic echocardiography is used to detect the potential presence of concomitant intracardiac anomalies and to assess biventricular function. Initial evaluation of the airway should focus on the presence of structural facial abnormalities that may influence management of the airway. For CoA repair approached via median sternotomy using cardiopulmonary bypass, a transesophageal echocardiogram probe should be placed in addition to standard monitors.
Routine monitoring for off-pump repair of CoA includes ECG leads, a urinary catheter, temperature probe, and arterial and central venous access. Central venous access is important for drug administration and pressure monitoring, particularly with more complex intracardiac lesions. Large-bore peripheral intravenous catheters are placed for volume infusion as needed. Packed red blood cells are available in the operating room during the repair of CoA in the event of hemorrhage. Irradiated blood products should be used to prevent graft-versus-host disease in all infant CoA repairs unless DiGeorge syndrome has been specifically excluded. Antibiotic prophylaxis (cefazolin 30 mg/kg, or 2 g for patients >60 kg, or cefuroxime 50 mg/kg, or 1.5 g for patients >50 kg) is administered preoperatively, within 60 minutes of skin incision. To ensure consistent antibiotic administration, it is our standard practice to give antibiotics at the time of skin preparation.
For systemic pressure monitoring, and to monitor acid-base status, hemoglobin, and calcium levels, a radial arterial line is placed. Use of the right radial artery allows for monitoring of coronary and cerebral perfusion because the right subclavian artery is typically proximal to the aortic cross-clamp during surgical repair. Infants with an aberrant right subclavian artery arising distal to the site of CoA may necessitate placement of a proximal aortic catheter for pressure monitoring. If sacrifice of the left subclavian artery is necessary during the repair, intraoperative and postoperative assessment of left upper extremity perfusion is imperative. A femoral arterial line is not routinely placed; however, a blood pressure cuff is placed on the lower extremity to evaluate adequacy of perfusion during and after cross-clamp.
Induction of anesthesia for neonates and infants is usually via the intravenous route with additional inhalational supplementation as needed. For maintenance of anesthesia, volatile agents (typically isoflurane or sevoflurane) are used throughout the operation and may be titrated to assist with blood pressure control. Intravenous narcotics are used for analgesia. A caudal block or epidural is an option in select patients. Neonates and infants are usually kept intubated at the end of the surgical procedure.
Nicardipine is used first line for blood pressure management because it provides direct pharmacologic action on the vascular smooth muscle with minimal myocardial depression. Acidosis and hypotension may immediately follow cross-clamp removal, necessitating aggressive correction of acid-base balance and management of mean arterial pressures with alpha-adrenergic agents to ensure adequacy of end-organ perfusion. This phenomenon is rare and minimized by thoughtful communication between surgeon and anesthesiologist to coordinate a slow cross-clamp removal with empiric supportive measures. Although spinal cord perfusion is a significant concern through the cross-clamp period, prevention of hypotension and acidosis, use of passive cooling, and minimization of cross-clamp times has resulted in a very rare incidence of ischemic spinal cord complications.
Surgical Repair of Coarctation
In general, we approach repair of CoA in neonates and infants with surgery. Four operative procedures are commonly used: (1) resection of the stenotic segment and end-to-end aortic anastomosis (EEA), (2) CoA resection with extended EEA, (3) patch augmentation, and (4) subclavian flap aortoplasty ( Fig. 45.6 ). The optimal procedure depends on the age of the patient, the need for growth of the repair, the length and complexity of the stenosis, and the surgeon’s preference. Table 45.2 shows the frequency of coarctation repair techniques used in 2474 patients (75% neonates or infants) with isolated CoA or hypoplastic aortic arch between 2006 and 2010.
| Repair Technique | Frequency (%) |
|---|---|
| Extended end-to-end anastomosis | 56 |
| End-to-end anastomosis | 33 |
| Patch aortoplasty | 4 |
| Subclavian flap repair | 3 |
| Interposition graft | 3 |
| Other | 0.4 |
Resection with EEA is a surgical technique that was historically used in neonates via a left thoracotomy. Advantages include removing all ductal tissue from the repair site and preserving the left subclavian artery. Unfortunately, many neonates have some degree of hypoplasia of the aortic arch as well as extensive ductal tissue in the periductal aorta, making simple resection and EEA insufficient to provide adequate relief from the coarctation. A modification of that technique, called extended EEA, uses a beveled end-to-side anastomosis of the descending aorta to a separate incision extended onto the underside of the aortic arch, proximal to the hypoplastic segment (see Fig. 45.6B ). This approach provides superior relief from the various levels of obstruction found in neonatal coarctation. The incidence of recurrent coarctation may be decreased with this approach because all ductal tissue and tissue with tubular hypoplasia is excised. Extended EEA repair has become the procedure of choice for neonatal coarctation in most centers. Extended EEA repair is usually performed through a left thoracotomy but can be performed via a median sternotomy on cardiopulmonary bypass when associated defects are repaired at the same setting (e.g., VSD closure).
The subclavian flap repair uses the ipsilateral subclavian artery as a fold-down flap to enlarge the coarctation site (see Fig. 45.6B ). It is performed via a left thoracotomy approach. The use of viable native tissue allows growth of the repaired segment, and tension is avoided at the anastomosis. Criticisms of the technique include the obligatory sacrifice of the subclavian artery, inability to correct arch hypoplasia in some cases, the low but constant risk of extremity ischemia, subtle impairment of arm temperature, strength or length over time, as well as late cerebral ischemic syndromes by a steal mechanism. The subclavian flap technique has fallen out of favor due to the higher late recurrence rate of coarctation following use of the subclavian flap compared with extended EEA. If a subclavian flap repair is contemplated, arterial monitoring lines, blood pressure cuffs, and even blood gas sampling should be avoided on the repair side to avoid ischemic complications.
Prosthetic patch augmentation is a third surgical option that has been used successfully in neonates. A longitudinal incision opens the coarcted segment, which is then covered with a Dacron (polyester) or polytetrafluoroethylene patch (see Fig. 45.6B ). This approach avoids an extensive dissection and the attendant risk of sacrificing intercostal collaterals. Unfortunately, long-term follow-up shows that children with a prosthetic patch aortoplasty are at risk for aneurysm development on the aortic wall opposite the patch (particularly if the posterior shelf is resected, thus theoretically weakening the aortic wall opposite the patch). This approach has generally been reserved for coarctation repair in selected circumstances.
When concomitant cardiac procedures or transverse arch repairs are performed, CoA should be repaired by the median sternotomy approach. In neonates in particular the proximal descending aorta can be mobilized and brought cephalad and anterior to join the undersurface of the arch. Alternately, the lesser curve of the aorta may be opened and the underside of the arch augmented with patch material such as pulmonary homograft in a Norwood-style arch reconstruction. Patch augmentation may be accomplished with or without coarctectomy and reanastomosis of the back wall. The incision in the descending aorta should extend 10 to 15 mm beyond the ductal insertion site, and the toe of the patch should be broad to create a wide anastomosis that will prevent recoarctation. Hypothermic circulatory arrest is generally used for these procedures, although novel selective perfusion techniques have been described.
Surgical Complications and Postoperative Critical Care Management
Surgical morbidity after repair of CoA includes anastomotic bleeding, cardiac arrest, chylothorax, gastrointestinal bleeding, phrenic nerve injury, postcoarctectomy hypertension, recurrent laryngeal nerve injury, seizures, and spinal cord injury ( Fig. 45.7 ). In the landmark review by Brewer and associates, 12,532 coarctectomies were described, and spinal cord ischemic injury occurred in 51 cases (0.41%), but rarely in infants and neonates. There was no association with cross-clamp time. Lack of collaterals and the intrinsic anatomy of the anterior spinal artery may contribute. A 2012 study of the STS Congenital Heart Surgery Database found no occurrences of spinal cord injury out of 973 coarctation repairs.
Respiratory Complications.
Newborns and infants with CoA and VSD may have a reactive pulmonary circulation and pulmonary hypertension. Patients at risk should receive intravenous sedation and controlled ventilation during the first 12 to 24 hours after surgery. Documented pulmonary hypertension should be initially treated with inhaled nitric oxide. Thereafter these patients can usually be weaned from mechanical ventilation and extubated.
Stridor may become evident at the time of extubation secondary to recurrent laryngeal nerve manipulation or injury, leading to unilateral vocal cord paresis or paralysis. Newborns and infants are at greatest risk of clinical compromise because the compliant chest wall retracts during partially obstructed inspiration and poor lung expansion may result. Patients with significant respiratory distress should be reintubated. If there is evidence of obstruction in a newborn, nasal continuous positive pressure can be tried. If the nerve was traumatized but not severed, function may return after several days. Nutrition should be optimized in preparation for another extubation attempt. Repeated failed extubation secondary to recurrent laryngeal nerve dysfunction warrants airway evaluation by an otolaryngologist.
Phrenic nerve injury leading to hemidiaphragmatic paralysis may be diagnosed initially by chest radiograph. Typically the hemidiaphragm is elevated, although this can be masked by positive pressure ventilation. Diagnosis is made by fluoroscopy or ultrasound study of the diaphragm, with the patient momentarily removed from positive pressure ventilation and breathing spontaneously. Older children are usually asymptomatic with hemidiaphragmatic paralysis, and intervention is not necessary. However, a paralyzed hemidiaphragm may prohibit separation of the infant from mechanical ventilation. In that setting, definitive management involves plication of the diaphragm, which some surgeons perform immediately on diagnosis. Others may optimize nutrition and offer a second attempt in several days. If the second extubation fails, a diaphragmatic plication may be indicated.
Lymphatic injury leading to chylothorax usually presents as a milky pleural effusion after the initiation of postoperative feeds. If the diagnosis is unclear, triglyceride levels (generally >1.1 mmol/L with fat intake) or lipoprotein electrophoresis looking for chylomicrons is diagnostic. Chylothorax may require prolonged chest tube drainage, which can improve lung function and enable monitoring of the amount drained. In addition to compromised lung function, persistent chylothorax may lead to hypoproteinemia, hypogammaglobulinemia, and lymphopenia with resultant nutritional debilitation. There is debate over whether chylothorax after CoA repair is best treated by immediate thoracic duct ligation or conservatively with dietary maneuvers alone, but institution of clinical practice guidelines has been shown to decrease hospital length of stay and use of mechanical ventilation. Conservative treatment with dietary manipulation alone excludes long-chain fatty acids in favor of medium-chain fatty acids, which can be absorbed directly by the portal system and bypass the thoracic duct. If necessary, flow through the thoracic duct can be further reduced by resting the gastrointestinal tract and providing total intravenous nutrition. Enteral feeds without long-chain fatty acids may resume after 1 to 2 weeks of rest. If the chyle recurs with restarting enteral feeds, the thoracic duct can be surgically ligated, or sometimes simple reexploration of the thoracotomy will reveal the area (most often in the region of the superior intercostal vein; just above the area of coarctation repair) that is oozing chyle, and this area can be easily controlled with a few ligatures. Nutrition is an important consideration during this process. If the patient’s nutritional status deteriorates during persistent chylothorax, surgical ligation of leaking lymphatics should be undertaken earlier in the course. Novel interventional techniques such as lymphangiography and obliteration of leaking chylous channels with embolization may be an option in select patients.
Postoperative Systemic Hypertension.
The cardiac problems for patients with isolated coarctation generally involve hypertension or ischemia. Early postoperative control of hypertension protects the aortic anastomosis, minimizes the risk of aneurysm formation in the dilated poststenotic segment, and alleviates postcoarctectomy syndrome. Hence mean arterial pressure should be rigidly maintained in the normal range for age. During the immediate postoperative period this may be achieved by titration of nitroprusside and esmolol infusions, nicardipine, or labetalol alone and adequate pain relief. Once the patient is ready for discharge from the intensive care unit, intermittent doses of propranolol, atenolol, labetalol, or captopril may be substituted. CoA repair before 1 year of age has been associated with a low incidence of late hypertension; relief after 1 year of age results in a sixfold increase in occurrence.
Management strategies for infants following surgical coarctation repair are shown in Table 45.3 .
Results of Surgery
Survival.
Early (perioperative), intermediate, and long-term morbidity and mortality define the outcomes of CoA. The operative mortality for coarctation depends primarily on the complexity of coexisting lesions. In a 2013 study of the Society of Thoracic Surgeons Congenital Heart Surgery Database (STS CHSD), Ungerleider and colleagues reported outcomes for 5025 patients undergoing primary repair of CoA at one of 95 participating centers between 2006 and 2010. They found that mortality was 1%, 2.5%, and 4.8% for patients with isolated CoA, CoA plus VSD, and CoA plus other cardiac diagnoses, respectively ( Table 45.4 ). When the group of infants with CoA and other major cardiac defects was further stratified into CoA plus Shone’s syndrome and CoA plus non-Shone’s other complex cardiac defects, the mortality rates were much higher for the non-Shone’s group (1.5% vs. 6.8%, respectively).
