Medical and Surgical Management of Critical Congenital Heart Disease

KEY POINTS

• 1.

  The natural history of congenital heart diseases (CHDs) varies tremendously. Some critical CHDs become symptomatic and require therapeutic intervention in the neonatal period.

• 2.

  Patients with CHDs that result in inadequate pulmonary blood flow typically demonstrate cyanosis within minutes of life that does not improve with the administration of oxygen. Many of these patients need treatment with a prostaglandin infusion (PGE1) while awaiting confirmation of CHD.

• 3.

  Infants with transposition of the great arteries with dextro-transposition of the great arteries (dTGA), tricuspid atresia, pulmonary atresia, critical pulmonary valve stenosis, total anomalous pulmonary venous return, or Ebstein anomaly may present with cyanosis soon after birth.

• 4.

  Patients with hypoplastic left heart syndrome, coarctation of the aorta, or critical aortic valve stenosis have inadequate systemic blood flow and typically present with poor pulses, poor perfusion, or cardiogenic shock.

• 5.

  Neonates with a surgical aortopulmonary shunt, patent ductus arteriosus, unrepaired aortopulmonary window or truncus arteriosus can develop pulmonary overcirculation.

• 6.

  Patients with dTGA sometimes do not have sufficient mixing of the blood from the two cardiac sides. Many of these infants require balloon septostomy to promote mixing.

• 7.

  Myocardial disease can present with either systolic or diastolic dysfunction.

The natural history of congenital heart disease varies tremendously, because some lesions will self-resolve or go unnoticed throughout a full lifetime, whereas other lesions cause patients to present in extremis at a very young age. Congenital heart disease that requires medical or surgical intervention in the neonatal period for survival or prevention of end organ compromise is often referred to as critical congenital heart disease (CCHD) and is the focus of this chapter. The management of CCHD in neonates has great variability but centers on several core tenets of cardiovascular function, maintaining (1) adequate systemic blood flow, (2) adequate but not excessive pulmonary blood flow, and (3) adequate return of oxygenated pulmonary blood flow. This chapter will discuss the evaluation and early management of patients with one of four common problems, including inadequate pulmonary blood flow, inadequate systemic blood flow, inadequate obligate intracardiac shunting, and abnormal myocardial function ( Fig. 38.1 ). Although different types of CCHD vary tremendously, a focus on these three basic tenets of cardiovascular function guides management in all described lesions.

It is not uncommon for a woman carrying a fetus with CCHD to have a full, seemingly uncomplicated pregnancy, yet for that infant to be critically ill shortly after birth. Fetal-placental circulation provides the means for adequate oxygen and nutrient delivery for the limited metabolic demands, even in many of the most severe cardiac lesions. Earlier prenatal diagnosis with fetal imaging allows the time for thoughtful planning of postnatal management and allows families time to begin learning about and coping with a new diagnosis. Multiple studies have demonstrated the benefit to allowing a full pregnancy for fetuses with CCHD, without early induction of birth. Although organ perfusion and oxygenation is intact throughout pregnancy, the heart may continue maldevelopment. In several specific cardiac lesions, such as critical aortic stenosis, pulmonary atresia with intact ventricular septum (PA/IVS), and hypoplastic left heart syndrome (HLHS) with intact atrial septum, some centers advocate for fetal intervention to palliate a cardiac lesion and halt further sequelae. However, these interventions remain novel with yet unestablished safety, efficacy, and optimal patient selection.

At the time of birth, the umbilical cord is clamped and placental flow is removed from circulation, causing systemic vascular resistance to abruptly rise and the supply of oxygenated blood to cease. With the first breaths, alveolar beds begin to open and the lungs are exposed to higher oxygen content, prompting pulmonary vascular resistance to begin to fall. In normal physiology these changes are accompanied by closure of the ductus venosus due to lack in placental flow, an increase in pulmonary venous return and functional closure of the foramen ovale, and beginning of closure of the ductus arteriosus.

Patients with critical anatomic or physiologic cardiac abnormalities often develop signs and symptoms during this transitional period ( Fig. 38.2 ) and may develop cardiogenic shock due to an inability to supply the body with adequate oxygenated blood for metabolic demands. This can be due to inadequate pulmonary blood flow, inadequate systemic blood flow, inadequate intracardiac mixing, or inadequate cardiac myocardial performance. Although these issues can individually be the subject of a textbook, this chapter serves as a brief review of common issues associated with the evaluation and management for common physiologies with references to further discussion ( Fig. 38.3 ).

Inadequate Pulmonary Blood Flow

Patients with CHD that results in inadequate pulmonary blood flow (e.g., tricuspid atresia, pulmonary atresia, critical pulmonary valve stenosis, etc.) typically demonstrate cyanosis within minutes of life and have a low oxygen tension that does not improve with the administration of oxygen. After confirmation of cardiac disease or while awaiting confirmation, initiation of a prostaglandin infusion (PGE1) to maintain patency of the ductus arteriosus often allows clinical stability to gather information for surgical planning. Meanwhile, initial patient management must address pulmonary etiologies of hypoxia and ensure adequate airway, respiratory drive, and lung expansion. These aspects must be addressed as appropriate. In the majority of patients with CHD that results in inadequate pulmonary blood flow, patency of the ductus arteriosus and basic respiratory care is sufficient to maintain adequate oxygen carrying delivery while awaiting surgical intervention. There are specific cardiac lesions that require special considerations, some of which are detailed below.

Total anomalous pulmonary venous return is a disease in which the pulmonary veins connect to a confluence that drains to the right atria through abnormal supracardiac, infracardiac, or intracardiac connections. In some patients, particularly those with infracardiac and supracardiac drainage, the pulmonary venous drainage may be obstructed by external compression or narrow vessels in its course back to the heart ( Fig. 38.4 ). All patients with total anomalous pulmonary venous return have some degree of cyanosis due to mixing of oxygenated and deoxygenated blood; however, patients with even minor obstruction may develop pulmonary edema and worse oxygen saturations. If the obstruction is more significant infants may develop elevated pulmonary artery pressures resulting in profound cyanosis from right-to-left shunting at the patent ductus arteriosus (PDA) or low cardiac output if a PDA is not present. Although the role of PGE1 is debated in this lesion, it can be detrimental if ductal patency results in greater left-to-right shunting and worsening pulmonary edema. These patients should be intubated and given high concentrations of oxygen as necessary to maintain adequate oxygen saturations; however, the only true treatment for obstructed pulmonary venous drainage is prompt surgical intervention. Obstructed pulmonary veins remain one of the few neonatal cardiac surgical emergencies. Unobstructed pulmonary venous drainage is often treated with diuretics in the neonatal period and repaired at a few weeks of age; however, results suggest that morbidity is decreased with earlier repair.

Ebstein anomaly is a heterogenous disease caused by a failure of normal development of the tricuspid valve in utero, causing tricuspid valve insufficiency and a decrease in the function cavity size of the right ventricle ( Fig. 38.5 ). Although mild forms of the disease may result in a long asymptomatic life, more severe subtypes may result in patients with inadequate pulmonary blood flow and potentially functional or structural pulmonary atresia if the right ventricle is unable to generate antegrade blood flow. These patients will present with hydrops fetalis or postnatal cyanosis and potentially cardiogenic shock. Given the poor outcomes associated with neonatal repair, surgery is only indicated in patients who have cyanosis, overt heart failure, or poor cardiac output causing inadequate organ perfusion. Neonatal intervention is typically only performed in patients who fail to wean from PGE1 or have an unacceptably low oxygen saturation after weaning. Overall, this represents a minority of patients with Ebstein malformation. There are several approaches to neonatal intervention, all of which have less than optimal outcomes. Although many patients are able to have a biventricular repair, neonatal surgical interventions are commonly performed in patients who will have a functionally single ventricle physiology and are focused on creation of adequate yet controlled pulmonary blood flow either through a surgical systemic to pulmonary shunt or placement of a stent in the ductus arteriosus. These patients often have poor cardiac output due to ventricular-ventricular interactions, in which the large right ventricle (RV) compresses the left ventricle (LV). Management of this complication remain controversial and include surgical reduction and potentially oversewing of the tricuspid valve. Neonates with anatomic pulmonary stenosis or atresia but reasonable RV function may rarely benefit from a balloon valvuloplasty as initial palliation. However, this procedure is likely to cause pulmonary insufficiency and is subject to the particular risk of the creation of a “circular shunt” in patients with significant tricuspid regurgitation ( Fig. 38.5 ). In the “circular shunt,” blood will flow from the aorta to the pulmonary artery via the PDA, enter the RV through the insufficient pulmonary valve, enter the right atria due to the tricuspid regurgitation, then cross the ASD and exit the left heart only to again cross the PDA. This ineffective circulation is poorly tolerated, and closure of the PDA is often performed in the same catheterization procedure.

Patients with PA/IVS have wide variability in their management and outcomes. After maintenance of a PDA is ensured with PGE1 administration, an echocardiogram is obtained to evaluate tricuspid valve effective orifice size and whether the right ventricle is of adequate size and function for an eventual biventricular repair. Patients with hypoplastic tricuspid valves commonly form coronary sinusoids, and those with more severe disease may rely upon these sinusoids for coronary circulation, a physiology termed right ventricular dependent coronary circulation. Many centers perform cardiac catheterization on all neonates with PA/IVS to define coronary anatomy and to determine coronary dependence. Catheterization data along with echocardiographic description of the tricuspid valve and right ventricle size, function, and morphology are often adequate to determine the initial course of management, which can include PDA stent or percutaneous pulmonary valvuloplasty in the catheterization lab, biventricular surgical repair, surgical aortopulmonary shunt, or primary listing for transplantation. The most classic management algorithm is based on a study that recommends biventricular repair in patients with a tricuspid valve z -score greater than −3. However, many centers favor a biventricular repair even for patients with smaller tricuspid valves. ^, Some centers advocate creation of a patent right ventricular outflow tract in all patients who do not have right ventricular dependent coronary circulation, because decompressing the RV may be beneficial to encourage ventricular growth and prevent hypertensive RV cavities and the associated negative ventricular-ventricular interactions.

Pulmonary valve stenosis is considered “critical” when maintenance of a ductus arteriosus is necessary to maintain adequate pulmonary blood flow. After diagnosis is confirmed with echocardiography, these patients are typically referred to the cardiac catheterization laboratory for transcutaneous pulmonary valve balloon dilation. Surgical approach to critical pulmonary valve stenosis is reserved for complex (particularly sub- or supravalvar) lesions or when catheterization has failed to relieve obstruction. Although balloon or surgical dilation is often effective at removing the valve gradient, the patient will often remain cyanotic due to hypertrophy of the right ventricle and right-to-left shunting at the atrial level. This may prompt use of prostaglandin to maintain ductal patency while waiting for the ventricular hypertrophy to regress. However, preservation of ductal patency causes the pulmonary artery to remain at systemic level pressure and may delay regression of hypertrophy. Judicious use of prostaglandin infusions to maintain oxygen saturations greater than 75% is certainly reasonable. In patients who have prolonged desaturation, it is reasonable to consider stenting of the PDA or surgical placement of a systemic-to-pulmonary shunt. In patients with severe infundibular hypertrophy, relief of valvar stenosis may create dynamic right ventricular outflow obstruction. Dynamic infundibular hypertrophy may be treated with fluid administration, sedation, and beta blockade and rarely requires surgical myomectomy.

An important scenario in which neonates may have inadequate pulmonary blood flow is when there is a source of shunting (either intracardiac or at a PDA) with severe elevation of pulmonary vascular resistance. In the neonatal population, there are a multitude of etiologies for this physiology. Initiation of medications to decrease the pulmonary vascular resistance (PVR) should be considered in patients with right-to-left shunting before shunts are removed due to the potential of precipitating right ventricular failure or inadequate cardiac output. This topic is more thoroughly discussed elsewhere in this text.