Congenital heart disease is the most common birth defect, occurring in nearly 1 per every 100 live births. There is a 10% estimated incidence of severe cardiac malformations observed in spontaneously aborted fetuses. CHD remains the leading cause of noninfectious death in the first year of life.^1,2 For these reasons, nurses must be able to recognize the signs and symptoms of CHD and to deliver effective treatments and nursing care to neonates with this disease.

The heart is the first organ to develop in humans. Ultimately, the heart forms into the four-chambered organ found in adults. Initially, the developing heart supports the rapidly growing embryo. The human embryo develops cardiac cells between days 15 to 20 postconception. These cells signal cell migration and organ formation that ultimately evolve into the heart. The initial heart is a tube structure that is formed from endoderm tissue — a germ layer formed during embryo development — and begins to beat by four weeks of age. This tube structure then transforms into the primitive chambers of the heart. The chambers undergo a looping process where they bend to form the right and left side of the heart and establish their position alongside the pulmonary and gastrointestinal systems.^1,3

Cardiac septation, or the formation of the chambers of the heart, occurs from the formation of endocardial cushions. These cushions are swellings in the cardiac tissue that provide valvelike function in the primitive heart and go on to form the atrioventricular valves (tricuspid and mitral) and the semilunar valves (pulmonary and aortic).^1,3

Septation of the atria begins at the end of the fourth week of gestation. A septum primum grows down from the roof of the atrium. By the sixth week, the septum primum fuses with two other endocardial cushions to form the atrioventricular septum that divides into the right (tricuspid) and left (mitral) inlets. A septum secundum grows down from the ceiling of the right atrium. The two septums create the foramen ovale, which is essentially an open flap.^1,3

As cardiac septation occurs, outflow tract regions begin to form. This is where blood is taken away from the heart to either the pulmonary or circulatory system of the body. A conotruncus (or a primitive tube) forms and matches with the developing ventricles. Endocardial ridges appear within the conotruncus, which then form a conotruncal septum that divides the truncus into the ascending aorta and pulmonary system.^1,3

Before delivery, the fetus receives oxygen and removes waste products via fetal circulation <http://mcb.berkeley.edu/courses/mcb135e/fetal.html>, during which oxygenated blood is supplied by the placenta. This oxygenated blood travels via the umbilical vein to the right atrium. Because of increased pulmonary pressure due to the lungs not being inflated, at the right atrium about 90% of the blood is shunted to the left side of the heart via the foramen ovale to the left atrium. It then passes through the mitral valve into the left ventricle. The left ventricle contracts and pushes blood out of the ventricle through the aortic valve to the ascending aorta. About 10% of the oxygenated blood flows from the right atrium through the tricuspid valve into the right ventricle. The right ventricle then contracts and blood flows through the pulmonary valve into the pulmonary artery through the pulmonary system. This blood leaves the pulmonary system and crosses the ductus arteriosus into the descending aorta.⁴

At birth, the newborn is no longer dependent upon the placenta. The lungs expand with the first breath. The pulmonary pressures begin to drop and blood flow within the heart changes. Deoxygenated blood now enters the right atrium and travels through the tricuspid valve into the right ventricle. Upon contraction of the right ventricle, blood passes through the pulmonary valve and enters the pulmonary circulation via the pulmonary arteries. Blood then travels to the lungs, where it becomes oxygenated. This oxygenated blood is delivered via the pulmonary veins to the left atrium. Blood passes through the mitral valve into the left ventricle. Upon contraction of the left ventricle, blood passes through the aortic valve into the ascending aorta. The intra-atrial shunt, or foramen ovale, is now functionally closed as the pressure in the left atrium rises because of more blood flow entering the left heart under higher pressure. This causes the flap from the primum, which is open during fetal circulation as the foramen ovale, to close upon the atria septum. In addition, the intra-arterial shunt, or PDA shunt, closes because of exposure to a higher oxygen level and loss of circulating prostaglandins.⁴

When the problem is CHD

Five percent to 10% of infants who have CHD require more than routine care at birth, and 1% to 10% require assisted ventilation. However, most infants with CHD require no more than routine assistance at delivery, such as drying, warming, and stimulating. About 20% to 30% of all infants with CHD require patency of the ductus arteriosus for postnatal survival. As the ductus begins to close shortly after birth, these infants need IV access and a prostaglandin infusion. A small group of infants with CHD require urgent surgical intervention. Trained providers and readiness of equipment are essential for effective neonatal resuscitation whether CHD is present or not.⁴

A fetus with severe CHD is generally stable in the antenatal environment. Transition to the neonatal period often results in hemodynamic compromise. This is especially true for newborns with ductal-dependent circulation. In right heart obstructive lesions, ductal closure results in severe hypoxemia from diminished pulmonary blood flow. In left heart obstructive lesions, there is usually a markedly diminished systemic blood flow. This leads to end-organ shock, severe metabolic acidosis, and eventual death. The identification of such lesions in utero allows caregivers to maintain ductal patency and hemodynamic stability by initiating prostaglandin E1 therapy.⁵ 

Pulse oximetry is not routinely used in the delivery room for healthy infants. Research suggests that healthy newborns remain relatively desaturated in the immediate postpartum period. A pulse oximeter may be beneficial for an infant with CHD, but judicious use of supplemental oxygen should be considered with or without the pulse oximeter. For example, oxygen must be used with caution in infants who have forms of single-ventricle physiology, such as hypoplastic left heart syndrome (HLHS) — a condition where the left side of the heart, including the aorta, aortic valve, left ventricle, and mitral valve, is underdeveloped — as a rapid decrease in pulmonary vascular resistance from oxygen exposure may compromise systemic blood flow. Blood tends to flow to the path of least resistance. The management goal in these patients is to maximize oxygen delivery and to not increase arterial saturation.^4,6

Hypovolemia is rarely the cause of hypotension in the newborn who does not have CHD, unless identified sources of fluid loss are present. The use of fluid is generally not recommended. If an infant is started on prostaglandin therapy, which causes vasodilatation, the judicious use of volume is recommended. Side effects of prostaglandin therapy include respiratory depression and fever.⁴

Three lesions cause significant hemodynamic compromise after the neonate separates from the placenta —

• Transposition of the great arteries (TGA) with an intact ventricular septum and a restrictive atrial septum
• Hypoplastic left heart syndrome with an intact atrial septum
• Obstructed total anomalous pulmonary venous return (TAPVR)

Each of these lesions is anatomically different, but all result in the failure to provide pulmonary venous blood to the systemic circulation, causing severe hypoxemia.⁴

TGA with intact atrial and ventricular septums includes two separate circulations that are not communicating. These circulations run parallel to each other. Deoxygenated blood arrives at the right atrium, passes through the tricuspid valve, and enters the right ventricle. The right ventricle contracts and pumps blood through the aortic valve. The deoxygenated blood enters the ascending aorta to the systemic circulation because of the transposition of the great arteries and returns to the right atrium. At the same time, oxygenated blood arrives in the left atrium from the lungs via the pulmonary veins. This blood passes through the mitral valve and flows into the left ventricle. The left ventricle contracts and pushes blood through the pulmonary valve into the pulmonary artery, which returns the blood to the pulmonary circulation and the left atrium. The newborn becomes progressively hypoxemic and acidotic as the two circulations do not meet. The goal of treatment is to mix the two circulations so that oxygenation in the systemic circulation can occur.

The PDA can provide some mixing of the two separate circulations, but infants usually benefit from a balloon atrial septostomy, a procedure that is typically performed in the cardiac catheterization laboratory. A catheter is passed through the right atrium and the foramen ovale. A balloon is inflated, the catheter is pulled back, and essentially, an atrial septal defect (ASD) is created to allow mixing of the blood to improve systemic arterial saturation. Infants may then undergo cardiac surgical repair, which can include the arterial switch procedure. During this surgery, the great arteries are moved to align with the appropriate ventricles.^4,6

HLHS that occurs with an intact atrial septum does not allow oxygenated blood to pass to the systemic circulation. In HLHS, there is a small or absent left ventricle with hypoplastic or atretic (incompletely developed) mitral and aortic valves. This is referred to in the literature as single-ventricle physiology. Because of a usually present ASD, both oxygenated and deoxygenated blood mix at the atrial level, which flows through the right ventricle through the PDA to provide blood flow to the systemic circulation. Remember that with HLHS, there is no blood flow from the left ventricle into the aorta. Blood flow is balanced within the heart to flow through both the pulmonary system and the systemic circulation via the pulmonary artery. In general, an infant with HLHS should not be treated with oxygen, as oxygen therapy decreases pulmonary vascular resistance and causes shunting of blood to occur to the pulmonary blood vessels instead of to the systemic circulation. Again, the initial therapy is to allow mixing of blood at the atrial level. Long-range surgical plans include the neonatal Norwood procedure <www.chw.org/display/PPF/DocID/21364/router.asp>, where the main pulmonary artery is separated from the left and right portions of the pulmonary artery and joined with the upper portion of the aorta-followed by a Fontan procedure <www.fontanoperation.com/fontan.htm>, which involves diverting the venous blood from the right atrium to the pulmonary arteries without passing through the morphologic right ventricle — or the infant can be referred for cardiac transplantation. The surgical management of HLHS remains controversial.^4,6

In obstructed TAPVR, the pulmonary veins connect with venous structures either above the heart (supracardiac) or below the diaphragm (infradiaphramatic) instead of returning to the left atrium. Nonobstructive TAPVR can go unrecognized until later in infancy. Obstructive TAPVR occurs with severe pulmonary venous hypertension and profound hypoxemia. Most cases have an obstructed pathway from pulmonary venous return below the diaphragm through the liver or from pulmonary venous narrowing between the bronchus and pulmonary artery. With severe obstruction, the diagnosis may be difficult to detect with ultrasonography. Many of these neonates are so severely ill that they are initially treated with extracorporeal membrane oxygenation — use of an artificial lung to oxygenate tissue — before diagnosis can be made <www.cincinnatichildrens.org/health/heart-encyclopedia/treat/surg/ecmo.htm>. This lesion requires emergent surgical management to relieve the obstruction. Surgical repair consists of direct anastomosis of the veins to the left atrium.^4,6

Additionally, tetralogy of Fallot (TOF) with an absent pulmonary valve can present with decompensation in the delivery room. TOF is a heart anomaly consisting of ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an aortic root (the area where the aorta begins) that overrides the ventricular septum. Most infants with this defect are asymptomatic. These infants usually present in the newborn period with a harsh murmur. Palliative correction in the newborn period is performed if the infant has significant hypoxemia. Correction includes the creation of a shunt to allow blood flow to the pulmonary artery, to first, oxygenate the blood and second, to allow for the pulmonary vessels to grow. This procedure is called Blalock-Taussig shunt <www.childrenheartinstitute.org/educate/gallery/btshunt.htm>. If the infant has not required a shunt when correction is considered — usually in the first six months — the Blalock-Taussig shunt offers relief of the pulmonary artery outflow tract obstruction and closure of the VSD. When an infant presents with an absent pulmonary valve, mortality risk is higher because of the more complex surgery required to relieve the obstruction.^4,6

Low-birth weight infants with CHD have a higher mortality risk and a higher morbidity risk than preterm counterparts without CHD and term counterparts with CHD. Low birth weight is defined as a birth weight of less than 2,500 grams. This occurs in about 8% of births. Morbidity ranges from 35% to 83% after surgery in this population. It is expected that as a greater understanding of the pathophysiology and treatment of the diseases associated with prematurity improves, so, too, will the outcomes.⁷

A unique opportunity

Fetal echocardiography has given medicine a unique opportunity to observe the natural history of CHD in utero. Introduced in the 1980s, this field has led to the development of fetal cardiac intervention. However, the use of such intervention and whether it has made a difference remains controversial. Many factors other than early recognition of the disease have made a positive impact on survival for the newborn with CHD; these include cardiopulmonary bypass time, circulatory arrest, surgical procedure, cardiac anesthesia, and postoperative intensive care. While the use of fetal echocardiography has not made a significant difference in hospital mortality, it has improved morbidity of these patients.^5,8

Prenatal diagnosis allows for extensive parental counseling and coordination of care. The diagnosis of CHD prompts genetic testing to identify chromosomal abnormalities, which are found in 10% of cases, and a detailed anatomic evaluation to assess associated extracardiac anomalies that coincide in 15% of cases. Serial ultrasounds are usually recommended to monitor the growth and well-being of the fetus and changes in the cardiac function and structure. In cases of poor prognosis, early prenatal diagnosis gives the parents the option of terminating the pregnancy. Otherwise, arrangements for delivery should be discussed, because lesions diagnosed prenatally may require prompt resuscitation or intervention. Delivery at a tertiary care facility with full cardiac services can avoid transport-related morbidity and delay in intervention. This also allows the parents to be close to their newborn while the mother recovers from the birthing process, and allows the family to have access to the medical and surgical team caring for the baby. This improves a stressful experience for families anticipating the delivery of a newborn with critical CHD.^5,8

Once a diagnosis of CHD is suspected, the neonate should be stabilized and arrangements made for complete cardiac evaluation and management. Usually such an evaluation requires the transport of the neonate to an ICU where both a pediatric cardiologist and pediatric cardiothoracic surgeon are available. The most important parts of stabilization and transport include the initial resuscitation, airway management, vascular access, prudent use of supplemental oxygen, prostaglandin therapy, inotropic support, and the details of the actual transportation of the infant.⁹

It’s the nurse who is in the delivery room with the parents and neonate who participates in the initial delivery room management. The newborn is kept with the parents in the birthing room or is transported to the well-baby nursery or neonatal ICU. In each setting, the nurse is responsible for the ongoing assessment — including physical examination and monitoring of vital signs — of the neonate. Therefore, the nurse is the healthcare team member who usually first identifies abnormal findings (tachypnea, respiratory distress, respiratory failure, cyanosis, and poor perfusion) in the neonate and who reports these to the medical staff. The nurse institutes medical therapy — including prostaglandins, oxygen, inotropes, pre- and postductal pulse oximetry, ECG, and taking four extremity blood pressures — and obtains laboratory results such as complete blood count, blood type and screen, genetic studies, and arterial blood gases. The nurse also assists with interventions including insertion of umbilical lines, placement of peripheral IVs, and intubation in the stabilization of the neonate and is responsible for bedside management of the neonate. In addition, the nurse typically has the most contact with the family and so needs to explain ongoing therapy and support the family through the neonate’s hospital stay until transfer, discharge, or death.

CHD is recognized as the most common birth defect and is closely associated with morbidity and mortality in low-birth weight infants. However, CHD can be effectively managed through application of evidence-based guidelines and increasing awareness among nurses.