89: Congenital Heart Disease

The diagnostic dilemma of the newborn with congenital heart disease must be resolved quickly because therapy may prove lifesaving for some of these infants. Congenital heart disease occurs in ∼1% of live-born infants. Nearly half of all cases of congenital heart disease are diagnosed during the first week of life. In patients with complex congenital heart disease, neonatal hospital mortality can be as high as 7%. These patients have a high frequency of multiple congenital anomalies, syndromes, low birthweight, and prolonged length of stay. The most frequently occurring anomalies seen during this first week are patent ductus arteriosus (PDA), D-transposition of the great arteries, hypoplastic left heart syndrome (HLHS), tetralogy of Fallot (TOF), and pulmonary atresia.

Symptoms and signs in newborns with heart disease permit grouping according to levels of arterial oxygen saturation based on the 100% oxygen test (see the following). Further classification (based on other physical findings, laboratory testing) facilitates delineation of the exact cardiac lesion present.

1. Cyanotic heart disease. Infants with cyanotic heart disease are usually unable to achieve a Pao₂ of >100 mm Hg after breathing 100% inspired oxygen for 10–20 minutes (hyperoxia test).

2. Acyanotic heart disease. Infants with acyanotic heart disease achieve Pao₂ levels of >100 mm Hg under the same conditions as noted in Section I.A.

See Figure 89–1. (See Chapter 51.)

1. Hyperoxia test. Because of intracardiac right-to-left shunting, the newborn with cyanotic congenital heart disease (in contrast to the infant with pulmonary disease) is unable to raise the arterial saturation, even in the presence of increased ambient oxygen.

   1. Determine Pao₂ while the infant is on room air.

   2. Give 100% oxygen for 10–20 minutes by mask, hood, or endotracheal tube.

   3. Obtain an arterial blood gas level while the infant is breathing 100% oxygen.

   4. Interpret results based on Section I.

2. Cyanosis. Care must be taken in evaluating cyanosis by skin color because polycythemia, jaundice, racial pigmentation, or anemia may make clinical recognition of cyanosis difficult. See Infectious.

3. Murmur. The infant with cyanotic congenital heart disease often does not have a distinctive murmur. The most serious of these anomalies may not be associated with a murmur at all.

4. Other studies. Cyanotic infants may be further classified on the basis of pulmonary circulation on chest radiograph and electrocardiographic findings.

5. Diagnosis and treatment. Figure 89–1 outlines the diagnosis and treatment of cyanotic heart disease.

6. Specific cyanotic heart disease abnormalities

   1. D-transposition of the great arteries (D-TGA). This is the most common cardiac cause of cyanosis in the first year of life, with a male-to-female ratio of 2:1. The aorta comes from the right ventricle and the pulmonary artery from the left ventricle, with resultant separate systemic and pulmonary circuits. With modern newborn care, the 1-year survival rate is ∼90%.

      1. Physical examination. Typical infant is large and vigorous, with cyanosis but little or no respiratory distress. There may be no murmur or a soft, systolic ejection murmur.

      2. Chest radiograph. This study may be normal, but typically it reveals a very narrow upper mediastinal shadow (“egg on a stick” appearance).

      3. Electrocardiography (ECG). There are no characteristic ECG findings.

      4. Echocardiography is diagnostic. Typical findings include branching of the anterior great vessel into the innominate, subclavian, and carotid vessels and branching of the posterior great vessel into the right and left pulmonary arteries.

      5. Cardiac catheterization. Like echocardiography, this study is diagnostic and often therapeutic, as outlined next.

      6. Treatment. If severe hypoxia or acidosis occurs, urgent balloon atrial septostomy can be done under echocardiogram guidance in the nursery. Cardiac catheterization with balloon septostomy and subsequent arterial switch operation are methods of treatment. Prostaglandin E₁ (PGE₁) may increase shunting.

   2. Tetralogy of Fallot (TOF). Tetralogy of Fallot is characterized by 4 anomalies: pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy (RVH). There is a slight male predominance. Cyanosis usually signifies complete or partial atresia of the right ventricular overflow tract or extremely severe pulmonary stenosis with hypoplastic pulmonary arteries. The degree of right ventricular outflow obstruction is inversely proportional to pulmonary blood flow and directly proportional to the degree of cyanosis. Tetralogy of Fallot with absent pulmonary valve may present with respiratory distress or poor feeding (because of compression of the esophagus or bronchi by the large pulmonary arteries).

      1. Physical examination. The patient is cyanotic with a systolic ejection murmur along the left sternal border. Loud murmurs are associated with more flow across the right ventricular outflow tract and milder degrees of desaturation. Softer murmurs are associated with less flow and more hypoxia.

      2. Chest radiograph. The chest radiograph film reveals a small, often “boot-shaped” heart, with decreased pulmonary vascular markings. A right aortic arch is seen in ∼20% of these infants.

      3. ECG. The ECG may be normal or may demonstrate RVH. The only sign of RVH may be an upright T wave in V₄R or V₁ after 72 hours of age.

      4. Echocardiography. Usually diagnostic, with an overriding aorta, ventricular septal defect (VSD), and small right ventricular outflow tract.

      5. Treatment. Pulmonary blood flow may be ductal dependent with severe cyanosis and may respond to ductal dilation using PGE₁ (see Chapter 148). This measure allows more flexibility for planning cardiac catheterization and surgical correction. Surgery (shunting or total correction) may be considered.

(Figure 89–2)

1. Hyperoxia test. See Section II.A.

2. Murmur. The infant who is not cyanotic will have either a heart murmur or symptoms of congestive heart failure.

3. Diagnosis and treatment. See Figure 89–2.

4. Specific acyanotic heart disease abnormalities

   1. Ventricular septal defect (VSD). The most common congenital heart abnormality with equal sex distribution. Murmurs can be heard at birth but typically appear between 3 days and 3 weeks of age. Congestive heart failure is unusual before 4 weeks of age but may develop earlier in premature infants. Symptoms and physical findings vary with patient age and defect size. Spontaneous closure occurs in half of the patients. Surgical correction is reserved for large, symptomatic VSDs only.

   2. Atrial septal defect (ASD). Not an important cause of morbidity or mortality in infancy. Occasionally, congestive heart failure can occur in infancy but not usually in the neonatal period.

   3. Endocardial cushion defects. Include ostium primum–type ASD with or without a cleft mitral valve and an atrioventricular (AV) canal. These defects are commonly associated with multiple congenital anomalies, especially Down syndrome. If marked AV valve insufficiency is present, the patient may have congestive heart failure at birth or in the neonatal period.

      1. Physical examination. On physical examination, a systolic murmur resulting from AV valve insufficiency may be heard. Cyanosis may be present but is often not severe. Infants with severe pulmonary artery hypertension may have little or no murmur.

      2. Chest radiograph. Variable findings may include a dilated pulmonary artery or a large heart secondary to atrial dilatation.

      3. ECG. Left axis deviation (left superior vector) is always found; the PR interval may be long, or there may be an RSR' pattern in V₄R and V₁.

      4. Echocardiography. Usually diagnostic; the echocardiogram usually demonstrates a common AV valve with inlet VSD or a defect in the septum primum with an abnormal mitral valve.

      5. Treatment. Congestive heart failure is treated with diuretics and digoxin (for dosages, see Chapter 148); early cardiac catheterization with corrective surgery may be needed to prevent pulmonary vascular obstructive disease.

Occurs in both cyanotic and acyanotic forms. In 15% of cases, the foramen ovale is intact and thus prevents mixing at the atrial level, causing cyanosis. Infants with mixing at the atria are acyanotic. HLHS accounts for 25% of all cardiac deaths during the first week of life.

1. Physical examination. The infant is typically pale and tachypneic, with poor perfusion and poor to absent peripheral pulses. A loud single S₂ is present, usually with a gallop and no murmur. There is hepatomegaly, and metabolic acidosis is usually present by 48 hours of age.

2. Electrocardiogram. Demonstrates small or absent left ventricular forces.

3. Chest radiograph. Moderate cardiomegaly is present, often with a large main pulmonary artery shadow.

4. Echocardiography. A diagnostic study demonstrates a small or slit-like left ventricle with a hypoplastic ascending aorta.

5. Treatment. Systemic blood flow is ductal dependent; therefore, PGE₁ is of value. Oxygen should not be given, as the resultant dilatation of the pulmonary vessels increases pulmonary blood flow. Respiratory compromise and subsequent dilatation and reduced right ventricular (RV) function are undesired effects of oxygen administration. In fact, infants with HLHS and pulmonary overcirculation may require oxygen concentrations <21%. Frequent monitoring of blood gases and lactate is required preoperatively. Surgical correction is done in 3 stages. The first is palliation (the Norwood procedure), redirecting the blood flow so that the right ventricle serves as the “systemic ventricle” and a surgically constructed “shunt” provides pulmonary blood flow. Some surgeons prefer to do a Sano modification of the Norwood, which involves placing a Gore-tex tube from the RV to the main pulmonary artery (MPA). Successful outcome is influenced by gestational age (term infants do much better than preterm infants) and the presence of other major anomalies. The second stage usually consists of a hemi-Fontan or bidirectional Glenn operation, routing superior vena cava blood to the lungs and closing the systemic-to-pulmonary artery shunt. The third stage (the Fontan procedure) directs remaining systemic venous return directly to the pulmonary circulation. Neonatal cardiac transplantation is a second option, but shortage of organs is a significant deterrent. Compassionate care (keeping the infant comfortable until death) may be appropriate in some instances.

(Table 89–1) A discussion of heart disease in neonates would not be complete without the inclusion of common multiple congenital anomaly (MCA) syndromes associated with heart defects. Many times, recognition of MCA syndromes facilitates identification of the heart defect. Syndromes that tend to present after the newborn period have not been included. See Chapter 88 for a complete discussion of anomalies and syndromes.

Several teratogens associated with congenital heart disease have been identified (Table 89–2), although there is not a 100% relationship between exposure and heart defects. A history of teratogen exposure may help in the diagnosis.

Syndromes of abnormal situs are associated with congenital heart disease. For example, an infant with situs inversus totalis and dextrocardia has the same incidence of congenital heart disease as the general population. If, however, there is disparity between thoracic and abdominal situs, the incidence of congenital heart disease is >90%. (Check the chest radiograph to see that the cardiac apex and the stomach bubble are on the same side. Both should be on the left.) Some of these syndromes involve bilateral left-sidedness (two bilobed lungs or multiple spleens) and complex cyanotic congenital heart disease, whereas others have bilateral right-sidedness (two trilobed lungs or an absent spleen) and complex cyanotic congenital heart disease.

1. Fetal echocardiography

   1. General considerations. Fetal echocardiography is now possible in many centers. The optimal gestational age to perform echocardiography is between 18 and 24 weeks when structural abnormalities and arrhythmias can be detected. With early detection of cardiac abnormalities, arrangements can be made for delivery at a center with pediatric cardiac and surgical facilities. If the anomaly is not consistent with life, some families may elect termination of pregnancy.

   2. Indications. See Table 89–3.

      1. Maternal factors. Oligohydramnios or polyhydramnios, diabetes, collagen vascular disease, teratogen exposure, or a previous child with congenital heart disease.

      2. Fetal factors. Suspected cardiac abnormality on obstetric ultrasound examination, pleural fluid, pericardial fluid, heart rate abnormalities, intrauterine growth retardation, or other abnormality on obstetric ultrasound examination.

      3. Genetic factors. Familial history of chromosomal disorders or congenital heart disease.

2. Emergency therapy. Once the specific lesion has been identified as emergent, a decision about therapy must be made. As an example, if confronted with a very cyanotic infant with no murmur, a normal chest radiograph, and a normal ECG, and it is believed that the diagnosis of D-transposition of the great arteries is likely, it is necessary to prepare for a balloon septostomy.

3. Prostaglandins. As a general principle, if an infant is cyanotic and has decreased pulmonary blood flow, the Pao₂ will be improved by promoting flow through the ductus arteriosus via a drip of prostaglandin E₁ (alprostadil or Prostin VR Pediatric). Maintaining patency of the ductus will enable stabilization of the infant and subsequent catheterization or surgery to be planned on an urgent rather than emergent basis. Similarly, if poor peripheral pulses and acidosis from poor perfusion are present, infusion of prostaglandin, using the same dose, will open the ductus arteriosus and allow right ventricular blood flow to augment the systemic circulation. This measure is beneficial in critical aortic stenosis, coarctation of the aorta, and HLHS. (For dosage and other pharmacologic information, see Chapter 148.)

4. Antiarrhythmic drugs. Rapid arrhythmias may occur during intrauterine life or after delivery. Arrhythmias are a cause of fetal hydrops and intrauterine death; most often, the rhythm disturbance is a rapid supraventricular tachycardia with a 1:1 ventricular response. Occasionally, atrial flutter with 2:1 block presents before or just after birth. Some anti-arrhythmia medications given to mothers can cross the placenta, enabling fetal treatment. Digitalis and propranolol have been successful antiarrhythmic agents in newborns, but treatment with adenosine or electrical cardioversion (see Chapter 28) is also sometimes necessary. Digitalis is contraindicated in Wolff-Parkinson-White syndrome.

5. Pacemaker. Fetal hydrops can result from congenital complete heart block. If cardiovascular demise is imminent, delivery and temporary transvenous ventricular pacing may be lifesaving. It should be followed by urgent surgical placement of a permanent pacemaker. Mothers may have anti-Rho or anti-LA antibodies.

6. Other imaging techniques. While magnetic resonance imaging (MRI) is enjoying increasing utility in the identification of congenital heart disease in children, MRI of the neonatal heart is of limited utility. The rapid heart rate of neonates makes gaiting for image acquisition very difficult. Computed tomography (CT) and CT angiography (CTA) may help identify anomalies of pulmonary venous return. CTA has become the gold standard of evaluation of vascular rings, but these do not usually present in the immediate neonatal period.

7. Other considerations. Optimal care of the infant prior to and immediately after heart surgery determines overall outcome. A perfectly executed corrective procedure cannot succeed without support of the infant postoperatively. Drugs that manipulate pulmonary vascular resistance (nitric oxide [NO], sildenafil, oxygen) and have a favorable influence on cardiac output and its distribution are required more often than not. Milrinone as an afterload reducer is often used and can be transitioned to the oral enalapril. Nesiritide (Natrecor), a recombinant form of human B-type natriuretic peptide, has both vasodilation and diuretic properties and can be safely used for shorter periods of time than milrinone. Levosimendan, a calcium-sensitizing agent, has inotropic and vasodilator effects. Studies with small numbers of infants/neonates have, to date, shown no advantage of levosimendan over milrinone in low cardiac output states following open-heart surgery. Milrinone use after surgical ductal ligation treats hemodynamic instability, facilitating central nervous system and gut perfusion.