A term 3700-g boy was delivered vaginally without complications. He breast-feeds well, voids, and passes meconium in the first 12 hours of life. At 15 hours of life he is no longer interested in feeding and appears dusky. His respiratory rate is 65 breaths/min, his oxygen saturation on pulse oximetry is 80%, and his capillary refill is 3 seconds. No heart murmur is audible, but a loud single second heart sound is noted.
What is the most likely diagnosis?
What is the best management for this condition?
ANSWERS TO CASE 25: Transposition of the Great Arteries
Summary: A healthy-appearing term infant suddenly loses interest in feeding and develops cyanosis, hypoxia, poor peripheral perfusion, and tachypnea. Cardiac examination reveals a loud single second heart sound and no murmur.
• Most likely diagnosis: Cyanotic congenital heart disease (CHD), likely transposition of the great arteries (TGA).
• Best initial management: Administer prostaglandin E1 to maintain patency of the ductus arteriosus.
1. Know the major types of cyanotic CHD and their most common clinical presentations.
2. Understand why some types of CHD result in cyanosis whereas others do not.
3. Understand the need to maintain ductus arteriosus patency in some types of CHD.
This boy has symptoms consistent with cyanotic CHD and likely has TGA. In this condition, the cardiac origins of the aorta and the pulmonary artery are switched, thus creating two parallel circuits of blood flow rather than the normal series circuit (Figure 25-1). This situation is incompatible with life unless a connection between the pulmonary and systemic circuits exists. During the first hours of life, the ductus arteriosus and the foramen ovale provide this connection; symptoms develop when these connections begin to close. Some TGA patients also have a ventricular septal defect (VSD) and may first show signs of disease later in infancy. Management of the infant in this scenario consists of immediate steps to maintain patency of the ductus arteriosus.
Figure 25-1. Schematic drawing of circulation of various cardiac defects: (A) Normal circulation; (B) Tetralogy of Fallot; (C) Pulmonary artresia; (D) Tricuspid atresia; (E) Transposition of the great arteries; (F) Truncus arteriosus. Black arrows indicate deoxygenated blood; cross-hatched arrows indicate mixed blood; white arrows indicate oxygenated blood. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
Congenital Cyanotic Heart Disease
CYANOSIS: Bluish discoloration of the skin and mucous membranes caused by insufficient saturation of the blood with oxygen. Peripheral cyanosis is common in neonates and involves the extremities; it may be normal. Central cyanosis is always abnormal and is seen on the tongue, gingiva, and buccal mucosa.
DUCTUS-DEPENDENT LESIONS: Cardiac defects that are incompatible with life in the absence of a patent ductus arteriosus (PDA).
RIGHT-TO-LEFT CARDIAC SHUNT: Abnormal flow of blood across a cardiac defect from the right side of the heart containing deoxygenated blood to the left side of the heart where it is then pumped into the systemic circulation. These lesions result in cyanosis.
Cyanotic CHD often manifests itself after the PDA begins to close (so the condition may be termed ductus dependent). Patency of the ductus maintains a connection between the pulmonary and systemic circulations; closure normally occurs on the first or second day of life in term infants. Previously, neonatal cyanotic CHD management involved emergency surgical repair on very sick infants; the introduction of prostaglandin E1, an intravenously administered medication that keeps the ductus open, now allows for infant stabilization prior to more definitive corrections.
Cyanotic CHD is characterized by decreased pulmonary blood flow. Unsaturated blood returning to the heart from the periphery is shunted into the systemic circulation, thus bypassing the lungs. This occurs whenever blood flow into the pulmonary system is compromised, as in pulmonary valve stenosis or if the origins of the pulmonary artery and aorta are switched (TGA).
Pulse oximetry can be used to measure the oxygen saturation of the tissues that are perfused by the portion of the aorta that is proximal to the ductus (the right handor an ear lobe) and then is compared to tissues perfused by the portion of the aorta that is distal to the ductus (the lower extremity). If there is a difference of more than 3% to 5%, then there may be a right-to-left shunt across the ductus.
Transposition of the great arteries occurs in approximately 5% of children with congenital heart disease; it is the most common cardiac cause of cyanosis in neonates. TGA typically causes an “egg-on-a-string” appearance on chest radiography (Table 25-1), although the appearance may be normal in the first few days of life. Electrocardiography (ECG) shows the normal right ventricular hypertrophy seen in neonates. Diagnosis is confirmed with echocardiography.
Table 25-1 • TYPICAL RADIOGRAPHIC FINDINGS OF COMMON HEART LESIONS
Initial management of TGA (after prostaglandins) involves creation of an atrial septum (“atrial septostomy”) via cardiac catheterization, which provides immediate symptom palliation. Definitive surgical care often occurs in the first 2 weeks of life; postoperative stenosis at the repair sites is a potential long-term complication.
Pulmonary valve stenosis, another cyanotic CHD, accounts for approximately 7% of CHD. Cyanosis and exercise intolerance, if any, are proportional to the degree of stenosis. Examination reveals an upper left sternal border systolic murmur that radiates to the left infraclavicular area and a systolic click. The ECG is normal in mild cases, but greater degrees of stenosis cause right-axis deviation, right atrial hypertrophy, and right ventricular hypertrophy. Valvuloplasty is achieved through cardiac catheterization. Pulmonary stenosis may occur in conditions such as glycogen storage disease and Noonan syndrome.
When pulmonary stenosis occurs with a large VSD, the result is known as tetralogy of Fallot (TOF). With TOF, the intraventricular septum is displaced anteriorly, resulting in right ventricular outflow obstruction and displacement of the aorta over the right ventricle. Right ventricular hypertrophy develops as a result of the hemodynamic changes caused by the other abnormalities. The characteristic finding on chest radiograph is a boot or wooden shoe appearance (“coeur en sabot,” Table 25-1). If pulmonary stenosis is mild at birth, neonates have normal color (so-called pink tetralogy), but by early childhood most become cyanotic as a result of stenosis progression. Many children with TOF also experience hypercyanotic spells (“tetralogy spells”) caused by a sudden increase in right-to-left shunting of blood. These spells may be brought on by activity or agitation, or they may occur without an apparent precipitant. Such children can be seen assuming a squatting posture, which compresses peripheral blood vessels, thus increasing pulmonary blood flow and systemic arterial oxygen saturation. With current surgical management, 90% of patients with TOF survive to adulthood.
Cyanosis is a hallmark of children who have tricuspid valve abnormalities of tricuspid atresia or Ebstein anomaly. In tricuspid atresia, no outlet exists between the right atrium and the right ventricle, forcing systemic venous return to enter the left atrium via the foramen ovale or an associated atrial septal defect; a VSD also is often present. The tricuspid valve of Ebstein anomaly is insufficient because two leaflets are displaced inferiorly into the right ventricle and unable to approximate each other; this also results in a smaller ventricle chamber and often obstructs ventricular outflow. Both conditions often are “ductal dependent” in the neonate, and both require surgical correction.
25.1 A 12-year-old boy requires a sports physical examination. He denies chronic health problems, including adverse exertion symptoms. The clinician notes a I to II/VI left upper sternal border systolic murmur that does not radiate. The second heart sounds splits normally, and no audible click is appreciated. Peripheral perfusion is normal, and the fingers are not clubbed. Which of the following is the best recommendation?
A. He should not play strenuous sports.
B. He can participate in sports without restrictions.
C. A chest radiograph and an ECG before further recommendation can be made.
D. A cardiology evaluation.
E. He may participate in sports, but he should seek immediate medical attention for dyspnea or other adverse symptoms.
25.2 A term, 3700-g infant is born vaginally without complications and has uneventful immediate neonatal course. At 2 weeks of age, a II/VI systolic murmur is noted in the mitral area that radiates to the back. A similar murmur is noted in the right axilla. The infant is pink and breathing easily, and the nurses notes show that he has been taking 30 cc of formula approximately every 2 hours. Initial management should include which of the following?
A. Chest radiography, ECG, and four extremity blood pressures
B. Immediate administration of prostaglandin E1
C. Admission to the pediatric intensive care unit
D. Consultation by a pediatric cardiologist
E. Close follow-up in your pediatric clinic
25.3 A 4-year-old boy presents for a well-child visit. His mother notes that he breathes fast and his lips turn “dusky” when he runs or plays hard. The symptoms resolve once he stops the activity. On examination, he has a II/VI left upper sternal border systolic murmur that radiates to the back; a faint click is heard. Which of the following is the most likely cause of this child’s exercise intolerance?
B. Atrial septal defect
C. Pulmonary valve stenosis
D. Tricuspid atresia
E. Ventricular septal defect
25.4 A 15-month-old girl is playing quietly in your waiting room. The skin around her mouth is faintly blue, but she appears comfortable. She arises from her squatting position to run after her brother, and she suddenly becomes dyspneic and cyanotic. She returns to a squatting position and soon is breathing comfortably with only slight perioral cyanosis. Which of the following would you expect to see on her chest radiograph?
A. A “boot-shaped” heart
B. An “egg on a string”
C. Lung hyperinflation
E. Pulmonary congestion
25.1 B. This child has a benign pulmonary flow murmur, differentiated from a pathologic pulmonary murmur in that it does not radiate, no click is heard, and no signs and symptoms of cardiac disease (digital clubbing, cyanosis, exercise intolerance) are found.
25.2 E. This infant has peripheral pulmonic stenosis, a benign childhood murmur. Other frequently encountered benign childhood murmurs are the venous hum (a low-pitched murmur heard at the sternal notch only when the child is upright) and the Still vibratory murmur (a high-pitched “musical” systolic murmur heard best at the left sternal border in the supine position). Although it may be difficult to diagnose the multitude of pathologic heart sounds, clinicians certainly should know the characteristics of the common benign childhood murmurs.
25.3 C. Although pulmonary stenosis and tricuspid atresia are cyanotic heart lesions, exercise-induced cyanosis and systolic murmur are characteristic of pulmonary stenosis.
25.4 A. This child has TOF; she experiences improvement when squatting and “tet” (hypercyanotic) spells when running. The “boot-shaped” heart is a characteristic chest radiographic finding.
Cyanotic congenital heart disease is characterized by decreased pulmonary blood flow (right-to-left shunt). Transposition of the great arteries and defects of the tricuspid valve and pulmonary outflow tract are examples of cyanotic heart defects.
Lesions of congenital heart disease incompatible with life except in the presence of a PDA are termed “ductus dependent.”
Prostaglandin E1 is often used in infants with cyanotic congenital heart disease to maintain the patent ductus arteriosus until more definitive surgical correction can be attempted.
The heart defects in tetralogy of Fallot are: (1) ventricular septal defect, (2) pulmonic stenosis, (3) overriding aorta, and (4) right ventricular hypertrophy.
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