Caring for Infants with Congenital Heart Disease and Their Families
Congenital heart defects are classified into two broad categories: acyanotic and cyanotic lesions. The most common acyanotic lesions are ventricular septal defect, atrial septal defect, atrioventricular canal, pulmonary stenosis, patent ductus arteriosus, aortic stenosis, and coarctation of the aorta. Congestive heart failure is the primary concern in infants with acyanotic lesions. The most common cyanotic lesions are tetralogy of Fallot and transposition of the great arteries. In infants with cyanotic lesions, hypoxia is more of a problem than congestive heart failure. Suspicion of a congenital heart defect should be raised by the presence of feeding difficulties in association with tachypnea, sweating and subcostal recession, or severe growth impairment. Follow-up of infants with congenital heart disease should follow the schedule of routine care for healthy babies with some modifications, such as the administration of influenza and pneumococcal vaccines. More frequent follow-up is required if congestive heart failure is present. Family psychosocial issues should also be addressed. One of the main roles for the family physician is to help the parents put the diagnosis in perspective by clarifying expectations and misconceptions and answering specific questions.
The reported incidence of congenital heart disease (CHD) is eight cases per 1,000 live births.1 Family physicians must know how to screen for cardiac defects in infants, how to stabilize infants with these problems, and how to manage their problems in teamwork with a pediatric cardiologist and a cardiac surgeon. As patient advocates, we also must be prepared to help the parents and other family members cope with the psychosocial aspects of chronic disease in a child.
Studies suggest that 30 to 60 percent of congenital heart defects can be detected prenatally by four-chamber screening. High-resolution four-chamber transvaginal echocardiography can provide detailed imaging of the cardiac anatomy in the fetus and can detect major abnormalities, although routine prenatal screening for CHD remains controversial. In one large study, however, reliance on only a four-chamber view would have resulted in overlooking 23 percent of the defects. More detailed fetal echocardiography with outflow-tract views can be particularly helpful in detecting anomalies of the great arteries and is indicated in pregnancies in which the risk of CHD is increased.
Women at high risk of having an infant with CHD include those with diabetes, a family history of CHD, or exposure to drugs such as indomethacin (Indocin). In addition, first-trimester rubella exposure and residence at high altitudes are associated with an increased incidence of patent ductus arteriosus. Other infants at high risk for CHD include those with abnormalities of other systems and those with syndromes related to abnormal karyotypes. If a cardiac malformation is identified, a complete evaluation of other systems is warranted. Karyotyping is also recommended. Although an early prenatal diagnosis is advantageous, lesions can also develop later in pregnancy. Thus, some anomalies may be missed entirely. The timing of scanning is controversial. In most studies, scanning has been performed between 18 and 22 weeks’ gestation.
One-third of infants born with CHD develop life-threatening symptoms within the first few days of life. The infant mortality rate in these cases is as high as 90 percent. In as many as 80 percent of infants with a critical disease, congestive heart failure is the presenting symptom. Difficulty in feeding is common and is often associated with tachypnea, sweating, and subcostal retraction. Suspicion of CHD should be raised if feeding takes more than 30 minutes. A history of feeding difficulty often precedes overt congestive heart failure, even if only by six to 12 hours. On examination, signs of congestive heart failure include an S3 gallop and pulmonary rales. Failure to recognize congestive heart failure as the cause of symptoms in infants with CHD often leads to misdiagnosis and treatment for septicemia.
The presence or absence of a heart murmur is unreliable as a basis for the diagnosis of CHD. Transient murmurs are often heard in infants without cardiac abnormalities. Furthermore, a murmur is not present in many severe forms of CHD, such as tricuspid atresia, coarctation of the aorta, and transposition of the great vessels. When a murmur is associated with a cardiac defect, the intensity of the murmur is unrelated to the severity of the abnormality. However, the nature of the murmur (harsh, blowing, or musical), along with other heart sounds, is useful in differentiating mild defects from severe abnormalities. The infant’s age at the time a murmur is first heard is also helpful. If a murmur is detected within 24 hours of birth, the risk of CHD is one in 12; in this situation, patent ductus arteriosus is usually the underlying cardiac defect, and it usually closes before the infant is discharged from the hospital. If a murmur is first heard when the infant is six months of age, the chance of CHD is one in seven; at 12 months of age, the risk of CHD is one in 50.
Femoral and brachial pulses should be palpated. In infants with some obstructive lesions on the left side of the heart, femoral pulses may be palpable, but one or both brachial pulses may not be palpable. In infants with patent ductus arteriosus, femoral pulses may be present at birth but may become diminished or absent with closure of the ductus arteriosus at three to 14 days of age.
Common Congenital Heart Defects
Congenital heart defects are classified into two broad categories: acyanotic and cyanotic. In acyanotic defects, congestive heart failure is the most common symptom. The most common acyanotic lesions are ventricular septal defect, atrial septal defect, atrioventricular canal, pulmonary stenosis, patent ductus arteriosus, aortic stenosis, and coarctation of the aorta. In infants with cyanotic defects, the primary concern is hypoxia. The most common defects associated with cyanosis are tetralogy of Fallot and transposition of the great arteries. These nine lesions constitute 85 percent of all congenital heart defects. The remaining 15 percent are often cyanotic defects and include tricuspid atresia, total anomalous pulmonary venous return, truncus arteriosus, and hypoplastic left heart.
Suspicion of cyanosis should be confirmed by pulse oximetry. When pulmonary disorders are the cause of the cyanosis, administration of 100 percent oxygen usually increases the arterial oxygen saturation to at least 95 percent. In patients with cyanotic CHD, oxygen saturation will only increase to 80 to 85 percent.
An electrocardiogram (ECG) is indicated if CHD or arrhythmia is suspected. If the index of suspicion is high on the basis of other findings, a normal ECG does not exclude the presence of CHD. Chest radiographs of an infant with congestive heart failure demonstrate cardiomegaly and increased pulmonary vascular markings. A serious underlying heart defect is unlikely if the infant is clinically well and electrocardiographic and radiographic findings are normal.
Definitive evaluation requires cardiac imaging. Echocardiography remains the primary diagnostic modality, but magnetic resonance imaging provides excellent anatomic evaluation and often yields even more information than angiography.