The Importance of Early Detection of Congenital Heart Disease: Who Should Be Offered Fetal Echocardiography?
By Huda Elshershari, MD
Introduction
Congenital heart disease is the most common serious congenital anomaly found at birth, affecting nearly 1 percent of live born infants and occurring in a higher percentage of fetuses. While many affected children have mild cardiac lesions, severe congenital heart disease remains one of the leading causes of mortality among infants. Most infants born with congenital heart disease have no known risk factors and are delivered after an uncomplicated pregnancy.
Prenatal detection of congenital heart disease usually is the result of careful examination of the fetal heart during a routine obstetric screening ultrasound. Ultrasound imaging uses high-frequency sound waves to produce dynamic images (sonograms) of organs, tissues or blood flow inside the body. It has been proved to be very safe to both the mother and the fetus. Fetal echocardiography is the term used for ultrasound imaging of the fetal heart.
Fetal echocardiography
Fetal echocardiography became available in the early 1980s. However, recent advancements in technology have allowed for earlier and improved detection of all forms of congenital heart disease. Most routine studies are performed transabdominally between 16 and 20 weeks' gestation. The studies can be done as an outpatient, and no maternal preparation is needed. Most studies can be completed within one hour.
The examiner begins with the assessment of the fetal position to identify the right and left sides of the body. The stomach, descending aorta and the spleen typically are found on the left side; the liver and the inferior vena cava on the right side. (See Figure 1.) The ultrasound transducer then is moved slightly cranially to visualize the four-chamber view. (See Figure 2.) This view is the key for identification of many complex cardiac lesions, such as hypo-plastic left heart syndrome or a complete atrioventricular septal defect. Additional views to incorporate imaging of the outflow tracts are critical to identify the conotruncal abnormalities, such as transposition of the great arteries and tetralogy of Fallot. Improved detection of fetal cardiac anomalies has been shown to be related to the experience of the examiner and the ability of the examiner to obtain these multiple views. Fetal echocardiography also is useful for diagnosis, monitoring and management of fetal arrhythmias.
Indications
Indications for fetal echocardiography generally are divided into fetal, maternal and familial indications. (See Table 1.) The most common fetal indication for a high-risk study by a fetal cardiologist is the presence of an abnormal obstetric screening ultrasound, where the likelihood of finding significant congenital heart disease often is greater than 50 percent. Other fetal indications include the presence of extracardiac or chromosomal anomalies, or an increased nuchal translucency. Maternal indications for a high-risk study include the presence of diabetes mellitus or exposure to teratogens such as lithium or anticonvulsants. Also, with continued advances in the treatment of congenital heart disease, many children will survive to become adults and raise families. Infants of these parents have an increased incidence of congenital heart disease related to an underlying genetic tendency.
Benefits
The detection of a cardiac abnormality prior to birth can be devastating news to a family. Close collaboration with a fetal cardiologist will provide timely assessment and accurate diagnosis. Counseling is best provided by the fetal cardiologist who has continuous access to the changing outcomes of congenital heart disease. Parents have the opportunity to ask questions and learn about the type of heart disease and its long-term implications. There also is the ability to plan for management of the pregnancy and delivery. Delivery at a tertiary care hospital can lead to improved postnatal outcomes, especially in those patients with cardiac lesions predisposing them to severe hypoxia or ischemia at the time of birth. Lastly, in some patients, fetal echocardiography may identify a lesion that may be amenable to fetal intervention.
Huda Elshershari, MD, is a pediatric cardiologist at Children's Hospital of Wisconsin and Children's Physician Group in Illinois.
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