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Congenital Heart DiseaseLearn More

• What is congenital heart disease?
• What is fetal dysrhythmia or arrhythmia?
• What causes problems with the fetal heart function?
• What is the outcome for a fetus with congenital heart disease?
• How serious is my fetus’s congenital heart disease?

What is congenital heart disease?

Fetal heart disease involves an abnormality of the heart, whether it be a structural defect (also known as congenital heart disease), a problem with the fetal heart beat or a functional problem with the heart squeeze or filling.

The fetal heart starts as a tube which folds and fuses in a complex dance that results in a muscular pump with four chambers and four valves. It is not surprising that small errors in development can lead to a wide variety of structural abnormalities in the 4 chambers, the 4 heart valves, the veins and great arteries. Most common heart defects, such as holes between the chambers (atrial septal defect, ventricular septal defect) and even more complex conditions, can be successfully managed after birth.

There are also a few abnormalities (such as narrowing of a valve) that can interfere with development of the pumping chambers, which can be very difficult to fix after birth. For instance, severe obstruction of the aortic valve, the outlet valve through which the left ventricle pumps blood to the body, may lead to poor growth and function of the left ventricle and other left heart structures. Ultimately this may result in the development of “hypoplastic left heart syndrome,” one of the most serious and common heart defects we encounter in sick newborns. In these cases, relief of the obstruction while the baby is still in the womb may allow more normal development of the ventricle, thus resulting in a very different outlook for the infant after birth.

In the same way, narrowing of the pulmonary valve can damage the developing right ventricle or pumping chamber that normally pumps to the lungs. Abnormal development of either one of the pumping chambers (right or left ventricle) can lead to devastating problems after birth, which often require multiple complex open heart surgeries and, even when successful, result in distinctly abnormal function (so-called ‘single ventricle physiology’).

Heart defects can now be accurately diagnosed before birth by fetal echocardiography. In most cases, this leads to improved postnatal management. In a few cases, it may also allow fetal intervention to open up an obstructed valve and thus prevent abnormal development of the pumping chamber.

What is fetal dysrhythmia or arrhythmia?

In addition to a structural heart problem, a fetus can also have an abnormal heart beat. The heart beat of a normal, healthy fetus ranges between 120-160 beats per minute and has a regular rhythm. When the rhythm is irregular, or the heart beat is too fast or too slow this is considered a “dysrhythmia” or “arrhythmia.” While most irregular rhythms do not get a baby into trouble before birth, fast or slow rhythm disturbances can cause the baby to develop heart failure and even die before birth. Fortunately, for most of these problems, when the dysrhythmia is evaluated by an experienced fetal echocardiographer/cardiologist, appropriate management can be offered to the mother that has been shown to significantly improve the outcome of such babies and pregnancies.

One of the most common abnormal rhythms is “supraventricular tachycardia” in which the fetal heart beat is very fast, at times even double the normal heart rate. The treatment primarily involves giving one or more medication to the mother which cross through the placenta to the baby, and corrects the abnormal rhythm. Proper treatment requires knowledge about the kind of abnormal rhythms that may present in the fetus and the specific medications, including their doses, that are most likely to convert the baby’s abnormal rhythm to a normal rhythm and heart rate without causing any harm to the mother. Even with conversion of the rhythm to a normal rhythm, delivery at a tertiary care center where the baby can be managed after birth by individuals experienced in rhythm disturbances in newborns is usually required.

Another problem with fetal heart rate and rhythm that is diagnosed before birth is fetal heart block. When it is in isolation, it may be associated with abnormal factors, known as antibodies, that pass through the placenta from the mother and alter the conduction system of the fetal heart. Through the use of medications that reduce inflammation and increase the baby’s heart rate as well as close monitoring and early delivery when necessary, we have significantly improved the survival and outcome of these babies.

What causes problems with the fetal heart function?

Before birth, babies can develop problems with the function of the heart, including its ability to fill and to eject blood to the body and back to the placenta. This may be due to primary problems with the muscle of the heart itself known as “cardiomyopathies” or may be secondary to added stress on the heart from other problems such as structural heart defects, rhythm disturbances, defects that compress the heart and do not allow it to fill normally (e.g. congenital cysti adenomatous malformation) or problems that result in increased work of the heart, (e.g. fetal anemia, acardiac twins, sacrococcygeal teratomas and other arteriovenous malformations, and twin-to-twin transfusion syndrome). For some of these conditions, there are ways to intervene before birth to improve the heart function and the baby’s overall outlook. Fetal echocardiography can help to identify those babies in whom intervention should be provided before birth, determine the best timing for intervention, and assists in determining how effective the intervention has been.

What is the outcome for a fetus with congenital heart disease?

Most congenital heart defects can be repaired after birth with excellent results. However, a few severe defects, such as those that lead to maldevelopment of one of the pumping chambers, may not be correctable after birth, or it may require a series of open heart surgeries that, even if successful, result in abnormal circulation (single ventricle physiology) and life-long limitations. It is those fetuses with distinct structural defects that lead to death or life-long difficulty that are candidates for fetal intervention.

For detail on fetal intervention for congenital heart disease visit out Treatment page or download our PDF Brochure about Fetal Intervention for Congenital Heart Disease

How serious is my fetus’s congenital heart disease?

Fortunately, fetal echocardiography has improved dramatically over the last decade, so that most abnormalities can be accurately diagnosed by an experienced fetal echocardiographer/cardiologist. This often requires evaluation at a tertiary or quaternary fetal echocardiography center.

Echocardiography will determine whether your fetus has the type of structural abnormality that can be successfully repaired after birth, or the unusual type that might make your fetus a candidate for fetal intervention: for example, critical aortic stenosis (narrowing of the aortic valve) with evidence of developing hypoplastic left heart syndrome, or critical pulmonic stenosis (narrowing of the pulmonic valve) with evidence of ongoing damage to the right side of the heart.

There are a number of complex heart defects that will not benefit from intervention before birth, but will benefit greatly from prenatal diagnosis and management at an appropriate referral center (for example, atrial septal defect, ventricular septal defect, tetralogy of Fallot, transposition of the great vessels). Most of these defects can be very successfully corrected after birth. Some will benefit from being delivered at the tertiary center, while others can be safely transported after birth elsewhere, or even electively repaired later in life. Some of the more severe heart defects require immediate attention in the newborn period or the babies can become very ill. Diagnosis of the heart defects before birth allows us to inform the parents and plan for the delivery of the baby to give the baby the best chance. Sometimes, a baby can even get into trouble with certain heart defects before birth. For many of these defects, an early delivery may be warranted to give the baby the best chance of survival, and occasionally an intervention before birth can be offered that improves the baby’s condition and prolongs the pregnancy.