Heart defects in fetuses

Heart defects occur in about one percent of babies and are called congenital heart defects (CHD). About half are benign, without major disruption of normal heart function. Along with the rest, the defect is severe enough to require treatment.

About a quarter of these babies have critical coronary heart disease. Left untreated, coronary artery disease will make the baby seriously ill and increase the risk of death.

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Anatomy of the heart

The heart is a dual circulatory system, with four chambers designed to supply the whole body with oxygen at different levels of pressure and demand. The right side is the collection and oxygenation department, pumping the deoxygenated blood to the lungs, while the left side receives the oxygenated blood and sends it to the whole body.

The heart is fully formed eight weeks after conception, and this is the vulnerable period for the formation of coronary artery disease.

What causes coronary artery disease?

About 80% of coronary artery disease occurs for unknown causes. Of the rest, about one in five is due to genetic factors; some are associated with congenital syndromes such as Down syndrome, and others are due to maternal illness or infection. Maternal medications, including anti-epileptics and acne medications, are known to increase the risk of coronary heart disease.

What are the most common CHDs?

The five most common heart defects in fetuses are:

  • Interventricular communication
  • Transposition of the great vessels
  • Coarctation of the aorta – the aorta is pinched, which reduces the blood that can reach the body under the block
  • Tetralogy of Fallot – a complex heart defect with multiple defects
  • Hypoplastic left heart syndrome – the left side of the heart is poorly developed, including the two chambers, the aorta and the aortic valve, so the left ventricle may be too weak to pump enough oxygenated blood to the body

Interventricular communication

The ventricles are the two lower chambers of the heart, with muscular walls to pump blood to the lungs (right ventricle) or the body (left ventricle). They must be separated from each other to avoid mixing the oxygenated blood with the deoxygenated blood, thus maintaining adequate oxygen saturation to supply the cells, tissues and organs of the body.

A defect in the dividing wall, called a septum, is called an interventricular communication (VSD). Small blemishes usually heal spontaneously. Larger VSDs produce symptoms soon after or at birth and may require surgical closure with a patch.

Symptoms of VSD occur due to the higher pressures in the left ventricle, which causes blood to return to the right ventricle and aorta with each heartbeat, causing blood to pool and congestion in the lungs.

Transposition of the Great Vessels

In this condition, the aorta and pulmonary artery change places. This converts the heart into two autonomous circuits pumping oxygenated and deoxygenated blood respectively.

The left ventricle now pumps its oxygenated blood to the lungs for additional oxygenation rather than the oxygen starving body. The right ventricle pumps deoxygenated blood to the body while receiving deoxygenated blood from the body through the right atrium. This defect will kill the fetus soon after birth and requires urgent treatment.

Congenital heart defects (CHD)

How does coronary heart disease affect children?

Children born with coronary heart disease are at risk for respiratory infections. They can suffer from a bacterial infection of the lining of the heart, called bacterial endocarditis, which can damage the heart valves. To prevent this, all surgeries, including minor dental procedures, are often covered with antibiotics.

Signs and symptoms

The type and severity of coronary artery disease determine the clinical features. Signs of deoxygenated blood entering the systemic circulation include a bluish tinge to the nails and lips, called cyanosis, while pulmonary congestion is signaled by rapid breathing or respiratory distress. Poor overall heart function can manifest as fatigue during feeding and excessive sleepiness.

Diagnosis and treatment

Prenatal tests are done to check for coronary heart disease. In the first trimester, maternal blood screening and ultrasound are done to look for chromosomal abnormalities associated with coronary heart disease.

Second trimester screening is done by detailed ultrasound for fetal abnormalities, including heart abnormalities, at 18-24 weeks gestation. If worrying results are present, fetal echocardiography is useful for follow-up. A second maternal serum test, called a triple or quadruple screening, also detects a higher risk of congenital disabilities.

Very few cases are asymptomatic and show no clinical signs until later in life. The physical exam can detect abnormal heart sounds called murmurs, supplemented by tests such as an EKG, echocardiogram, chest x-ray, and cardiac catheterization.

Treatment depends on the specific coronary artery disease present. Some children only need simple surgeries to fix the defect, while others need complex, multi-step procedures for their repair.

Cardiac catheterization is a less invasive procedure than open heart surgery. Here, a long flexible tube (catheter) is introduced into the heart chambers. It can be used to inject dye or introduce a camera or instruments to treat the defect.

In some cases, coronary artery disease is not cured by surgery, but the purpose of the procedure is to allow the heart to pump well enough for the individual to lead a normal life.

The long-term outcome of coronary artery disease

Since surgeries do not cure all people with coronary artery disease, they can develop other diseases over time. Some people may have arrhythmias or an irregular heartbeat. Infectious endocarditis is a constant risk. With continued pressure on one or more chambers of the heart, cardiomyopathy or weakness of the heart muscle may develop.

Pulmonary hypertension, along with secondary heart disease, is another possible complication. For all of these reasons, people with coronary artery disease should schedule regular visits for their long-term care.

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