Congenital Heart Defects

What is a congenital heart defect?

When the heart or blood vessels near the heart do not develop normally before birth, a condition called congenital heart defect occurs (congenital means "inborn" or "existing at birth").

Congenital heart defects occur in about 8 percent to 10 percent of every 1,000 infants. About 500,000 adults in the US have congenital heart disease. Many young people with congenital heart defects are living in adulthood now.

In most cases, the cause is unknown. Sometimes a viral infection or hereditary causes the condition. Some congenital heart defects are the result of too much alcohol or drug use during pregnancy.

Most heart defects either cause an abnormal blood flow through the heart, or obstruct blood flow in the heart or vessels (obstructions are called stenoses and can occur in heart valves, arteries, or veins).

Rarely, defects include those in which:

• the right or left side of the heart is incompletely formed - called hypoplastic heart.
• only one ventricle is present.
• both the pulmonary artery and aorta arise from the same ventricle.

Types of congenital heart defects:

There are many disorders of the heart that require clinical care by a physician or other healthcare professional. Listed below are some of the conditions, for which we have provided a brief overview.

Obstructive defects:

• aortic stenosis (AS)
  In this condition, the aortic valve between the left ventricle and the aorta did not form properly and is narrowed, making it difficult for the heart to pump blood to the body. A normal valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid).
  
  In some children, chest pain, unusual tiring, dizziness or fainting may occur. Otherwise, most children with aortic stenosis have no symptoms. But, even mild stenosis may worsen over time, and surgery may be needed to correct the blockage - or the valve may need to be replaced with an artificial one.

• pulmonary stenosis (PS)
  The pulmonary, or pulmonic, valve, located between the right ventricle and the pulmonary artery, opens to allow blood to flow from the right ventricle to the lungs. When a defective pulmonary valve does not open properly, it causes the heart to pump harder than normal to overcome the obstruction. Usually, the obstruction can be corrected by balloon valvuloplasty, although in some patients, open heart surgery may be needed.

• bicuspid aortic valve
  In this condition, an infant is born with a bicuspid valve which has only two flaps. (A normal aortic valve has three flaps that open and close). If the valve becomes narrowed, it is more difficult for the blood to flow through, and often the blood leaks backward. Symptoms usually do not develop during childhood, but are often detected during the adult years.

• subaortic stenosis
  This condition refers to a narrowing of the left ventricle just below the aortic valve. Normally, blood passes through it to go into the aorta. However, subaortic stenosis limits the blood flow out of the left ventricle, often resulting in an increased workload for the left ventricle. Subaortic stenosis may be congenital or caused by a form of cardiomyopathy.

• coarctation of the aorta (coarct)
  In this condition, the aorta is narrowed or constricted, obstructing blood flow to the lower part of the body and increasing blood pressure above the constriction. Usually there are no symptoms at birth, but they can develop as early as the first week after birth. If severe symptoms of high blood pressure and congestive heart failure develop, surgery may be considered.

Septal defects:

Some congenital heart defects allow blood to flow between the right and left chambers of the heart because an infant is born with an opening in the septum wall that separates the right and left sides of the heart.

• atrial septal defect (ASD)
  In this condition, there is an abnormal opening between the two upper chambers of the heart - the right and left atria - causing an abnormal blood flow through the heart. Children with ASD have few symptoms. Closing the atrial defect by open heart surgery in childhood can often prevent serious problems later in life.
• Ebstein's anomaly
  In this defect, there is a downward displacement of the tricuspid valve (located between the upper and lower chambers on the right side of the heart) into the right bottom chamber of the heart (or right ventricle). It is usually associated with an atrial septal defect.
• ventricular septal defect (VSD)
  In this condition, a hole occurs between the two lower chambers of the heart. Because of this hole, blood from the left ventricle flows back into the right ventricle, due to higher pressure in the left ventricle. This causes an extra volume of blood to be pumped into the lungs by the right ventricle, which can create congestion in the lungs.

Cyanotic defects:

Cyanotic defects are defects in which blood pumped to the body contains less-than-normal amounts of oxygen, resulting in a condition called cyanosis. It causes a blue discoloration of the skin. Infants with cyanosis are often called "blue babies."

• tetralogy of Fallot
  This condition is characterized by four defects, including the following:
  • an abnormal opening, or ventricular septal defect, that allows blood to pass from the right ventricle to the left ventricle without going through the lungs
  • a narrowing (stenosis) at or just beneath the pulmonary valve that partially blocks the flow of blood from the right side of the heart to the lungs
  • the right ventricle is more muscular than normal
  • the aorta lies directly over the ventricular septal defect
  
  Tetralogy of Fallot is the most common defect causing cyanosis in persons beyond 2 years of age. Most children with tetralogy of Fallot have open-heart surgery before school age to close the ventricular septal defect and remove the obstructing muscle. Lifelong medical follow-up is needed.

• tricuspid atresia
  In this condition, there is no tricuspid valve, therefore, no blood flows from the right atrium to the right ventricle. Tricuspid atresia defect is characterized by the following:
  • a small right ventricle
  • a large left ventricle
  • diminished pulmonary circulation
  • cyanosis
  
  A surgical shunting procedure is often necessary to increase the blood flow to the lungs.

• transposition of the great arteries
  In this embryologic defect, the positions of the pulmonary artery and the aorta are reversed, thus:
  • the aorta originates from the right ventricle, so most of the blood returning to the heart from the body is pumped back out without first going to the lungs.
  • the pulmonary artery originates from the left ventricle, so that most of the blood returning from the lungs goes back to the lungs again.
  
  Immediate medical intervention is necessary to correct this condition.

Other defects:

• left heart syndrome
  In this condition, the left side of the heart is underdeveloped, including the aorta, aortic valve, left ventricle, and mitral valve. Blood reaches the aorta through a patent ductus arteriosus, and if this ductus closes, as is normal, the baby will die. The baby often seems normal at birth, but the condition will become noticeable within a few days of birth, as the ductus closes. Babies with this syndrome become pale, have difficulty breathing, and are unable to feed. Treatment may include complex surgery or a heart transplant.
• patent ductus arteriosus (PDA)
  This defect, which normally occurs during the fetal life, short circuits the normal pulmonary vascular system and allows blood to mix between the pulmonary artery and the aorta. Prior to birth, there is an open passageway between the two blood vessels, which closes soon after birth. When it does not close, some blood returns to the lungs. Patent ductus arteriosus is often seen in premature infants.

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