Ventricular Septal Defects

Heart with Ventricular Septal Defects

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Simple ventricular septal defects are the most common form of congenital heart disease. A ventricular septal defect is a hole in the wall between the right and left ventricles (ventricular septum). A VSD can potentially cause a shunting of blood from the left ventricle to the right ventricle or from the right ventricle to the left ventricle. The position and size of the VSD determine the physiology and, in turn, dictate the timing of intervention.

The ventricular septum is made up of two components, the truncal portion and the conoseptal portion. These two sections fit together like two pieces of a puzzle. The position of the VSD among these two portions of the septum determines the type of VSD.


Five Types of VSD

 
Conoventricular

A conoventricular VSD results when there is a space between where the two portions of the ventricular septum meet. This type of VSD is not typically associated with other forms of congenital heart disease. The size of a conoventricular VSD is the predominate indicator of physiology. A small conoventricular VSD may close on its own as the child grows. A larger VSD may cause greater strain on the heart and need to be repaired surgically. Surgical repair entails patch closure of the VSD using a synthetic material.

 
Muscular

Muscular VSDs are the most common type of VSD and are not usually associated with other forms of congenital heart disease. A muscular VSD is a hole located in the truncal portion of the ventricular septum. Again, size is the predominate indicator of physiology. This type of VSD has the highest chance of spontaneous closure and therefore requires less surgery.

 
Conoseptal

A conoseptal VSD is a hole located in the conoseptal portion of the ventricular septum. This type of VSD has almost no chance for spontaneous closure and often requires surgical repair.

 
Atrioventricular Canal Type

An Atrioventricular Canal Type VSD is a hole located in the upper portion of the ventricular septum. Often, this type of VSD is associated with a large ASD as well as malformed atrioventricular valves in a complex congenital heart disease known as Complete Common Atrioventricular Canal Defect (see below).

An Atrioventricular Canal Type VSD allows oxygen-rich blood from the left ventricle to pass into the right ventricle resulting in increased blood flow to the lungs. This type of VSD has no chance of spontaneous closure. Surgical repair is required and involves patch closure of the VSD using a synthetic material

 
Malalignment

Malalignment of the conoseptal portion of the ventricular septum results in a malalignment VSD. This type of VSD causes one of the most common forms of congenital heart disease known as Tetralogy of Fallot. Because the two portions of the ventricular septum have failed to align properly, the anatomy of other structures in the heart are affected. Namely, there is less space for the growth of the pulmonary valve and artery resulting in pulmonary stenosis. In addition, the aorta is not aligned properly resulting in an overriding aorta (i.e. the aorta lies directly over the VSD). Finally, the right ventricle typically works at the lower, pulmonary pressure. Due to the presence of the VSD, the right and left ventricles are pumping at the same pressure. A secondary condition, known as right ventricular hypertrophy (enlargement of the right ventricle), is a result of the right ventricle working at systemic pressure.

The resistance of blood flow through the stenotic pulmonary valve results in deoxygenated blood flowing from the right ventricle through the VSD directly into the left ventricle. This deoxygenated blood is then pumped from the left ventricle out to the body causing the baby to appear cyanotic or blue. Corrective surgery involves patch closure of the VSD and enlargement of the narrow area of the pulmonary artery and right ventricle.


What Is Normal Cardiac Anatomy?

When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

 
Learn More About Normal Cardiac Anatomy

Heart With Normal Cardiac Anatomy

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When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.

The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.

There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.

Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.

Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.

Tetralogy of Fallot

Each year, 4 out of every 10,000 babies born in the United States have the condition, which was named after the French doctor who first described it in the late 1800s, Étienne Fallot. About 10% of all babies born with a heart problem have tetralogy of Fallot.

The four defects that together make up tetralogy of Fallot are:

  1. Ventricular septal defect (VSD), which is a hole in the septum, or wall, separating the two lower chambers, or ventricles, of the heart. The septum acts as a barrier that prevents blood from both sides of the heart from mixing together. But when there is a VSD, blood high in oxygen from the left ventricle can mix with blood low in oxygen from the right ventricle.
  2. Pulmonary stenosis, a narrowing or thickening of the valve that connects the right ventricle to the pulmonary artery, a blood vessel that carries low-oxygen blood from the heart to the lungs, where the blood receives more oxygen and then returns to the heart. With pulmonary stenosis, the heart has to work harder than normal to pump blood to the lungs. Often, the amount of blood reaching the lungs is below normal.
  3. Right ventricular hypertrophy (say hi-PER-truh-fee), which is a thickening of the muscular wall of the right ventricle.
  4. An "overriding aorta," which means the artery that carries high-oxygen blood to the body is out of place and arises above both ventricles, instead of just the left ventricle, as in a healthy heart. This allows some blood that is low in oxygen to flow into the aorta and out to the body, instead of to the pulmonary artery, which would normally take it to the lungs to pick up oxygen.

The combined effect of these defects is an inadequate supply of blood to the lungs, which causes blood low in oxygen to circulate to the rest of the body. This lower oxygen level causes cyanosis, which is a blue or purple tint to the skin, lips, and fingernails.

Children with tetralogy of Fallot:

  • might experience dizziness, fainting, or seizures
  • are at a higher risk of developing an infection of the inner layer of the heart called endocarditis
  • can have an irregular heartbeat, called an arrhythmia, which with TOF is caused by elevated pressure in the right side of the heart

A child whose TOF is not repaired might need to limit his or her participation in competitive sports and other physical activities. Many infants who have surgery to correct the defect do very well, participate in normal kid activities, and live to adulthood.

Causes

Science has not yet identified a specific cause for tetralogy of Fallot in all cases, but genetics is believed to play a role. Someone born with TOF seems more likely to have a child with it.

Mothers who contract rubella or other viral illnesses during their pregnancies are at a higher risk of giving birth to babies with TOF. Other risk factors and conditions include poor nutrition, alcohol abuse, diabetes, and mother's age (over 40).

According to the Centers for Disease Control and Prevention (CDC), the presence of certain environmental factors, such as carbon monoxide, might increase a mother's chances of delivering a baby with TOF. In addition, children who have certain genetic disorders, such as Down syndrome and DiGeorge syndrome, often have congenital heart defects, including tetralogy of Fallot.

Signs

One of the most common signs of tetralogy of Fallot is cyanosis (a blue or purple tint to the baby's skin, lips, and fingernails). A child with TOF might experience sudden episodes of cyanosis, called "Tet spells," during crying or feeding.

Other signs include:

  • heart murmur
  • fussiness
  • easy tiring with exertion
  • difficulty breathing
  • fatigue
  • rapid heartbeat (palpitations)
  • fainting
  • "clubbing," where the skin or bones around the tips of fingers are widened or rounded

Diagnosis

Your doctor may use several diagnostic tests to determine if your child has tetralogy of Fallot, including:

  • pulse oximeter: a small sensor that clips onto the fingertip, toe, or ear and measures how much oxygen is in the blood
  • electrocardiogram (or EKG): a test that records the electrical activity of the heart
  • echocardiogram, or "echo": an ultrasound picture of the heart structures (chambers, walls, and valves). It records the motion of the blood through the heart and can measure the direction and speed of blood flow within the heart structures.
  • chest X-ray
  • cardiac catheterization: a thin, flexible tube called a catheter is inserted into the heart, usually through a vein in the leg or arm, and provides information about the heart structures as well as blood pressure and blood oxygen levels within the heart chambers. Sometimes a device will be inserted into the heart or blood vessels through the heart catheter.

Treatment

Tetralogy of Fallot is repaired through open-heart surgery soon after birth or later in infancy, depending on the baby's health and weight and severity of defects and symptoms.

The two surgical options are:

  1. Complete intracardiac repair: the surgeon widens or replaces the pulmonary valve and enlarges the passageway between the right ventricle and the pulmonary artery to improve blood flow to the lungs. Then, the ventricular septal defect is patched to stop the mixing of high-oxygen blood with low-oxygen blood between the ventricles.

    These repairs also fix the two remaining defects (overriding aorta and right ventricular hypertrophy). Because the right ventricle doesn't have to work as hard to pump blood into the lungs, the thickness of the ventricle wall will decrease. And the patched VSD prevents blood with low oxygen from flowing into the aorta.
  2. Temporary or palliative surgery: only minor repairs are made to improve blood flow to the lungs. This usually only occurs when the baby is too weak or small to undergo full surgery. In the temporary surgery, the surgeon creates a secondary route for blood to travel to the lungs for oxygen. This is done by placing a small tube, called a shunt, between a large artery branching off the aorta and the pulmonary artery.

    Later when the baby grows stronger, the full repair is performed.

Most babies born with tetralogy of Fallot do very well and survive to adulthood, but require yearly follow-up with a heart specialist.

Reviewed by: Gina Baffa, MD
Date reviewed: February 2012