Types of Holes in the Heart

Atrial Septal Defect

An atrial septal defect (ASD) is a hole in the part of the septum that separates the atria (upper chambers of the heart). This heart defect allows oxygen-rich blood from the left atrium to flow across the atrial septum into the right atrium instead of flowing down to the left ventricle as it should. This is inefficient because oxygen-rich blood gets pumped back to the lungs, where it has just been, instead of going to the body.

Cross-Section of a Normal Heart and a Heart With Atrial Septal Defect

Figure A shows the normal structure and blood flow in the interior of the heart. Figure B shows a heart with an atrial septal defect, which allows oxygen-rich blood from the left atrium to mix with oxygen-poor blood from the right atrium.

An ASD can be small or large. Small ASDs allow only a little blood to flow from one atrium to the other. Small ASDs don't affect the way the heart works and therefore don't need any special treatment. Many small ASDs close on their own as the heart grows during childhood.

Medium to large ASDs allow more blood to leak from one atrium to the other, and they are less likely to close on their own. Most children with ASDs have no symptoms, even if they have large ASDs.

There are three major types of ASD:

• Secundum. This defect is in the middle of the atrial septum. It’s the most common form of ASD. About 8 out of every 10 babies born with ASD have secundum defects. At least half of all secundum ASDs close on their own. This is less likely if the defect is large.
• Primum. This defect is in the lower part of the atrial septum. It often occurs along with abnormalities in the heart valves that connect the upper and lower heart chambers. Primum defects aren’t very common. This type of defect doesn’t close on its own.
• Sinus venosus. This defect is in the upper part of the atrial septum, near where a large vein (the superior vena cava) brings oxygen-poor blood from the upper body to the right atrium. Sinus venosus is a rare defect. Sinus venosus defects don’t close on their own.

Long-Term Effects of Atrial Septal Defects That Aren’t Repaired

Over time, the extra blood flow to the right side of the heart and the lungs may cause problems for a heart that has an ASD. Usually, most of these problems don’t show up until adulthood, often around age 30 or later. They are rare in infants and children. These possible problems include:

• Right heart failure. The right side of the heart has to work harder to pump extra blood to the lungs. Over time, the heart may become tired from this extra work and not pump efficiently.
• Arrhythmias (irregular heartbeats). Extra blood flowing into the right atrium through an ASD can cause the atrium to stretch and enlarge. Over time, this can lead to problems with the heart’s rhythm. When this occurs, an arrhythmia can develop, with signs or symptoms such as palpitations (a feeling that your heart has skipped a beat or is beating too hard) or a rapid heartbeat.
• Stroke. Usually, the lungs filter out small clots that can form on the right side of the heart. Sometimes a blood clot formed on the right side of the heart can pass through an ASD to the left side and be pumped out to the body. A clot like this can travel to an artery in the brain, blocking blood flow through it and causing a stroke. This doesn’t occur in childhood.
• Pulmonary arterial hypertension (PAH). PAH is high blood pressure in the arteries in the lungs. Over time, high blood pressure in the lungs can damage the arteries and the small blood vessels in the lungs. They thicken and become stiff, making it harder for blood to flow through them.

These problems develop over many years and don’t occur in children. They also are rare in adults because most ASDs either close on their own or are repaired in early childhood.

Ventricular Septal Defect

A ventricular septal defect (VSD) is a hole in the part of the septum that separates the ventricles, the lower chambers of the heart. The hole allows oxygen-rich blood to flow from the left ventricle across the heart into the right ventricle instead of flowing up into the aorta and out to the body as it should.

Cross-Section of a Normal Heart and a Heart With Ventricular Septal Defect

Figure A shows the normal structure and blood flow in the interior of the heart. Figure B shows two common locations for a ventricular septal defect. The defect allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood in the right ventricle.

An infant born with a VSD may have a single hole or more than one hole in the wall that separates the two ventricles. The defect also may occur by itself or with other congenital heart defects.

Doctors classify VSDs based on the:

• Size of the defect.
• Location of the defect.
• Number of defects.
• Presence or absence of a ventricular septal aneurysm—a thin flap of tissue on the septum. This tissue is harmless and can help a VSD close on its own.

VSDs can be small or large. A small VSD doesn’t cause problems and may often close on its own. Because small VSDs allow only a small amount of blood to flow between the ventricles, they’re sometimes called restrictive VSDs. Small VSDs don’t cause any symptoms.

Medium VSDs are less likely than small defects to close on their own. They may require surgery to close and may cause symptoms during infancy and childhood.

Large VSDs allow a large amount of blood to flow from the left ventricle to the right ventricle and are sometimes called nonrestrictive VSDs. A large VSD is less likely to close completely on its own, but it may get smaller over time. Large VSDs often cause symptoms in infants and children, and surgery is usually needed to close them.

VSDs are found in different parts of the septum.

• Membranous VSDs are located near the heart valves. They can close at any time.
• Muscular VSDs are found in the lower part of the septum. They’re surrounded by muscle, and most close on their own during early childhood.
• Inlet VSDs are located close to where blood enters the ventricles. They’re less common than membranous and muscular VSDs.
• Outlet VSDs are found in the part of the ventricle where the blood leaves the heart. This is the rarest type of VSD.

Long-Term Effects of Large Ventricular Septal Defects That Aren’t Repaired

A moderate to large VSD can cause:

• Heart failure. Infants with large VSDs may develop heart failure because the left side of the heart pumps blood into the right ventricle in addition to its normal work of pumping blood to the body. The increased workload on the heart also increases the heart rate and the body’s demand for energy.
• Growth failure, especially in infancy. A baby may not be able to eat enough to keep up with his or her body’s increased energy demands. As a result, the baby may lose weight or fail to grow and develop normally.
• Arrhythmias (irregular heartbeats). The extra blood flowing through the heart can cause areas of the heart to stretch and enlarge. This can disturb the normal electrical activity of the heart, leading to fast and irregular heart rhythms.
• PAH. The high pressure and high volume of extra blood pumped through a large VSD into the lungs can cause scarring of the delicate arteries in the lungs. Today, PAH rarely develops because most large VSDs are repaired in infancy.

Author/Source: National Heart, Lung & Blood Institute, Division of the National Institutes of Health [NIH]

Retrieved: June 2008

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