Ventricular Septal Defect (VSD)

A ventricular septal defect is a condition where you’re born with a hole in the wall between the two lower chambers of your heart. Often shortened to VSD, this condition is the most common congenital (meaning you have it when you’re born) heart defect and often happens alongside other types of heart problems or defects. A small VSD is usually minor and has few or no symptoms. However, a larger hole may need to be repaired to avoid permanent damage and complications.

What happens inside my heart if I have a ventricular septal defect?

Your heart has four chambers. To pump blood efficiently, the chambers much seal shut. A VSD is a leak that disrupts that efficient pumping ability.

Under normal circumstances, the right ventricle pumps oxygen-poor blood that just arrived from your body out of your heart and into your lungs so the blood can pick up oxygen. The blood then returns to the heart, and its last stop in the heart is the left ventricle, which pumps oxygen-rich blood out to your entire body.

A VSD is a potential problem because it can act as a shunt (a connection) between the heart’s two lower chambers, the left ventricle and the right ventricle. Because the pressure in the left ventricle is higher than the pressure in the right ventricle, oxygen-rich blood mixes with oxygen-poor blood in the right ventricle and then goes to the lungs. That leads to extra blood in the lungs which can cause serious problems.

Who does it affect?

Almost all VSDs are present at birth. A VSD diagnosis most likely happen during childhood, though adults can also receive this diagnosis. However, this only happens in 10% or less of cases. VSD is also slightly more likely to happen in premature babies and babies with certain genetic conditions.

In very rare cases, a heart attack can tear a hole between the ventricles and create a VSD. While this type of VSD — sometimes called ventricular septal rupture (VSR) — is technically a side effect, it is still a dangerous problem that needs to be repaired.

How common is this condition?

VSD happens in about one-third of 1% of all newborns. However, a VSD diagnosis in adults is much less likely because the defect closes on its own during childhood in 90% of cases.

VSDs that are a side effect of a heart attack are extremely rare, especially because of modern heart attack treatment methods. Today, it happens in less than 1% of all heart attacks.

What are the different types of VSD?

There are four main types of VSD, which differ in their location and the structure of the hole (or holes). The types of VSD are:

• Membranous: This is the most common type of VSD and makes up about 80% of cases. These VSDs happen in the upper section of the wall between the ventricles.
• Muscular: These account for about 20% of VSDs in infants, and there is often more than one hole that’s part of the defect.
• Inlet: This is a hole that happens just below the tricuspid valve in the right ventricle and the mitral valve in the left ventricle. That means when blood enters the ventricles, it must pass a VSD that connects the two chambers.
• Outlet (conoventricular): This kind of VSD creates a hole just before the pulmonary valve in the right ventricle and just before the aortic valve in the left ventricle, connecting the two chambers. That means blood has to go by the VSD on its way through both valves.

How does this condition affect my body?

VSD doesn’t cause symptoms in most cases because the hole isn’t large enough to cause problems. However, in cases where the hole is large enough (or if there are multiple holes), it can cause problems with blood leaking between the two chambers instead of circulating through the heart in the correct order.

That leaking makes your heart’s pumping efforts less efficient, though if the leak is smaller, it may not be enough to cause any symptoms or problems. However, your heart needs to pump harder to compensate for the reduced blood flow when the leak is larger. When your heart works harder like that long-term, it can cause symptoms and problems in the heart and lungs that may become severe.

VSD size and effects

VSDs range in size from small to large, with the size playing a role in what effects — if any — the VSD will cause.

• Small (3 mm in diameter or less): Most VSDs fall in this category and don’t cause symptoms. About nine out of 10 of this type will close on their own by the time a child is 6 years old. Surgery for these is rare.
• Moderate (3-5 mm in diameter): These VSDs don’t usually cause symptoms. If they aren’t causing symptoms or problems elsewhere in the heart and lungs, delaying surgery is usually advised because some also close on their own.
• Large (6-10 mm in diameter): These VSDs often require surgery (the timing of the surgery can vary slightly). Repair of a large VSD before age 2 can prevent damage to the heart and lungs. Without repair before age 2, the damage becomes permanent and gets worse over time.

When a moderate or large VSD is not treated in time, Eisenmenger syndrome can develop. This is a condition where long-term damage to blood vessels in the lungs forces oxygen-poor blood from the right ventricle through a large VSD and into the left ventricle. That means some of the blood pumped to the body doesn’t contain enough oxygen. That causes an overall oxygen shortage throughout the body. This condition is typically severe and can have major consequences on a person’s life and the activities in which they can participate.

The left ventricle has greater pumping strength than the right, which means it can force blood into the right ventricle. The right ventricle can’t push the extra blood back, so the extra blood instead gets pumped into the lungs. That puts too much pressure on and damages the lung’s blood vessels. Over time, the damage in the lung’s blood vessels starts to force the leak in the heart to reverse direction, forcing oxygen-poor blood from the right ventricle into the left.

Once the direction of the leak reverses, the damage is permanent and repairing the hole will cause right-sided heart failure. Surgical repair of a moderate or large VSD before age 2 is vital to prevent permanent damage and developing Eisenmenger syndrome.