What is a ventricular septal defect (VSD)?

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A VSD occurs when the wall between the ventricles does not completely close during development. The ventricles are the lower two chambers of the heart.

In people without VSD, the left ventricle pumps blood to the body, and the right ventricle pumps blood to the lungs. However, in people with VSD, blood can travel between these chambers. If the hole is large enough, this can affect blood flow to the lungs, body, or both.

Small holes typically cause no symptoms, but larger holes may cause rapid breathing, fatigue, and feeding difficulties. These symptoms can affect an infant’s growth.

Some children with VSD also develop pulmonary artery hypertension, a type of high blood pressure in an artery of the heart. Over time, this may damage the heart.

After confirming a diagnosis of VSD, a doctor will recommend treatment based on the size of the hole and the symptoms.

People with a small hole may need no treatment at all. In about 90% of people with VSD, the condition resolves on its own.

There are four main types of VSD. The type that an infant has helps a doctor determine the appropriate treatment.

The four types are:

• Type 1, known as outlet or infundibular: In this type of VSD, the hole is just below the semilunar valves, which are valves that prevent blood from flowing back into the heart. It is the least common type, but it is more prevalent among people of Asian descent. Typically, it does not resolve on its own.
• Type 2, known as membrane: This is the most common type of VSD. The hole affects the membrane of the septum below the crista supraventricular crest, a muscular structure in the right ventricle. It will often close on its own in time.
• Type 3, known as atrioventricular canal or inlet: This VSD hole is just below the inlet valves of the heart. These valves allow blood into the heart. It is more common among people with Down syndrome.
• Type 4, known as trabecular or muscular: The hole with this type of VSD is in the muscular septum, which is the wall of muscle separating the ventricles. It often closes on its own.

No single cause explains all cases of VSD.

It is a developmental abnormality that occurs when something disrupts the growth of the septum very early in pregnancy. The condition often occurs in isolation, without any apparent cause.

Sometimes, however, it appears alongside other heart defects, such as atrial septal defects, pulmonic stenosis, patent ductus arteriosus, or right aortic arch.

Some potential risk factors include:

• genetic mutations, such as mutations in the TBX5 gene
• infections in the birthing parent
• diabetes in the birthing parent
• exposure to medications and toxins
• phenylketonuria

About 0.3% of newborns — equating to 3 out of every 1,000 — have VSD. As the hole usually closes on its own, the prevalence among adults is much lower.

Some research suggests that VSD accounts for 37% of all congenital heart defects. However, a 2017 study puts the figure much higher at 64%. Most research concludes that VSD is the most common congenital heart defect.

During a routine newborn exam, a healthcare professional may hear a whooshing sound coming from the heart.

This is an early sign of VSD. If the healthcare professional suspects this condition, they will order additional tests.

The most accurate way to diagnose VSD is with transthoracic Doppler echocardiography. This test measures blood flow in the heart and is more accurate than an EKG alone.

A doctor may recommend additional imaging tests to look for other heart defects or to confirm the diagnosis. These tests may include:

• CT scan
• MRI scan
• X-ray

Many infants with VSD require no treatment because the hole closes on its own in the majority of cases.

However, some infants do need treatment, which may involve:

• feeding support, such as special formula or additional pumped breast milk
• medication to lower blood pressure, reduce fluid retention, or strengthen the heart muscle
• surgery to close the hole
• antibiotics to prevent infections after surgery

People with VSD typically receive ongoing care from a cardiologist. After the hole closes, most people will not need additional treatment.

The outlook for people with VSD is generally good, despite the fact that many people do not receive treatment.

A 2017 study of Italian children — all of whom were Caucasian — found that the hole closed in 91.8% of children by the time they were 6 years old. Certain risk factors increased the risk of the hole remaining open, including:

• male sex
• multiple defects
• perimembranous location, which is a small part of the septum

The mortality rate for this condition, including for people who have surgery, is less than 1%.

Children with VSD may have a higher risk of endocarditis, a serious heart infection, but most people with VSD have a typical life expectancy, with or without treatment.

VSD can be scary, especially for parents or caregivers of newborns with the condition. However, it typically resolves on its own without treatment, and it has a very low mortality rate.

Even when surgery is necessary, the outcomes are very good, and children typically live a regular, healthy life.