A hole in the heart is medically called a septal defect. The specific name depends on where the hole is located: an atrial septal defect (ASD) sits between the upper chambers, a ventricular septal defect (VSD) sits between the lower chambers, and a patent foramen ovale (PFO) is a small flaplike opening between the upper chambers that should have closed after birth but didn’t. These are among the most common congenital heart conditions, meaning they’re present from birth.
Types of Holes in the Heart
The wall separating the left and right sides of the heart is called the septum. A hole anywhere in that wall allows blood to flow between the two sides in ways it shouldn’t. Each type has a different name, location, and level of concern.
A ventricular septal defect (VSD) is a hole between the heart’s two lower pumping chambers. It’s the most common congenital heart defect. Small VSDs often produce no symptoms and may close on their own during childhood. Larger ones force the heart to pump extra blood to the lungs, which over time can raise pressure in the lung arteries and strain the heart.
An atrial septal defect (ASD) is a hole between the two upper chambers. Because pressure differences between these chambers are smaller, ASDs can go undetected for years or even decades. Many people don’t learn they have one until adulthood.
A patent foramen ovale (PFO) is a specific kind of opening between the upper chambers. Every baby has a small flap called the foramen ovale while developing in the womb. It normally seals shut shortly after birth. When it doesn’t, it’s called “patent,” meaning it stayed open. About one in four people have a PFO, and most never know it.
There’s also a less common type called an atrioventricular septal defect (AVSD), which involves holes in both the upper and lower parts of the septum along with abnormalities in the heart valves. This is a more complex defect that typically requires surgical repair.
How a Hole Affects Blood Flow
In a healthy heart, the left side pumps oxygen-rich blood to the body while the right side sends oxygen-poor blood to the lungs. A hole in the septum lets blood leak from one side to the other. Because pressure is normally higher on the left side, blood usually flows left to right, sending extra blood toward the lungs.
With a small defect, this extra flow is minimal and the lungs and heart handle it without trouble. With a larger hole, the volume of blood flooding the lungs increases significantly. The heart has to work harder to compensate, and over time the lung arteries can thicken and stiffen in response to the excess pressure. In severe, untreated cases, the damage to the lung arteries eventually becomes so severe that blood flow reverses direction, sending oxygen-poor blood out to the body. This irreversible condition is called Eisenmenger syndrome, and it makes surgical repair too dangerous.
Symptoms in Babies and Adults
Many small holes produce no noticeable symptoms at all. A heart murmur, a whooshing sound heard through a stethoscope, is often the first clue. Pediatricians frequently pick up VSDs during routine newborn exams just by listening to the chest.
Babies with larger defects may show more obvious signs: poor feeding, slow weight gain, fast breathing, and tiring easily. These symptoms appear because the heart is working overtime to keep up with the extra blood flowing through the hole.
Adults with undiagnosed holes, particularly ASDs and PFOs, often have milder or no symptoms for years. When symptoms do appear, shortness of breath during exercise is the most common complaint. Some adults are only diagnosed after a stroke or other complication prompts further testing.
PFOs and Stroke Risk
A PFO deserves special attention because of its link to stroke. Normally, the lungs act as a filter, catching small blood clots before they reach the brain. A PFO creates a shortcut that lets clots bypass the lungs entirely and travel directly to the brain’s blood vessels. This is called a paradoxical embolism.
Having a PFO, especially a larger one, is linked to a higher risk of ischemic stroke. Beyond letting clots slip through, a PFO may also allow unfiltered harmful substances into the circulation, making clots more likely to form in the first place. Growing evidence from Harvard Health suggests that people with large PFOs face a higher risk of vascular dementia as well, likely because these harmful substances accumulate over time and damage blood vessels in the brain.
How a Hole Is Diagnosed
The primary tool is an echocardiogram, an ultrasound of the heart that shows blood flowing through the chambers in real time. It can pinpoint the hole’s location and size. A fetal echocardiogram can even detect a septal defect before birth.
For PFOs, doctors sometimes use a bubble study. A small amount of saline mixed with tiny air bubbles is injected into a vein. If bubbles appear on the left side of the heart on the ultrasound screen, it confirms that blood is crossing through an opening that shouldn’t be there.
When Treatment Is Needed
Small holes that don’t overload the heart are typically monitored rather than repaired. Many small VSDs close on their own during childhood, and small PFOs rarely cause problems. The general threshold for considering closure is when the hole is large enough that blood flow to the lungs is at least 1.5 times the normal amount flowing to the body. At that point, the extra volume starts to enlarge the heart chambers and stress the lungs.
If someone with a PFO or ASD has had a stroke believed to be caused by a clot passing through the hole, closure is recommended to prevent it from happening again.
What Repair Looks Like
There are two main approaches. The less invasive option is transcatheter closure: a thin tube is threaded through a blood vessel, usually in the groin, up to the heart. A small device is guided through the tube and positioned to plug the hole. This works well for many ASDs and PFOs. Recovery is quick. Most people return to normal activity within about a week.
Larger or more complex defects, including most AVSDs and some VSDs, require open-heart surgery. A surgeon patches or stitches the hole closed directly. Recovery takes longer, and physical activity is usually limited for several weeks afterward. Both approaches have high success rates, and it’s rare for a properly closed hole to reopen.
For adults with severe, longstanding pulmonary hypertension caused by an uncorrected defect, closing the hole can actually be dangerous. When lung artery pressure has climbed too high, the hole serves as a pressure relief valve. Sealing it off could overload the right side of the heart. In these cases, the 2025 guidelines from the American College of Cardiology and American Heart Association consider closure contraindicated.