Most holes in the heart found in adults are congenital, meaning they formed before birth when the heart’s internal walls didn’t fully develop. About 25% of adults have a small opening called a patent foramen ovale (PFO) without ever knowing it. Less commonly, a hole can develop later in life as a complication of a heart attack. Whether congenital or acquired, these openings allow blood to flow between heart chambers in ways it shouldn’t, sometimes causing problems that don’t surface until decades after the hole first formed.
How Heart Holes Form Before Birth
During fetal development, a wall called the septum grows to divide the heart into left and right sides. If that wall doesn’t close completely, the baby is born with a gap. In the upper chambers, this is called an atrial septal defect (ASD). In the lower chambers, it’s a ventricular septal defect (VSD). A third type, the patent foramen ovale, is slightly different: every fetus has a small flap-like opening between the upper chambers that normally seals shut shortly after birth. When it doesn’t seal, it remains as a PFO.
The exact reason the septum fails to close isn’t always clear. Genetic factors play a role, and some heart holes occur alongside other congenital heart conditions. Many small VSDs close on their own during childhood, which is why the holes that persist into adulthood tend to be ASDs and PFOs. The most common ASD type, the secundum defect, sits in the middle of the wall between the upper chambers and accounts for about 8 out of 10 cases.
Why Symptoms Often Appear Late
A small hole may never cause noticeable symptoms. The heart compensates for years, quietly pumping extra blood through the opening without triggering fatigue, breathlessness, or irregular heartbeats. This is why many adults are surprised to learn they have a congenital heart defect in their 30s, 40s, or later.
Over time, though, the extra workload takes a toll. A left-to-right shunt (blood leaking from the left side of the heart to the right) forces the right side of the heart to handle more blood than it was designed for. The right ventricle gradually stretches and weakens. Pressure builds in the blood vessels of the lungs. Some people first notice symptoms during pregnancy or intense exercise, when the heart’s demand spikes and the defect can no longer be silently absorbed. Common signs include unexplained shortness of breath, fatigue that worsens with activity, heart palpitations, and swelling in the legs or feet.
Heart Attacks as a Cause in Adults
Unlike congenital holes, a ventricular septal rupture is an acquired defect that develops after a major heart attack. When a large area of heart muscle loses its blood supply, the tissue dies. If that dead zone includes part of the septum between the lower chambers, the weakened wall can tear open. The force of the still-healthy muscle contracting around the damaged area creates shear stress that worsens the rupture.
This is a medical emergency. The sudden hole allows blood to shunt between the ventricles, dropping blood pressure and straining both sides of the heart at once. Ventricular septal rupture is uncommon with modern heart attack treatment, but it remains one of the few ways an adult can develop a new hole in the heart rather than discovering one that was always there.
The Stroke Connection
One of the most alarming ways people discover a heart hole is after a stroke, particularly a stroke with no obvious cause (called a cryptogenic stroke). In someone with a PFO, a blood clot that forms in a vein can travel to the right side of the heart and slip through the opening directly into the left side. From there, it enters the arteries heading to the brain. Normally, the lungs filter out these clots before they can reach the arterial circulation. A PFO bypasses that filter entirely.
The average PFO is about 10 mm across, large enough for clots to pass through and block the middle cerebral artery (which is only about 3 mm wide) or its smaller branches. Research also suggests that clots can form inside the PFO tunnel itself, not just in distant veins. This is why doctors routinely screen for a PFO after a stroke in a younger adult who has no traditional risk factors like high blood pressure or atrial fibrillation.
How a Heart Hole Is Diagnosed
The primary tool is an echocardiogram, an ultrasound of the heart. A standard echocardiogram can often reveal an ASD and show whether the right side of the heart is enlarged. For smaller openings like a PFO, doctors use a technique called a bubble study. A sterile saline solution containing tiny air bubbles is injected into a vein. The bubbles travel to the right side of the heart and show up clearly on the ultrasound image.
If no hole exists, the lungs filter out all the bubbles before they reach the left side. If bubbles appear on the left side of the heart, it confirms that blood is crossing through an opening in the septum. You may be asked to bear down or cough during the test to briefly raise pressure in the chest, which can push open a PFO that stays closed at rest.
When Closure Is Recommended
Not every heart hole needs to be fixed. A small PFO that has never caused symptoms or a stroke is typically monitored rather than treated. Current guidelines from the American College of Cardiology and American Heart Association (updated in 2025) recommend closure in specific situations: when an ASD causes a significant amount of extra blood flow to the right side of the heart, when the right ventricle is dilated, or when there’s strong evidence that a clot has already passed through the hole and caused a stroke.
For the most common type of ASD (secundum), the preferred approach is catheter-based closure rather than open-heart surgery. A thin tube is threaded from a vein in the groin up to the heart, and a small closure device is placed into the hole. The device acts as a plug, and over time heart tissue grows over it. Most people stay in the hospital for one night and return to normal activity within a week. You’ll typically take blood-thinning medication for about six months afterward while the device integrates with your heart tissue, and antibiotics before dental procedures during that same window to prevent infection.
Surgical closure through the chest is reserved for holes that are too large for a catheter device or for less common ASD types (like sinus venosus defects) where the anatomy doesn’t allow catheter access. Recovery from surgical repair takes longer, with physical activity restricted for several weeks.
Eisenmenger Syndrome: A Serious Complication
When a large heart hole goes unrepaired for many years, the constant overflow of blood into the lungs can permanently damage the small blood vessels there. The vessel walls thicken and stiffen, raising resistance to blood flow. Eventually, the pressure on the right side of the heart exceeds the left side, and blood starts flowing the wrong direction: from right to left. This reversal is called Eisenmenger syndrome.
Once it develops, closing the hole is no longer safe because the right side of the heart now depends on that opening as a pressure relief valve. Eisenmenger syndrome causes progressive cyanosis (a bluish tint to the skin from oxygen-poor blood mixing into the arterial circulation), initially during exertion and eventually at rest. About half of people with a large VSD eventually develop this condition. For ASDs, the onset tends to come later, often not until adulthood, because the pressure differences between the upper chambers are smaller and the damage accumulates more slowly.
This is the strongest argument for detecting and treating significant heart holes before irreversible lung damage sets in. Even people whose congenital holes were surgically repaired in childhood need ongoing follow-up, since scar tissue from the original surgery can cause irregular heart rhythms or other complications years later.