The leading cause of a heart aneurysm is a heart attack. When a section of heart muscle loses its blood supply during a heart attack, the damaged tissue can thin out and bulge outward, forming a balloon-like weak spot in the heart wall. About 5% of heart attack survivors develop this type of aneurysm, known as a left ventricular aneurysm, though the rate was much higher before modern treatments for heart attacks became widespread.
How a Heart Attack Creates an Aneurysm
During a heart attack, a coronary artery becomes completely blocked, cutting off oxygen to a section of heart muscle. If blood flow isn’t restored quickly, the muscle cells in that area die. Unlike a cut on your skin, dead heart muscle doesn’t regenerate. Instead, it’s replaced by stiff scar tissue that’s much thinner and weaker than healthy muscle.
The surviving muscle around the damaged zone keeps contracting normally with each heartbeat. That creates a problem: every time the heart pumps, the pressure pushes against the thin, scarred patch. Over days to weeks, that patch stretches outward and forms a bulge. The two biggest risk factors are a complete blockage of the left anterior descending artery (the major vessel running down the front of the heart) and failure to reopen the blocked artery with emergency treatment. This is why the front wall of the left ventricle is the most common location for heart aneurysms.
Several conditions make aneurysm formation more likely after a heart attack:
- High blood pressure, which increases the force pushing against the weakened wall
- No backup blood supply from nearby arteries (called collateral circulation) to partially feed the damaged area
- Delayed or absent treatment to reopen the blocked artery
- A large area of damage that extends through the full thickness of the heart wall
Before clot-busting drugs and stent procedures became routine, historical studies found aneurysm rates as high as 38% among heart attack survivors. Modern emergency treatment, which restores blood flow faster and saves more muscle tissue, has dropped that figure dramatically to around 4.5 to 5%.
Causes Beyond Heart Attacks
While heart attacks account for the vast majority of cardiac aneurysms, other conditions can weaken the heart wall in similar ways. Chronic high blood pressure on its own, even without a heart attack, can stress the ventricular wall enough to contribute to aneurysm formation. Long-term use of steroids and certain anti-inflammatory painkillers (NSAIDs) has also been linked to increased risk, likely because these drugs can interfere with normal healing of heart tissue.
Infections that affect the heart, including Chagas disease and bacterial endocarditis, can damage or erode the muscle wall. Cardiac surgery can occasionally leave a vulnerable spot at the operative site, particularly around valve repair areas. Blunt chest trauma from a car accident or similar injury is a rarer but recognized cause.
Congenital Heart Aneurysms
In rare cases, people are born with an aneurysm in the heart wall. These congenital aneurysms form during fetal development and aren’t related to heart attacks or blocked arteries at all. The exact mechanism is still poorly understood, but researchers have identified certain genes involved in the structural proteins of heart muscle cells as areas of interest. Some congenital aneurysms are associated with unusually prominent muscle ridges (trabeculations) inside the ventricle, a pattern that overlaps with a condition called left ventricular noncompaction. Many congenital aneurysms are discovered incidentally on imaging done for other reasons, sometimes not until adulthood.
True Aneurysms vs. Pseudoaneurysms
Not all cardiac aneurysms are the same structurally. A true aneurysm involves all three layers of the heart wall bulging outward. The wall is thin but intact, and the bulge has a wide opening where it connects to the rest of the ventricle. These tend to develop gradually after a heart attack and, while serious, often remain stable for years.
A pseudoaneurysm (or “false aneurysm”) is a more dangerous situation. Here, the heart wall actually ruptures, but the tear is contained by the outer lining of the heart (the pericardium). What looks like a bulge on imaging is really a pocket of blood held in place by surrounding tissue rather than by intact heart muscle. The most common cause is also a heart attack, but pseudoaneurysms can result from cardiac surgery, chest trauma, or infection. Because the wall holding them together is so fragile, pseudoaneurysms carry a higher risk of complete rupture and typically require more urgent treatment.
Aortic Aneurysms Near the Heart
Some people searching for “aneurysm in the heart” may actually be thinking of aneurysms in the aorta, the large artery that exits the heart and carries blood to the rest of the body. These are a different condition with different causes, though they can occur very close to the heart itself.
Thoracic aortic aneurysms, which form in the section of the aorta running through the chest, are typically caused by high blood pressure or sudden injury. Inherited connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome weaken the aortic wall from a young age and significantly raise the risk. Abdominal aortic aneurysms, which form lower in the body, are most often caused by atherosclerosis, the same buildup of fatty plaques in artery walls that leads to heart attacks.
Why Heart Aneurysms Are Dangerous
A heart aneurysm doesn’t pump effectively. Instead of contracting and pushing blood forward, the bulging section stretches outward with each heartbeat, wasting energy and reducing the heart’s overall pumping power. Over time, this can contribute to heart failure.
The bigger immediate concern is blood clots. Blood tends to pool and swirl slowly inside the aneurysm’s pouch rather than flowing through normally, and stagnant blood clots more easily. If a clot forms inside the aneurysm and then breaks free, it can travel to the brain and cause a stroke. The risk of these embolic events is highest in the first three months after a heart attack, with reported rates ranging from about 5.5% to over 20% depending on how quickly the original blockage was treated. Even when clots are detected and initially resolve, about 5% of patients still experience a stroke.
Abnormal heart rhythms are another complication. The scar tissue and stretched muscle around the aneurysm can disrupt the electrical signals that coordinate heartbeats, triggering irregular and sometimes dangerous rhythms originating from the ventricle.