Aortic Aneurysm

IWBCA
Feb 6
16 min read

An aortic aneurysm is a weakened, stretched area of the aorta that bulges outward. Because the aorta carries blood under high pressure, an aneurysm can enlarge over time and may become dangerous if it ruptures or if the aortic wall tears. A tear in the aortic wall is called an aortic dissection, and it can reduce blood flow to the brain, kidneys, intestines, or legs, in addition to causing internal bleeding.

Overview

What is an aortic aneurysm?

An aortic aneurysm is a localized bulge or dilation of the aorta, the largest artery in the body that carries oxygen-rich blood from the heart to every organ.

The aorta begins at the heart, passes through the aortic valve, and then continues as the aortic root and ascending aorta, curves through the aortic arch, and runs downward as the descending thoracic aorta through the chest and the abdominal aorta through the abdomen. Clinicians often describe aneurysms by the segment involved, such as ascending, arch, descending thoracic, abdominal, or thoracoabdominal.

An aortic aneurysm forms when a segment of the aortic wall loses strength and stretches beyond its normal diameter. Over time, repeated pulses of blood with each heartbeat put pressure on this weakened area, and the wall can widen further. In medical terms, an aneurysm is usually defined as an enlargement that is at least 50% greater than the expected normal diameter for that aortic segment and body size.

Many aneurysms remain clinically silent for years and are found incidentally on imaging performed for other reasons. The main concern is not the presence of dilation alone, but how that dilation behaves over time. The risk of future problems depends on the aneurysm's location in the aorta, its current size, the rate of enlargement, and whether imaging reveals features suggesting the wall is under increased stress or beginning to lose stability.

Categorization

What are the different types?

Aortic aneurysms are named for the section of the aorta involved.

Abdominal Aortic Aneurysm (AAA): An AAA develops in the portion of the aorta that runs through the abdomen, often below the renal arteries. Many AAAs are identified during screening ultrasound or on imaging performed for another reason. The key clinical focus is size and growth rate, as these features drive the risk of rupture.

Thoracic Aortic Aneurysm (TAA): A TAA develops in the chest portion of the aorta and may involve the ascending aorta, the arch, or the descending thoracic aorta. Some are related to long-standing hypertension and age-related vascular changes. Others are linked to inherited connective tissue conditions or a bicuspid aortic valve, which can raise risk at younger ages.

Prevalence

How common are they?

Abdominal aortic aneurysm (AAA) remains the most frequently detected type of aortic aneurysm, although its prevalence has fallen in many countries during the past two decades as smoking rates and overall cardiovascular risk have declined. Population screening programs in Europe and North America consistently report AAA prevalence in the low single digits among older male ever-smokers, typically around 1% to 3% in the 65 to 75 age group, with higher rates among current smokers and in the oldest participants.

This decline is supported by large registry and screening analyses showing that both AAA prevalence and rupture rates have dropped in parallel with reduced smoking and improved cardiovascular prevention strategies. In men 65 to 75 years old who have ever smoked, contemporary screening-era prevalence is often reported in the 1% to 3% range in organized ultrasound programs. In men of the same age who have never smoked, prevalence is consistently lower, which is why major guideline groups such as the U.S. Preventive Services Task Force recommend routine one-time ultrasound screening for male ever smokers in this age band and a more selective, individualized approach for those who have never smoked.

In women, AAA is uncommon in broad screening cohorts, frequently reported below 1% in unselected groups, although female ever smokers have measurable risk, with some analyses showing AAA in around 1% to 2% of women aged 65 to 75 who have smoked. Risk rises with age, current or prior smoking, hypertension, and family history. Women with AAA are often diagnosed at older ages and at smaller diameters at the time of rupture, which is one reason clinicians pay close attention to symptoms and risk factors even when screening yields fewer aneurysms in women than in men.

Thoracic aortic aneurysm (TAA) is less common than abdominal aneurysm in population terms, but carries high clinical significance because it often remains silent until dissection or rupture. Modern meta-analyses estimate a pooled TAA prevalence around 0.16% in the general population, with an incidence on the order of 5 new cases per 100,000 people each year. Earlier population-based studies reported similar incidence rates, indicating that TAA is relatively infrequent but far from rare in aging populations. The apparent frequency of TAA has increased in recent decades, in part because chest CT and MRI are used more frequently for other indications, which makes incidental aneurysms easier to detect.

A key limitation of all prevalence estimates is that they describe diagnosed aneurysms. Many aortic aneurysms never come to medical attention during life. Epidemiologic data indicate that most aneurysms develop without warning symptoms and that rupture often leads to sudden death, with survival after rupture in the range of about 20% once prehospital deaths are included. A large analysis of sudden death in Japan estimated that aortic disease, including aneurysm and dissection, accounts for approximately one in ten sudden deaths, which implies that a substantial number of people die from aortic events without ever receiving a diagnosis.

The gap between clinical and autopsy data illustrates this undercounting. A meta-analysis of TAA epidemiology found that, when autopsy-only studies were included, the prevalence of thoracic aneurysm in those series was approximately 0.8%, whereas prevalence dropped by an order of magnitude when autopsy data were excluded and only imaging-based clinical studies were considered. This pattern supports the idea that a significant share of aortic aneurysms is detected only at autopsy or remains unrecognized, which means real-world prevalence is higher than what screening and imaging registries alone can capture.

One practical takeaway matters for patients and clinicians. Prevalence is not evenly distributed across the population. Age, smoking history, blood pressure control, sex, family history, and underlying connective tissue or aortic disease create very different risk profiles. People in higher-risk categories gain the most from targeted screening and longitudinal monitoring, while population averages likely underestimate the true burden of disease in groups that are underdiagnosed or that experience sudden fatal events before a formal diagnosis is made.

Risk Factors

What are the most common risk factors associated with an aortic aneurysm?

Risk is shaped by a combination of inherited factors and long-term stress on the aortic wall. Several factors increase the likelihood of an aneurysm developing. Others increase the likelihood it will enlarge, dissect, or rupture once present.

Aortic aneurysms occur most often in people who:

Smoke Cigarettes or Use Other Nicotine Products: Smoking tobacco or using nicotine products is one of the strongest modifiable risk factors for abdominal aortic aneurysm. Toxins in smoke injure the inner lining of the aorta, accelerate atherosclerosis, and damage the elastic and muscular components of the wall. People who currently smoke are more likely to develop an aneurysm, and aneurysms in active smokers tend to grow faster and reach dangerous sizes sooner than in people who never smoked or who quit.
Are Over Age 65: Age-related changes in the aortic wall accumulate over decades. Elastic fibers gradually fragment, smooth muscle cells decline in number, and collagen becomes stiffer. These changes reduce the aorta's resilience to blood pressure and pulsatile stress. As a result, the likelihood of both abdominal and thoracic aortic aneurysms rises with age, especially after 65, even in people without a strong family history.
Are Male: Abdominal aortic aneurysm is diagnosed more often in males, particularly those over age 65. Hormonal influences, differences in body size, and differing patterns of atherosclerosis and smoking exposure are thought to contribute. Although females develop abdominal aneurysms less frequently, aneurysms in females can behave aggressively and may rupture at smaller diameters, so sex-specific screening and treatment thresholds are important.
Have a Family History of Aortic Aneurysms or Dissections: Having a first-degree relative with an aortic aneurysm, dissection, or unexplained sudden death raises the likelihood of inherited vulnerability in the aortic wall. This can reflect known syndromes such as Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, or familial thoracic aortic aneurysm conditions, as well as yet-unidentified genetic factors. Family history often leads clinicians to recommend earlier and more frequent imaging and to consider repair at smaller diameters.
Have High Blood Pressure (Hypertension): Chronic high blood pressure increases mechanical stress on the aortic wall with every heartbeat. Over the years, this elevated pressure accelerates wear on elastic fibers, worsens atherosclerotic changes, and promotes progressive dilation of susceptible segments. Poorly controlled hypertension also increases the risk that an existing aneurysm will dissect or rupture, especially when pressures spike during exertion, pain, or intense emotional stress.
Have Atherosclerotic Cardiovascular Disease or High Cholesterol: Atherosclerosis is a common underlying process in abdominal aortic aneurysm. Elevated LDL cholesterol, low HDL cholesterol, and other lipid abnormalities promote plaque formation in the aortic wall. Plaque-related inflammation and calcification weaken the media, reduce elasticity, and create focal areas that are vulnerable to aneurysmal dilation. People with coronary artery disease, peripheral artery disease, or long-standing hyperlipidemia often have a parallel risk in the abdominal aorta.
Have Inherited Connective Tissue or Aortic Disorders: Genetic conditions that affect connective tissue or aortic structure can predispose to aneurysm at younger ages and smaller diameters. Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, and some forms of familial thoracic aortic aneurysm disrupt proteins such as fibrillin or collagen and alter signaling pathways that regulate vessel wall architecture. A bicuspid aortic valve is also associated with ascending aortic dilation, even when the valve functions reasonably well.
Have Blood Clotting Disorders or Chronic Thrombotic Disease: Conditions that increase the tendency to form blood clots can complicate existing aneurysms and, in some cases, intersect with processes that injure the aortic wall. Inherited or acquired thrombophilias, such as factor V Leiden mutation, prothrombin gene mutation, antiphospholipid antibody syndrome, or deficiencies in protein C, protein S, or antithrombin, can promote clot formation within an aneurysmal segment and in downstream arteries. These intraluminal clots can fragment and embolize to the kidneys, intestines, or limbs, adding ischemic risk on top of aneurysm risk. Some autoimmune or inflammatory clotting disorders also involve the vessel wall and can indirectly contribute to aneurysm formation or progression.
Have Chronic Inflammatory or Autoimmune Conditions Affecting Blood Vessels: Large-vessel vasculitides such as giant cell arteritis and Takayasu arteritis, as well as other inflammatory diseases that target arteries, can weaken the aortic wall through immune-mediated injury. Persistent inflammation, followed by scarring and remodeling, can lead to segments that are both narrowed and dilated. These structural changes increase the chance that aneurysms will form and later expand.
Have a History of Aortic Injury or Prior Aortic Procedures: Previous trauma to the chest or abdomen, such as high-speed motor vehicle collisions or major falls, can injure the aortic wall and leave behind areas of weakness. A history of prior aortic surgery, stent placement, or catheter-based interventions can also alter local wall structure. These injured segments may be more prone to later dilation and aneurysm formation, especially in the presence of hypertension, smoking, or other vascular risk factors.
Have Infections of the Arterial Wall or Circulation: Certain infections can seed atherosclerotic plaques or directly involve the aortic wall, leading to infected (mycotic) aneurysms. People with uncontrolled bloodstream infections, endocarditis, immunosuppression, or intravascular devices can be at higher risk. Infected aneurysms often enlarge quickly, carry a high risk of rupture, and require urgent specialist care.
Have Other Cardiovascular Risk Factors Over Time: Diabetes, obesity, physical inactivity, and long-standing exposure to environmental or occupational toxins can work alongside smoking, hypertension, and high cholesterol to accelerate vascular aging. This combination magnifies stress on the aortic wall and increases the likelihood that aneurysms will emerge in susceptible individuals, even when no single cause is obvious.

Causes

What are the most common causes of an aortic aneurysm?

In many cases, no single cause is identified. Clinicians typically think in terms of processes that weaken the vessel wall over time or change how force is distributed across the aorta with every heartbeat.

The causes of an aortic aneurysm are often unknown, but can include:

Atherosclerosis (Narrowing of the Arteries): Atherosclerosis involves the buildup of fatty, cholesterol-rich plaque within the inner lining of arteries. In the aorta, plaque and associated inflammation can damage the elastic fibers and smooth muscle cells that give the wall strength and flexibility. Over time, this damage can thin and weaken the media (middle layer of the artery), reduce its ability to withstand pressure, and promote localized bulging. Atherosclerotic changes are especially common in the abdominal aorta, where long-standing plaque, calcification, and smoking-related injury frequently contribute to aneurysm formation.
Inflammation of the Arteries: Inflammatory conditions can directly attack the aortic wall and surrounding tissues. Large-vessel vasculitides, such as giant cell arteritis and Takayasu arteritis, as well as chronic inflammatory diseases affecting the aorta, can cause immune cell infiltration, destruction of normal tissue architecture, and scarring. This process weakens the structural layers of the aorta, can cause segmental narrowing and dilation, and can set the stage for aneurysm formation and progressive enlargement even after active inflammation has subsided.
Inherited Conditions Affecting Connective Tissue: Genetic disorders that alter connective tissue proteins make the aortic wall more fragile, even at younger ages. In Marfan syndrome, abnormalities of fibrillin-1 and related pathways reduce the strength and elasticity of the aortic media, particularly in the root and ascending aorta, which predisposes to early aneurysm formation and dissection at smaller diameters. Certain forms of Ehlers-Danlos syndrome, especially the vascular type, involve defects in type III collagen that leave arteries thin, fragile, and prone to aneurysm and rupture. Other inherited conditions, such as Loeys-Dietz syndrome, familial thoracic aortic aneurysm syndromes, and some bicuspid aortic valve–associated aortopathies, similarly disturb the balance of structural proteins and signaling pathways that maintain aortic integrity.
Injury to the Aorta: Direct injury can disrupt the layers of the aortic wall and create a weak point that later enlarges into an aneurysm. High-speed motor vehicle crashes, major falls, or crush injuries can cause blunt traumatic aortic injury, most often near the ligamentum arteriosum in the thoracic aorta. Iatrogenic injuries can occur during catheter-based procedures, cardiac surgery, or aortic interventions when devices or instruments inadvertently damage the vessel. Even when the initial tear is repaired or heals, the affected segment may remain structurally compromised and may gradually dilate over time.
Infections (Mycotic Aneurysms): Certain infections can invade or erode the aortic wall and lead to an infected (mycotic) aneurysm. Bacteria such as Staphylococcus aureus, Salmonella species, and other pathogens can reach the aorta through the bloodstream, from nearby infected tissues, or from infected atherosclerotic plaque. Historically, untreated syphilis was a well-known cause of ascending aortic aneurysms. Infected aneurysms often enlarge quickly, have irregular or lobulated shapes on imaging, and carry a high risk of rupture. They usually require urgent evaluation, prolonged antibiotic therapy, and surgical or endovascular repair.
Chronic High Blood Pressure: Long-standing hypertension increases the force exerted on the aortic wall with every heartbeat. Elevated pressure accelerates wear on the elastic components of the media, promotes microscopic tears and degeneration, and worsens the impact of atherosclerosis and other risk factors. Over the years, this constant mechanical load can contribute to progressive dilation of susceptible segments of the aorta and raise the likelihood of aneurysm formation and dissection.
Degenerative Changes With Aging and Other Risk Factors: Age-related degeneration of elastic fibers and smooth muscle cells gradually reduces the strength and resilience of the aortic wall. These changes often occur alongside cumulative exposures such as smoking, high cholesterol, and long-term inflammation. In older adults, this combination of intrinsic aging of the aorta and acquired risk factors commonly underlies abdominal aortic aneurysm development, even when no single “trigger” can be identified.

Symptoms

What are the most common symptoms of an aortic aneurysm?

Many people have no symptoms, especially when an aneurysm is small or growing slowly. Symptoms are more likely when an aneurysm enlarges, presses on nearby structures, leaks, dissects, or ruptures. A rupture is a medical emergency. Call 911 if symptoms begin suddenly and feel severe.

Symptoms of Ruptured Aneurysm

Symptoms of a ruptured aortic aneurysm usually begin without warning and progress quickly. They can include:

Sudden, Severe Pain: Pain often starts abruptly and may feel tearing, ripping, or stabbing. It can occur in the chest, upper back, abdomen, lower back, flank, or groin, depending on the aneurysm’s location, and may radiate to the shoulders, neck, jaw, or legs. Pain usually does not improve with rest or position changes and often worsens over minutes.
Dizziness or Lightheadedness: Dizziness, lightheadedness, or feeling faint may indicate a rapid drop in blood pressure due to internal bleeding. This may progress to near-fainting or complete loss of consciousness as blood loss continues.
Rapid Heart Rate: A fast heart rate can be the body’s immediate response to sudden blood loss and developing shock. The heartbeat may feel pounding or racing even while resting.
Low Blood Pressure or Fainting: Very low blood pressure can cause pale, cool skin, weakness, confusion, or collapse. Some people faint suddenly without much warning if the rupture is large.
Cold, Clammy, or Sweaty Skin: Profuse sweating, cold and clammy skin, and a feeling of impending doom are common signs that the body is in shock from major internal bleeding.
Shortness of Breath: Sudden difficulty breathing can occur if blood accumulates in the chest, if the heart cannot pump effectively, or if pain and anxiety limit the ability to take a full breath.

An aortic aneurysm found before rupture often has a better outlook because monitoring and planned treatment are possible.

Symptoms of Aneurysm Before Rupture

As an aortic aneurysm grows, it can begin to press on nearby organs, nerves, or blood vessels and cause symptoms such as:

Difficulty Breathing or Shortness of Breath: Larger thoracic aneurysms can compress the trachea or main airways, limit lung expansion, or affect how well the heart pumps blood. People may notice breathlessness during activity, trouble catching their breath when lying flat, or a new need to sleep propped up on pillows.
Feeling Full After a Small Meal: Abdominal aortic aneurysms can press on the stomach, intestines, or nearby organs. This compression can cause early satiety, bloating, or a sense of pressure after eating only a small amount of food, sometimes accompanied by nausea or mild abdominal discomfort.
Pain Near the Aneurysm Site: Pain may develop at the site where the aneurysm is stretching the aortic wall or affecting adjacent tissues. Depending on which aortic segment is involved, pain may occur in the chest, upper back, lower back, abdomen, flank, groin, neck, or jaw. Pain can be constant or intermittent and may worsen with activity, coughing, or changes in position.
Painful or Difficult Swallowing: A thoracic aneurysm can compress the esophagus, causing discomfort or difficulty with swallowing. People may notice chest discomfort or a sensation that food is “sticking” when they swallow, even if the food is soft.
Swelling of the Arms, Neck, or Face: Compression of large veins in the chest, such as the superior vena cava, can slow blood return to the heart. This can cause visible swelling of the neck veins and puffiness of the face, upper chest, or arms, sometimes accompanied by a feeling of tightness in rings, collars, or shirt necklines.
Hoarseness or Voice Changes: A thoracic aneurysm can press on the nerve that controls one of the vocal cords. This pressure can cause hoarseness, a breathy or weak voice, or changes in vocal pitch that do not improve with rest.
Cough or Wheezing: Irritation or compression of the airway can lead to a persistent dry cough or wheezing that is not explained by infection or asthma and persists despite usual treatments.
Pulsating Sensation in the Abdomen: An abdominal aortic aneurysm can produce a noticeable throbbing or pulsing sensation in the mid-abdomen, particularly when lying flat. Some individuals or clinicians may detect a pulsating mass on examination.

Any new, unexplained chest, back, abdominal, or neck pain, especially when combined with dizziness, shortness of breath, or fainting, should prompt immediate medical evaluation to rule out an aortic emergency.

Complications

What are the complications of an aortic aneurysm?

Complications can occur with rupture, with dissection, or from reduced blood flow to organs and limbs. The risk rises as the aneurysm enlarges or the aortic wall weakens.

If an aortic aneurysm ruptures, it causes internal bleeding that can become fatal within minutes to hours without emergency treatment. With prompt intervention, some individuals recover, but the risk of serious complications remains high.

A growing aortic aneurysm can also lead to a tear in the artery wall called an aortic dissection. A dissection creates a new channel within the wall layers, allowing blood to track between them. This can narrow or block the true artery pathway and reduce blood flow from the heart to critical areas.

Complications include:

Internal Bleeding After Rupture: Rupture allows blood to escape from the aorta into the chest, abdomen, or surrounding tissues, often at a very rapid rate. Bleeding can be massive, leading to a sudden drop in blood pressure, shock, and failure of vital organs such as the brain, kidneys, and heart. Even with immediate surgery, people who experience rupture face high risks of death and long-term health problems related to prolonged low blood flow.
Aortic Dissection: In a dissection, a tear in the inner layer of the aorta allows blood to force its way between the wall layers and create a false channel. This can rapidly become life-threatening and requires immediate evaluation. Dissection can interrupt blood supply to the heart, brain, kidneys, intestines, or limbs, further weaken the aortic wall, and extend along the length of the aorta. It can also damage the aortic valve or coronary artery openings, leading to acute heart failure or a heart attack.
Organ Ischemia: Reduced blood flow through the true aortic channel or its branches can injure organs that depend on those vessels. When arteries to the brain are affected, people can experience stroke-like symptoms such as weakness, difficulty speaking, or vision changes. Involvement of the arteries to the kidneys can cause acute kidney injury and may lead to chronic kidney disease. Reduced flow to the intestines can cause severe abdominal pain, tissue death in the bowel, and the need for emergency surgery. If the arteries supplying the spinal cord are compromised, individuals may develop weakness, paralysis, or loss of bowel and bladder control.
Limb Ischemia: When blood flow to the legs or arms is reduced or abruptly blocked, it can cause sudden pain, weakness, numbness, a cold sensation, or a change in skin color. In severe cases, the affected limb may lose pulses or function, and tissue can begin to die if blood flow is not restored quickly. This can lead to permanent nerve and muscle damage and may sometimes require amputation if the limb cannot be saved.
Rupture Triggered By Dissection: A dissection can destabilize the aortic wall by separating its layers and thinning the outer wall. Rising pressure within the wall layers increases the likelihood that the weakened segment will tear completely, leading to frank rupture. When rupture follows dissection, the combined effects of wall injury, bleeding, and organ ischemia markedly increase the risk of death and serious disability.
Aortic Valve Problems and Heart Failure: When an aneurysm involves the aortic root or the ascending aorta near the heart, it can stretch the attachment of the aortic valve. This stretching can prevent the valve from closing tightly, allowing blood to leak backward into the heart (aortic regurgitation). Over time, the heart must work harder to compensate, which can lead to shortness of breath, fatigue, swelling in the legs, and eventual heart failure if not treated.
Blood Clots and Embolism: Slow or disturbed blood flow inside an aneurysm can promote clot formation along the inner wall. Fragments of clot can dislodge and travel downstream, obstructing smaller arteries. This can cause sudden loss of blood flow to a leg, kidney, intestine, or other organ, leading to pain, tissue damage, and possible loss of function even if the aneurysm itself has not ruptured.
Long-Term Disability or Death: Even when people survive rupture, dissection, or major ischemic events, they may face lasting health effects. These can include chronic kidney disease requiring dialysis, persistent neurologic problems after stroke or spinal cord injury, heart failure, ongoing pain, or reduced ability to walk or perform daily activities. Many aortic aneurysm complications are life-threatening, and some lead to death despite rapid, expert treatment.

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