A pulmonary aneurysm is an abnormal ballooning of the pulmonary artery, the major blood vessel that carries blood from the heart to the lungs. Based on autopsy data from over 109,000 cases at the Mayo Clinic, its estimated incidence is roughly 1 in 14,000, making it far rarer than aneurysms in the aorta or brain vessels.1PubMed Central. Pulmonary artery aneurysm: a review Treatment ranges from immunosuppressive drugs to catheter-based procedures to open surgery, depending on what caused the aneurysm, how large it is, and whether it threatens to rupture. Despite its rarity, understanding the condition matters because a ruptured pulmonary aneurysm can be rapidly fatal.
True Aneurysms Versus Pseudoaneurysms
The pulmonary artery wall has three layers, and the distinction between a true aneurysm and a pseudoaneurysm hinges on which layers are involved. In a true aneurysm, all three layers of the vessel wall stretch outward, forming a balloon-like dilation. The underlying damage involves destruction of the middle layer of the artery wall, with loss of elastic tissue, heavy collagen buildup, and degeneration of the cells lining the vessel along with surrounding inflammation.2European Society of Radiology. Pulmonary artery aneurysms and pseudo aneurysms: a rare but potentially fatal finding A pseudoaneurysm, by contrast, is a contained leak. The inner vessel wall tears, and blood pools in a sac held together only by the outer layer or surrounding tissue. Pseudoaneurysms tend to be more immediately dangerous because that thin containment can give way with little warning.
This distinction is more than academic. Pseudoaneurysms are most often caused by trauma or infection and carry a high risk of massive bleeding if they rupture.3Europe PMC. Acquired pulmonary artery pseudoaneurysms: a pictorial review True aneurysms, while they can also rupture, often grow slowly and may be discovered incidentally on imaging performed for an unrelated reason. Treatment strategies differ accordingly: a pseudoaneurysm from an infected artery needs urgent attention and antimicrobial therapy, whereas a true aneurysm linked to longstanding high blood pressure in the lungs may be watched for years before requiring intervention.
Where They Form and How Common They Are
About nine out of ten pulmonary artery aneurysms develop in the main pulmonary artery, the large trunk that exits the right side of the heart before branching into the left and right pulmonary arteries. The largest reported diameters have reached 106 to 170 millimeters, dwarfing the normal main pulmonary artery width of roughly 25 to 29 millimeters.4PubMed Central. Pulmonary artery aneurysm as a result of group 2 pulmonary artery hypertension in a patient with significant mitral and aortic valve disease – review and case report Peripheral pulmonary artery aneurysms, those arising in the smaller branches deeper in the lung, are even rarer but tend to present more dramatically because they can erode into nearby airways and cause bleeding into the lungs.
What Causes Pulmonary Aneurysms
Pulmonary hypertension, or chronically elevated blood pressure in the lung vessels, is the single most common driver of true pulmonary artery aneurysms. A systematic review analyzing the existing literature found that pulmonary artery dilation was most frequently associated with pulmonary hypertension. The same analysis identified several predictors of high-risk patients: pulmonary hypertension in the setting of congenital heart disease, rapid growth of the artery diameter (more than 2 millimeters per year), tissue weakening from infection, and possibly pregnancy, especially when combined with other risk factors.5PubMed. Aneurysm of the Pulmonary Artery, a Systematic Review and Critical Analysis of Current Literature
Beyond pulmonary hypertension, the causes break into several broad categories:
- Congenital heart defects: Conditions such as ventricular septal defects or patent ductus arteriosus can chronically overload the pulmonary circulation, stressing the artery wall over years or decades.
- Connective tissue disorders: Marfan syndrome and related conditions weaken the structural proteins in blood vessel walls. In a study of 135 pediatric Marfan patients, about 8 percent had measurable main pulmonary artery dilation, and those children also tended to develop aortic problems and other systemic features of the disease earlier than their peers without pulmonary involvement.6PubMed. The Pulmonary Artery in Pediatric Patients with Marfan Syndrome: An Underestimated Aspect of the Disease
- Vasculitis and autoimmune disease: Behçet’s disease, a chronic inflammatory condition affecting blood vessels throughout the body, is one of the better-recognized causes of pulmonary artery aneurysms. A related and even rarer entity called Hughes-Stovin syndrome is characterized by multiple pulmonary artery aneurysms combined with blood clots in the veins, and is widely considered a cardiovascular variant of Behçet’s disease.7PubMed Central. Hughes Stovin Syndrome, a Rare Form of Behcet’s Disease Presenting as Recurrent Intracardiac Thrombus8PubMed. Is Hughes-Stovin syndrome Behçet’s disease?
- Infection: So-called mycotic aneurysms form when bacteria or fungi infect and weaken the artery wall. These can be difficult to distinguish from Rasmussen aneurysms, which develop when tuberculosis erodes into a pulmonary artery branch.9PubMed Central. Mycotic Pulmonary Artery Aneurysm Mimicking a Rasmussen Aneurysm
- Iatrogenic injury: Medical procedures themselves can cause pseudoaneurysms. Swan-Ganz catheterization, a common intensive-care procedure that threads a catheter through the heart into the pulmonary artery, is a recognized cause. The catheter tip can perforate the vessel wall, creating a small tear that balloons into a pseudoaneurysm.10PubMed Central. Iatrogenic Pulmonary Artery Pseudoaneurysm Following Swan-Ganz Catheterization: Successful Endovascular Coil Embolization
Symptoms and How They Show Up
Many pulmonary artery aneurysms produce no symptoms at all, particularly when they are small or growing slowly. When symptoms do appear, they tend to be vague and overlap with many other heart and lung conditions. The aneurysm can press on nearby structures in the chest, leading to shortness of breath, chest pain, hoarseness from pressure on a nerve that controls the vocal cords, palpitations, or fainting spells.11PubMed Central. Pulmonary artery aneurysm and hemoptysis as uncommon sequelae of COVID-19 infection: a case report from Syria A very large main pulmonary artery aneurysm can also cause symptoms of right heart failure, leaking of the pulmonary valve, or compression of the airways.4PubMed Central. Pulmonary artery aneurysm as a result of group 2 pulmonary artery hypertension in a patient with significant mitral and aortic valve disease – review and case report
The most alarming symptom is hemoptysis, or coughing up blood. This happens when the aneurysm leaks or ruptures into an airway, and it can escalate from mild blood-tinged sputum to life-threatening hemorrhage within minutes. Sudden cardiac death, though uncommon, has also been reported as a first presentation, underscoring that the condition can remain silent until a catastrophic event.
How Pulmonary Aneurysms Are Diagnosed
Because symptoms are nonspecific, pulmonary artery aneurysms are often caught incidentally on chest imaging done for other reasons. CT angiography of the pulmonary arteries, usually called CTPA, is the primary diagnostic tool. Dual-phase CTPA is particularly valuable because it images the vessel in two phases of contrast enhancement, allowing doctors to evaluate both the blood flow inside the aneurysm and the condition of the artery wall itself. This makes it especially useful for distinguishing between a true aneurysm and a pseudoaneurysm and for identifying signs of impending rupture.12PubMed Central. Pulmonary artery aneurysm: computed tomography (CT) imaging findings and diagnosis
On CT, the hallmarks of a peripheral pulmonary artery aneurysm include a lobulated vascular mass, an irregular or indistinct artery wall, and sometimes clot inside the aneurysm or calcium in its wall. Warning signs that rupture may be imminent include swelling around the aneurysm, pockets of gas, or a soft tissue mass adjacent to the vessel.13PubMed. Acquired peripheral pulmonary artery aneurysms: morphological spectrum of disease and multidetector computed tomography angiography findings-cases series and literature review Beyond CT, echocardiography can measure the main pulmonary artery diameter and assess right heart function, and MRI can be useful for serial monitoring in patients who need repeated imaging without radiation exposure. An aneurysm of the main pulmonary artery is generally defined as a diameter exceeding 40 millimeters.
Medical Treatment
Not every pulmonary artery aneurysm requires a procedure. When the underlying cause is an inflammatory or autoimmune condition like Behçet’s disease, immunosuppressive medications can sometimes shrink or even completely resolve the aneurysm. The standard first-line approach is a combination of corticosteroids and cyclophosphamide.14PubMed Central. Pulmonary Artery Aneurysm in Behcet Disease: Medical, Endovascular or Surgical Intervention In cases where those drugs fail, biologic agents that block a specific inflammatory signal called TNF-alpha have shown promise.
Published case reports have documented complete resolution of pulmonary artery aneurysms with medical therapy alone. In one case, multiple aneurysms in a Behçet’s patient resolved entirely after treatment with corticosteroids and azathioprine, an immunosuppressive drug.15PubMed. Pulmonary aneurysms in Behçet’s disease completely resolved after medical therapy Another report described a patient who received intravenous corticosteroid pulses followed by oral corticosteroids and monthly cyclophosphamide for six months, then maintenance azathioprine. Two years later, imaging showed complete disappearance of the aneurysms on both sides, with resolution of cough and hemoptysis.16Annals of Case Reports. Behçet’s Disease: Pulmonary Aneurysms Resolution with Immunosuppressive Therapy
For aneurysms caused by infection, prolonged courses of antibiotics or antifungals are the medical backbone of treatment. The drugs target the organism weakening the vessel wall, ideally halting its growth while other interventions address the structural problem. When pulmonary hypertension is the root cause, treating the elevated lung pressures with vasodilator medications can reduce the stress on the artery wall, though this rarely reverses an established aneurysm on its own.
Catheter-Based and Endovascular Procedures
When an aneurysm needs to be sealed off but open surgery poses too high a risk, interventional radiologists can work through catheters threaded from a vein into the pulmonary artery. One common approach is coil embolization: tiny metal coils are deposited inside the aneurysm sac, causing blood to clot around them and effectively sealing the outpouching. In one reported case, a peripheral pulmonary artery aneurysm was treated using a triple coaxial catheter technique under local anesthesia. Metallic coils were placed inside the aneurysm, and follow-up imaging confirmed complete exclusion of the aneurysm with no loss of blood supply to the surrounding lung and no procedural complications.17PubMed Central. Endovascular treatment of pulmonary artery aneurysm: Single case experience
For larger or more proximal aneurysms, stent grafts can be placed endovascularly. These are fabric-covered metal tubes that line the inside of the artery, bridging across the weakened section and redirecting blood flow away from the aneurysm sac. In one case of a ruptured proximal pseudoaneurysm causing massive hemoptysis that had not responded to prior bronchial artery embolization, a rescue stent graft was placed and successfully stopped the bleeding.18PubMed Central. Ruptured pulmonary artery pseudoaneurysm treated with stent graft: case report and literature review These endovascular options have become increasingly important because they avoid the need for major surgery and cardiopulmonary bypass, which matters greatly for patients who are already critically ill.
When Surgery Is Needed
Open surgical repair is reserved for large or rapidly growing aneurysms, those compressing nearby structures, or cases where catheter-based methods are not feasible. Current recommendations suggest surgical intervention once the pulmonary artery diameter exceeds 55 millimeters or has grown by more than 5 millimeters in six months. Additional triggers for surgery include blood clot forming inside the aneurysm, compression of the airway or other chest structures, and the appearance of new symptoms.19PubMed Central. Surgical Therapy for Pulmonary Artery Aneurysm
The most common surgical approach is to replace the diseased section of artery with a synthetic graft, typically made of Dacron. The aneurysmal segment is cut out, and the graft is sewn in place. An older and simpler technique called aneurysmorrhaphy involves excising part of the ballooned wall and stitching the remaining edges together to narrow the artery back to a normal diameter. While quicker, aneurysmorrhaphy leaves the weakened native artery wall in place, and there is a real risk the dilation will recur, particularly if pulmonary hypertension persists. For that reason, graft replacement is generally preferred over simple repair.19PubMed Central. Surgical Therapy for Pulmonary Artery Aneurysm
For infected pseudoaneurysms that do not respond to antibiotics and catheter-based treatments, surgeons may need to perform a lobectomy, removing the entire lobe of lung containing the aneurysm. This is considered a last resort, typically reserved for patients with uncontrolled bleeding or pleural hemorrhage.20PubMed Central. Pulmonary Artery Pseudoaneurysm: A Rare Cause of Fatal Massive Hemoptysis
Surgical Outcomes
The largest published surgical series tracked 38 patients who underwent pulmonary artery aneurysm repair at a single center. There were no deaths during or immediately after surgery. Over longer follow-up, three patients died (about 8 percent), but none of those deaths were related to the heart or the aneurysm. Late reoperations were also needed in about 8 percent of cases, and again, none were for recurrence of the aneurysm itself.21PubMed. Outcome of Surgical Repair of Pulmonary Artery Aneurysms: A Single-Center Experience With 38 Patients These numbers are reassuring, though they come from a specialized center experienced in the procedure. Individual outcomes depend heavily on the underlying cause, the patient’s overall health, and whether pulmonary hypertension can be managed long term.
Long-term survival after surgery can be quite good when the driving condition is addressed simultaneously. In one early case report, a patient with a pulmonary artery aneurysm caused by a ventricular septal defect underwent aneurysmorrhaphy along with closure of the heart defect. Despite a rocky early recovery with heart failure, the patient stabilized and remained well without aneurysm recurrence or cardiac problems for at least six years of follow-up.22PubMed. Aneurysm of the main pulmonary artery: long-term survival after aneurysmorrhaphy and closure of a ventricular septal defect
Pulmonary Aneurysms in Children and Genetic Conditions
In pediatric patients, pulmonary artery dilation most often shows up in the context of congenital heart defects or inherited connective tissue disorders. Marfan syndrome is the prime example. The aorta gets the lion’s share of clinical attention in Marfan patients, but the pulmonary artery can be affected too, and when it is, it tends to signal a more severe form of the disease. In a study of 135 children with Marfan syndrome, those who had main pulmonary artery dilation were more likely to develop aortic dilation earlier, had a higher rate of mitral valve prolapse, and showed more systemic manifestations of the syndrome than those with normal pulmonary arteries. Medical treatment, typically beta-blockers or other drugs to reduce stress on weakened arteries, was started earlier in the group with pulmonary artery involvement.6PubMed. The Pulmonary Artery in Pediatric Patients with Marfan Syndrome: An Underestimated Aspect of the Disease
In rare instances, pulmonary artery aneurysms can even be detected before birth. One case report described a fetus diagnosed with early-onset Marfan syndrome who had both aortic dilation and a giant pulmonary artery aneurysm identified on prenatal imaging and confirmed after delivery by genetic testing.23PubMed Central. Early-onset Marfan syndrome with aortic dilatation and giant pulmonary artery aneurysm: A case report Findings like these are exceptionally uncommon, but they highlight that pulmonary artery dilation in a child or infant should prompt a thorough workup for underlying genetic conditions, since early diagnosis of Marfan syndrome or similar disorders can change the management plan for the patient’s entire cardiovascular system.
Managing Emergencies
A ruptured pulmonary aneurysm or pseudoaneurysm is one of the most dramatic emergencies in chest medicine. The patient typically presents with massive hemoptysis, and every minute counts. In the acute setting, the first priority is keeping the airway open and preventing the patient from drowning in their own blood. This can involve positioning the patient with the bleeding side down, placing a double-lumen breathing tube to isolate the affected lung, and aggressive blood transfusion.
Once the patient is stabilized enough to reach an interventional suite, endovascular approaches are the preferred route for stopping the hemorrhage. Options include coil embolization of the aneurysm or the feeding artery, stent graft placement, or embolization of the bronchial artery if that vessel is contributing to the bleed. In one surgical case, massive intraoperative hemoptysis from a pseudoaneurysm was initially controlled by temporarily clamping the right pulmonary artery, buying time for a delayed endovascular procedure to permanently seal the feeding vessel.24PubMed Central. Massive Hemoptysis from a Pulmonary Artery Pseudoaneurysm during Cardiac Surgery Surgical resection of the affected lung segment or lobe remains the backup option when endovascular methods cannot control the bleeding.20PubMed Central. Pulmonary Artery Pseudoaneurysm: A Rare Cause of Fatal Massive Hemoptysis
The rarity of the condition works against patients here. Most emergency physicians will never see a ruptured pulmonary artery aneurysm in their careers, and the imaging findings can be mistaken for other causes of pulmonary hemorrhage. A high index of suspicion in the right clinical context, such as hemoptysis in a patient with known Behçet’s disease, a recent Swan-Ganz catheter placement, or longstanding pulmonary hypertension, can mean the difference between a timely diagnosis and a fatal delay.