Silent but Deadly: A Conservative Approach to Pulmonary Artery Pseudoaneurysm

Abstract

Pulmonary artery pseudoaneurysms (PAPAs) are rare and potentially fatal vascular complications that often require early detection. Most common etiologies are infection and trauma (including iatrogenic from procedures like pulmonary artery catheterization or lung biopsy). Early clinical signs include hemoptysis, dyspnea, and hemodynamic instability. Diagnostic workup should always include appropriate imaging modality, with computerized tomography (CT) and CT angiography as important diagnostic tools. Given the limited number of reported cases, treatment is not definitive and is largely guided by symptoms and patient present. In the case of massive hemoptysis, coil embolization or pulmonary vascular stenting is the preferred option. In the current case of asymptomatic PAPA, we will outline a more conservative approach to treating PAPA.

Introduction

The term “pulmonary artery aneurysm” (PAA) was first described in medical literature in 1947, defined as persistent dilation of the pulmonary artery trunk or major branches accompanied by cystic necrosis of the vessel wall’s media. These were incredibly rare, diagnosed in only 1 out of every 13 969 autopsies. In contrast, pulmonary artery pseudoaneurysms (PAPAs) involve the enlargement of the pulmonary artery due to the destruction of the entire vessel wall. Due to their scarcity, both conditions were often grouped in earlier studies. While congenital heart defects are the usual culprits for PAPAs, acquired PAPAs may be associated with conditions such as pulmonary hypertension, atherosclerosis, inflammatory processes such as giant cell arteritis, iatrogenic causes (eg, pulmonary catheterization), and infections.^1,2 When an infectious process leads to PAPA formation, the condition is classified as a mycotic pseudoaneurysm (MPA). In the past, Rasmussen aneurysms, resulting from cavitary tuberculosis, and proximal aneurysms, attributed to syphilis, were notable causes of mycotic PAPAs. Due to the rarity of mycotic pseudoaneurysms in the pulmonary artery, a comprehensive understanding of their natural history and rupture risk remains limited. ¹ Presently, mycotic PAAs are predominantly associated with complications arising from infective endocarditis (IE). ² Patients with MPA have been reported to have a mortality rate slightly exceeding 50%. ²

Current treatment options for PAPA are determined by the risk of rupture, clinical presentation, and anatomical considerations. Endovascular intervention is the mainstay of treatment for PAPA due to the high risk of rupture and bleeding,^3,4 with surgical management reserved for select cases. ⁵ Conservative management should be considered in carefully selected, low-risk patients with close follow-up. ⁶

Case Presentation

A 39-year-old female with a history of drug use disorder presented from outside hospital with known IE. Patient had blood cultures positive for methicillin-resistant Staphylococcus aureus (MRSA) and tricuspid valve (TV) vegetation. At that time patient was treated with intravenous vancomycin for a planned total of 6 weeks. She completed 2 out of 6 weeks of the antibiotic regimen but continued to have intermittent fevers. The patient was then transferred to our facility for further evaluation. Upon physical examination, vital signs showed mild tachycardia at 101 beats/minute with intermittent fevers, otherwise hemodynamically stable. Cardiovascular exam revealed a pansystolic murmur heard best at the left sternal border. Labs were significant for white blood cell count of 22 k/cmm, hemoglobin of 7.9 g/dL, with remainder of labs otherwise unremarkable. Repeat blood cultures showed no growth. Patient had transthoracic echocardiogram at this facility which showed large TV vegetation (Figure 1). The patient was continued on vancomycin, and cefepime was added. Trans-esophageal echo was then performed which showed 2.6 × 1.2 cm TV vegetation with moderate tricuspid regurgitation, indicating interval increase in vegetation size. Given a history of TV endocarditis and concerns for empyema, a computerized tomography (CT) of the chest was performed, which showed multiple septic embolic and incidental findings of the right distal lower lobe PAPP measuring 1.6 cm with small associated thrombus. Cardiovascular and thoracic surgery was consulted in need for surgical intervention of TV vegetation as well as new finding of PAPP (Figures 2 and 3).

Figure 1.

Transthoracic echocardiogram apical 4 chamber view demonstrating large vegetation on tricuspid valve (Red arrow).

Figure 2.

CT chest with IV contrast in axial view demonstrating pseudoaneurysm of right lower lobe pulmonary artery aneurysm (Red arrow). CT, computerized tomography.

Figure 3.

CTA chest with IV contrast in axial view of demonstrating pulmonary artery pseudoaneurysm, now showing associated small volume thrombus (Red arrow). CTA, computerized tomography angiography.

In regard to the PAPP with associated thrombus, given the small size, without any overt hemoptysis, or signs of rupture there was no indication for endovascular embolization. Patient was placed on IV heparin for management of the thrombus. On hospital day 13, the patient was taken to the operating room for transvenous removal of TV vegetation with AlphaVAC device (AngioDynamics, Marlborough, MA, USA), which the patient tolerated without complication. Patient had repeat CT chest at that time which showed no change in size of PAPP. Patient was continued on heparin intravenously postprocedure. On hospital day 15, the patient was able to transition to oral anticoagulation and was placed on Eliquis 5 mg twice a day. ⁷ Given the relatively small size of PAPP, without any evidence of PAPP rupture, decision was made to forego endovascular management of PAPP and treated conservatively. After consultation with cardiothoracic surgery, in the setting of provoked thrombus secondary to endocarditis it was decided that patient would need a minimum 3 months of anticoagulation.

After further consultation with infectious disease specialist, cefepime was discontinued on day 3 of hospitalization. This decision was made based on low suspicion of both Gram-negative infection, as well as low suspicion of PICC line infection. However, vancomycin was continued to cover for MRSA infection. Antibiotics therapy was maintained for 6 weeks after source control, which in this case would be placement of AngioVac. The patient tolerated the procedure well. She continued to remain hemodynamically stable with improvement of clinical symptoms as well as improvement of white blood cell. She was discharged from hospital on day 22 and was scheduled to have repeat echocardiographic imaging; however, patient was lost to follow-up.

Discussion

The term “mycotic” historically referred to any infectious aneurysm, although it is now more commonly associated with fungal infections. However, bacterial infections remain a frequent cause. Common pathogens include S. aureus, Streptococcus species, and fungi. Infectious aneurysms are rare, and their occurrence within pulmonary arteries is even more uncommon. Currently, there are no established predictors for the development of infectious aneurysms following septic pulmonary embolism. To date, only a limited number of cases have been documented in the literature, with a reported mortality rate exceeding 50%, particularly in cases complicated by pulmonary hemorrhage. ⁸ Other common cause of mycotic aneurysm is fungi like Aspergillus. ⁹

When considering an infectious cause, it is important to consider pyogenic bacterial infections. Risk factors for development of MPA include intravenous drug use (IVDU), TV endocarditis, and congenital heart defects.^10,11 Proximal PAPAs are located on the pulmonary trunk, and peripheral PAPAs are situated on the intrapulmonary artery and tend to have a higher risk of rupture. The current classification of PAPAs is based on location within the pulmonary vasculature. Early clinical detection remains key in these patients. The most reported clinical manifestation is hemoptysis, which if not recognized early lead to poor prognostic outcomes. ¹²

Pathophysiology regarding development of MPA in the current case is thought to be from hematogenous spread from TV endocarditis and septic emboli. Previous reports have described similar mechanisms, where infectious emboli cause direct vascular injury, resulting in pseudoaneurysm formation. ¹³ Currently, MPAs are believed to result from various mechanisms. These include the direct extension of pneumonia involving the vessel wall, endovascular seeding of the vessel wall from the bronchial arteries due to septicemia, which can result in the destruction of 1 or all layers of the vessel, and intimal invasion of the vessel wall from a septic embolism, as detected in our case. This invasion can cause damage to the vessel wall and subsequent dilatation, leading to aneurysm formation.

In the absence of serious complications from PAPA rupture, patients may remain asymptomatic. However, in symptomatic patients, hemoptysis is the most commonly reported presentation, which carries a high mortality risk indicating the need for early detection. ¹⁴ In the present case patient reported fevers, generalized fatigue, and malaise all of which could have been explained by result of underlying TV endocarditis. Given the high mortality associated with PAPA rupture, prompt, and accurate diagnosis is critical. When there is high suspicion of PAPA imaging is perhaps the most important diagnostic tool. Chest radiography is easily accessible and may show early signs of nonfocal consolidation. However, the use of CT is more beneficial in making a clear diagnosis. In the present case the patient remained stable, asymptomatic throughout presentation, so angiography was withheld.

A comprehensive review of the literature identified more than 100 reported cases of infectious PAPAs. Management strategies in these cases have included surgical intervention, such as lobectomy or pseudoaneurysm ligation, transcatheter embolization, and conservative approaches utilizing antibiotic therapy in conjunction with systemic hemostatic agents. However, no standardized guidelines have been established to determine the optimal treatment approach based on pseudoaneurysm size.

Conservative management of MPAs has shown variable success, with case reports demonstrating favorable outcomes in selected patients. Iki et al reported a case of MPA caused by MRSA that was successfully managed with an extensive antimicrobial regimen, ultimately achieving infection control and aneurysm resolution. ¹⁵ The American Heart Association (AHA) guidelines recommend antimicrobial therapy tailored to the causative pathogen, with a treatment duration ranging from 6 weeks to 6 months, or even lifelong suppressive therapy in select cases. ¹⁶ However, conservative management is contraindicated in patients with hemodynamic instability, rapidly expanding aneurysms, refractory infections, or severe symptoms such as massive hemoptysis, as these conditions significantly increase the risk of fatal complications. Multidrug-resistant infections further necessitate surgical intervention, as they may not respond adequately to antibiotic therapy alone. Therefore, conservative treatment is primarily reserved for clinically stable patients with small aneurysms who show a favorable initial response.^6,15,16

Nonconservative approaches, including surgical resection and endovascular therapy (EVT), are recommended for patients at high risk of rupture or those unresponsive to antimicrobial therapy. Surgical resection, involving aneurysmectomy, lobectomy, or pneumonectomy, remains the preferred approach for large, symptomatic, or ruptured aneurysms, as supported by the AHA guidelines. EVT, which utilizes stent grafts or coil embolization, provides a minimally invasive alternative, particularly for patients with significant comorbidities or aneurysms in surgically inaccessible locations. Studies by Deshmukh et al ¹⁷ and Chou et al ¹⁸ have demonstrated successful outcomes with EVT, highlighting its utility in high-risk surgical candidates. In some cases, a combination of EVT and surgery may be employed, where EVT serves as an initial stabilizing measure before definitive surgical repair. Despite their advantages, both surgical and endovascular approaches have contraindications, including severe comorbidities, poor general health, and complex aneurysm anatomy. EVT is further contraindicated in cases of active infection, severe sepsis, or inability to achieve immediate hemostasis, particularly in patients with massive hemoptysis. Surgical intervention is particularly beneficial for patients with large or rapidly expanding aneurysms, pulmonary hypertension, anatomical anomalies, or persistent infections despite antimicrobial therapy. Thus, individualized treatment strategies, guided by aneurysm characteristics and patient stability, are essential in optimizing clinical outcomes.

The selection of a nonconservative approach is guided by factors such as aneurysm size, rupture risk, and patient stability, with intervention being crucial for individuals at high risk of complications or those unresponsive to medical therapy. Nonconservative management of MPAs primarily includes surgical resection, EVT, or a combination of both approaches. Surgical resection, including aneurysmectomy, lobectomy, or pneumonectomy, is the preferred treatment for large, symptomatic, or ruptured aneurysms, as recommended by the AHA guidelines. ¹⁹ Alternatively, EVT, utilizing stent-grafts or coil embolization, provides a minimally invasive option for patients with significant comorbidities or surgically inaccessible aneurysms.

Despite their therapeutic value, both surgical and endovascular approaches have contraindications that necessitate careful patient selection. Patients who benefit most from surgical resection include those with large, rapidly expanding aneurysms, pulmonary hypertension, anatomical anomalies, or compression of critical structures, as well as those with persistent infection despite antimicrobial therapy. ²⁰

In the current case, the patient presented with an incidental finding of PAPA, which was relatively small in size. The patient remained asymptomatic throughout the duration of hospital stay and it was thought that there was a larger risk for adverse outcomes with surgical or endovascular intervention.

Conclusion

PAPAs remain a rare but potentially life-threatening vascular anomaly, most associated with IE in modern clinical practice. Early recognition and appropriate imaging are critical for diagnosis, and management should be tailored to the individual patient based on symptomatology and risk of rupture. In asymptomatic, hemodynamically stable patients, conservative management with targeted antibiotic therapy may be a viable alternative to invasive intervention. This case highlights the importance of maintaining a high index of suspicion for PAPA in at-risk individuals, even in the absence of overt clinical symptoms.