The patient is a 29 year old woman with a history of intravenous drug abuse, admitted six weeks postpartum for MSSA bacteremia and tricuspid valve endocarditis (4 x 2.5 cm vegetation) complicated by bilateral pulmonary septic emboli with loculated empyema.
She was started on nafcillin, which complicated the course with acute interstitial nephritis and leukocytoclastic vasculitis. She was switched to cefazolin, which caused leucopenia requiring a final change to clindamycin that she completed for six weeks. Her repeat blood cultures were negative.
Follow up CT for empyema after tPA administration showed dilated pulmonary arteries. On CT with contrast these were characterized as saccular pseudoaneurysms, largest in the left lower lobe measuring 2.6 x 1.9 cm with additional bilateral pulmonary artery aneurysms in the anterior perihilar areas, 2.3 cm on the right and 2.7 cm on the left. However, the patient was asymptomatic without chest pain, dyspnea, or cough.
The patient was transferred to the University of Washington for possible aneurysmal repair or thoracotomy after evaluation by Interventional Radiology. Ultimately, the recommendations were to continue four weeks of additional antibiotics as the interventional risk weighed greater than the potential benefits.
Discussion:
Pulmonary hypertension, chronic pulmonary embolism and vasculitis are important causes of PAP. Infections, especially tuberculosis and syphilis, are other causes of PAP. Septic emboli tend to cause multiple mycotic aneurysms.
In healthy adults the upper limits of the main, right, and left PA diameters are 2.9 cm, 1.98 cm, and 2.2 cm, respectively. CT angiography evidence for infected aneurysms include: saccular or eccentric aneurysms; aneurysms with intramural air or perivascular soft tissue inflammation, or air/fluid collections.
Clinical manifestations of PAP are nonspecific, but if present include: chest pain, dyspnea, hoarseness, etc. Rupture may lead to massive hemoptysis, and result in lethal asphyxiation and sudden death.
PAP are rare and therefore have no definitive therapeutic guidelines. Conservative treatment with antibiotics is a reasonable option for asymptomatic patients with stable aneurysmal diameter without significant PAH or aneurysmal sac thrombus formation if regular reevaluation is available.
Endovascular techniques such as embolization acompanyed by antibiotic therapy are emerging as a treatment method for infected aneurysms; however, evidence suggesting an absolute diameter threshold for embolization is lacking.
Although some believe it is necessary to eradicate infection via antibiotics preceding intervention, there is no strong evidence within the literature suggesting deployment of coils within a mycotic aneurysm leads to reinfection.
Conclusions:
Pulmonary artery aneurisms (PAA) and pseudoaneurysms (PAPs) are uncommon, yet are associated with high mortality. Hemoptysis is the most frequent presenting sign and may range from incidental finding on imaging study to life threatening haemoptysis.
There is little evidence based management guidelines despite possible fatal outcomes due to aneurysmal rupture or dissection.