Giant Aneurysm of Main Pulmonary Artery

Clinical History

A 80 year-old-man was admitted to the hospital because of haemoptysis, cough and loss of weight

Imaging Findings

The patient performed an X-ray chest examination, showing a big para-ilear left mass; after that, a chest CT and percutaneous needle biopsy of the mass were requested to our Radiology Institute suspecting for a lung neoplasm.
We decided to perform a CT Angiography instead of a study for the research of a neoplastic lesion because the absence of the “Silhouette” sign at the X-ray chest, suggested the possible vascular or mediastinic origin of the mass.
The CT scan confirmed mediastinal nature of the lesion due to a large aneurysm of the main pulmonary artery, with normal vascular pattern; indeed main pulmonary arterial vessels were not dilated and no sign of pulmonary hypertension was despited.
Pulmonary valve was thicker, with no calcium apposition, while aortic valve was profusely calcified.
The echocardiography confirmed a severe calcific stenosis of aortic valve and a severe prolapsing pulmonary insufficiency and an important reduction of Ejection Fraction (EF=30%).
The patient underwent cardiosurgical operation of Aortic Valve Replacement using a biologic prosthesis, a single venous bypass graft on the LAD and Pulmonary Valve and Artery Replacement with an Aortic Homograft of IV grade with a 27 mm of diameter.
Postoperative period was regular and
after 7 days of recovery the patient was regularly discharged and introduced to a cardiopulmonary rehabilitation.

Discussion

Aneurysms of the main pulmonary artery are defined as a pulmonary artery dilatation >4 cm; they are rare lesions, representing less than 1% of all thoracic artery aneurysms and on average are discovered in 1 of every 14.000 autopsies.
The aetiology of Pulmonary Artery Aneurysm (PAA) includes congenital defects, infections such as syphilis, rheumatologic diseases such as in Behcet’s syndrome, vascular abnormalities (cystic medial necrosis, Marfan syndrome and Takayasu disease), connective tissue disease, atherosclerotic disease, degenerative disease and trauma related events. Infective endocarditis may involve (Main Pulmonary Artery) MPA, causing an aneurysm.
Familiar PAA aneurysms have been reported in a mother and daughter.
Medial degeneration and fragmentation of elastic fibres with deposition of ground substance may be seen on pathologic examination. Intrinsic wall weakness seems to predispose to massive dilation in some cases of giant aneurysms.
In our patient the poststenotic dilation is more likely secondary to pulmonary valve stenosis and histopatological analysis did not show parietal anomalies.
Early diagnosis is crucial: the mortality rate for patients with a ruptured pulmonary artery aneurysm is 100%; they may dissect into the pericardium causing sudden cardiac death from acute tamponade. Rupture into the bronchial tree results in haemoptysis, which can be catastrophic. Also thrombi may form within the aneurysm and acute massive dislodgement can lead to death, as chronic pulmonary artery embolisation may also occur.
First diagnostic approach is based on clinical symptoms (dyspnoea on exertion, cough, haemoptysis and thoracic pain; cianosis and clubbing are late signs, whereas oedema and ascites are associated with right heart failure) and on X-ray chest examination, showing a hilar enlargement.
CT is considered the non-invasive imaging modality of choice for the work-up of pulmonary artery aneurysm, excluding hilar lung neoplastic masses (they have a similar clinical presentation), prior to therapeutic interventions or during the follow-up of the patient with aneurysm but without indication for surgical intervention.
Also Magnetic Resonance Imaging (MRI) is another useful modality for estimating the size of the lesion and assessing the severity of PAA.
Echocardiography is an important methodic to evaluate non-invasively the valvular mechanism and morphology, hemodynamic parameters and pulmonary artery pressure.
Invasive pulmonary angiography was considered the “gold standard” for the evaluation of the extent and the pressure gradients of pulmonary aneurysms and for surgical planning; however today the CT is a non-invasive and cost-effective methodic to evaluate accurately aneurysms. Although no accepted standard diameter is deemed necessary for surgical intervention in a PAA, the literature suggests surgery at 6 cm or greater of diameter, in patient with apparent clinical symptoms or potential risk of progressive enlargement with possible rupture or dissection.
Surgical resection and repair is possible using aneurysmectomy and replacement of the pulmonary artery with a Dacron prothesis or with pericardial patch.
Where possible also aneurysmoraphy is applicable as surgical treatment.

Differential Diagnosis List

Final Diagnosis

Main Pulmonary Artery giant aneurysm

URL:	https://www.eurorad.org/case/8208
DOI:	10.1594/EURORAD/CASE.8208
ISSN:	1563-4086