Pulmonary arterial aneurysm

Pulmonary arterial aneurysms refer to a focal dilatation of the pulmonary arterial system.

Epidemiology

Overall it is considered a rare entity with autopsy prevalence rates of around 1 in 14,000 to 100,000 ^4,5.

Pathology

A true pulmonary artery aneurysm results from dilatation of all three layers of the vessel wall while a pulmonary artery pseudoaneurysm does not involve all layers of the arterial wall. Most of the aneurysms are central, affecting the main pulmonary arteries ⁴.

Aetiology

The differential for aetiologies of pulmonary artery aneurysms can be broad. Different sources differ as to the most frequent aetiologies, likely due to the rarity of the entity and reliance on limited case series.

• vascular

  • pulmonary arterial hypertension ^3,12

    • pulmonary valvular / post-valvular stenosis and regurgitation ¹¹

  • cystic medial degeneration

  • tuberous sclerosis (secondary to vascular dysplasia) ^13,14

• infectious

  • mycotic aneurysm (e.g. intravenous drug users)

  • tuberculosis: Rasmussen aneurysm

  • syphilis

• traumatic (often pseudoaneurysm)

  • blunt or penetrating trauma, most commonly extravascular due to stab wound ⁹

  • iatrogenic, most commonly endovascular due to malpositioned pulmonary artery catheter ⁹

• autoimmune

  • Behçet disease (most common) ¹⁰ and its variant Hughes-Stovin syndrome ⁷

  • giant cell arteritis

• idiopathic ⁴

• congenital

  • congenital left-to-right shunts, most commonly patent ductus arteriosus

Radiographic features

Plain radiograph

Radiographic features are non-specific and may appear as hilar enlargement or a lung nodule.

CT 

CT angiography (CTA) allows a much better appreciation of the anatomy. Some consider enlargement or ectasia of the pulmonary trunk on CT scan to be 29 mm and the right interlobar artery to be 17 mm ¹. Proximal pulmonary artery aneurysms are defined by a pulmonary trunk diameter >4 cm ⁹.

Treatment and prognosis

Patients with pulmonary hypertension and pulmonary artery aneurysm may be challenging and potentially carry high surgical risk. These patients should be evaluated by an experienced heart and lung transplantation centres. Strategies can be variable depending upon underlying disease, aetiology, centre dependent expertise, and resources available. Multidisciplinary consensus should be obtained to offer patients individualised treatment options. In patients with severe pulmonary hypertension, the available case reports describe the need for replacement of the entire main pulmonary artery.

See also

• pulmonary arterial ectasia

• bronchial artery aneurysm

• pulmonary artery pseudoaneurysm

• idiopathic dilatation of the pulmonary trunk