Penetrating atherosclerotic ulcer

Penetrating atherosclerotic ulcers (PAU) are a pathology that involves the aortic wall which along with aortic dissection and aortic intramural haematoma form the spectrum known as acute aortic syndrome. 

Epidemiology

Typically, penetrating atherosclerotic ulcers are seen in elderly male patients with a history of hypertension (up to 92%), smoking (up to 77%) and coronary artery disease (up to 46%) as well as chronic obstructive pulmonary disease (24-68%) ¹.

Penetrating atherosclerotic ulcers account for ~7.5% (range 2.3-11%) of all cases of acute aortic syndrome ¹. In ~50% (range 42-61%) of cases, there are concurrent aortic aneurysms, most often in the abdomen ¹.

Clinical presentation

Typically patients present with symptoms of an acute aortic syndrome, namely acute intense chest pain, often described as tearing, ripping, migrating or pulsating ^1,8.

Some of the patients with penetrating atherosclerotic ulcers are asymptomatic and the diagnosis is made incidentally. A Mayo Clinic series showed just 75% of the patients had been symptomatic ².

Pathology

The term "penetrating atherosclerotic ulcer" describes an ulcerating atherosclerotic lesion that penetrates the intima and progresses through the internal elastic lamina into the media ¹⁷. In the early stages, the lesions just ulcerate the intima and are often asymptomatic. With further progression, they ulcerate into the media and lead to an intramural haematoma of variable size within the media ³.

The penetrating atherosclerotic ulcer can resolve completely or stay stable, but they can also progress to aortic dissection, aortic saccular aneurysms, perforation and spontaneous aortic rupture. There are conflicting reports about the most common course of penetrating atherosclerotic ulcers ¹.

Currently, imaging modalities can not reliably determine if an ulcer has penetrated the internal elastic lamina ¹⁷. Due to this limitation, it is also difficult to differentiate an ulcerated plaque from a PUA. Some features that may aid this differentiation are:

Patients with PUAs and aortic IMHs have an increased risk of concomitant abdominal aortic aneurysm ¹⁷.

Location

There is a greater predilection to involve the aortic arch and mid to distal thoracic aorta ^6,22.

Size

PAUs with a depth greater than 10 mm or diameter greater than 20 mm are associated with a higher rate of progression ¹⁷.

Classification

As with classical aortic dissection, PAUs are classified according to the Stanford scheme.

Radiographic features

CT

On CT aortography, the typical finding is a contrast-filled, out-pouching of the wall of the aorta or into the thickened aortic wall in absence of an intimal flap or a false lumen. The protrusion is said to resemble a mushroom ¹⁴ and can appear similar to an ulcerated plaque ¹⁷. These can progress to an intramural haematoma and often have intramural haematoma adjacent to the ulcer. Often there are signs of extensive atherosclerosis in other sites apart from the ulceration ⁴. 

Usually, the ulcer is found in the descending part of the thoracic aorta. Ulcers of the aortic arch are less common, and rare in the ascending aorta ⁴.

Although associated pleural effusion correlates with clinical instability there are no validated imaging features for the prediction of the course of a PAU ¹. It is often difficult to determine if a PAU is the source of a patient's pain or if it is an incidental finding.

In follow-up studies increasing maximum diameter and depth of the ulcer is an obvious sign of progression ¹. However, there is currently no consensus for ulcer depth or diameter that warrants treatment ¹⁴.

A CTA radiology report of PAUs should include ¹⁷:

• proximal and distal extent of the PUAs
• presence and thickness of associated intramural haematoma
• maximal diameter of the affected aortic lumen
• ulcer saccular depth

Transesophageal echocardiography

• usually, transoesophageal echocardiography demonstrates a localized, crater-like protrusion of the aortic lumen into the thickened aortic wall ⁹
• often there are signs of extensive atherosclerosis in other sites apart from the ulceration ⁹

MRI and MRA

• T1-weighted SE sequences show a hyperintense haematoma in acute or subacute disease and can distinguish between haematoma and atherosclerotic plaque ⁹
• otherwise similar findings to CTA ⁹

DSA

• the typical finding is a contrast-filled, pouch-like protrusion of the aortic lumen ⁹
• mostly several oblique projections are required ⁹

Treatment and prognosis

No set guidelines on when to treat and practices vary between hospitals, however the general consensus is as follows:

• ascending aorta
  • although the involvement of the ascending aorta in penetrating atherosclerotic ulcers is rare, the ulcers usually rupture
  • therefore early/urgent or emergent surgical intervention is recommended ⁴
• descending aorta
  • asymptomatic:
    • may initially be managed with an aggressive (antihypertensive) medical therapy in combination with close clinical and radiographic follow-up
      • annual CT imaging follow-up has been suggested ¹⁰
  • symptomatic or signs of progression:
    • higher risk for spinal cord ischaemia
    • endovascular stent-grafting (TEVAR) ⁴
• iliac arteries
  • generally asymptomatic/incidental and slow-growing ¹⁵
  • mortality is determined by concurrent co-morbidities such as concurrent aortic aneurysm

Complications

Recognised complications include:

• transmural aortic rupture
• embolic phenomena
• pseudoaneurysm formation
• progressive aneurysmal dilatation

History and etymology

They were first described as a distinct clinical and pathological entity by Stanson et al. in 1986 ³. 

Differential diagnosis

General imaging differential considerations include:

• focal indentation as part of irregularity along mural aortic plaque: could represent a non-penetrating atheromatous ulcer.
• aortic intramural haematoma
• aortic dissection
• saccular aneurysm
• (thoracic) aortic injury