Acute Aortic Syndromes: Intramural Haematoma and Penetrating Atherosclerotic Ulcer

Definition and Pathophysiology

Acute aortic syndromes comprise classic aortic dissection, intramural haematoma (IMH), and penetrating atherosclerotic ulcer (PAU). Aortic dissection accounts for approximately 80%–90% of acute aortic syndromes, IMH for approximately 10%–20%, and PAU for about 5%; reported proportions vary by population and region.

Intramural haematoma

IMH is haemorrhage within the aortic media without an identifiable communication between the aortic lumen and the haematoma and without a visible intimal flap or false lumen. It is commonly attributed to rupture of the vasa vasorum, although improved imaging demonstrates small intimal disruptions in approximately 20%–60% of cases. These disruptions may initiate or complicate the haematoma.

IMH most frequently involves the descending thoracic aorta, which is affected in approximately 60%–70% of cases. The ascending aorta is involved in about 30% and the arch in approximately 10%. Because the haematoma lies close to the adventitia, pleural effusion, pericardial effusion, peri-aortic haematoma, and rupture may occur. Compared with classic type A dissection, aortic regurgitation, pulse deficits, and malperfusion are less frequent in type A IMH.

IMH is classified anatomically according to the Stanford system:

• Type A IMH: involves the ascending aorta.

• Type B IMH: involves the descending aorta distal to the left subclavian artery.

Penetrating atherosclerotic ulcer

PAU is focal ulceration of an atherosclerotic plaque that penetrates through the internal elastic lamina into the media. The lesion may produce a localized medial haematoma and can progress to IMH, pseudoaneurysm, dissection, aneurysm, or rupture.

PAUs are usually located in the middle or distal descending thoracic aorta. The arch and ascending aorta are less commonly involved, and ascending-aortic PAU is rare. Lesions may be solitary or multiple and typically measure approximately 5–25 mm in diameter and 4–30 mm in depth. PAU is strongly associated with extensive atherosclerosis and frequently occurs in older patients with multiple vascular comorbidities.

An isolated PAU is one without associated IMH, dissection, or saccular aneurysm. Symptomatic isolated lesions may represent early periulcer haemorrhage or developing IMH and carry greater risk of progression or rupture than asymptomatic lesions.

Predisposing conditions

Aortic dissection and its variants are associated with conditions that cause medial degeneration or increase aortic wall stress. Relevant associations include:

• Systemic hypertension

• Marfan syndrome

• Loeys–Dietz syndrome

• Ehlers–Danlos syndrome

• Inflammatory aortitis, including Takayasu arteritis and giant-cell arteritis

• Bicuspid aortic valve

• Coarctation of the aorta

• Previous aortic trauma

• Pregnancy, particularly the third trimester

• Weightlifting

• Cocaine use

• Deceleration injury

Systemic hypertension coexists in approximately 70% of patients with aortic dissection. PAU is particularly associated with advanced age, smoking, coronary artery disease, chronic obstructive pulmonary disease, renal insufficiency, systemic hypertension, and concomitant abdominal aortic aneurysm.

Clinical Presentation and Symptoms

Acute chest and/or back pain is the predominant symptom of both IMH and PAU. PAU pain may resemble the abrupt pain of classic aortic dissection. Symptom onset in PAU may indicate lesion expansion and involvement of the adventitia, requiring urgent imaging because of the risk of rupture.

Type A IMH may cause:

• Aortic regurgitation

• Haemopericardium or pericardial effusion

• Aortic rupture

• Proximal aortic complications

Malperfusion and pulse deficits are less common in type A IMH than in classic type A dissection.

PAU often differs clinically from classic dissection in that most patients do not have aortic regurgitation, pulse deficits, or visceral ischaemia. Approximately 25% of PAUs are discovered incidentally on imaging, although an incidental lesion may subsequently become symptomatic or progress.

The clinical distinction between uncomplicated and complicated IMH is important. Complicating features include recurrent or persistent pain, expansion of the haematoma, peri-aortic haematoma, and intimal disruption. Organ malperfusion, haemodynamic instability, haemopericardium, and rupture indicate a high-risk presentation.

Evaluation and Physical Examination

The source material emphasises urgent assessment and imaging but provides limited detail regarding a formal physical-examination protocol. Evaluation should establish whether the patient has:

• Haemodynamic instability

• Persistent or recurrent pain despite blood-pressure control

• Pericardial or pleural involvement

• Organ malperfusion

• Aortic regurgitation

• Pulse deficits

• Features of rupture

The absence of pulse deficits, aortic regurgitation, or visceral ischaemia does not exclude PAU or IMH. In PAU, these findings are often absent.

The assessment should also identify relevant risk factors and comorbidity, including hypertension, heritable aortic disease, atherosclerotic vascular disease, smoking, renal impairment, chronic lung disease, pregnancy, recent trauma, weightlifting, and cocaine exposure.

Diagnostics

Imaging objectives

Imaging in acute aortic syndromes should determine:

• Whether the abnormality is classic dissection, IMH, or PAU.

• Whether the ascending aorta is involved.

• The longitudinal extent of disease.

• The sites and dimensions of entry, re-entry, or focal intimal disruption.

• The patency and dimensions of any false lumen.

• The presence of aortic regurgitation, coronary involvement, pericardial effusion, or haemopericardium.

• Evidence of rupture or impending rupture.

• Branch-vessel involvement and malperfusion.

• Aneurysmal enlargement.

• High-risk features associated with IMH or PAU.

Computed tomography

Computed tomography, particularly contrast-enhanced CT angiography, is central to the evaluation of IMH and PAU.

In IMH:

• Non-contrast CT shows high attenuation within the aortic wall caused by blood products.

• Contrast-enhanced CT shows low attenuation within the wall because contrast does not enter the haematoma.

• The typical appearance is crescentic or circumferential aortic-wall thickening without a visible intimal flap.

• The aortic lumen is usually not substantially compromised.

• CT can identify progression to dissection, peri-aortic haematoma, pleural effusion, pericardial involvement, or rupture.

In PAU:

• CT shows focal ulceration with a crater-like outpouching and irregular margins.

• A calcified and displaced intima may be visible.

• Associated IMH, pleural effusion, mediastinal haemorrhage, pseudoaneurysm, contained rupture, frank rupture, or coexisting aneurysm may be demonstrated.

• A PAU associated with IMH may be difficult to distinguish from an IMH with an ulcer-like projection.

CT angiography may also provide three-dimensional volume-rendered, oblique-coronal, and centreline reconstructions. Centreline reconstruction permits measurement perpendicular to the true short axis of the aorta despite tortuosity.

Transoesophageal echocardiography

Transoesophageal echocardiography (TEE) is useful for evaluating IMH and proximal aortic disease. Typical IMH findings include:

• Crescentic or circumferential aortic-wall thickening

• Wall thickness of at least 5 mm

• An eccentric aortic lumen

• Displacement of intimal calcification

• Echolucent regions within the aortic wall

• Absence of an intimal flap

• Absence of flow within the aortic wall

TEE can demonstrate focal atherosclerosis, ulceration, and associated haematoma in PAU. It is also useful for assessing proximal complications, including aortic regurgitation and pericardial effusion.

Transthoracic echocardiography has very low sensitivity for diagnosing IMH, although it may occasionally visualize a proximal aortic abnormality or a dissection flap.

Magnetic resonance imaging

Magnetic resonance imaging and magnetic resonance angiography can characterize both IMH and PAU. In IMH, MRI may show:

• Focal aortic-wall thickening

• Absence of flow within the haematoma

• Blood products within the aortic wall

• Differentiation from mural thrombus

• Tiny intimal disruptions and ulcer-like projections

MRI findings in PAU include localized high signal intensity within the aortic wall consistent with IMH, focal intimal thickening, and ulcer-like projections.

Aortography and catheter-based angiography

Aortography can demonstrate the true and false lumens and may identify coronary involvement. However, catheterization in acute dissection carries specific hazards: arterial access may enter the false rather than the true lumen, and catheter or guidewire manipulation may extend the dissection or perforate the aorta. In selected stable patients with previous coronary bypass surgery, additional coronary imaging may be useful; CT angiography may demonstrate graft patency.

Differentiation from other aortic wall abnormalities

IMH may be difficult to distinguish from:

• Thrombosed false-lumen dissection

• Mural thrombus within an aneurysm

• Aortic atherosclerosis

• Aortitis

IMH generally has a smooth lumen and a curvilinear wall. On TEE, thickening beneath the intima favours IMH, whereas thickening on the luminal side of the intima favours mural thrombus. Diffuse intimal irregularity is more typical of atherosclerosis, unless it is caused by an associated penetrating ulcer.

High-Risk Imaging Features

Intramural haematoma

Additional high-risk clinical or imaging findings include:

• Ascending-aorta involvement

• Difficult blood-pressure control

• Persistent or recurrent pain despite intensive blood-pressure treatment

• Detection of organ malperfusion

• Recurrent pleural effusion

• Pericardial effusion at presentation in type A IMH

Tiny intimal disruptions measuring ≤3 mm may occur frequently and are not necessarily associated with adverse aortic events. Larger focal intimal disruptions have greater prognostic significance. In the acute phase, focal intimal disruption is associated with a high risk of rupture, particularly when the defect is large.

Penetrating atherosclerotic ulcer

High-risk PAU features include:

• Maximum ulcer diameter ≥13–20 mm

• Maximum ulcer depth ≥10 mm

• Significant increase in ulcer diameter or depth

• Associated saccular aneurysm

• Increasing pleural effusion

Larger and deeper ulcers, particularly those associated with IMH or a saccular aneurysm, are more likely to progress.

Biomarkers and Laboratory Findings

The source material does not provide specific biomarker profiles, laboratory thresholds, or recommended laboratory testing for IMH or PAU. Diagnosis and risk assessment are described primarily as clinical and imaging-based.

Treatment and Management

Initial management

The initial treatment principle for IMH and related acute aortic syndromes is prompt control of pain and blood pressure, irrespective of the precise pathological subtype. Patients require urgent evaluation and management in an appropriate aortic centre or multidisciplinary setting, particularly when high-risk features or complications are present.

The source material specifies pain and blood-pressure control but does not provide drug names, target pressures, heart-rate targets, or dosing regimens.

Type A intramural haematoma

Type A IMH involves the ascending aorta and is generally managed with emergency or urgent surgery. Surgery is particularly indicated when there is:

• Haemodynamic instability

• Haemopericardium or pericardial effusion

• Rupture or impending rupture

• Proximal aortic complications

• Progression to classic dissection

• High-risk imaging features

• Organ malperfusion

A carefully selected patient with uncomplicated type A IMH, no high-risk imaging features, and increased operative risk from multiple comorbidities may be considered for an observational strategy in an experienced reference centre with close clinical and imaging surveillance. Nevertheless, current guideline-based practice recommends surgery for most type A IMH.

Type B intramural haematoma

Uncomplicated type B IMH is initially treated medically with intensive clinical observation and thorough serial imaging.

Endovascular repair should be considered when uncomplicated type B IMH has high-risk imaging characteristics. Complicated type B IMH warrants consideration of thoracic endovascular aortic repair (TEVAR), particularly in the presence of:

• Persistent or recurrent pain

• Expansion of the IMH

• Peri-aortic haematoma

• Progression to dissection

• Aneurysmal enlargement

• Focal intimal disruption or ulcer-like projection

• Impending rupture

• Rupture

• Organ malperfusion

When anatomy is unsuitable for endovascular treatment, open surgery remains an alternative. TEVAR generally covers the proximal involved segment, particularly the region containing the focal intimal disruption or ulcer-like projection. Retrograde type A dissection is a recognised technical concern.

Penetrating atherosclerotic ulcer

Management depends on symptoms, anatomical location, associated IMH or rupture, imaging risk features, operative risk, anatomy, and life expectancy.

Urgent repair is recommended for:

• PAU with rupture

• PAU of the ascending aorta with associated IMH

Urgent repair is reasonable for PAU of the aortic arch or descending thoracic aorta with associated IMH. For abdominal-aortic PAU with associated IMH, urgent repair may be considered.

Ascending-aortic and proximal arch PAUs are generally treated with surgical resection. In selected patients, especially those with descending thoracic disease, endovascular repair is preferred when anatomy permits because PAU commonly affects older patients with severe atherosclerosis and substantial comorbidity, making open surgery high risk.

TEVAR or, less frequently, open repair should be considered for:

• Haemorrhage

• Peri-aortic haematoma

• Expanding pseudoaneurysm

• Saccular aneurysm formation

• Persistent pain

• Significant associated IMH

• Rupture

• Progressive high-risk ulcer morphology

Stable type B PAU without high-risk features may be managed medically with close follow-up and serial imaging. In symptomatic patients whose symptoms resolve with directed medical treatment, or in patients for whom repair carries particularly high morbidity and mortality, medical management with early and frequent surveillance imaging may be pursued.

Drugs and Practical Considerations

The available source material states that the first-line medical approach consists principally of pain control and blood-pressure control. It does not specify the agents, doses, routes, blood-pressure targets, heart-rate targets, or duration of treatment. Consequently, no drug regimen can be stated from the available material.

Guideline Recommendations

Recommendations for PAU with IMH, rupture, or both

Summary of guideline-based management

• Type A IMH generally requires emergency or urgent surgery.

• A selected, stable, uncomplicated type A IMH patient with increased operative risk and no high-risk imaging features may undergo close observation in an experienced centre.

• Uncomplicated type B IMH is managed initially with medical treatment and serial clinical and imaging assessment.

• Complicated type B IMH should prompt consideration of TEVAR.

• High-risk imaging features in type B IMH may justify endovascular treatment even before overt complications develop.

• Ruptured PAU requires urgent repair.

• Ascending-aortic PAU with IMH requires urgent repair.

• Symptomatic, enlarging, deep, or aneurysm-associated PAU has a higher likelihood of progression and rupture and requires prompt specialist assessment.

Prognosis and Follow-up

Intramural haematoma

IMH may regress completely or partially, but it can also evolve into classic dissection, saccular or fusiform aneurysm, or aortic rupture. Reported evolution includes classic dissection in approximately 12% of patients, saccular aneurysm in 8%, fusiform aneurysm in 2%, and regression in approximately 34%; the source material also reports intramural dissection in 54% of patients.

Reported in-hospital mortality is approximately:

• Type A IMH: 26.6% overall

• Type B IMH: 4.4% overall

Type A IMH involving the aortic valvular complex is associated with higher mortality. Serious complications may develop during the first days to weeks, including dissection, haemopericardium, and rupture. Among patients initially managed medically, surgery may ultimately be required in approximately 30%–50%.

More than half of type B IMHs may resolve completely, although some progress to dissection, rupture, or late aneurysm formation. Reported 30-day mortality for type B IMH is approximately 4% with medical treatment, 2%–6% with TEVAR, and 16% with open surgery.

Penetrating atherosclerotic ulcer

The natural history of PAU is variable. Lesions may remain stable, but may also progress to:

• IMH

• Aortic dissection

• Distal embolization

• Pseudoaneurysm or contained rupture

• Frank rupture

• Saccular or fusiform aneurysm

Approximately 30% of incidentally discovered asymptomatic PAUs demonstrate progression on serial imaging. Symptomatic PAUs, larger or deeper ulcers, lesions associated with IMH, and those associated with saccular aneurysms have a less favourable prognosis.

For descending-aortic PAU treated with TEVAR, reported in-hospital mortality is approximately 4%–11%. The risk of endoleak may be reduced with advanced endovascular or hybrid techniques.

Surveillance

Close imaging surveillance is required after diagnosis of IMH, particularly when focal intimal disruption is present. All patients with intimal disruption require close imaging follow-up because some small disruptions may enlarge or evolve into prognostically important focal lesions.

Stable type B PAU managed medically requires serial imaging. Surveillance is also necessary for asymptomatic PAU because a substantial proportion progresses despite the absence of symptoms. Follow-up should assess:

• Aortic diameter

• Ulcer diameter and depth

• Haematoma thickness

• Development of focal intimal disruption or ulcer-like projection

• Progression to classic dissection

• Pseudoaneurysm or aneurysm formation

• Increasing pleural or pericardial effusion

• Peri-aortic haematoma

• Evidence of rupture

The source material does not specify fixed surveillance intervals or a standardized post-repair imaging schedule.