Overview
Thoracic Aortic Aneurysm & Dissection
Topic Overview
Summary
Thoracic aortic aneurysm (TAA) is dilatation of the thoracic aorta (ascending, arch, or descending segments). TAA may be asymptomatic until rupture or dissection. Acute aortic dissection is a tear in the intimal layer, creating a false lumen — it is a surgical emergency. Classic presentation is sudden severe "tearing" chest or back pain. Diagnosis is by CT aortic angiogram. Type A dissection (involving ascending aorta) requires emergency surgery; Type B is usually managed medically unless complicated.
Key Facts
- TAA definition: Aortic diameter over 4cm (ascending); over 3cm (descending)
- Risk of rupture: Increases exponentially with size (over 5.5-6cm high risk)
- Dissection presentation: Sudden severe "tearing" chest/inter-scapular pain
- Type A dissection: Involves ascending aorta — emergency surgery
- Type B dissection: Distal to left subclavian — usually medical management
- Imaging: CT aortic angiogram is gold standard
Clinical Pearls
Aortic dissection can mimic MI — but D-dimer is elevated in dissection (not specific but can help rule out if low)
Pulse or BP asymmetry strongly suggests dissection — check both arms
Type A mortality = 1-2% per hour if untreated — time to diagnosis and surgery is critical
Why This Matters Clinically
Acute aortic dissection kills 1-2% per hour if untreated. Misdiagnosis as MI or musculoskeletal pain is common. All clinicians must recognise the red flags and escalate immediately.
Visual Summary
Visual assets to be added:
- Stanford and DeBakey classification diagrams
- CXR showing widened mediastinum
- CTA showing dissection flap
- Aortic anatomy diagram
Epidemiology
Thoracic Aortic Aneurysm
- Prevalence increases with age
- More common in men
- Often incidental finding
Acute Aortic Dissection
- Incidence: 5-30 per million/year
- Peak age: 60-70 years
- Male:female = 2:1
- Mortality: 1-2% per hour in Type A if untreated
Risk Factors
| Factor | Notes |
|---|---|
| Hypertension | Most common risk factor |
| Smoking | Accelerates aortic degeneration |
| Bicuspid aortic valve | Associated with ascending aortopathy |
| Marfan syndrome | FBN1 mutation; aortic root dilatation |
| Ehlers-Danlos (type IV) | Vascular fragility |
| Turner syndrome | Aortic coarctation, bicuspid valve |
| Cocaine use | Hypertensive crisis precipitant |
| Previous aortic surgery | Site of anastomosis vulnerability |
| Pregnancy | Third trimester; post-partum |
Pathophysiology
Aneurysm Formation
- Cystic medial degeneration
- Loss of elastic fibres and smooth muscle
- Wall weakening → progressive dilatation
- Increased wall stress (Laplace's law) → further expansion
Dissection Mechanism
- Intimal tear (usually at points of maximal shear stress)
- Blood enters media → creates false lumen
- False lumen propagates proximally and/or distally
- Complications: Rupture, malperfusion, aortic regurgitation
Sites of Intimal Tear
- Ascending aorta (65%)
- Aortic arch (10%)
- Proximal descending aorta (20%)
- Distal aorta (5%)
Malperfusion Syndromes
- Coronary (MI)
- Cerebral (stroke)
- Spinal cord (paraplegia)
- Mesenteric (ischaemic gut)
- Renal (AKI)
- Limb (acute limb ischaemia)
Clinical Presentation
Thoracic Aortic Aneurysm
Acute Aortic Dissection
| Feature | Frequency | Description |
|---|---|---|
| Chest pain | 85-90% | Severe, sudden onset |
| Back pain | 50% | Interscapular ("tearing") |
| Radiation | Common | Follows dissection path |
| Syncope | 10-15% | Cardiac tamponade, malperfusion |
| Hypertension | 50% | Or hypotension if tamponade |
| Pulse asymmetry | 15-30% | Strong indicator |
Red Flags
| Finding | Significance |
|---|---|
| Sudden severe pain | Vascular catastrophe |
| Tearing/ripping quality | Classic for dissection |
| Pulse or BP asymmetry | Subclavian involvement |
| New aortic regurgitation | Ascending aorta involvement |
| Neurological deficit | Malperfusion |
| Known Marfan/BAV | High-risk population |
Often asymptomatic (incidental finding)
Common presentation.
Symptoms if large or compressive
Chest or back pain
Dysphagia (oesophageal compression)
Hoarseness (recurrent laryngeal nerve)
Dyspnoea (airway compression)
Clinical Examination
Vital Signs
- Hypertension (common) or hypotension (shock/tamponade)
- Tachycardia
- Check BP in BOTH arms (greater than 20 mmHg asymmetry suggestive)
Cardiovascular
- Early diastolic murmur (aortic regurgitation)
- Muffled heart sounds (tamponade)
- Absent pulses (malperfusion)
Neurological
- Stroke signs (carotid involvement)
- Paraplegia (spinal cord malperfusion)
- Horner syndrome (sympathetic involvement)
Abdominal
- Mesenteric ischaemia features
- Renal bruit
Investigations
Immediate
| Test | Purpose |
|---|---|
| ECG | Exclude MI (or show malperfusion-related changes) |
| CXR | Widened mediastinum (not always present) |
| Troponin | May be elevated (type 2 MI or coronary malperfusion) |
| D-dimer | Elevated in dissection (non-specific; low D-dimer may help rule out) |
Definitive Imaging — CT Aortic Angiogram
- Gold standard
- Shows intimal flap, true/false lumen, extent
- Entry/exit tears
- Branch vessel involvement
Echocardiography
- TTE: Ascending aorta, aortic regurgitation, pericardial effusion
- TOE: High sensitivity for ascending and descending aorta (invasive)
MRI Aorta
- High accuracy but less available in emergency
- Useful for surveillance
Classification & Staging
Stanford Classification (Most Clinically Useful)
| Type | Definition | Management |
|---|---|---|
| Type A | Involves ascending aorta (regardless of entry site) | Emergency surgery |
| Type B | Distal to left subclavian only | Medical (unless complicated) |
DeBakey Classification
| Type | Description |
|---|---|
| I | Originates in ascending, propagates to arch/descending |
| II | Confined to ascending aorta |
| III | Originates in descending aorta |
Complicated vs Uncomplicated Type B
| Complicated | Features |
|---|---|
| Malperfusion | Limb, renal, mesenteric, spinal |
| Rupture | Haemothorax, mediastinal haematoma |
| Refractory pain | Despite adequate analgesia and BP control |
| Rapid expansion | Imaging evidence |
Management
Immediate Stabilisation
- IV access, monitoring
- Analgesia (morphine)
- BP control (target SBP 100-120): IV labetalol, esmolol, GTN
- Heart rate control (under 60 bpm): Beta-blocker first-line
- Avoid increasing shear stress (reduce BP and HR before vasodilators)
Type A Dissection — Emergency Surgery
- Cardiothoracic surgery consultation immediately
- Ascending aortic replacement ± aortic root/valve
- Mortality 20-30% even with surgery (vs 60% without)
Type B Dissection — Uncomplicated
| Intervention | Details |
|---|---|
| Medical management | BP control, pain control |
| Surveillance imaging | Repeat CT at 48-72h, then serial |
| Long-term BP | Target under 130/80 |
Type B Dissection — Complicated
| Intervention | Details |
|---|---|
| Endovascular (TEVAR) | Thoracic endovascular aortic repair for malperfusion, impending rupture |
| Open surgery | If TEVAR not feasible |
Long-Term Surveillance
- Serial imaging (CT or MRI)
- Lifelong BP control
- Genetic testing if connective tissue disorder suspected
- Family screening
Complications
Of Dissection
- Aortic rupture
- Cardiac tamponade
- Aortic regurgitation
- Malperfusion syndromes (MI, stroke, paraplegia, mesenteric ischaemia, AKI, limb ischaemia)
Of Treatment
- Surgical mortality
- Stroke
- Paraplegia (spinal cord ischaemia)
- Renal failure
- Endoleak (after TEVAR)
Prognosis & Outcomes
Type A Dissection
| Management | Mortality |
|---|---|
| Emergency surgery | 20-30% |
| No surgery | 60-70% at 1 week |
Type B Dissection
| Type | 30-Day Mortality |
|---|---|
| Uncomplicated (medical) | 10% |
| Complicated | 30-50% |
Long-Term
- Surveillance for aneurysm development
- Late complications: Re-dissection, aneurysm formation at repair site
Evidence & Guidelines
Key Guidelines
- ESC/EACTS Guidelines on Aortic Diseases (2014, updated)
- ACC/AHA Thoracic Aortic Disease Guidelines (2022)
Key Evidence
- Early surgery improves survival in Type A
- BP and HR control reduce extension and rupture risk
- TEVAR has improved outcomes in complicated Type B
Patient & Family Information
What is Aortic Dissection?
Aortic dissection is a tear in the wall of the main blood vessel from the heart (aorta). It is an emergency and needs urgent treatment.
Symptoms
- Sudden, severe chest or back pain
- Pain described as "tearing" or "ripping"
- Feeling faint or passing out
- Different blood pressure in each arm
Treatment
- Medication to lower blood pressure and heart rate
- Surgery to repair the aorta (sometimes emergency)
- Keyhole repair with a stent (in some cases)
After Treatment
- Lifelong blood pressure control
- Regular scans to monitor the aorta
- Family members may need screening
Resources
References
Primary Guidelines
- Erbel R, et al. 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases. Eur Heart J. 2014;35(41):2873-2926. PMID: 25173340
- Isselbacher EM, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease. J Am Coll Cardiol. 2022;80(24):e223-e393. PMID: 36334952
Key Studies
- Nienaber CA, et al. Randomized comparison of strategies for type B aortic dissection (INSTEAD). Circulation. 2009;120(25):2519-2528. PMID: 19996018