Overview
Thoracic Aortic Dissection
1. Clinical Overview
Summary
Thoracic Aortic Dissection is a life-threatening emergency caused by a tear in the aortic intima, allowing blood to enter the media and create a false lumen. This false lumen can propagate proximally or distally, causing branch vessel occlusion (stroke, mesenteric ischaemia, limb ischaemia), aortic rupture, pericardial tamponade, or aortic regurgitation. Classification is by Stanford (Type A = Ascending aorta involved = Surgical Emergency; Type B = Descending only = Medical management unless complicated) or DeBakey. Classic presentation is sudden, severe, tearing chest pain radiating to the back. Diagnosis is by CT Aortogram (Gold Standard) or TOE. Type A requires emergency surgery; Type B is managed with aggressive BP control (Target SBP less than 120 mmHg). Mortality is ~1-2% per hour if untreated. [1,2]
Clinical Pearls
"Tearing Pain to the Back = Dissection Until Proven Otherwise": Classic description. Pain may migrate as dissection propagates.
Stanford Type A = Surgery, Type B = Medical: Type A (involving ascending aorta) is a surgical emergency. Type B (descending only) is managed medically unless complicated (rupture, malperfusion, uncontrolled pain/BP).
Pulse Deficit / BP Asymmetry: >20mmHg difference between arms (branch vessel involvement) is a red flag.
Don't Give Thrombolysis!: Dissection can mimic MI (if dissection occludes coronaries). Always exclude dissection before thrombolysing an STEMI if the pain is atypical.
2. Epidemiology
Incidence
- Incidence: ~5-30 per million per year.
- Peak Age: 60-70 years.
- Sex: Male > Female (2:1).
Risk Factors
| Factor | Notes |
|---|---|
| Hypertension | Present in 70-90%. Most important modifiable risk factor. |
| Connective Tissue Disorders | Marfan Syndrome, Ehlers-Danlos (Type IV), Loeys-Dietz Syndrome. |
| Bicuspid Aortic Valve | Associated with aortopathy. |
| Aortic Coarctation | |
| Previous Aortic Surgery / Intervention | |
| Cocaine / Amphetamine Use | Acute hypertension. |
| Pregnancy | 3rd Trimester / Peripartum. |
| Turner Syndrome | |
| Trauma | Deceleration injury. |
3. Pathophysiology
Mechanism
- Intimal Tear: Usually in ascending aorta (Proximal aorta > most stress) or just distal to left subclavian (Isthmus).
- Blood Enters Media: Creates a False Lumen between intima and adventitia.
- Propagation: False lumen can extend distally (towards abdominal aorta) and/or proximally (towards aortic root).
- Complications of Propagation:
- Branch Vessel Occlusion (Dynamic/Static malperfusion): Coronaries (MI), Brachiocephalic (Stroke, Arm ischaemia), Mesenteric (Gut ischaemia), Renal, Iliacs (Leg ischaemia).
- Aortic Rupture: Into pericardium (Tamponade), Pleura (Haemothorax), Mediastinum.
- Aortic Regurgitation: Dissection extends to aortic root, disrupts valve ring.
- Cystic Medial Necrosis: Underlying medial degeneration (especially in Marfan's, Hypertension, Bicuspid AV) predisposes to dissection.
Classification Systems
| System | Classification |
|---|---|
| Stanford | Type A: Ascending aorta involved (Regardless of entry site). Type B: Descending aorta only (Distal to left subclavian). |
| DeBakey | Type I: Ascending + Descending. Type II: Ascending only. Type III: Descending only. |
Stanford Classification is Most Clinically Useful (Determines surgical vs medical management).
4. Differential Diagnosis
| Condition | Key Features |
|---|---|
| Aortic Dissection | Sudden, Tearing, Radiating to back. Pulse deficit. New AR murmur. Widened mediastinum. |
| Acute Coronary Syndrome (STEMI/NSTEMI) | Crushing chest pain. ST changes. Troponin rise. Can coexist if dissection occludes coronaries! |
| Pulmonary Embolism | Dyspnoea predominant. Pleuritic pain. DVT history/risk. D-dimer, CTPA. |
| Tension Pneumothorax | Sudden dyspnoea, Hypotension. Absent breath sounds. Tracheal deviation. |
| Oesophageal Rupture (Boerhaave's) | Post-vomiting. Subcutaneous emphysema. Contrast swallow. |
| Pericarditis | Pleuritic, Positional. Diffuse ST elevation. Pericardial rub. |
| Musculoskeletal Pain | Reproducible on palpation. No haemodynamic compromise. |
5. Clinical Presentation
Symptoms
| Symptom | Notes |
|---|---|
| Chest Pain | Sudden onset (Abrupt, not gradual). Severe, "Tearing" or "Ripping" quality. Maximal at onset. Anterior (Type A) or Interscapular (Type B). Migration as dissection propagates. |
| Back Pain | Interscapular. More common in Type B. |
| Syncope | Due to tamponade, Stroke, or Hypovolaemia. |
| Dyspnoea | Haemothorax, Tamponade, Severe AR. |
| Limb Pain / Weakness | Branch vessel occlusion. |
| Abdominal Pain | Mesenteric ischaemia. |
Signs
| Sign | Notes |
|---|---|
| Hypertension | Often severe. (May be hypotensive if tamponade/rupture). |
| Pulse Deficit | Absent or reduced pulse in one or more limbs. BP difference >20mmHg between arms. |
| New Diastolic Murmur (Aortic Regurgitation) | Dissection involving aortic root. |
| Neurological Deficit | Altered consciousness, Hemiplegia (Stroke from carotid/brachiocephalic involvement). |
| Signs of Tamponade | Hypotension, Raised JVP, Muffled heart sounds (Beck's Triad). |
| Mottled / Cold Limb | Limb ischaemia. |
| Abdominal Tenderness | Mesenteric ischaemia. |
6. Investigations
Bedside
| Test | Findings |
|---|---|
| ECG | May be normal. May show LVH (Hypertension). May show STEMI if coronary involvement (Dissection can cause MI!). |
| CXR | Widened Mediastinum (Most common). May be normal. Left pleural effusion (Haemothorax). |
Blood Tests
| Test | Findings |
|---|---|
| FBC, U&E, Coag | Baseline. |
| Troponin | May be elevated if coronary involvement. |
| D-Dimer | Often elevated (less than 500ng/mL may help rule out if low clinical suspicion – Limited utility). |
| Lactate | Elevated if malperfusion/shock. |
| Group & Save / Crossmatch | Essential for surgery. |
Imaging (Definitive Diagnosis)
| Imaging | Notes |
|---|---|
| CT Aortogram (CTA) | Gold Standard. Shows intimal flap, True and False lumens, Entry tear site, Branch involvement. Fast, widely available. |
| TOE (Transoesophageal Echo) | Highly sensitive/specific. Can be done in unstable patients (at bedside/in theatre). Shows intimal flap, AR. Blind spot at distal ascending aorta. |
| MR Angiography | High accuracy. Takes time. Not suitable for unstable patients. |
| TTE (Transthoracic Echo) | Limited for aortic arch. May show Ascending dilatation, AR, Pericardial effusion. Good for quick bedside assessment of LV, AR, Tamponade. |
7. Management
Management Algorithm
SUSPECTED AORTIC DISSECTION
(Sudden Tearing Chest/Back Pain, Pulse Deficit)
↓
IMMEDIATE RESUSCITATION (ABCDE)
- High-flow Oxygen
- Large-bore IV Access x2
- Cardiac Monitoring
- Analgesia (IV Morphine)
- Crossmatch 6-10 Units Blood
↓
URGENT BP / HEART RATE CONTROL
┌──────────────────────────────────────────────┐
│ TARGET: SBP 100-120 mmHg, HR less than 60 bpm │
│ │
│ FIRST-LINE: IV BETA-BLOCKER │
│ - Labetalol (Alpha + Beta block) │
│ 5-20mg IV bolus, then 1-2mg/min infusion │
│ - OR Esmolol Infusion (Short-acting) │
│ │
│ IF BP STILL HIGH AFTER BETA-BLOCKADE: │
│ - Add GTN Infusion (Vasodilator) │
│ - OR Sodium Nitroprusside │
│ (DO NOT give vasodilators BEFORE beta-block │
│ – Reflex tachycardia worsens shear stress) │
└──────────────────────────────────────────────┘
↓
URGENT CT AORTOGRAM (Or TOE if unstable)
↓
STANFORD CLASSIFICATION?
┌────────────────┴────────────────┐
TYPE A TYPE B
(Ascending Aorta Involved) (Descending Only)
↓ ↓
EMERGENCY SURGERY MEDICAL MANAGEMENT
(Cardiothoracic at (ICU Admission)
Specialist Centre) ↓
- Ascending Aorta Replacement ┌───────────────────────┐
- +/- Aortic Root Replacement │ - Strict BP Control │
- +/- Aortic Valve │ (SBP 100-120, HRless than 60)│
- +/- Arch Repair │ - Pain Management │
- +/- CABG (if Coronaries) │ - Serial Imaging │
│ - Long-term BP Rx │
└───────────────────────┘
↓
COMPLICATED TYPE B?
(Rupture, Malperfusion,
Refractory Pain/HTN,
Rapid Expansion)
┌────────────┴────────────┐
YES NO
↓ ↓
TEVAR CONTINUE
(Thoracic Endovascular MEDICAL Rx
Aortic Repair)
OR Open Surgery
Blood Pressure and Heart Rate Control (Critical)
- Goal: Reduce aortic wall stress (dP/dt – rate of rise of ventricular pressure).
- Target: SBP 100-120 mmHg, HR less than 60 bpm.
- Agent: IV Beta-Blocker FIRST (Labetalol, Esmolol). Reduces HR and contractility.
- Then Vasodilator (GTN, Nitroprusside) if BP still high.
- Avoid giving vasodilators before beta-blockers (Causes reflex tachycardia → Increases shear stress → Worsens dissection).
Type A: Surgical Emergency
- Mortality without surgery: 1-2% per hour in first 24-48 hours.
- Surgery: Replacement of ascending aorta +/- aortic root +/- aortic valve +/- arch (Depends on extent).
Type B: Medical Management
- Uncomplicated Type B: IV BP control initially, then oral antihypertensives. Serial imaging.
- Complicated Type B: Rupture, Malperfusion (Limb, Renal, Mesenteric, Spinal), Refractory pain or hypertension, Rapid expansion.
- Intervention for Complicated Type B: TEVAR (Thoracic Endovascular Aortic Repair) – Stent covers entry tear. Or open surgery.
8. Complications
| Complication | Notes |
|---|---|
| Death | High mortality if untreated. |
| Aortic Rupture | Tamponade, Haemothorax. |
| Stroke | Carotid/Brachiocephalic involvement. |
| Myocardial Infarction | Coronary ostia occlusion (Usually RCA). |
| Aortic Regurgitation | Root dissection disrupts valve. |
| Mesenteric Ischaemia | Branch occlusion → Gut necrosis. |
| Acute Renal Failure | Renal artery occlusion. |
| Limb Ischaemia | Iliac/Femoral involvement. |
| Spinal Cord Ischaemia (Paraplegia) | Intercostal artery/Artery of Adamkiewicz involvement. |
9. Prognosis and Outcomes
- Type A (Untreated): 1-2% mortality per hour for first 48 hours. ~50% dead by Day 2.
- Type A (Surgical): 15-25% operative mortality. Better if early surgery.
- Type B (Uncomplicated): ~10% in-hospital mortality with medical management.
- Type B (Complicated): Higher mortality, requires intervention.
- Long-Term: Lifelong BP control and surveillance imaging essential. Risk of aneurysm formation in false lumen.
10. Evidence and Guidelines
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| ESC Guidelines on Aortic Diseases | ESC (2014, 2022 Update) | Stanford classification, BP targets, Type A = Surgery, Type B = Medical/TEVAR if complicated. |
| STS/STScVS Guidelines | STS/AAO | Surgical management of Type A, TEVAR role. |
11. Patient and Layperson Explanation
What is an Aortic Dissection?
The aorta is the main blood vessel carrying blood from your heart to the rest of your body. In a dissection, the inner lining of the aorta tears, and blood forces its way between the layers of the wall, creating a false channel. This can block blood supply to vital organs or cause the aorta to rupture.
How serious is it?
It is a medical emergency. Without treatment, it is often fatal within hours to days.
How is it treated?
- Type A (involving the upper part of the aorta): Requires emergency surgery to replace the damaged section.
- Type B (lower aorta only): Usually treated with medications to lower blood pressure and heart rate. Some need a stent if there are complications.
What happens long-term?
You will need to take blood pressure medications for life and have regular scans to monitor the aorta.
12. References
Primary Sources
- Erbel R, et al. 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases. Eur Heart J. 2014;35(41):2873-926. PMID: 25173340.
- Nienaber CA, et al. Aortic dissection. Nat Rev Dis Primers. 2016;2:16053. PMID: 27440162.
13. Examination Focus
Common Exam Questions
- Classification: "What is Stanford Type A vs Type B Dissection?"
- Answer: Type A = Ascending aorta involved (Surgery). Type B = Descending aorta only (Medical unless complicated).
- Classic Presentation: "Describe the classic chest pain of Aortic Dissection."
- Answer: Sudden onset, Severe, "Tearing" or "Ripping" quality, Maximal at onset, Radiates to back (Interscapular for Type B).
- BP Management: "Why give Beta-blocker BEFORE vasodilator?"
- Answer: Vasodilators alone cause reflex tachycardia, increasing aortic wall shear stress. Beta-blockers reduce HR and dP/dt first.
- CXR Finding: "Classic CXR finding in Aortic Dissection?"
- Answer: Widened Mediastinum.
Viva Points
- Pulse Deficit: Emphasise this clinical sign and its significance.
- Type A = Surgical Emergency: Explain the urgency and mortality.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.