Key Facts

Aortic dissection is a cardiovascular emergency in which a tear in the aortic intima allows blood to enter the media, creating a false lumen that can propagate proximally or distally, compromising branch vessel perfusion and risking aortic rupture.

Epidemiology

• Incidence: ~3-5 per 100,000 per year
• Male:female ratio ~3:1
• Peak incidence: 60-70 years (degenerative); younger in connective tissue disorders
• Type A: ~65% of dissections; Type B: ~35%

Aetiology

• Hypertension: most important risk factor (~70-80% of patients)
• Connective tissue disorders: Marfan syndrome (FBN1), Ehlers-Danlos type IV (COL3A1), Loeys-Dietz
• Bicuspid aortic valve: associated aortopathy
• Aortic aneurysm: pre-existing dilatation
• Cocaine use: acute hypertensive surge
• Turner syndrome, coarctation of the aorta
• Pregnancy: typically 3rd trimester or peripartum
• Iatrogenic: post-cardiac surgery, catheterisation
• Trauma: deceleration injuries

Pathophysiology

• Intimal tear allows high-pressure blood to enter the media → dissection plane propagates
• False lumen may compress true lumen → branch vessel malperfusion
• Propagation can extend proximally (into aortic root → AR, coronary occlusion, tamponade) or distally (abdominal aorta, iliac arteries)
• Rupture may occur into pericardium (tamponade), pleural space, or mediastinum

Typical Presentation

• Sudden-onset severe chest or interscapular back pain: described as 'tearing' or 'ripping'
• Pain may migrate as dissection propagates
• Type A: anterior chest pain
• Type B: interscapular back pain
• Associated: diaphoresis, nausea, syncope

Examination Findings

• Blood pressure differential >20 mmHg between arms
• Pulse deficit (absent or reduced pulse in one limb)
• Aortic regurgitation murmur (type A involving aortic root)
• Hypotension/shock (tamponade, rupture, severe AR)
• Unilateral weakness: stroke from carotid malperfusion
• Abdominal pain: mesenteric ischaemia
• Leg ischaemia: iliac/femoral malperfusion

Red Flags

• Hypotension with distended neck veins (tamponade)
• Limb ischaemia
• Stroke symptoms
• Acute abdominal pain with dissection
• Known Marfan syndrome with acute chest pain

Bedside

• ECG: may be normal; may show LVH (chronic HTN), inferior ST elevation (RCA involvement in type A), non-specific changes
• Observations: BP both arms, HR, SpO₂
• CXR: widened mediastinum (~60%), left pleural effusion, abnormal aortic contour, displaced intimal calcification

Bloods

• FBC, U&Es, LFTs: organ perfusion assessment
• Troponin: may be elevated if coronary malperfusion (type A involving RCA)
• D-dimer: markedly elevated (>500 ng/mL has high sensitivity for dissection but low specificity)
• Lactate: elevated in malperfusion syndromes
• Group and save/crossmatch: emergency surgery preparation
• Coagulation: baseline

Imaging

• CT aortography (CTA): investigation of choice — sensitivity and specificity both >95%
  • Demonstrates intimal flap, true and false lumen, extent, branch vessel involvement
  • Rapid and widely available
• TOE: excellent for type A; can be performed at bedside/in theatre; operator-dependent
• MR angiography: gold standard for anatomy but too slow for emergency
• Bedside TTE: may show aortic root dilatation, pericardial effusion (tamponade), aortic regurgitation, intimal flap in ascending aorta

Stanford Classification

Non-pharmacological

• Resuscitation ABC approach: large-bore IV access, crossmatch, O-negative blood if haemodynamic collapse
• Continuous arterial line BP monitoring
• Urinary catheter (monitor renal perfusion)
• Nil by mouth: in preparation for potential emergency surgery

Pharmacological

Immediate (all dissections):

• Target: SBP 100-120 mmHg, HR <60 bpm
• IV labetalol: first-line; 20mg bolus then 1-2mg/min infusion
• IV esmolol: alternative short-acting beta-blocker (500mcg/kg loading, then 50-200mcg/kg/min)
• IV GTN infusion: added if BP not controlled with beta-blocker alone
• IV sodium nitroprusside: if refractory (must give with beta-blocker to prevent reflex tachycardia)
• IV morphine: for pain
• AVOID: thrombolysis (catastrophic if dissection misdiagnosed as MI)

Surgical/Interventional

Type A (emergency surgery):

• Open surgical repair: replacement of ascending aorta ± aortic root (Bentall procedure if Marfan)
• ± Aortic valve repair/replacement if AR present
• ± Coronary reimplantation
• Operative mortality: ~15-25% (but untreated mortality ~1-2% per hour)

Type B:

• Uncomplicated: medical management (BP and HR control); long-term oral beta-blocker + antihypertensive
• Complicated (malperfusion, rupture, rapid expansion, refractory pain/HTN): TEVAR (thoracic endovascular aortic repair) — stent graft placement
• TEVAR mortality: ~5-10%

Referral Criteria

• All suspected dissections: emergency transfer to cardiothoracic centre
• Type A: immediate surgical consultation
• Type B complicated: vascular/interventional radiology
• All survivors: lifelong surveillance with serial CT/MRI

• Type A untreated: mortality ~1-2% per hour in first 48 hours; ~50% dead by 48 hours
• Type A post-surgery: in-hospital mortality ~15-25%
• Type B uncomplicated: in-hospital mortality ~10% with medical management
• Type B complicated: mortality ~30% without intervention; improved with TEVAR
• 5-year survival: ~70-80% for type A post-repair; ~80-90% for type B medically managed
• Long-term risks: re-dissection, aneurysmal dilatation of false lumen, need for further intervention
• Lifelong surveillance: annual CT/MRI to monitor aortic dimensions
• Marfan patients: higher re-intervention rate

Stanford vs DeBakey Classification

Complications of Aortic Dissection