Aortic dissection
Description
- Intimal tear -> blood enters the media -> false lumen propagating antegrade or retrograde
- The most lethal aortic emergency: ~1-2% mortality per hour for the first 48 h in untreated type A
Classification
| Stanford | DeBakey | Involves | Treatment |
|---|---|---|---|
| A (~60%) | I (asc + arch + desc), II (asc only) | Ascending aorta | Emergency surgery |
| B (~40%) | III | Distal to left subclavian, ascending spared | Medical, unless complicated |
- Stanford is the one that matters: does it involve the ascending aorta? That single question drives everything
- Non-A non-B: arch involvement without ascending - managed case by case
Timing
- Acute <14 days, subacute 15-90 days, chronic >90 days
Acute aortic syndromes - the same clinical presentation
- Classic dissection
- Intramural haematoma (IMH) - no intimal flap; ~10-20%; may evolve into dissection or regress
- Penetrating atherosclerotic ulcer (PAU) - ulcerated plaque through the internal elastic lamina; elderly, atherosclerotic, often descending
- Contained rupture
Epidemiology
- Incidence ~3-6 per 100,000/yr
- M>F (~2-3:1); women present later and have higher mortality
- Peak age 60-70 (type A can present at any age with a connective tissue disorder or bicuspid valve)
- Circadian/seasonal peak: morning, winter
- <40 years: think Marfan, Loeys-Dietz, vascular EDS, Turner, bicuspid aortic valve, pregnancy, cocaine/amphetamine
Aetiopathogenesis
Substrate = medial degeneration + haemodynamic stress
- Hypertension - present in ~70%, the dominant risk factor
- Atherosclerosis and ageing
- Pre-existing aneurysm
- Connective tissue disease - Marfan (FBN1), Loeys-Dietz (TGFBR1/2, SMAD3 - dissects at smaller diameters), vascular EDS (COL3A1)
- Bicuspid aortic valve (inc risk ~8x, independent of stenosis severity), coarctation, Turner syndrome
- Pregnancy - third trimester and early postpartum, especially with Marfan or a root >40 mm
- Inflammatory aortitis - giant cell arteritis, Takayasu, syphilis, Behcet
- Iatrogenic - cardiac surgery, catheterisation, IABP, cannulation (~5%)
- Trauma - deceleration injury at the ligamentum arteriosum
- Stimulants - cocaine, amphetamines; weightlifting (Valsalva -> BP surge)
- Fluoroquinolones (association with dissection/aneurysm)
Why complications happen
- Propagation -> branch vessel ostia sheared or compressed -> malperfusion (coronary, cerebral, spinal, renal, mesenteric, limb)
- Retrograde into the root -> acute AR, coronary occlusion (right coronary -> inferior STEMI), rupture into pericardium -> tamponade
- Rupture -> left haemothorax, mediastinum, retroperitoneum
Diagnosis
Clinical - the classic triad is often absent
- Sudden, severe, "tearing"/"ripping" chest or interscapular pain, maximal at onset
- Migratory pain follows propagation
- Anterior chest -> ascending; interscapular/back -> descending
- Painless in ~5-10% (diabetes, elderly, prior aortic surgery) - presents as stroke, syncope or limb ischaemia
- Syncope in ~10% - implies tamponade, rupture or arch vessel involvement
- Hypertension (type B) vs hypotension/shock (type A - tamponade, AR, rupture)
Examination
- Pulse deficit / radial-radial or radial-femoral delay (~30%)
- Differential: large-vessel atherosclerosis or aneurysm, unilateral subclavian stenosis, thoracic aortic dissection, coarctation, prior surgery
- BP differential between arms >20 mmHg
- Early diastolic murmur of acute AR (~40-50% of type A)
- Focal neurology - stroke (~5-10%), Horner, paraplegia (spinal artery), hoarseness (recurrent laryngeal)
- Signs of tamponade, or abdominal tenderness (mesenteric malperfusion)
- Mesenteric/limb ischaemia with chest pain = dissection, not embolus, until imaged
Investigation
- CT angiography aorta (arch to femorals) = investigation of choice, sens/spec >95%
- ECG-gated to avoid root motion artefact
- TOE - if too unstable to move; excellent for ascending aorta, root, AR, pericardium; blind spot at the distal ascending/proximal arch
- TTE - bedside; may show flap, AR, effusion/tamponade, root dilatation. A normal TTE does not exclude
- MRA - best for chronic/follow-up, not the acute unstable patient
Supportive
- ECG - normal or non-specific in most; inferior STEMI pattern in ~1-2% from RCA involvement
- *Thrombolysis for this is catastrophic - the reason to consider dissection in every acute chest pain*
- CXR - widened mediastinum (~60%), abnormal aortic contour, left pleural effusion, calcium sign. A normal CXR does not exclude
- D-dimer - very high negative predictive value if <500 ng/mL within 24 h of onset combined with low pre-test probability
- Never use it alone to rule out when suspicion is high
- Troponin, lactate (malperfusion), FBE, group and hold, renal function
Risk score
- Aortic Dissection Detection Risk Score (ADD-RS, 0-3) - one point each for:
- Predisposing conditions (Marfan, family history, known aortic disease/aneurysm, valve disease, recent aortic manipulation)
- Pain features (abrupt, severe, tearing/ripping)
- Examination features (pulse deficit, BP differential, focal neurology, new AR, hypotension/shock)
- ADD-RS >=2 -> straight to CT angiography
Management
A. Immediate - all dissections
Target: dec dP/dt (rate of rise of aortic pressure), not just BP
- Rate first, then pressure - a vasodilator alone causes reflex tachycardia and increases shear stress
1. IV beta blocker - esmolol or labetalol; target HR <60
2. Then vasodilator - sodium nitroprusside or GTN; target SBP 100-120 mmHg while preserving end-organ perfusion
- If beta blocker contraindicated: verapamil/diltiazem
3. Analgesia - IV opioid (pain drives catecholamines)
4. Arterial line (the arm with the higher pressure), large-bore access, group and crossmatch, urgent cardiothoracic/vascular referral
B. Type A - surgical emergency
- Open repair: resect the intimal tear, replace the ascending aorta +/- hemi-arch; root replacement (valve-sparing David, or Bentall) if root involved; arch replacement/frozen elephant trunk if arch tear
- Operative mortality ~15-25%; medical management mortality ~50% at 48 h
- *Do not drain the pericardium* in tamponade from type A - relieves tamponade, restores BP, exsanguinates. Straight to theatre
- Avoid: thrombolysis, anticoagulation, antiplatelets pre-operatively
C. Type B
Uncomplicated -> medical
- Optimal medical therapy: beta blocker + additional agents, BP <120/80 long-term, smoking cessation, lifelong surveillance imaging
- TEVAR now also considered in uncomplicated type B in the subacute phase where high-risk features are present (false lumen diameter >22 mm, entry tear >10 mm, total aortic diameter >40 mm, refractory pain/hypertension) - improves aortic remodelling and late survival (INSTEAD-XL)
Complicated -> TEVAR
- Complications: rupture/impending rupture, malperfusion (renal, mesenteric, limb, spinal), refractory pain or hypertension, rapid expansion, retrograde extension
- TEVAR is first-line for complicated type B (lower mortality than open repair)
- Open repair preferred in connective tissue disease - poor landing zones, risk of new dissection
- Adjuncts: fenestration, branch stenting, CSF drainage for spinal cord protection
D. Long-term - all survivors
- Lifelong strict BP control (beta blocker backbone), target <120/80
- Surveillance CT/MR at 1, 3, 6, 12 months then annually
- Avoid isometric/heavy resistance exercise, stimulants
- Genetic testing and first-degree relative screening if young, syndromic, or family history
- Counsel on pregnancy risk
Associations
- Bicuspid aortic valve, coarctation, Turner syndrome
- Marfan, Loeys-Dietz, vascular EDS, familial thoracic aortic aneurysm and dissection (ACTA2, MYH11, TGFBR)
- Giant cell arteritis, Takayasu, syphilitic aortitis, Behcet
- Polycystic kidney disease
- Pregnancy
- Cocaine and amphetamine use, anabolic steroids
- Prior cardiac surgery or catheterisation
Natural history & complications
- Untreated type A: ~1-2% mortality per hour in the first 48 h; ~50% dead at 48 h, ~90% at 30 days
- Operated type A: in-hospital mortality ~15-25%; 10-year survival ~50-60%
- Uncomplicated type B: in-hospital mortality ~10%; but ~25-40% need intervention within 5 years for aneurysmal degeneration of the false lumen
Complications
- Early - tamponade, acute severe AR, coronary malperfusion/MI, stroke, paraplegia, mesenteric/renal/limb ischaemia, rupture
- Late - false lumen aneurysmal degeneration and rupture (the main driver of late death), re-dissection, anastomotic pseudoaneurysm, progressive AR, endoleak after TEVAR
- Patent false lumen is the strongest predictor of late aneurysm formation
Poor prognostic markers
- Hypotension/shock at presentation, tamponade, malperfusion, age, renal failure, painless presentation (delayed diagnosis)
- Median time to diagnosis remains hours - the commonest reason for a bad outcome is not considering it
🔒
6 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access