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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Aortic dissection = tear in the intima → blood tracks through the media creating a false lumen
- Stanford A (ascending aorta involved) = surgical emergency; Stanford B (descending only) = medical management with IV antihypertensives
- Classic presentation: sudden-onset severe tearing/ripping interscapular chest or back pain + blood pressure differential between arms
- Diagnosis: CT aortogram (gold standard); do NOT wait for D-dimer or troponin to exclude dissection if clinical suspicion is high
- Immediate management: IV labetalol (target SBP 100–120 mmHg, HR <60), analgesia, and urgent surgical referral for Type A
Overview
Aortic dissection occurs when a tear in the aortic intima allows blood to enter the media, creating a false lumen that propagates along the aorta. The Stanford classification divides dissections into Type A (involves the ascending aorta, regardless of where the tear originates — 60–70% of cases) and Type B (confined to the descending aorta distal to the left subclavian artery). The DeBakey classification subdivides further but Stanford is more clinically useful. Hypertension is the single most important risk factor, present in 70–80% of cases. Other risk factors include Marfan syndrome, bicuspid aortic valve, Turner syndrome, coarctation of the aorta, previous cardiac surgery, and cocaine use.
Epidemiology
Incidence is approximately 3–5 per 100,000 per year. Peak age is 50–70 years. Men are affected twice as often as women. Without treatment, Type A dissection has a mortality of 1–2% per hour in the first 48 hours — making rapid diagnosis and surgical intervention critical. Risk factors include uncontrolled hypertension (most common), connective tissue disorders (Marfan syndrome, Ehlers-Danlos), bicuspid aortic valve, aortic aneurysm, cocaine use, and third-trimester pregnancy.
Clinical Features
Symptoms
Sudden-onset severe tearing or ripping chest pain — often described as the worst pain ever experienced
Pain radiating to the back (interscapular — classic for Type A extending to descending aorta)
Pain may migrate as dissection propagates
Syncope (cardiac tamponade, cerebral malperfusion)
Neurological symptoms: stroke (carotid involvement), paraplegia (spinal artery occlusion)
Limb ischaemia (subclavian/iliac/femoral branch occlusion)
Abdominal pain (mesenteric ischaemia)
Signs
Blood pressure differential between arms (>20 mmHg systolic) — classic but not always present
Pulse deficit (absent or reduced pulse in one or more limbs)
Hypertension (common) or hypotension/shock (tamponade, aortic rupture)
New early diastolic murmur of aortic regurgitation (Type A — valve disruption)
Muffled heart sounds, raised JVP (cardiac tamponade)
Focal neurological deficit
Investigations
First-line
CT aortogram (contrast-enhanced)Gold standard. Shows intimal flap, true and false lumens, extent of dissection, branch vessel involvement. Should be performed URGENTLY if dissection suspected
ECGExclude MI (but dissection can cause MI by occluding coronary ostia — inferior STEMI with Type A dissection). May show LVH or non-specific changes
BloodsFBC, U&Es, coagulation, group and save (crossmatch urgently), troponin (may be positive if coronary involvement), lactate
Second-line
Chest X-rayWidened mediastinum (>8 cm at aortic knuckle), left pleural effusion (blood), irregular aortic contour. Can be normal — does NOT exclude dissection
TOE (transoesophageal echo)Alternative to CT if patient too unstable to transfer to scanner; high sensitivity for Type A dissection
Specialist
MR angiographyExcellent for chronic dissection follow-up but too slow for acute presentation
AortographyInvasive; rarely performed now with high-quality CT available
1
Immediate stabilisation
- ABC approach, large-bore IV access, crossmatch blood urgently
- IV beta-blocker first-line: labetalol IV to target SBP 100–120 mmHg and HR <60 bpm
- If beta-blocker contraindicated, use IV GTN or sodium nitroprusside (but must add beta-blocker first to prevent reflex tachycardia)
- IV opioid analgesia (morphine) — pain drives sympathetic response and raises BP further
2
Type A (ascending aorta) — emergency surgery
- Emergency open surgical repair — replacement of the ascending aorta ± aortic root (Bentall procedure if aortic root involved)
- Aortic valve repair or replacement if aortic regurgitation present
- Coronary reimplantation if coronary ostia involved
- Mortality without surgery: >50% at 48 hours; with surgery: 15–25%
3
Type B (descending aorta) — medical management
- Aggressive blood pressure control (IV → oral antihypertensives: labetalol, amlodipine, ramipril)
- Close monitoring in HDU/ITU
- Endovascular repair (TEVAR) if complicated: malperfusion, refractory pain, rupture, rapid expansion
- Long-term surveillance with serial CT/MR imaging
Complications
- Cardiac tamponade: Haemopericardium from Type A dissection — most common cause of death
- Aortic regurgitation: Disruption of aortic valve commissures (Type A)
- Myocardial infarction: Coronary ostial occlusion (usually RCA → inferior STEMI)
- Stroke: Carotid artery involvement
- Mesenteric ischaemia: SMA occlusion
- Renal failure: Renal artery occlusion
- Limb ischaemia: Iliac/subclavian occlusion
- Aortic rupture: Free rupture into mediastinum/pleural cavity — rapidly fatal
UKMLA Exam Tips
- 1Sudden tearing chest/back pain + BP differential between arms = aortic dissection until proven otherwise
- 2Type A = Ascending = sUrgery; Type B = Below (descending) = Blood pressure control (medical)
- 3If a STEMI scenario also mentions tearing back pain or BP differential → think dissection with coronary involvement; thrombolysis would be FATAL
- 4CT aortogram is the investigation of choice — do not delay for other tests if high clinical suspicion
- 5Marfan syndrome (tall, thin, hyperextensible joints, lens subluxation) + chest pain = dissection until proven otherwise
- 6Widened mediastinum on CXR supports the diagnosis but a normal CXR does NOT exclude dissection
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