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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Sudden severe "tearing/ripping" chest or back pain maximal at onset (not crescendo like ACS)
- Stanford A = ascending aorta involved = surgical emergency
- Stanford B = descending aorta only = medical management unless complicated
- CTA with IV contrast is preferred imaging (sensitivity >95%)
- IV esmolol/labetalol to HR <60 and SBP <120 BEFORE adding vasodilators
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. Stanford Type A involves the ascending aorta (regardless of origin) and is a surgical emergency; Type B involves only the descending aorta and is typically managed medically unless complicated by malperfusion, rupture, or rapid expansion. Hypertension is the most important risk factor (70-80% of cases).
Epidemiology
Incidence ~3-4 per 100,000/year in the US. Peak age 60s-70s. Men 2-3x more than women. Risk factors: chronic HTN (most common), connective tissue disorders (Marfan, Ehlers-Danlos IV, Loeys-Dietz), bicuspid aortic valve, prior cardiac surgery, cocaine/amphetamines, coarctation, and third-trimester pregnancy. Untreated Type A mortality: ~1-2% per hour in first 48 hours.
Clinical Features
Symptoms
Sudden "tearing/ripping" chest pain maximal at onset (distinguishes from ACS which builds)
Anterior chest (Type A) or interscapular back (Type B) or migratory as dissection propagates
Syncope (tamponade, stroke, or vasovagal)
Neurological symptoms: stroke (carotid), paraplegia (spinal artery occlusion)
Abdominal/leg pain or cold extremity (visceral or limb malperfusion)
Signs
BP differential >20 mmHg between arms (subclavian involvement)
Pulse deficit (absent or diminished peripheral pulse)
New diastolic murmur of aortic regurgitation (Type A)
Hypotension + muffled heart sounds + JVD = cardiac tamponade (pericardial rupture)
Severe hypertension (common presenting finding)
Investigations
First-line
CT angiography (CTA)Preferred: sensitivity >95%, fast, shows intimal flap, true/false lumens, extent, branch vessel involvement, complications
ECGRule out STEMI (thrombolytics in dissection are catastrophic). May show LVH or inferior ST changes if RCA ostium involved
CXRWidened mediastinum (most common, ~60-70%), left pleural effusion (hemothorax). Can be normal in 10-20%
Second-line
TEEExcellent for Type A (~99% sensitivity), can be done at bedside if too unstable for CT
D-dimerElevated in >95% of acute dissections; normal D-dimer has high NPV if pre-test probability is low
Basic labsCBC, BMP, type and screen, troponin (coronary malperfusion), lactate (visceral malperfusion)
Specialist
MRAExcellent accuracy but impractical acutely. Good for chronic dissection follow-up
Management
2022 ACC/AHA Aortic Disease Guideline1
Immediate (all dissections)
- IV beta-blocker FIRST: esmolol drip (preferred) or labetalol IV
- Target HR <60, SBP 100-120 mmHg
- Add vasodilator (nicardipine, nitroprusside) ONLY AFTER HR controlled
- Adequate analgesia (morphine/fentanyl — pain increases sympathetic drive)
- Two large-bore IVs, type and crossmatch, arterial line
2
Type A — surgical emergency
- Emergent open repair: ascending aorta graft +/- valve/root replacement
- Operative mortality ~15-25% but non-operative ~50% at 48h
- Do NOT delay for additional workup once confirmed
3
Type B — uncomplicated
- Medical: IV anti-impulse therapy transitioned to oral
- Lifelong BB + antihypertensive to SBP <130/80
- Serial imaging at 1, 3, 6, 12 months then annually
4
Type B — complicated
- Indications: malperfusion, rapid expansion, rupture, refractory pain/HTN
- TEVAR (thoracic endovascular repair) preferred over open for complicated Type B
Complications
- Cardiac tamponade: Pericardial rupture (Type A) — rapidly fatal
- Acute aortic regurgitation: Type A disrupts valve support
- Coronary malperfusion: Flap covers coronary ostium, mimics primary STEMI (RCA most common)
- Stroke: Carotid/brachiocephalic involvement
- Malperfusion: Renal failure, mesenteric ischemia, limb ischemia
- Aortic rupture: Into mediastinum, pleura, or peritoneum
- Paraplegia: Spinal cord ischemia (artery of Adamkiewicz)
USMLE Step 2 CK Exam Tips
- 1Tearing chest/back pain maximal at onset + BP differential between arms = dissection until proven otherwise
- 2Type A = Ascending = Surgery. Type B = descending = Medical (unless complicated)
- 3Beta-blocker BEFORE vasodilator — classic Step 2 CK question. Vasodilator alone causes reflex tachycardia increasing shear stress
- 4CTA is best initial test. TEE if too unstable for CT
- 5Dissection + STEMI on ECG: do NOT give thrombolytics — catastrophic. Take to OR
- 6Marfan + chest pain = dissection until proven otherwise (even if young)
- 7Widened mediastinum on CXR is most common finding but CXR can be normal — get CTA if high suspicion
- 8Cocaine chest pain: rule out BOTH ACS and dissection before treatment
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