Aortic Dissection
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Direct answer
Aortic dissection begins with an intimal tear allowing pulsatile blood into the media, creating a false lumen. Stanford type A involves the ascending aorta and is a surgical emergency; type B is confined to the descending aorta and is treated medically unless complicated. Diagnosis is by CT angiography (transoesophageal echo if unstable or contrast-contraindicated). Immediate management is intravenous beta-blockade first (esmolol or labetalol), adding a vasodilator only afterwards, targeting a systolic pressure around 100–120 mmHg. Complicated type B disease (malperfusion, rupture, rapid expansion) is treated with thoracic endovascular aortic repair.
What you must remember
- Classification: Stanford A (any ascending involvement) versus B (descending only); DeBakey I, II and III subtypes; intramural haematoma and penetrating atherosclerotic ulcer are acute aortic syndromes managed along the same pathways.
- Presentation: abrupt tearing interscapular pain, pulse deficits, an inter-limb blood pressure differential over 20 mmHg, new aortic regurgitation murmur in type A, syncope, or malperfusion — stroke, paraplegia, limb or gut ischaemia.
- The STEMI trap: a dissection extending into the right coronary ostium produces an inferior STEMI pattern; fibrinolysis is fatal — always screen for pulse deficits and a wide mediastinum before lysis in atypical infarcts.
- Risk factors: hypertension is the commonest; bicuspid aortic valve, Marfan, Loeys-Dietz and vascular Ehlers-Danlos syndromes, Turner syndrome, pregnancy with aortopathy and cocaine use follow.
- Type A: emergency surgery — untreated mortality rises steeply in the first days (classically 1–2 per cent per hour early on); complications include tamponade, acute aortic regurgitation and coronary occlusion.
- Type B management: intravenous beta-blockade first (a pure vasodilator given first causes reflex tachycardia and raises wall stress); target heart rate below roughly 60–80 beats per minute and systolic pressure 100–120 mmHg; complicated dissection — malperfusion, contained rupture, refractory pain or hypertension, rapid extension — goes to thoracic endovascular repair; uncomplicated disease is medical with surveillance imaging.
- Long-term care: lifelong beta-blocker-based blood-pressure control, serial CT or MR imaging, genetic assessment in young patients, and specialist management of future pregnancy.
Common confusion
Dissection is confused with STEMI (tearing pain, pulse deficits and a pressure differential point to the aorta), and with pulmonary embolism as the great mimic of sudden dyspnoea with shock. Candidates also mix up the treatment logic: beta-blockade precedes vasodilation, and uncomplicated type B is a medical condition — TEVAR is the answer only with malperfusion, rupture or refractory features. A normal D-dimer makes dissection unlikely in low-risk patients; a raised level never confirms it.
Exam-focused takeaway
NEET-SS and INI-SS stems test classification (A versus B from the tear extent), drug sequencing (beta-blocker before nitroprusside) and complication recognition (a type A with sudden hypotension and jugular distension means haemopericardium). Malperfusion scenarios — limb ischaemia, paraplegia, renal failure — test TEVAR indications. Keep the numbers crisp: the 20 mmHg differential and the 100–120 mmHg systolic target.
Frequently asked questions
What distinguishes Stanford type A from type B?
Type A involves the ascending aorta (with or without arch extension) and requires emergency surgery; type B is confined to the descending aorta and is managed medically unless complicated.
Why is a beta-blocker given before a vasodilator?
Vasodilation causes reflex tachycardia, which raises the rate of pressure change (dP/dt) and propagates the dissection; beta-blockade lowers heart rate, contractility and wall stress first.
What features define a complicated type B dissection?
Malperfusion syndromes (renal, mesenteric, limb or spinal ischaemia), rupture or contained rupture, rapid extension or enlargement, and refractory pain or hypertension — indications for thoracic endovascular repair.
Which imaging test confirms dissection?
CT angiography is the standard first-line test; transoesophageal echocardiography suits unstable patients and those with renal impairment, and MR angiography is an alternative in stable patients.