Aortic Dissection
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Direct answer
Aortic dissection is a tear in the aortic intima allowing blood to split the media, creating a false lumen; it presents with abrupt, tearing chest or interscapular pain, often with pulse deficits, a blood pressure difference between arms, or acute aortic regurgitation. Stanford type A involves the ascending aorta and is a surgical emergency; type B is confined to the descending aorta and is managed medically with heart-rate-first blood pressure control. Diagnosis is by CT angiography (transoesophageal echo in the unstable patient), and immediate treatment includes intravenous beta blockade before vasodilators.
What you must remember
- Stanford classification: type A involves the ascending aorta (surgical emergency); type B spares the ascending aorta (medical management unless complicated). DeBakey refines this into type I (whole aorta), II (ascending only) and III (descending only).
- Presentation: tearing or ripping maximal-at-onset pain radiating to the back, syncope, pulse or blood pressure differential between limbs (over 20 mmHg), new aortic regurgitation murmur, limb or renal ischaemia, and cardiac tamponade in proximal dissection.
- Risk factors: longstanding hypertension (dominant), Marfan, Ehlers-Danlos and Loeys-Dietz syndromes, bicuspid aortic valve, coarctation, pregnancy and cocaine.
- Chest radiograph may show a widened mediastinum, but a normal film never excludes dissection; CT angiography is the diagnostic standard, with transoesophageal echocardiography preferred in unstable patients; D-dimer helps exclude dissection in low-risk pain.
- Management before diagnosis is firm: analgesia and heart rate control first — intravenous esmolol or labetalol targeting a heart rate near 60 per minute — then vasodilators to bring systolic pressure to about 100 to 120 mmHg; a vasodilator given before a beta blocker causes reflex tachycardia and worsens shear stress.
- Type A: urgent surgical repair; intramural haematoma and penetrating ulcer of the ascending aorta are treated as type A equivalents.
- Type B: medical therapy unless complicated by rupture, malperfusion, rapid enlargement or uncontrolled pain — then thoracic endovascular aortic repair is preferred.
- Long term: lifelong strict blood pressure control with beta blockade and serial imaging; screen relatives in syndromic cases.
A tearing pain, worked through
A 58-year-old hypertensive man describes chest pain that reached maximal intensity the instant it began and now bores through to the interscapular area; his right radial pulse is barely palpable, arm pressures differ by 30 mmHg, and a new early diastolic murmur sounds at the left sternal edge. Pain maximal at onset, a pulse deficit and new aortic regurgitation make dissection the working diagnosis before any scan. Resist the myocardial infarction reflex — even if the ECG shows inferior ischaemia, because the right coronary ostium can be involved, and thrombolysis here is catastrophic. The chest radiograph may show a widened mediastinum, but a normal film never excludes the diagnosis. He is stable, so CT angiography is the diagnostic standard (transoesophageal echocardiography if unstable; D-dimer helps exclude only in low-risk pain). While awaiting it, treat in strict order: analgesia, then a beta blocker — esmolol or labetalol — targeting a heart rate near 60, and only then vasodilators to 100 to 120 mmHg, because a vasodilator first causes reflex tachycardia and raises dP/dt, extending the tear. The scan shows Stanford type A: Had it been type B (descending, DeBakey III), the answer would be continued medical control, reserving thoracic endovascular repair for rupture, malperfusion, rapid enlargement or uncontrolled pain. Either way, the rest of his life is beta-blocked pressure and serial imaging, with relatives screened if he has Marfan, Ehlers-Danlos or Loeys-Dietz syndrome.
Where students slip
The mimic costs the most: dissection read as infarction, and the thrombolysis option taken — check the pulse and pressure asymmetries and the maximal-at-onset, migrating pain before touching a lytic. The sequencing error follows: rate before pressure, beta blocker before vasodilator, always. Classification anchors on Stanford A involving the ascending aorta and surgical, B not and medical unless complicated. The associations supply the single-liners:
Frequently asked questions
How is aortic dissection classified?
Stanford type A involves the ascending aorta; type B does not. DeBakey subdivides into I (entire aorta), II (ascending) and III (descending).
What is the diagnostic investigation of choice?
CT angiography in stable patients; transoesophageal echocardiography in unstable or intubated patients.
Why must a beta blocker precede vasodilators?
A vasodilator given first causes reflex tachycardia, increasing dP/dt and extending the dissection.
How is uncomplicated type B dissection managed?
Medical therapy — pain relief, intravenous heart-rate and blood pressure control, then lifelong oral beta blockade and surveillance imaging.
Which patients need urgent surgery?
All type A dissections, and type B with rupture, malperfusion of organs or limbs, rapid expansion or refractory pain.
What is seen if dissection involves the aortic root?
Acute severe aortic regurgitation with a diastolic murmur, and haemopericardium with tamponade — both indicate type A disease.