Level 2 of 6Must-remember

Acute aortic syndromes and aortic dissection

Assess, manage and stay safe — enough on its own

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The card — assess, manage, caution

Assessment— look, ask, measure

Know what you are looking for: acute aortic syndrome is the collective name for classic aortic dissection, intramural haematoma and penetrating atherosclerotic ulcer — three conditions that differ on imaging but present alike, carry a comparable early mortality and are managed alike; ascending intramural haematoma is treated with exactly the urgency of a type A dissection.
Ask about the pain in the right way: it is abrupt in onset and maximal at onset rather than crescendo — ischaemic cardiac pain builds over minutes, aortic pain arrives complete — and is typically described as 'tearing', also ripping, sharp, stabbing, or 'the worst pain of my life'; let the patient choose the adjective.
Site follows the anatomy: ascending aortic involvement typically gives anterior chest pain and descending involvement intrascapular back pain, so severe pain radiating to the back, particularly between the shoulder blades, should prompt consideration of acute aortic syndrome; migration from chest to back to abdomen to loin tracks the propagating dissection; and abdominal pain radiating to the sacral region, flank or genitalia should always signal the possible presence of a rupturing abdominal aortic aneurysm.
Collapse is common: syncope or presyncope should prompt consideration of aortic dissection as well as of haemodynamically significant pulmonary embolism and ischaemic arrhythmia — here it usually signifies tamponade, rupture or cerebral vessel occlusion and carries a poor prognosis.
Blood pressure in both arms. A significant inter-arm systolic differential, or an unobtainable pressure on one side, is a hard finding; set your targets thereafter against the *higher* reading, since the lower arm may be perfused through a compressed subclavian artery.
All four limb pulses, compared and re-examined serially. There may be asymmetry of the brachial, carotid or femoral pulses, and a pulse present at one examination and absent at the next means the dissection is propagating.
Listen for a new early diastolic murmur at the left sternal edge with the patient sitting forward in held expiration, with a wide pulse pressure and a collapsing pulse — acute aortic regurgitation, which complicates more than 50% of proximal dissections.
A focal neurological deficit accompanying chest pain is dissection until proved otherwise; sudden painless leg weakness with chest or back pain is dissection until proved otherwise.
Unless there is major haemorrhage the patient is invariably hypertensive — hypertension is present in about 80% of patients — but a systolic blood pressure below 100 mmHg is present in up to 25%, signifying tamponade, external rupture or severe acute aortic regurgitation, so seek raised jugular venous pressure, muffled heart sounds and pulsus paradoxus in every hypotensive patient.
A normal physical examination should never be used as the sole basis for ruling out aortic dissection, and neither should a normal ECG or a normal chest film.
Score it with the Aortic Dissection Detection Risk Score (ADD-RS): one point for the presence of any feature within each of three categories (high-risk conditions, high-risk pain features, high-risk examination findings), giving a total of 0 to 3. A score of 2 or 3 makes acute aortic syndrome the working diagnosis and mandates imaging without delay; 1 should prompt imaging unless a firm, positively established alternative exists; 0 permits an alternative to be pursued.
Ask for the risk factors: hypertension (about 80%), aortic coarctation, cocaine or amphetamine use, severe isometric exertion, atherosclerosis, increasing age, a known thoracic aortic aneurysm, Marfan syndrome (a rare disorder affecting 0.02% of the population, autosomal dominant, caused by *FBN1* mutation and fibrillin-1 deficiency), Loeys–Dietz and vascular Ehlers–Danlos syndromes, Turner syndrome, fibromuscular dysplasia, non-syndromic familial thoracic aortic aneurysm and dissection, bicuspid aortic valve (present in 0.5–1.4% of the population, with an associated aortopathy in about 30–40%), aortitis, pregnancy (usually third trimester and early puerperium), blunt deceleration trauma, previous cardiac surgery, cardiac catheterisation and intra-aortic balloon pumping.
Know who gets it: the peak incidence is in the sixth and seventh decades, men are affected roughly twice as often as women, and patients under about 40 almost always have an identifiable reason. Any patient with Marfan syndrome in whom severe or unusual chest pain develops should be admitted to exclude pneumothorax and aortic dissection.
Danger signs that mean it is progressing now: systolic below 100 mmHg, shock, or raised jugular venous pressure with muffled heart sounds and pulsus paradoxus (tamponade or rupture); a new early diastolic murmur with pulmonary oedema (acute severe aortic regurgitation); any focal neurological deficit; a pulse that has disappeared since the last examination; a cold or painful limb; abdominal pain out of proportion to the signs or a rising lactate (mesenteric malperfusion); falling urine output (renal malperfusion, not dehydration); pain that will not settle despite adequate opioid and controlled pressure; refractory hypertension; and a new or enlarging left pleural effusion, which in this context is blood.
Classify it, because it decides the next hour: the Stanford system — type A involves the ascending aorta and is a surgical emergency, type B does not and is usually medical; type A dissections account for two-thirds of cases and frequently also extend into the descending aorta. Dissection is also classified by interval since onset: acute, less than 2 weeks; subacute, 2–8 weeks; chronic, more than 8 weeks, with mortality and extension decreasing with time.
Beware the four labels that habitually conceal it: *inferior ST-elevation myocardial infarction* (a proximal flap occluding the right coronary ostium — the most dangerous electrocardiogram in acute medicine, because antiplatelet therapy, anticoagulation and thrombolysis are lethal in dissection); *stroke* in a patient nobody asked about chest pain; *renal colic* with an unequal femoral pulse nobody felt; and the *young patient with a hypertensive crisis* in whom youth closed the differential. Aortic disease accounts for approximately 1% of final discharge diagnoses in non-traumatic chest pain, and painless presentations are over-represented among patients with diabetes, prior aortic surgery and impaired consciousness.

Management— do this, in order

Start treatment as soon as the diagnosis is considered. When dissection is suspected, aggressive measures to lower blood pressure and heart rate should be initiated even before a definitive diagnosis is made — if imaging later shows something else, the patient has received an opioid and a beta-blocker, a survivable error unlike the alternative.Doctor / Nurse
Actively withhold antiplatelet drugs, anticoagulants and thrombolytics wherever the aortic question is unsettled, since they convert a contained dissection into an uncontained haemorrhage; if they have already been given, this must be conveyed to the surgical team.
Set the targets: systolic blood pressure and heart rate should be reduced within 30 minutes to below 120 mmHg and below 60 beats per minute, using a combination of vasodilation and beta-blockade, with a target mean arterial pressure of 60–75 mmHg to reduce the force of ejection of blood from the left ventricle. The correct pressure is the *lowest* that preserves consciousness, urine output and perfusion.
Give analgesia — it treats the aorta, because pain drives the catecholamine surge that drives the dissection forward: morphine 2.5–5 mg by slow intravenous injection, titrated and repeated every 5–10 minutes as required; in children 100 micrograms/kg (0.1 mg/kg) intravenously, maximum initial dose 5 mg, repeated at 10-minute intervals.Doctor / Nurse
Give an antiemetic with the opioid: metoclopramide 10 mg intravenously in adults, but ondansetron 100 micrograms/kg (maximum 4 mg) in anyone under 20 years, in whom metoclopramide risks extrapyramidal reactions.Doctor / Nurse
Rate before pressure — first-line therapy is with beta-blockers, and the additional alpha-blocking properties of labetalol make it especially useful, since it lowers rate and pressure with a single agent.
Labetalol (first line): 20 mg by slow intravenous injection over 2 minutes; repeat 20–80 mg every 10 minutes until heart rate is below 60/min and systolic below 120 mmHg, to a cumulative maximum of 300 mg; then infusion 0.5–2 mg/minute. Oral maintenance 200 mg to 2.4 g daily in divided doses. Labetalol is the beta-blocker of choice in pregnancy.Doctor / Nurse
Labetalol, paediatric: 0.2–1 mg/kg by slow intravenous injection (maximum 20 mg per dose, 40 mg in an adolescent), repeated at 10-minute intervals; then infusion 0.25–3 mg/kg/hour. Adult targets do not apply in children, where the aim is the low-normal heart rate and blood pressure *for age*.Doctor / Nurse
Esmolol where the response is uncertain, because it is ultra-short-acting: 500 micrograms/kg intravenously over 1 minute, then an infusion of 50 micrograms/kg/minute titrated to 200 micrograms/kg/minute; paediatric 100–500 micrograms/kg intravenously over 1 minute, then 25–200 micrograms/kg/minute.Doctor / NurseNot available at your setup — Infusion pump.
Metoprolol or propranolol as alternatives: metoprolol 5 mg by slow intravenous injection over 2 minutes, repeated every 5 minutes to 15 mg, then 25–50 mg orally twice daily; or propranolol 1 mg intravenously every 2 minutes to a maximum of 10 mg.Doctor / Nurse
If beta-blockers are contraindicated, use a rate-limiting calcium channel blocker: diltiazem 0.25 mg/kg by slow intravenous injection over 2 minutes (about 20 mg in an 80 kg adult); if inadequate at 15 minutes, 0.35 mg/kg over 2 minutes; then 5–15 mg/hour by infusion titrated to heart rate. The alternative is verapamil 5–10 mg by slow intravenous injection over at least 2 minutes with continuous monitoring.Doctor / Nurse
Add a vasodilator only once the heart rate is controlled and the systolic pressure remains above 120 mmHg. Sodium nitroprusside 0.3 micrograms/kg/minute by intravenous infusion, titrated; usual range 0.5–3, maximum 8 micrograms/kg/minute (paediatric 0.5–8 micrograms/kg/minute), through a pump on a light-protected line with continuous pressure monitoring. Alternatives are glyceryl trinitrate 2–10 mg/hour by infusion titrated to systolic pressure, or hydralazine by intermittent intravenous boluses under continued beta-blockade.Doctor / NurseNot available at your setup — Infusion pump.
The hypotensive patient — everything inverts. Hypotension means tamponade, rupture or acute severe aortic regurgitation: beta-blockers and vasodilators are withheld, volume is given cautiously as 250 mL crystalloid boluses in adults, or 10 mL/kg in children, reassessing after each and aiming only to preserve cerebration and urine output, and blood is transfused where there is evidence of haemorrhage.Doctor / NurseNot available at your setup — Blood & blood products.
Send the blood work early: group, save and crossmatch should be requested at the point of suspicion, not at the point of haemorrhage — with a full blood count for a baseline haemoglobin, creatinine as a pre-contrast baseline and marker of renal malperfusion, and lactate.Not available at your setup — Renal function (creatinine/urea), Arterial blood gas.
Image definitively: CT or MR angiography are the investigations of choice, and acutely CT angiography is the test — coverage from the thoracic inlet to the femoral heads, with an unenhanced acquisition before contrast (intramural haematoma appears as a hyperattenuating crescent and may be invisible once contrast is given), a correctly timed arterial phase, and ECG gating to remove pulsation artefact at the aortic root.Not available at your setup — CT scan. Where CT is unavailable, transthoracic echocardiography may show aortic regurgitation, a dilated root, a flap or tamponade, and transoesophageal echocardiography can be performed on a patient too unstable for CT — but neither a negative transthoracic study nor a normal chest film may cancel transfer for definitive imaging.
Definitive treatment: emergent or urgent surgical correction is the preferred treatment for acute ascending aortic dissections and intramural haematomas (type A), which require emergency surgery to replace the ascending aorta. Type B dissections are treated medically unless there is actual or impending external rupture, or vital organ (gut, kidneys) or limb ischaemia, as the morbidity and mortality associated with surgery are very high.
Medical therapy in type B is not 'no treatment': it is sustained anti-impulse therapy with continuous monitoring, serial examination of pulses, neurology and urine output, and repeat imaging.
When first-line measures fail: if the heart rate is not controlled, confirm adequate dosing before escalating and treat pain and anxiety, both of which sustain tachycardia; if blood pressure is not controlled despite full beta-blockade, add and titrate a vasodilator infusion; refractory hypertension in type B disease is itself an indication for intervention, as is refractory pain, which signifies propagation once inadequate analgesia is excluded; and new malperfusion — a lost pulse, new deficit, or rising creatinine or lactate — means the anatomy has changed, so repeat imaging and reassess for mechanical relief.Doctor / Nurse

Caution— what harms

Antiplatelet drugs, anticoagulants and thrombolytics are contraindicated and must be actively withheld while the aortic question is unsettled — the most dangerous presentation is the dissection occluding the right coronary ostium that looks like an inferior ST-elevation myocardial infarction, where the reflexive treatment is lethal.
Never give a vasodilator before beta-blockade. A vasodilator given alone produces reflex tachycardia and a greater force of ejection, so that dP/dt — the rate of rise of aortic pressure, which is what propagates the dissection — actually rises; it should not be given without beta-blockers in patients with possible coronary disease or aortic dissection.
Neither verapamil nor diltiazem should be given intravenously to a patient who has already received a beta-blocker, or who has heart failure or atrioventricular block — the combination causes asystole and refractory shock.
Pericardiocentesis for tamponade complicating dissection is not a reflex manoeuvre. Decompressing the pericardium can relieve the tamponade containing the bleed, restore aortic pressure and precipitate fatal haemorrhage; the definitive treatment is surgical, and needle drainage is a bridging measure for the peri-arrest patient only.
A normal ECG excludes nothing, and neither does a normal chest radiograph: the characteristic broadening of the upper mediastinum and distortion of the aortic knuckle are absent in 10% of cases, and a normal film must not cancel definitive imaging.
A raised troponin does not exclude dissection; it may be caused by it — from demand ischaemia or from coronary ostial occlusion.
A normal D-dimer never overrides a high clinical suspicion and must not delay imaging where the ADD-RS is 2 or 3. D-dimer sensitivity is high but specificity is poor, and intramural haematoma and thrombosed false lumens may generate little D-dimer.
Do not accept a poor scan as negative: cardiac motion at the aortic root produces a linear artefact closely mimicking a flap, and a non-gated, venous-phase or unenhanced study is not a negative aortogram — where the story is convincing, establish the protocol used before discarding the diagnosis.Not available at your setup — CT scan.
Do not trust transthoracic echocardiography to rule out: its overall sensitivity is only 60–85%, it images just the first 3–4 cm of the ascending aorta, and it is less useful for the arch and descending thoracic aorta — though for proximal ascending dissections sensitivity exceeds 80%.Not available at your setup — Ultrasound.
Beware the falsely reassuring blood pressure: hypertension is the rule but systolic is below 100 mmHg in up to 25%, and set targets against the higher arm reading because the lower arm may be perfused through a compressed subclavian artery.
Recognise overshoot: confusion, oliguria or a rising lactate means the pressure target has been overshot — the correct pressure is the lowest that preserves consciousness, urine output and perfusion.
Avoid sodium nitroprusside in pregnancy, where hydralazine under continued beta-blockade is useful instead; nitroprusside also causes cyanide and thiocyanate toxicity with prolonged or high-dose use and in renal impairment.
Do not give metoclopramide to anyone under 20 years — use ondansetron 100 micrograms/kg (maximum 4 mg) because of the risk of extrapyramidal reactions.
Do not dismiss an adolescent's chest pain because 'children do not dissect' — the paediatric error is not over-diagnosis but dismissal, and blood pressure must be read against age-specific ranges with a correctly sized cuff, since an undersized cuff reads falsely high.

Refer / escalate

Refer immediately, in parallel with starting analgesia and beta-blockade, any patient with an ADD-RS of 2 or 3 or a convincing story, and transfer without delay to a centre with CT aortography and cardiothoracic surgery — type A dissection and ascending intramural haematoma require emergency surgery to replace the ascending aorta, while type B disease needs urgent intervention if there is actual or impending rupture, malperfusion of a vital organ or limb, refractory pain, refractory hypertension or rapid aortic expansion.

The card — assess, manage, caution

Acute aortic syndromes and aortic dissection — Level 1: CorePrevious Acute aortic syndromes and aortic dissection — Level 3: Core practiceNext

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