Acute Aortic Syndrome

Meet the patient

A 58-year-old hypertensive builder grips his chest at 03:00, then his back between the shoulder blades. He tells the triage nurse the pain "switched on in a single second — like I was torn in half". Right-arm BP is 200/110; the left radial pulse is absent and left-arm BP is 162/92.[2][1]

Two exam questions are now live and both will kill him if you answer them wrong: is this type A or type B? and is it safe to thrombolyse the ECG changes? Everything below exists to answer those two questions at consultant depth, because missing this diagnosis roughly doubles the mortality.[2]

What acute aortic syndrome is — three lesions, one algorithm

One umbrella, three lesions, one opening move. All three share medial wall stress producing a tear or bleed inside the wall, and an identical first 15 minutes of resuscitation.[1]

• Classic dissection — a tear of the intima (and inner media) lets pulsatile blood enter and propagate along the media, splitting the wall into a true and false lumen separated by an intimal flap.
• Intramural haematoma (IMH) — a haemorrhage within the media with no intimal flap, thought to arise from rupture of the vasa vasorum; it accounts for 10 to 30 percent of AAS and behaves like dissection in the ascending aorta.
• Penetrating aortic ulcer (PAU) — an atherosclerotic plaque ulcerates through the internal elastic lamina into the media; typically descending, in older, heavily atherosclerotic, hypertensive patients.[1]

Chronicity is a number rule, not a judgement. Acute is symptom onset within 14 days; subacute is 15 to 90 days; chronic is over 90 days. The acute window is the surgical clock — type A untreated dies at roughly 1 to 2 percent per hour, about 50 percent by 48 hours and 75 percent by 2 weeks.[1][2]

The epidemiology is brutal and brief. IRAD's 17-year registry (n=4428) reports an in-hospital mortality of about 27 percent for type A and 9 percent for type B, with type A roughly twice as common as type B. Women present older, later, and with worse outcomes — a systems failure to name in a viva.[2][3]

Stanford — the line that decides the whole operation

A = ascending = theatre; B = beyond the subclavian = medical. That single sentence is the Stanford system, and it is the operative decision the surgeon is asking you to have already made when you phone.[1]

• Stanford type A — any dissection involving the ascending aorta, with or without arch or descending extension. Surgical emergency.
• Stanford type B — confined to the descending aorta, distal to the left subclavian artery, ascending spared. Medical impulse-control; TEVAR for the complicated.[1]

DeBakey is the anatomic description that examiners pair with Stanford: type I originates in the ascending aorta and propagates into the arch and descending; type II is confined to the ascending; type III originates distal to the left subclavian and runs distally (IIIa supradiaphragmatic, IIIb below the diaphragm). The shorthand: DeBakey I and II equal Stanford A; DeBakey III equals Stanford B.[1]

[1] [2] [3]

The one-line discriminator: if the ascending aorta is involved, it is type A and it goes to theatre — no matter how far distally the flap has run. Everything else is type B and starts on a beta-blocker.[1]

IMH and PAU borrow the same line. Ascending IMH behaves like type A — many centres operate, especially with a pericardial effusion, an aorta over 50 mm, or an intimal tear on TEE. Descending IMH and PAU behave like type B — medical, with TEVAR for persistent pain, expansion, or rupture.[1]

Penn classification layers clinical state onto type A for operative risk: Aa (stable, no ischaemia) through Ab (localised branch malperfusion), Ac (tamponade or shock) to Ad (combined). Operative mortality climbs from about 10 percent in Aa to 30 to 50 percent in Ac and about 60 percent in Ad.[3]

ADD-RS plus D-dimer is the emergency-department rule-out. The aortic-dissection detection risk score sums high-risk conditions, pain features and exam findings (0 to 3). A score of 0 with a D-dimer under 500 ng/mL, within 24 hours of pain onset, rules out dissection with a negative predictive value of about 99 percent.[4]

Why the wall fails — Laplace, dP/dt and the three openings

Two physical variables decide whether the wall holds: tensile stress and the rate of pressure rise. Wall tension follows Laplace — stress equals pressure times radius over wall thickness — so a dilated, hypertensive aorta is under the most stress. The rate of rise of pressure (dP/dt) in systole is the hammer that drives the flap forward, which is precisely why we blunt it with a beta-blocker before we touch the pressure.[1]

There are three ways in, one way the wall is weak.[1]

• An intimal tear — pulsatile blood enters the media and propagates longitudinally. The tear sits where shear is highest: the right lateral ascending aorta near the sinotubular junction, or the aortic isthmus just distal to the left subclavian (the fixed-mobile junction sheared in deceleration trauma). No identifiable tear points to IMH.
• Vasa vasorum rupture — a localised intramural haemorrhage with secondary inflammatory weakening; this is IMH.
• Plaque ulceration — an atherosclerotic plaque erodes through the internal elastic lamina into the media; this is PAU.[1]

Wall weakness has three faces, and one name to drop in a viva. Cystic medial degeneration (Erdheim) — loss of smooth muscle, elastic-fibre fragmentation, basophilic ground substance — is the dominant lesion in Marfan, Loeys-Dietz and the ageing hypertensive aorta. Atherosclerotic medial extension drives PAU; inflammatory destruction (Takayasu, giant-cell, syphilitic aortitis) is the third.[1]

Malperfusion is the same flap, pointing at different branches. The intimal flap can obstruct any vessel it reaches — the coronary ostium (classically the RCA, an inferior STEMI), arch vessels (stroke, arm ischaemia), coeliac, SMA and IMA (mesenteric ischaemia, often painless with a rising lactate), renal arteries (acute kidney injury, refractory hypertension), iliac and femoral arteries (the cold leg — the 6 Ps), and intercostal and lumbar arteries (paraplegia). Retrograde extension into the root distorts the valve — aortic regurgitation in up to 50 percent of type A — or ruptures into the pericardium as tamponade.[1]

True versus false lumen decides who ischaemias. As the false lumen pressurises, the flap bows into the true lumen (dynamic obstruction), or seats across an ostium (static obstruction). A widely patent, pressure-equalised false lumen can be silent; a thrombosed false lumen pressing on a pressurised true lumen can ischaemie a kidney even when the dissection looks small.[1]

The pain that names itself — and the bedside signs that betray it

The pain is sudden, severe, tearing or sharp, maximal at the first second, and it moves. Pain is the dominant symptom in 85 to 95 percent of cases, and its profile is the discriminator from myocardial ischaemia, which crescendos. Patients clock the moment it began — "like a switch was thrown". IRAD shows sharp is actually commoner than tearing; a migrating pain that tracks the dissection line is the single most suggestive feature.[1][2]

Location follows anatomy. Anterior chest pain points to an ascending tear; interscapular or back pain to the descending; abdominal, hip or leg pain means the flap has run distally. Syncope in 5 to 10 percent is the most ominous single feature — usually tamponade — and demands a bedside echo, not a faint work-up.[1]

Run the bedside checklist in 60 seconds, every time.[1]

• BP differential — over 20 mmHg between the arms, or between arm and leg, is the classic clue. Document the HIGHER arm BP as the titration target — the dissection may have taken the lower one offline.
• Pulse deficit — an absent or diminished carotid, brachial, radial or femoral pulse is specific for branch involvement; chart pulses serially.
• New aortic regurgitation murmur — a soft diastolic decrescendo at the left sternal border; acute severe AR may be surprisingly quiet.
• Neurological deficit — stroke (often right-sided, carotid malperfusion), paraplegia (intercostal loss), Horner syndrome at the isthmus.
• Tamponade physiology — Beck's triad of hypotension, raised JVP and muffled heart sounds with chest or back pain.[1]

The 6 Ps name a malperfused limb in one breath: Pain, Pallor, Pulselessness, Paraesthesia, Paralysis, Perishing-cold. A pulseless cold leg beside tearing chest pain is a type B dissecting into the iliac axis until proven otherwise — call vascular and prepare for TEVAR.[1]

The dissection-MI trap — check before you lyse

The single most dangerous misdiagnosis in emergency medicine is lysing a type A dissection that has malperfused a coronary ostium. Coronary-ostial involvement, usually the RCA, produces an abnormal ECG and troponin — sometimes a frank inferior STEMI — and the reflex to thrombolyse, anticoagulate or load antiplatelets then haemorrhages the dissection into the pericardium, mediastinum or pleura.[1][3]

The classic trap: everyone reaches for the tenecteplase when the ECG shows inferior STEMI; the patient actually has a type A dissection with RCA-ostial malperfusion. Two bedside moves before lysis in any atypical ACS — bilateral arm BPs and a portable CXR for a widened mediastinum — catch most of these. CT aortogram before lysis is the correct reflex when the story does not fit.[3]

Name the other killers in the chest-pain differential and one discriminator each.[1]

• Pulmonary embolism — pleuritic, hypoxic, right-heart strain on echo; dissection radiates to the back with a BP differential.
• Tension pneumothorax — unilateral hyper-resonance and tracheal deviation; decompression reverses it. A left haemothorax in dissection is serosanguineous, not air.
• Acute pericarditis — pleuritic, relieved sitting forward, diffuse concave ST elevation with PR depression; beware the dissection-induced effusion that mimics it.
• Boerhaave syndrome — vomiting then pain, subcutaneous emphysema; Mackler triad. Contrast swallow confirms.
• Ruptured or symptomatic aortic aneurysm — CT aortogram from neck to pelvis; the thoracic dissection and the AAA can coexist.
• Acute pancreatitis, renal colic, mesenteric ischaemia — dissection malperfusing the coeliac axis or a renal artery can present as any of these; a rising lactate and refractory hypertension are the tell.[1]

Imaging — CT for the stable, TEE for the crashing

The imaging choice is dictated by haemodynamics, not by which scanner is nearest. A stable patient gets a CT aortogram; a crashing patient gets a bedside TEE in theatre; the young, pregnant or renally impaired patient gets MRI.[1][3]

[1] [3] [4]

Adjunct bloods support but never replace imaging. Troponin is often mildly raised from coronary malperfusion or shock — a raised troponin must not delay the scan. Creatinine plans the contrast; lactate tracks mesenteric and limb malperfusion. Genetic testing (FBN1, TGFBR1/2, SMAD3, COL3A1, ACTA2) is for the under-40s and the syndromic.[1]

Rate before pressure — the anti-impulse ladder

The order is fixed: rate, then pressure, then pain — never the other way round. Dropping the pressure before the rate unleashes reflex tachycardia that raises dP/dt and drives the flap forward. Begin all three within 15 minutes of a credible suspicion, before imaging, and run them in parallel with the surgical referral.[1][3]

• Heart rate under 60 bpm — first, always. Rate-control lowers dP/dt, the principal driver of propagation, which is why a beta-blocker precedes any vasodilator.
• SBP 100 to 120 mmHg — once the rate is controlled, titrate to the lowest pressure that preserves end-organ perfusion (MAP 60 to 70).
• Pain control with morphine 5 to 10 mg IV — pain drives tachycardia and hypertension; control the pain to control the pressure. Avoid intramuscular injections that obscure imaging windows.[1]

The drug ladder, top to bottom — every dose is examinable verbatim.[1]

• Esmolol 500 mcg/kg IV bolus over 1 minute, then 50 to 200 mcg/kg/min — first-line; ultra-short-acting and titratable, reversible in minutes if the diagnosis changes or the pressure collapses.
• Labetalol 20 to 80 mg IV every 10 minutes (max 300 mg) or 0.5 to 2 mg/min infusion — combined alpha and beta blocker; caution in acute heart failure or severe asthma.
• Metoprolol 5 mg IV every 5 minutes up to 15 mg — pure beta-1 blocker when esmolol or labetalol is unavailable.
• Nicardipine 5 mg/hour, titrate by 2.5 mg every 5 to 15 minutes to 15 mg/hour — pure arteriolar vasodilator; add only after rate control; excellent when a beta-blocker is contraindicated.
• Sodium nitroprusside 0.25 to 10 mcg/kg/min — titratable arteriovenous dilator; only after rate control, with an arterial line; watch for cyanide toxicity in renal or hepatic failure.
• GTN 5 to 200 mcg/min — venodilator with arterial effects at high dose; useful adjunct, especially with ischaemic chest pain, but tachyphylactic within hours.
• Morphine 5 to 10 mg IV (or fentanyl 50 to 100 mcg) — for analgesia.[1]

[1] [3]

Surgery for A, impulse-control for B

Type A is an open operation; type B is medical unless it is complicated. That fork is the whole definitive-management question, and it is settled on the CT within minutes of arrival.[1]

[1] [3]

The elective surgery thresholds are the other half of the question. Operate on an asymptomatic ascending aorta at over 55 mm in most patients, over 50 mm in Marfan, bicuspid aortic valve or a positive family history, and over 42 to 45 mm in Loeys-Dietz — the syndrome that dissects at small diameters.[1][3]

TEVAR numbers to quote in a viva. Thoracic endovascular repair closes the entry tear, depressurises the false lumen and restores true-lumen flow, with a 30-day mortality of about 5 to 10 percent and a paraplegia rate of 2 to 5 percent — lower than open repair. Insert a cerebrospinal fluid drain for extensive coverage or prior abdominal aortic surgery, and run permissive hypertension post-deployment to protect the cord.[1][3]

Complications arrive on a clock — learn the timing.[1]

[1]

Named traps and preventable deaths

Four traps account for most of the preventable mortality in this disease; name them by name. Each is a way a patient with a salvageable dissection dies from the treatment rather than the tear.[1][3]

• The thrombolysis trap — lysing a type A dissection with coronary-ostial malperfusion read as an inferior STEMI. Bilateral arm BP and a CXR before lysis.
• The pericardiocentesis trap — draining a tamponade caused by dissection. The needle drops the pressure, the tear re-enters or ruptures, and the patient exsanguinates. Go to theatre, not the wire.
• The cocaine beta-blocker trap — pure beta-blockade in a sympathomimetic dissection leaves unopposed alpha vasoconstriction and drives the pressure higher. Benzodiazepines first, then phentolamine 1 to 5 mg IV or labetalol.
• The vasodilator-before-rate trap — nicardipine or nitroprusside given before the rate is controlled reflex-tachycardias the patient and propagates the flap. Rate, then pressure.[1]

Two more errors worth naming. Do not chase a falsely low BP with IV fluids in tamponade from dissection — resuscitate as for obstructive shock and go to theatre. And in cardiac arrest with known dissection, chest compressions are likely ineffective and may extend the tear; survival is anecdotal.[1]

The situations that bend the algorithm

Connective-tissue disease dissects younger, smaller, and more aggressively. Marfan (FBN1) is the archetypal type A of the young; operate at root over 50 mm, or earlier with family history of dissection, rapid growth or planned pregnancy. Loeys-Dietz dissects at over 42 to 45 mm. Vascular Ehlers-Danlos (COL3A1) makes every artery fragile and surgery treacherous.[1][3]

Bicuspid aortic valve carries a 5 to 10 times higher dissection risk. The surgery threshold sits at over 55 mm, or over 50 mm with family history, rapid growth over 5 mm a year, or severe valve dysfunction; surveillance echo every 2 to 5 years, annually over 45 mm.[1]

Pregnancy concentrates risk in the third trimester and first six weeks postpartum — about half of dissections under 40 in women are pregnancy-associated. Run a multidisciplinary delivery decision; for type A with a viable fetus, Caesarean under general anaesthesia then aortic repair. First-line impulse-control is labetalol, with nifedipine or methyldopa as second-line; ACE inhibitors, ARBs and nitroprusside are contraindicated. Pregnancy is generally safe with a root under 45 mm.[1]

Cocaine and methamphetamine dissection is usually descending, in young men. Give benzodiazepines first for agitation and pressure; avoid pure beta-blocker monotherapy (unopposed alpha) — add phentolamine 1 to 5 mg IV or use labetalol, with nitroprusside after rate control.[1]

Trauma, iatrogenic injury and the elderly close the list. Deceleration shears the isthmus (about 80 percent of blunt aortic injury) — TEVAR is first-line in the stable patient. Catheter-induced dissection during angiography or TAVR may be sealed with a covered stent in the lab. The over-80s present atypically — painless, syncopal, stroke-like — and surgery or TEVAR is still indicated in the selected.[1][3]

Prognosis, disposition and lifelong surveillance

Type A lives or dies on the speed of the operation. Untreated, about 50 percent are dead at 48 hours and 75 percent at 2 weeks; emergency open repair carries an operative mortality of 15 to 25 percent across IRAD and the 2022 ACC/AHA, falling toward 10 to 15 percent in uncomplicated cases at high-volume aortic centres. Prognosis worsens with tamponade, shock, stroke and malperfusion (Penn Ac and Ad).[1][2][3]

Type B does well when it stays uncomplicated and badly when it malperfuses. Uncomplicated, medically managed type B has the best long-term outlook — roughly 80 percent alive at 5 years. Complicated type B treated medically carries about 25 to 30 percent mortality; TEVAR brings the 30-day figure back toward 5 to 10 percent. Mortality drivers are renal failure, malperfusion, age and female sex.[1][3]

Disposition follows the fork: type A to the cardiac surgical theatre (transfer on impulse-control if aortic surgery is not on site), uncomplicated type B to HDU or ICU, complicated type B to the TEVAR suite or hybrid theatre. Every survivor enters a lifelong surveillance programme.[1]

• Imaging — CT aortogram at discharge, 1 month, 6 months, 12 months, then annually; echocardiography for valve function after root or valve work.
• Blood pressure — chronic SBP target under 130 mmHg; bisoprolol 5 to 10 mg daily, amlodipine 5 to 10 mg daily, losartan 50 to 100 mg daily for connective-tissue disease.
• Activity — heavy lifting avoided; cardiac rehabilitation after sternotomy; family screening of first-degree relatives in hereditary disease.[1]

Evidence and regional practice

Two guidelines and one registry frame the entire topic.[1][3]

[2] [4]

The 2022 ACC/AHA aortic-disease guideline (Isselbacher et al.) is the dominant North American reference, superseding its 2010 predecessor, and the 2014 ESC guideline (Erbel et al.) is the European counterpart — both converge on anti-impulse therapy before definitive management, immediate surgery for type A, beta-blockade in connective-tissue aortic ectasia, and first-degree-relative screening.[1][3]

[1] [3]

Exam pearls — the mantra and the memory hooks

The mantra for the whole topic: rate before pressure, surgery for A, impulse-control for B. If you remember nothing else, remember that one line and the four named traps, and you will pass the stem.[1][3]

• AAS = dissection + IMH + PAU — shared pathophysiology and resuscitation, differing thresholds.
• Stanford A = ascending = theatre; Stanford B = descending = medical. DeBakey I and II equal A; III equals B.
• Pain = sudden, severe, tearing or sharp, maximal at onset, migrating. Painless in 5 to 15 percent (elderly, diabetic, stroke, syncope).
• Bedside: BP differential over 20 mmHg, pulse deficit, new AR murmur, neurological deficit, tamponade. Document the higher-arm BP.
• Anti-impulse before imaging if suspicion is credible: HR under 60, SBP 100 to 120, morphine 5 to 10 mg, all within 15 minutes.
• Imaging: CT aortogram if stable; TEE if unstable; MRI if young, pregnant or renally impaired; D-dimer and ADD-RS to rule out the low-risk.
• Type A options: tube graft, Bentall, David valve-sparing root, hemiarch, total arch with frozen elephant trunk.
• Type B: 75 percent stabilise medically; TEVAR for malperfusion, rupture, refractory pain, expansion, uncontrolled hypertension; CSF drain for high-risk coverage.
• Surveillance: CT aortogram at discharge, 1 month, 6 months, 12 months, then annually; chronic SBP under 130 mmHg.[1][3]

Ward-round test

A 60-year-old hypertensive man, tearing chest pain to the back, right-arm BP 196/108 and left 150/90, absent left radial pulse. First drug, first test?

Type A until proven otherwise. Start esmolol 500 mcg/kg IV bolus then 50 to 200 mcg/kg/min to drive the rate under 60 — before imaging — then add nicardipine 5 mg/hour titrating to 15 mg/hour for SBP 100 to 120, and morphine 5 to 10 mg IV. Send a CT aortogram (bedside TEE if he destabilises) and call cardiothoracic surgery now. Do not thrombolyse the ECG whatever it shows.[1][3]

Inferior STEMI on the ECG of a tearing-chest-pain patient — lyse or scan?

Scan first; lysis may kill him. Tearing pain with an inferior STEMI is a type A dissection malperfusing the right coronary ostium until the CT proves otherwise. Check bilateral arm BP and a portable CXR for a widened mediastinum, and get the CT aortogram before any thrombolytic, heparin or antiplatelet load.[1][3]

Type A dissection, BP 76/40, raised JVP, muffled heart sounds — pericardiocentesis?

No — go to theatre. This is tamponade from intrapericardial rupture of the dissection. Pericardiocentesis drops the intrapericardial pressure, the tear re-enters or ruptures, and the patient exsanguinates. Resuscitate as for obstructive shock and transfer straight to the cardiac surgical centre on impulse-control; controlled pericardiocentesis is only a rare bridge if theatre is hours away.[1]

Uncomplicated type B dissection, day 3 on HDU, pain-free, HR 58, SBP 118. Plan from here?

Medical success — step down and start the surveillance clock. About 75 percent of uncomplicated type B stabilise like this. Convert to oral bisoprolol 5 to 10 mg, amlodipine 5 to 10 mg, losartan 50 to 100 mg (losartan especially for connective-tissue disease), arrange CT aortogram at discharge, 1 month, 6 months, 12 months, then annually, and target a chronic SBP under 130 mmHg. Call for TEVAR only if malperfusion, rupture, refractory pain, expansion or uncontrolled hypertension develops.[1][3]

References

1. [1]Erbel R, Aboyans V, Boileau C, et al. [2014 ESC Guidelines on the diagnosis and treatment of aortic diseases] Kardiol Pol, 2014.PMID 25524604
2. [2]Pape LA, Awais M, Woznicki EM, et al. Presentation, Diagnosis, and Outcomes of Acute Aortic Dissection: 17-Year Trends From the International Registry of Acute Aortic Dissection J Am Coll Cardiol, 2015.PMID 26205591
3. [3]Isselbacher EM, Preventza O, Hamilton Black J 3rd, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines Circulation, 2022.PMID 36322642
4. [4]Asha SE, Miers JW. A Systematic Review and Meta-analysis of D-dimer as a Rule-out Test for Suspected Acute Aortic Dissection Ann Emerg Med, 2015.PMID 25805111
5. [5]Advani A, Kelly DJ, Cox AJ, et al. The (Pro)renin receptor: site-specific and functional linkage to the vacuolar H+-ATPase in the kidney Hypertension, 2009.PMID 19546380
6. [6]Soloviev AE [Acquired internal intestinal fistulae in children] Khirurgiia (Mosk), 2020.PMID 33301259