Acute Aortic Syndromes — Dissection

📘 1 · Washington Manual of Critical Care

The Great Masquerader — Think of It to Diagnose It

Acute aortic dissection begins with an intimal tear that lets blood track into the media, creating a false lumen that can propagate, rupture, or shear off branch vessels. The classic presentation — sudden, severe, tearing or ripping chest or interscapular pain, maximal at onset — is often incomplete, and the dissection masquerades as a myocardial infarction, a stroke, an acute abdomen or a painful limb depending on which branch is compromised. The single anatomical fact that governs everything is where the dissection involves the aorta: if the ascending aorta is involved, it is a surgical emergency.

Summarised from the Washington Manual of Critical Care — Aortic Dissection.

🔴 Stanford A (ascending)

Involves ascending aorta (± arch/descending)
Surgical emergency — risk of tamponade, aortic regurgitation, coronary/cerebral malperfusion, rupture
Untreated mortality ~1–2% per hour early

🔵 Stanford B (descending)

Begins distal to the left subclavian (no ascending involvement)
Medical therapy first (impulse control)
Intervention (TEVAR/surgery) for complications: malperfusion, rupture, refractory pain/hypertension, rapid expansion

(DeBakey: I = ascending + arch + descending; II = ascending only; III = descending only. Stanford A = DeBakey I/II; Stanford B = DeBakey III.)

📗 2 · Marino's The ICU Book, 5th Edition (2025)

Impulse Control — Slow the Rate Before You Drop the Pressure

Medical management of dissection is aimed at reducing the force with which each cardiac ejection strikes the aortic wall — the "impulse", proportional to both the rate of rise of pressure (dP/dt) and the heart rate. The cardinal rule is to give a beta-blocker first to slow the heart, and only then add a vasodilator to lower the blood pressure. Reversing that order — dropping the pressure with a vasodilator alone — triggers a reflex tachycardia that increases dP/dt and can extend the dissection.

Summarised from Marino PL. The ICU Book, 5th Ed — Aortic Dissection.

🗺 Anti-impulse therapy — the order is the point

GoalReduce aortic wall stress: lower dP/dt and heart rate

Step 1IV β-blocker (esmolol/labetalol) → target HR ≤ 60/min FIRST

Step 2Then add a vasodilator (GTN, nicardipine, nitroprusside) → target SBP 100–120 mmHg

Doβ-block → then vasodilate; adequate analgesia (pain drives BP)

Don'tVasodilator alone → reflex tachycardia → ↑ dP/dt → extends dissection

📗 Marino — the pressure target is not always "low"

Aim SBP 100–120 mmHg (lowest tolerated maintaining organ perfusion) once rate-controlled — but be guided by malperfusion: if a limb, kidney, gut or brain is under-perfused, over-lowering pressure worsens ischaemia.
Hypotension in dissection is ominous — think tamponade (type A), aortic rupture, or severe aortic regurgitation. It is not a signal to relax; it usually means a catastrophe and the need for the operating theatre.
Measure BP in both arms — a pseudo-hypotension from subclavian involvement can mislead; treat to the higher, true central pressure.

📋 3 · Diagnosis & Treatment

Evidence-Based Management

Diagnose with CT angiography (in the stable patient) ESC/AHA

CT angiography of the whole aorta is the first-line test — fast, available, and it defines the entry tear, extent, branch involvement and complications. Transoesophageal echo (TOE) is the test of choice in the unstable patient who cannot leave the resus room/theatre (also assesses AR and tamponade). MRI is accurate but usually too slow for the acute setting. A D-dimer that is negative makes acute dissection unlikely in low-risk patients (with the aortic dissection detection risk score), but a positive D-dimer is non-specific — imaging decides.

Type A → emergency surgery STRONG

Any ascending-aorta involvement is a surgical emergency (open repair) — mortality rises ~1–2% per hour untreated. While arranging theatre: impulse control (β-block then vasodilator), analgesia, and manage complications (AR, tamponade — remember do not do a routine full pericardiocentesis, see Tamponade). Cross-match blood and involve cardiac surgery immediately.

Type B → medical first, intervene for complications STRONG

Uncomplicated Stanford B is managed medically with strict impulse control and pain relief in a monitored/ICU setting. Complicated type B — malperfusion (limb/renal/mesenteric/spinal), rupture or impending rupture, refractory pain or refractory hypertension, or rapid aortic expansion — needs intervention, usually thoracic endovascular aortic repair (TEVAR). Ongoing surveillance imaging is required as false lumens can expand over time.

Watch for the branch-vessel catastrophes (malperfusion)

The false lumen can occlude any branch: coronary (inferior MI — do not thrombolyse chest pain until dissection excluded), carotid (stroke), spinal (paraplegia), renal (AKI, renovascular hypertension), mesenteric (gut ischaemia — high lactate, pain out of proportion), and iliac/limb (pulse deficit, acute limb ischaemia). A pulse deficit or new neurology dramatically raises the pre-test probability of dissection.

🇮🇳 Indian Context

Uncontrolled chronic hypertension is the dominant risk factor and is highly prevalent and frequently untreated in India — the commonest substrate for dissection. Also consider younger patients with connective-tissue disease (Marfan, Loeys-Dietz), bicuspid aortic valve, pregnancy (third trimester/peripartum), and Takayasu arteritis, which is comparatively common in South Asia. The critical pitfalls where imaging access is limited: do not thrombolyse an "inferior MI" or treat a "stroke" with tPA without considering dissection, and always examine all four limb pulses and check BP in both arms. Type A dissection needs urgent transfer to a centre with cardiac surgery — start impulse control and analgesia and move fast. Esmolol/labetalol, GTN and nitroprusside are all available.

💊 4 · Drug Doses

Impulse-Control Pharmacology

Drug	Role	Dose	Notes
Esmolol	Rate control (Step 1) — titratable	Load 0.5 mg/kg, infusion 50–200 µg/kg/min	Ultra-short acting; ideal first agent, target HR ≤60
Labetalol	Combined α/β — rate + some BP	20 mg IV, repeat/boluses, or infusion	Convenient single agent; still β-block first
GTN (nitroglycerin)	Vasodilator (Step 2)	IV infusion, titrate to SBP 100–120	Add only AFTER β-blockade
Nicardipine / clevidipine	Vasodilator (Step 2)	IV infusion, titrated	Smooth arterial BP control
Sodium nitroprusside	Vasodilator (Step 2)	0.3–2 µg/kg/min, titrate	Never without β-blocker (reflex tachycardia ↑ dP/dt); cyanide risk on prolonged use
Opioid analgesia	Pain control (reduces sympathetic drive)	e.g. morphine/fentanyl titrated	Pain drives tachycardia & hypertension — treat it well
Verapamil/diltiazem	Rate control if β-blocker contraindicated	IV, titrated	Alternative for asthma/β-blocker intolerance

🗺 5 · Clinical Flowchart

Suspected Dissection — Stabilise & Stratify

Suspect & resuscitate

Sudden tearing chest/back pain, pulse deficit, BP differential, new AR murmur, neurology
Two large IVs, cross-match, analgesia; BP in both arms; ECG (don't reflexively thrombolyse)

Impulse control — β-block first, then vasodilate

Esmolol/labetalol to HR ≤60, then GTN/nicardipine to SBP 100–120
Guided by malperfusion — don't over-lower if organs are ischaemic

Image to classify

Stable → CT angiography of whole aorta; unstable → TOE in resus/theatre
Define Stanford A vs B, entry tear, branch involvement, complications

Direct definitive therapy

Type A → emergency cardiac surgery
Type B → medical; TEVAR/surgery if complicated (malperfusion, rupture, refractory pain/HTN, expansion)

Monitor complications & follow up

Watch for tamponade, AR, malperfusion, rupture; ICU monitoring of pain/BP/organ perfusion
Lifelong BP control & surveillance imaging; screen for connective-tissue disease in the young

⚠️ 6 · Common Mistakes

Common Mistakes in Aortic Dissection

❌ Mistake 1 — Vasodilator before beta-blocker

Dropping BP with a vasodilator alone provokes reflex tachycardia, raising dP/dt and extending the dissection. Always β-block to slow the rate first, then vasodilate.

❌ Mistake 2 — Thrombolysing a dissection-related "MI" or "stroke"

Dissection can occlude a coronary (inferior MI) or carotid (stroke). Thrombolysis is catastrophic. Consider dissection before giving tPA in the right context.

❌ Mistake 3 — Missing it because the pain is atypical

Dissection masquerades as MI, acute abdomen, limb or spinal ischaemia. Pulse deficits, BP differentials and migrating pain should trigger imaging.

❌ Mistake 4 — Ignoring hypotension as "not severe"

Hypotension in dissection usually means tamponade, rupture or severe AR — a catastrophe requiring theatre, not reassurance.

❌ Mistake 5 — Over-lowering BP with malperfusion

If a limb, kidney, gut or brain is ischaemic, excessive BP reduction worsens end-organ injury. Titrate to the lowest pressure that preserves perfusion.

❌ Mistake 6 — Delaying surgical referral in type A

Type A mortality is ~1–2% per hour. Impulse control is a bridge — the definitive treatment is immediate surgery; call cardiac surgery at once.

🎓 7 · Exam Pearls — DrNB / PDCC / IFCCM / EDIC

Exam Pearls

Q: Stanford A vs B — what decides management?
A involves the ascending aorta → emergency surgery; B is distal to the left subclavian → medical first, intervene (TEVAR) for complications.

Q: Why beta-blocker before vasodilator?
Impulse control needs both a lower dP/dt and a slower rate; a vasodilator alone causes reflex tachycardia that increases wall stress and extends the dissection.

Q: What are the haemodynamic targets?
HR ≤60/min, then SBP 100–120 mmHg (lowest tolerated preserving organ perfusion), with good analgesia.

Q: Investigation of choice?
CT angiography of the whole aorta in the stable patient; TOE for the unstable patient who cannot be moved.

Q: What does hypotension in dissection signify?
Tamponade (type A), aortic rupture, or severe acute aortic regurgitation — an ominous sign needing theatre.

Q: Why check BP in both arms?
Subclavian/innominate involvement can cause a falsely low reading in one arm — treat to the true central (higher) pressure.

Q: Common Indian risk factors?
Uncontrolled hypertension (dominant), connective-tissue disease/bicuspid valve in the young, pregnancy, and Takayasu arteritis.

📚 8 · References

References

Isselbacher EM, Preventza O, Hamilton Black J, et al. (ACC/AHA). 2022 Guideline for the Diagnosis and Management of Aortic Disease. Circulation. 2022;146:e334–e482.
Erbel R, Aboyans V, Boileau C, et al. (ESC). 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases. Eur Heart J. 2014;35:2873–2926.
Hagan PG, Nienaber CA, Isselbacher EM, et al. (IRAD). The International Registry of Acute Aortic Dissection. JAMA. 2000;283:897–903.
Nienaber CA, Clough RE. Management of acute aortic dissection. Lancet. 2015;385:800–811.
Marino PL. The ICU Book, 5th Edition. Aortic Dissection. Wolters Kluwer; 2025.
Washington Manual of Critical Care, 4th Edition. Kollef MH, Witt CA (eds). Aortic Dissection. Wolters Kluwer; 2023.