Aortic dissection

Overview

A life-threatening emergency caused by an intimal tear allowing blood to track between aortic wall layers, creating a false lumen. Classification drives management.

Risk Factors

Hypertension - most important modifiable risk factor
Marfan syndrome / connective tissue disorders
Bicuspid aortic valve
Coarctation of the aorta
Male sex
Age 60s-70s
Pregnancy
Pre-existing aortic aneurysm

Classification

Stanford classification
FeatureType AType B
Ascending aorta involved?YesNo
Proportion of cases60-70%30-40%
Definitive treatmentEmergency surgeryMedical management (BP/HR control)
Acute mortality (untreated)~1-2% per hour~10% in-hospital

Feature	Type A	Type B
Ascending aorta involved?	Yes	No
Proportion of cases	60-70%	30-40%
Definitive treatment	Emergency surgery	Medical management (BP/HR control)
Acute mortality (untreated)	~1-2% per hour	~10% in-hospital

Presentation

•Chest pain - sudden-onset, severe, tearing/ripping quality; maximal at onset (distinguishes from ACS where pain builds gradually)

•Back pain - interscapular radiation suggests descending aorta involvement

•BP differential - >20 mmHg between arms, or absent radial pulse; due to subclavian artery compromise

•Aortic regurgitation murmur - early diastolic at left sternal edge; Type A complication from annular distortion

•Hypertension - present in majority at onset due to catecholamine surge; paradoxical hypotension = red flag for tamponade or rupture

•Neurological deficits - stroke/TIA from carotid malperfusion (Type A); paraplegia from spinal artery involvement (Type B)

•Syncope - Type A; due to tamponade or cerebral malperfusion

💡
Aortic dissection is the great mimic - it can present as ACS, stroke, acute abdomen, or limb ischaemia. Always consider it in severe sudden-onset pain with hypertension, Marfan habitus, or pulse/BP differential.

Investigations

🏆 Gold standard

•CT angiography of the aorta (with contrast, aortic root to iliac bifurcation) - identifies intimal flap, true/false lumens, branch vessel involvement, pericardial effusion

🥇 First-line

•ECG - often normal (key negative distinguishing from STEMI); LVH if hypertensive background; ST changes if coronary ostia involved

•chest X-ray - widened mediastinum (>8 cm), blurred aortic knuckle, left-sided pleural effusion; normal CXR does not exclude dissection

•troponin - usually normal or only mildly raised; helps differentiate from primary ACS but does not exclude dissection

•D-dimer - negative result in low-probability cases has high negative predictive value; positive is non-specific

🥈 Second-line

•TOE - highly sensitive/specific; use in haemodynamically unstable patients who cannot go for CT; assesses AR and pericardial effusion

•TTE - bedside tool for pericardial effusion, tamponade, and AR in suspected Type A; limited full aortic visualisation

Differential Diagnosis

Key differentials for acute chest pain
DiagnosisDistinguishing features
ACSPain builds gradually; significant troponin rise; ST changes on ECG
Pulmonary embolismPleuritic pain, dyspnoea, hypoxia; different risk factors; CTPA differentiates
Boerhaave syndromePreceded by vomiting; surgical emphysema; pneumomediastinum on CXR
Cardiac tamponadeBeck's triad (hypotension, muffled heart sounds, raised JVP); can be a complication of Type A rather than a primary diagnosis

Diagnosis	Distinguishing features
ACS	Pain builds gradually; significant troponin rise; ST changes on ECG
Pulmonary embolism	Pleuritic pain, dyspnoea, hypoxia; different risk factors; CTPA differentiates
Boerhaave syndrome	Preceded by vomiting; surgical emphysema; pneumomediastinum on CXR
Cardiac tamponade	Beck's triad (hypotension, muffled heart sounds, raised JVP); can be a complication of Type A rather than a primary diagnosis

Management

•All patients: IV access, continuous monitoring (BP, HR, urine output), HDU/ICU setting

•Analgesia: morphine IV, titrated to pain

•Heart rate control (first): IV esmolol (short-acting beta-blocker) - target HR <60 bpm; reduces dP/dt and prevents dissection propagation

•Blood pressure control (after HR controlled): target SBP 100-120 mmHg; vasodilators alone cause reflex tachycardia - always control HR first

•Type A: emergency cardiothoracic surgery

•Type B (uncomplicated): medical management - BP and HR control

🚨
If a patient presents with apparent STEMI and any feature suggesting aortic dissection (tearing pain, BP differential, wide mediastinum), do NOT give thrombolysis or anticoagulation until dissection is excluded - thrombolysing a Type A dissection is potentially fatal.

Complications

•Aortic rupture - haemopericardium (tamponade) or haemothorax; immediately life-threatening

•Cardiac tamponade - Type A complication; Beck's triad

•Acute aortic regurgitation - Type A; annular distortion; acute pulmonary oedema and haemodynamic collapse

•Stroke/TIA - carotid malperfusion; up to 10% of Type A dissections

•Paraplegia - spinal artery (artery of Adamkiewicz) occlusion; more common in Type B

•Acute kidney injury - renal artery malperfusion

•Mesenteric ischaemia - bowel infarction; contributes to multiorgan failure