Aortic dissection

An aortic dissection is a tear in the inner layer of the aorta that leads to a progressively growing hematoma in the intima-media space. Risk factors for aortic dissection include age and hypertension. Patients typically present with sudden onset severe pain radiating into the chest, back, or abdomen. A widened mediastinum on chest x-ray is characteristic of the diagnosis. The diagnosis is usually confirmed with CT angiogram in stable patients and transesophageal echocardiography (TEE) in unstable patients. Treatment options range from conservative measures (e.g., blood pressure optimization) to surgery (aortic stent graft), depending on the localization and severity of the dissection. Complete occlusion of branching vessels and aortic rupture are common complications. Even with treatment, mortality rates associated with aortic dissection are high.

• Incidence
  • Peak incidence: 60–80 years of age ^[1]
  • In patients with connective tissue disease: peak incidence 30–50 years of age ^[2]
• Sex: ♂ > ♀ ^[1]
• Localization ^[3]
  • Ascending aorta: ∼ 65% of cases
  • Descending aorta, distal to the left subclavian artery: 20% of cases
  • Aortic arch: 10% of cases
  • Abdominal aorta: 5% of cases

Epidemiological data refers to the US, unless otherwise specified.

• Acquired
  • Hypertension (most common risk factor)
    • Approx. 70% of patients with aortic dissection have elevated blood pressure, which can lead to propagation of the dissection and increases the risk of rupture.
    • Exception: In patients < 40 years of age, less than 40% of cases are due to hypertension.
  • Trauma; , e.g., deceleration injury in a motor vehicle collision, or iatrogenic injury during valve replacements or graft surgery (traumatic aortic dissection)
  • Vasculitis; with aortic involvement (e.g., syphilis, Takayasu arteritis)
  • Use of amphetamines and cocaine
  • Third-trimester pregnancy (or early postpartum period)
  • Atherosclerosis
• Congenital
  • Connective tissue disease (Marfan syndrome, Ehlers-Danlos syndrome)
  • Bicuspid aortic valve (e.g., in Turner syndrome)
  • Coarctation of the aorta

There are two classifications of aortic dissection to help direct management. Stanford classification groups dissections by whether the ascending or descending aorta is involved. DeBakey classification categorizes dissections according to their origin and extent.

Stanford classification ^[4]

• Stanford type A aortic dissection: any dissection involving the ascending aorta (defined as proximal to the brachiocephalic artery), regardless of origin
  • Can extend proximally to the aortic valve and distally to the descending aorta
  • Generally requires surgery
  • Complications include aortic regurgitation and cardiac tamponade.
• Stanford type B aortic dissection: any dissection not involving the ascending aorta
  • Descending aorta; originating distal to the left subclavian artery
  • Most cases can be managed with medical therapy (e.g., beta blockers, vasodilators).

Stanford A = Affects ascending aorta; Stanford B = Begins beyond brachiocephalic vessels

DeBakey classification (rarely used) ^[4]

• Type I
  • Dissections originate in the ascending aorta and continue to at least the aortic arch but typically as far as the descending aorta.
  • Generally requires surgery
• Type II
  • Dissections originate in, and are restricted to, the ascending aorta.
  • Generally requires surgery
• Type III
  • Dissections originate in the descending aorta and most often extend distally.
  • Most cases can be managed by medical therapy.
  • Can be further subdivided into:
    • Type IIIa: limited to the descending thoracic aorta above the level of the diaphragm
    • Type IIIb: extends below the diaphragm

• Common anatomic sites of origin
  • Above the aortic root
  • Aortic arch
  • Distal to left subclavian artery
• Transverse tear in the aortic intima (“entry”) → blood enters the media of the aorta and forms a false lumen in the intima-media space ; → hematoma forms and propagates longitudinally downwards ^[5]
  • Rising pressure within the aortic wall → rupture
  • Occlusion of branching vessels; (e.g., coronary arteries, arteries supplying the brain, renal arteries, arteries supplying the lower limbs) → ischemia in the affected areas (see “Complications” below)
  • A second intimal tear may result in a “reentry” into the primary aortic lumen.

• Sudden and severe tearing/ripping pain
  • Location
    • Anterior chest (ascending) or back (descending)
    • Interscapular or retrosternal pain
    • Neck and jaw
    • Abdomen or periumbilical, colicky pain
  • Character: migrates as the dissected wall propagates caudally
• Hypertension or hypotension
• Asymmetrical blood pressure and pulse readings between limbs
• Wide pulse pressure ^[6]
• Syncope, diaphoresis, confusion, or agitation

The optimal management approach depends on the clinical presentation, e.g., acute aortic syndrome. ^{[4][7][8][9][10]}

Consult cardiothoracic surgery for all patients with highly suspected or confirmed aortic dissection, regardless of Stanford classification. ^[4]

Hemodynamically unstable patients ^{[4][7][11][12]}

Patients may present with shock or cardiac arrest due to complications of aortic dissection, e.g., aortic rupture, acute coronary syndrome, cardiac tamponade, acute aortic regurgitation.

• Resuscitate with ACLS and/or stabilize using ABCDE approach.
• Perform simultaneous bedside investigations, e.g., ECG, portable CXR, and/or bedside echocardiography (TEE, TTE, or POCUS) based on availability. ^[8]
• Immediately treat life-threatening complications, e.g., immediate hemodynamic support, management of cardiac tamponade.
• Expedite surgical management.
• Consider additional consultations: e.g., cardiology, critical care
• Consider definitive imaging (e.g., CTA) if the patient is stabilized, in consultation with a specialist.
• Admit to critical care unit or transfer to OR.

An initial low blood pressure reading in a limb could be falsely low due to an intimal flap obstructing its blood supply. Confirm hypotension by measuring blood pressure in a second limb. ^[11]

Patients with critical organ dysfunction ^{[4][7][11][12]}

Aortic dissection can present as a mimic of another time-dependent life-threatening condition, e.g., ACS, CVA, or pulmonary embolism.

• Follow the management approach of the suspected condition.
  • Consider aortic dissection as a potential cause of acute ischemic stroke or STEMI
  • Rule out aortic dissection as a differential diagnosis of acute PE.
• Evaluate prior to administering thrombolytics or other invasive therapy (e.g., PCI) if time permits.
  • Do not rely on ECG alone as findings of aortic dissection can resemble those of ACS and PE.
  • Consider portable CXR to rapidly identify classic radiographic signs of aortic dissection
  • Consider including CTA in the diagnostic evaluation to rule out aortic dissection, e.g., add CTA Chest to CTA head and neck for stroke.
  • Consider bedside TEE, TTE, or POCUS to rule in aortic dissection, if this can be done without delay. ^[13]
• Treat aortic dissection if identified (see “Treatment”).

Stable patients ^{[4][7][11][12]}

Most patients (∼ 70%) with aortic dissection are stable upon initial presentation. Some may present atypically. ^[12]

• Determine pretest probability, e.g., based on clinical evaluation and/or aortic dissection detection risk score.
• Order initial investigations, e.g., CXR, ECG, laboratory studies.
• Concurrently investigate other potential causes of symptoms: See “Chest pain”, “Syncope”, and “Dyspnea.”
• Maintain a low threshold to obtain definitive imaging for aortic dissection, e.g., CTA. ^[4][7][8]
• Begin therapy based on imaging findings and Stanford classification: See “Treatment.”
• Admit to surgical ICU with close monitoring and surveillance imaging. ^[4]

Mortality from a type A aortic dissection increases by 1–2% per hour until management is initiated. Maintain a high level of clinical suspicion and order diagnostic studies early! ^[13]

Pretest probability

The following can help determine the likelihood of aortic dissection compared to other life-threatening causes with overlapping features (e.g., MI, stroke, PE).

• Red flag features accompanying chest pain: These increase the likelihood of aortic dissection. ^[12]
  • Truncal and/or neck pain
  • Neurological features
  • Syncope
  • Acute limb ischemia
• Aortic dissection detection risk score (ADD-RS): a bedside clinical tool used to assess the risk of acute aortic dissection based on high-risk conditions, pain, and examination features. ^[14]
• ADvISED tool (not externally validated): A variant clinical prediction rule that combines the ADD-RS and the D-dimer. ^[15]

Approach ^{[4][7][9][10]}

The optimal diagnostic approach depends on each individual's pretest probability, clinical presentation, and risk profile (see “Management”).

• Order ECG for all patients.
• Order laboratory studies (consider including D-dimer). ^[8]
• CXR, TTE, and POCUS are considered screening imaging and are usually only obtained as the initial study if:
  • Invasive or risky testing is not desired for low-risk patients.
  • Definitive imaging is not readily available.
  • Patients are too unstable to undergo definitive imaging. ^[13][16]
• Definitive imaging includes CTA (gold standard), TEE, and MRA and should be obtained as the:
  • Initial study for high-risk patients
  • Confirmatory study if the diagnosis remains uncertain

Definitive imaging can determine the type of lumen, location, and extent of the dissecting membrane. The identification of a false lumen on imaging is highly suggestive of aortic dissection.

D-dimer, CXR, TTE, and POCUS are not sensitive enough to reliably rule out aortic dissection. ^[8]

ECG

Findings are variable and include: ^[18]

• Normal findings
• Signs of left ventricular hypertrophy ^[11]
• Nonspecific changes, such as ST depression and T-wave changes
• ST elevation due to coronary artery occlusion ^[4]

Laboratory studies

• D-dimer: elevated levels ^[15]
• Studies to evaluate end-organ damage: e.g., troponin, BMP, lactate
• Preoperative studies: CBC, type and screen, BMP, coagulation panel

Chest x-ray (AP view) ^[19][20]

Chest x-ray is often normal.

• Classic radiographic findings of aortic dissection
  • Widened mediastinum (> 8 cm) at the level of the aortic knuckle
  • Alteration of the mediastinal contour seen on serial imaging
  • Mediastinal mass
  • Calcium sign: displacement of the intimal calcification of > 6 mm
• Additional findings: may be present
  • Double aortic contour
  • Pleural cap
  • Pleural effusion
  • Blurring of the aortic knuckle
  • Tracheal shift
  • Widening of the paratracheal stripe

Normal chest x-ray findings do not rule out aortic dissection. If clinical suspicion for acute aortic dissection persists, perform a second imaging study.

CTA chest, abdomen, and pelvis ^[4]

• Indications: stable patients, surgical planning
• Suggestive findings
  • Intimal dissection flap
  • Double lumen
  • Aortic dilatation
  • Regions of malperfusion
  • Aortic hematoma (high-attenuation)
  • Contrast leak: indicates rupture

Magnetic resonance angiography (MRA) chest, abdomen, and pelvis

• Indications: stable patients, contraindications to CTA
• Suggestive findings: similar to CT angiography

Transesophageal echocardiography (TEE)

• Indications
  • Unstable patients
  • Intraoperative visualization
  • Renal insufficiency or contrast allergy
• Findings may include:
  • Dissection flap (with differential Doppler flow)
  • Double lumen in the ascending aorta
  • Thrombosis in false lumen
  • Evidence of aortic regurgitation ^[16]
  • Pericardial effusion

For other differential diagnosis considerations, see “Differential diagnoses of acute chest pain”.

Acute aortic occlusion ^[21][22]

• Etiology
  • Aortic embolism
    • Referred to as a saddle embolus when located at the aortic bifurcation
    • Commonly caused by cardiac emboli
      • Myocardial infarction
      • Atrial fibrillation
      • Rheumatic heart disease
  • Thrombosis of atherosclerotic aorta
  • Stent or graft occlusion
  • Aortic dissection
• Clinical features: The clinical features of acute aortic occlusion are due to ischemia of the tissues distal to the level of occlusion.
  • Occlusion at aortic bifurcation: bilateral acute limb ischemia (most common presentation)
    • Limb pain
    • Pallor or cyanosis
    • Absent pulse
    • Paresthesia and paralysis
  • Occlusion above aortic bifurcation
    • Bilateral acute limb ischemia
    • Acute abdomen
    • Acute renal failure
• Diagnostics
  • CT angiography (confirmatory test)
  • Investigate the underlying cause
    • ECG
    • Echocardiography
• Treatment
  • Bilateral transfemoral embolectomy
  • Aortobifemoral bypass
  • Thrombolysis

The differential diagnoses listed here are not exhaustive.

Approach ^[4]

• Stanford A dissection: immediate surgery.
• Stanford B dissection: treat conservatively; (watchful waiting and ongoing medical therapy) unless complications occur. ^[4][23]
• Blood pressure control: essential in all patients to prevent progression of the dissection
• Supportive care

Avoid thrombolytic therapy in patients with suspected aortic dissection, e.g., for patients presenting with features of stroke or MI.

Surgical therapy ^[4]

• Indications
  • All patients with Stanford A dissection ^[4]
  • Patients with Stanford B dissection who develop complications:
    • End-organ damage (ischemia)
    • Hypotension
    • Persistent severe chest pain or hypertension
    • Propagation of dissection
    • Expanding aneurysm
    • Expanding hematoma
    • Rupture
• Procedure
  • Open surgery with the replacement of the dissection with a polyester graft implantation ^[4]
  • Endovascular treatment; with aortic stent implantation (only in type B dissections and if the open operative risk is too high) ^[4]

Ascending aortic dissection is a surgical emergency!

Medical therapy

Hypotensive patients ^[4]

• Hemodynamic support: target MAP of 70 mm Hg or euvolemia ^[4]
  • IV fluids
  • Vasopressor support: if the patient remains hypotensive ^[4][24]
    • Norepinephrine
    • Phenylephrine
    • Inotropes should be avoided as they can increase shear stress on the aortic wall through increased force of ventricular contraction.
• Identify and treat, if possible, any comorbidities that may be contributing to the hypotension
  • Severe aortic insufficiency
  • Cardiac tamponade: Consider urgent pericardial fluid drainage if the patient is unlikely to survive until surgery can be performed without intervention (See “Management of cardiac tamponade”). ^[4]
• Expedite operative management.

Avoid inotropes as they can worsen aortic wall stress.

Hypertensive patients ^[4]

• Control hypertension and heart rate: target SBP 100–120 mm Hg and HR ≤ 60 beats per minute ; ^[4][25]
  • Start with an IV beta blocker: to avoid reflex tachycardia
    • Esmolol
    • Labetalol
  • Followed by vasodilator (e.g., IV sodium nitroprusside) ^[4]
  • Contraindications to beta blockers: Start a calcium channel blocker.
    • Verapamil
    • Diltiazem
• Patients with dissection of the descending aorta who remain stable on IV treatment can be transitioned to oral medications and discharged with outpatient imaging surveillance.

Start beta blocker therapy before vasodilators to avoid reflex tachycardia!

Supportive care

Adequate treatment of pain and anxiety helps reduce sympathetic tone, which reduces blood pressure and heart rate, thereby lowering shear stress. ^[11]

• Initiate pain management (e.g., morphine).
• Consider procedural sedation.
• For patients taking anticoagulants, urgently consult hematology for consideration of anticoagulant reversal. ^[26]
• Identify and treat any complications (e.g., mesenteric ischemia, acute kidney injury).

All patients

• Consult cardiothoracic surgery urgently.
• Establish IV access: two large-bore peripheral IV lines.
• Obtain ECG.
• Order laboratory studies: D-dimer, type and screen, CBC, coagulation panel, BMP, troponin
• Begin hemodynamic monitoring, e.g., continuous telemetry, pulse oximetry, urine output, frequent BP checks.
• Control blood pressure within safe limits (i.e., MAP ≥ 70 mm Hg with SBP < 120 mm Hg)
• Initiate supportive care, e.g., pain management with IV morphine
• Admit to critical care unit and monitor for complications.
• Consult hematology if the patient is taking anticoagulants.

Stable patients

• Determine pretest probability (e.g., ADD-RS score) and order imaging based on risk.
• Order definitive imaging (e.g. CTA chest, abdomen, and pelvis) if suspicion is elevated.
• Stanford A dissection OR complicated Stanford B dissection: Expedite surgery.
• Uncomplicated Standford B dissection: Continue medical therapy only.

Hypotensive patients

• Initiate immediate hemodynamic support to target MAP ∼ 70 mm Hg.
• Obtain urgent bedside imaging: e.g., TEE (preferred), portable CXR, TTE, POCUS.
• Treat life-threatening complications immediately, e.g., management of cardiac tamponade.
• Expedite surgical management.

Hypertensive patients

• Maintain SBP < 120 mm Hg and HR < 60/min.
• Start beta blocker (use nondihydropyridine CCB if β-blocker contraindications are present).
• Add sodium nitroprusside if HR is < 60/min but SBP remains > 120 mm Hg despite beta blocker.

• In-hospital mortality due to aortic dissection ranges from 9 to 39%, depending on the type of dissection and treatment modality. ^[27][28]

• Malperfusion syndrome
  • A complication of aortic dissection where blood flow to major vascular beds is interrupted, resulting in ischemia and end-organ damage
  • Malperfusion syndrome may affect the gut, kidneys, upper or lower limbs, as well as coronary, spinal, or cerebral circulation
• Aortic rupture and acute blood loss: acute back and flank pain; (tearing pain), symptoms of shock → indication for emergency surgery
• Complications of Stanford type A dissections
  • Myocardial infarction (coronary artery occlusion)
  • Aortic regurgitation (extension of the dissection into the aortic valve)
  • Cardiac tamponade progressing to cardiogenic shock
  • Pericarditis, pericardial effusion, and pericardial tamponade (slow extension of the dissection into the pericardium)
  • Stroke (extension of the dissection into the carotids)
• Complications of both Stanford type A dissection and Stanford type B dissections
  • Bleeding into the thorax, mediastinum, and abdomen
  • Arterial occlusion followed by ischemia of the:
    • Celiac trunk, superior/inferior mesenteric artery → acute abdomen, ischemic colitis
    • Renal arteries → acute renal failure (oliguria, anuria)
    • Spinal arteries → weakness of lower extremities or acute paraplegia
    • Complete occlusion of the distal aorta → Leriche syndrome (aortoiliac occlusive disease)

We list the most important complications. The selection is not exhaustive.

• Blood pressure control
• Smoking cessation ^[4]
• Age-appropriate AAA screening