Nontraumatic thoracic aortic dissection

Not to be confused with traumatic aortic transection

Background

Aortic segments

Branches of the aorta

Aortic anatomy. The aorta is divided into 5 anatomical segments– aortic root, ascending aorta, aortic arch, descending thoracic aorta, and abdominal aorta. Its wall is composed of three layers – intima, media, and adventitia.

• Most commonly seen in men 60-80 yrs old
• Intimal tear with blood leaking into media
• Mortality in first 48 hours of acute presentation is high
  • Commonly quoted as 1-2% per hour, but this is based on a series from the 1950s
  • More recent data suggests mortality for type A dissection is 0.5% per hour when treated medically, and 0.1% per hour when managed surgically
• Diagnosis delayed > 24hr in 50% of cases
• Bimodal age distribution
  • Young with risk factors
    • Connective tissue disease (e.g. Marfan syndrome, Ehlers-Danlos, collagen vascular disease)
    • Pregnancy, especially 3rd trimester
    • Recent cardiac catheterization
    • Bicuspid aortic valve
    • Aortic coarctation
  • Elderly males with chronic hypertension
  • Atherosclerotic risk factors (smoking, hypertension, HLD, DM)

Clinical Features

General

• Symptoms
  • Tearing/ripping pain (10.8x increased disease probability)
    • 64% described the pain as sharp vs 50.6% who described it as tearing or ripping
  • Migrating pain (7.6x)
  • Sudden chest pain (2.6x)
  • History of hypertension (1.5x)
• Signs
  • Focal neurologic deficit (33x)
  • Diastolic heart murmur (acute aortic regurg) (4.9x)
  • Pulse deficit (2.7x)
  • Hypertension at time of presentation (49% of all cases)

Specific

• Ascending Aorta
  • Acute aortic regurgitation, leading to a diastolic decrescendo murmur, hypotension, or heart failure, in 50%-66%
  • MI/Ischemia on ECG, usually inferior (dissection affects the right coronary artery more often than the left coronary artery)
  • Cardiac Tamponade
  • Hemothorax - if adventitia disruption
  • Horners, partial - sympathetic ganglion
  • Voice hoarseness - recurrent laryngeal nerve compression
  • CVA/Syncope - if carotid extension
  • Neurological deficits
  • SBP>20mmhg difference between arms
  • Hypertension at time of presentation (35.7% of all cases)
• Descending Aorta
  • Chest pain, back pain, abdominal pain
    • Pain abrupt, severe (90% of patients) radiating to back
  • Hypertension at time of presentation (70.1% of all cases)
  • Hemiplegia, neuropathy (15%)
  • Renal failure
  • Distal Pulse deficits/ limb ischemia
  • Mesenteric ischemia

Differential Diagnosis

Chest pain

Critical

• Acute coronary syndromes (ACS)
  • STEMI
  • Non-STEMI
  • Unstable angina
• Aortic dissection
• Cardiac tamponade
• Coronary artery dissection
• Esophageal perforation (Boerhhaave's syndrome)
• Pulmonary embolism
• Tension pneumothorax

Emergent

• Cholecystitis
• Cocaine-associated chest pain
• Mediastinitis
• Myocardial rupture
• Myocarditis
• Pancreatitis
• Pericarditis
• Pneumothorax

Nonemergent

• Aortic stenosis
• Arthritis
• Asthma exacerbation
• Biliary colic
• Costochondritis
• Esophageal spasm
• Gastroesophageal reflux disease
• Herpes zoster / Postherpetic Neuralgia
• Hypertrophic cardiomyopathy
• Hyperventilation
• Mitral valve prolapse
• Panic attack
• Peptic ulcer disease
• Pleuritis
• Pneumomediastinum
• Pneumonia
• Rib fracture
• Stable angina
• Thoracic outlet syndrome
• Valvular heart disease
• Muscle sprain
• Psychologic / Somatic Chest Pain
• Spinal Root Compression
• Tumor

Hypertension

• Hypertensive emergency
• Stroke
• Sympathetic crashing acute pulmonary edema
• Ischemic stroke
• Intracranial hemorrhage
• Preeclampsia/Eclampsia
• Autonomic dysreflexia
• Scleroderma renal crisis
• Acute glomerulonephritis
• Type- I myocardial infarction
• Volume overload
• Urinary obstruction
• Drug use or overdose (e.g stimulants, especially alcohol, cocaine, or Synthroid)
• Renal Artery Stenosis
• Nephritic and nephrotic syndrome
• Polycystic kidney disease
• Tyramine reaction
• Cushing's syndrome
• Obstructive sleep apnea
• Pheochromocytoma
• Hyperaldosteronism
• Hyperthyroidism
• Anxiety
• Pain
• Oral contraceptive use

Evaluation

Dissection of the aortic arch: initial CXR normal visualization of the calcification shadow in the aortic arch (left); CXR 4 months later with calcification shifted centrally into the shadow of the aortic arch with a blurred external border (middle); CT scan coronal (top right) and axial (lower right).

CXR showing widened mediastinum and porminent aortic knob

Type A dissection with pericardial effusion as a result. Red arrows showing ascending and descending thoracic aorta. The blue arrows pericardial effusion.

CT chest with contrast of thoracic aortic dissection.

Aortic Dissection Detection Risk Score (ADD-RS)

A score 1 should be awarded for each of the 3 categories that contain at least one of the listed features

Predisposing conditions	Pain features	Physical findings
Marfan syndrome Connective tissue disease Family history of aortic disease Recent aortic manipulation Known thoracic aortic aneurysm	Chest, back, or abdominal pain described as: Abrupt in onset/severe in intensity AND Ripping/tearing/sharp or stabbing quality	Evidence of perfusion deficit Pulse deficit Systolic BP differential Focal neurological deficit (in conjunction with pain) Murmur of aortic insufficiency (new or not known to be old and in conjunction with pain) Hypotension of shock state

Score	Category	Prevalence
0	Low	6%
1	Intermediate	27%
>1	High	39%

No Risk Factor Screening

• CXR
  • Abnormal in 90% (3.4x)
  • Mediastinal widening (seen in 56-63%)
  • Left sided pleural effusion (seen in 19%)
  • Widening of aortic contour (seen in 48%), displaced calcification (6mm), Calcium sign (look for white line of calcium within aortic knob and measure to outer edge of the aortic knob - distance greater than 0.5 cm is positive and > 1 cm is highly suspicious for dissection), aortic kinking, double density sign

Low-Intermediate

(Based on ADD-RS)

• D-dimer for ADD-RS ≤ 1 (low or intermediate risk)

High Risk/Definitive

• CT aortogram chest
  • Study of choice
  • Similar sensitivity/specificity to TEE and MRA
• TEE
  • If CT delayed due to contrast allergy or availability, or patient instability.
  • TEE has a sensitivity of 98% and 95% specific

Other Findings

Type A Aortic Dissection

Abdominal Aortic Dissection on Ultrasound

• ECG
  • LVH on admission ECG (3.2x)
  • Ischemia (esp inferior) - 15%
  • Nonspec ST-T changes - 40%
• Bedside US
  • Can help in ruling in patients when AOFT is >4cm
  • Rule out pericardial effusion and tamponade, especially in hypotension, syncope, dyspnea

Aortic Dissection Classification

• Stanford
  • Type A: Involves any portion of ascending aorta
  • Type B: Isolated to descending aorta
• De Bakey
  • Type I: Involves the ascending and descending aorta
  • Type II: Involves only the ascending aorta
  • Type III: Involves only the descending aorta

Classification of aortic dissection

Image
Percentage	60%	10–15%	25–30%
Type	DeBakey I	DeBakey II	DeBakey III
Classification	Stanford A (Proximal)		Stanford B (Distal)

Management

General Principles

• Control pain to reduce sympathetic stimulation.
  • Fentanyl is easily titratable with minimal cardiovascular effects
• Right radial arterial line or right arm blood pressure will generally be the most accurate
• Reducing heart rate while maintaining low-normal blood pressure reduces aortic flow acceleration, thereby reducing shear force on the intimal wall
  • Goal: HR < 60 bpm, SBP 100-120 mmHg
  • Control heart rate before blood pressure
  • Beta blockers are good first-line option, since they reduce heart rate and aortic wall tension
    • Use β-blockers with caution in severe, acute aortic regurgitation - may worsen shock if dependent on compensatory tachycardia

Heart Rate control

1. Esmolol
   • Advantage of short half life, easily titratable
   • Bolus 0.5mg/kg over 1min; infuse 0.05mg/kg/min (titrate upward in 0.05mg/kg/min increments to a maximum of 0.3 mg/kg/min)
   • Esmolol Drip Sheet
2. Labetalol - has both α and beta effects
   • Push dose - 10-20mg with repeat doses of 20-40mg q10min up to 300mg
   • Drip - Load 15-20mg IV, followed by 5mg/hr
3. Metoprolol
   • 5mg IV x 3; infuse at 2-5mg/hr
4. Diltiazem - Use if contraindications to beta-blockers
   • Loading 0.25mg/kg over 2–5 min, followed by a drip of 5mg/h

Blood pressure control (vasodilators)

Use if needed after beta-blockade.

1. Nicardipine:
   • 5mg/hr start, then titrate up by 2.5mg/hr every 10 min until goal
   • Once at goal, drop to 3mg/hr and re-titrate from there
   • May initially bolus 2mg IV
2. Clevidipine
   • 1-2 mg/hr
   • Double dose every 90 seconds until approaching goal BP, then increase in smaller amounts every 5-10 minutes until goal achieved.
3. Nitroprusside 0.3-0.5mcg/kg/min - Risk of cerebral blood vessel vasodilation and CN/Thiocynate toxicity
4. Fenoldopam
5. Enalapril

Surgery

• Type A (any portion of ascending aorta)
  • Requires surgery
• Type B (isolated to descending aorta)
  • Primarily medical management with surgery consultation

Medication Dosing

Esmolol 0.5mg/kg bolus, then 50-200mcg/kg/min infusion IV — Bolus over 1 minute Labetalol 20mg bolus, then 40-80mg q10min (max 300mg) or 1-2mg/min drip IV Diltiazem 0.25mg/kg load over 2-5min, then 5mg/hr infusion IV Nicardipine 5mg/hr, titrate by 2.5mg/hr q10min IV — Once at goal, drop to 3mg/hr and re-titrate Clevidipine 1-2mg/hr, double q90sec until approaching goal IV Nitroprusside 0.3-0.5mcg/kg/min IV — Risk of cerebral vasodilation and cyanide/thiocyanate toxicity

Disposition

• Admission to OR or ICU

Complications

• AV Regurgitation/Insufficiency
  • CHF with diastolic murmur
• Rupture
  • Pericardium: cardiac tamponade
  • Mediastinum: hemothorax
• Vascular obstruction
  • Coronary: ACS
  • Carotid: CVA
  • Lumbar: Paraplegia

See Also

• Hypertensive emergency
• Traumatic aortic transection
• Abdominal aortic aneurysm
• IRAD

External Links

• NNT Aortic Dissection LRs
• AHA Full Guidelines
• AHA Quick Summary
• ALiEM Paucis Verbis: International Registry on Aortic Dissection (IRAD)
• MDcalc ADD Score