Last edited: 10/25/2021

AORTIC DISSECTION
Aortic Dissection Medical Editor: Donya Moslemzadeh

OUTLINE I) OVERVIEW

I) OVERVIEW Blood vessel Layers from the lumen outward:

II) ETIOLOGY o Tunica Intima (Interna)
III) PATHOPHYSIOLOGY o Tunica Media
IV) CLINICAL FEATURES o Tunica Externa (Adventitia)
V) DIAGNOSIS
VI) TREATMENT What is an Aortic Dissection?
VII) APPENDIX o A tear through the Tunica Intima (Between Tunica
VIII) REVIEW QUESTIONS Intima and Tunica Media)
IX) REFRENCES
 Most common site is Aorta
o Tear in the intima

Figure 1. Artery Structure (AMBOSS).

Figure 2 Aortic Dissection (AMBOSS)

Aortic Dissection CARDIOVASCULAR PATHOLOGY: Note #6. 1 of 8

 Giant Cell Arthritis
II) ETIOLOGY
=Temporal Arthritis
(A) ACQUIRED CAUSES Autoimmune Vasculitis
chronic inflammatory disease involving large- and
(1) Hypertension medium-sized arteries
o Most Common→ Involvement of the cranial
Most Common cause
branches of the carotid arteries
High risk Hypertensive patients for Aortic Dissection are
patients with: Age >50
o Age > 40-60
Table 1. Takayasu vs Giant Cell Arthritis.
o Tobacco Use
o Hyperlipidemia Takayasu Giant Cell
Arthritis Arthritis
Secondary Hypertension
o Transient elevation in blood pressure Age <50 >50
 Cocaine or Amphetamines Use Affected Mostly Aorta and Mostly Temporal
 High intensity weightlifting→ Heavy Valsalva Vessels its branches Vessels
maneuver → Brief rise of Blood Pressure
Clinical Constitutional
Mechanism: Features symptoms:
o ↑Sheer Forces on the vessel wall → Tear in the Constitutional
Weight loss symptoms:
Tunica Intima→ Blood tracks in between Tunica Fever, Weight loss
Intima and Tunica Media Layer Fatigue. Fever, Fatigue.
Absent or Headache
o Arteriosclerosis of the Vasa Vasorum weak Ocular
 In HTN patients → Atherosclerosis of the Vasa Peripheral Involvement
Vasorum → ↓Blood Flow to the Tunica Media→ Pulse Jaw Claudication
necrotic processes → Weak Vessel walls → ↑ Discrepant
Risk of having a tear → ↑ Risk of Dissection blood
pressure
between arms
Blood Supply of the Blood Vessels
Tunica Intima→ directly from blood in the lumen
Tunica Media and Tunica Externa → Vasa Vasorum

Vasa vasorum
small blood vessels supply oxygen and nutrients to
the outer layers of the arterial wall

(2) Trauma

Motor Vehicle Collision

o Secondary to Deceleration type of Injury

Iatrogenic Injuries
o Catheterization
o Valve Repairs
(3) Vasculitis
= Inflammation of the blood Vessel wall
Triggers :
o Tertiary Syphilis
 Inflammation of the Vasa vasorum caused by
Treponema pallidum→↓Blood Supply to the
arterial walls → Cystic Medial Degeneration of the
Tunica Media → Weak wall →↑ Risk of Dissection

o Takayasu Arthritis
 Inflammatory granulomas deposit in the vessel
walls → Medial Degeneration of the Tunica Media
→ Weak wall →↑ Risk of Dissection
 Age < 50
 Usually, Aorta is Involved
 Less Facial and Ocular involvement compared to
Giant cell. Arthritis

Figure 3. Acquired Causes of Aortic Dissection

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 (B) CONGENITAL CAUSES (3) Coarctation of Aorta

(1) Connective Tissue Diseases A narrowing of the descending aorta (after aortic arch), at
the level of Left Subclavian artery , near Ductus
Defect in the connective tissues of the blood vessels Arteriosus
→Weak vessel wall → ↑ Risk of having a tear, ↑ Risk Mechanism: Narrowing cause a lot of resistance →
Aneurysm → ↑ Risk of Dissection ↑Blood pressure proximal to the affected area → HTN →
→↑ Risk Aortic Dissection , ↑ Risk Aneurysm
Connective tissues of the blood vessels Figure 1 Patients with Coarctation of Aorta probably have
o Subendothelial Layer o History of Turner Syndrome
o Elastic Laminas o Associated Bicuspid aortic Valve
o Tunica Externa

Aneurysm
True Aneurysm
o abnormal dilation of an artery due to a weakened
vessel wall, ≥50% dilation of all 3 layers of aorta
False Aneurysm
o external hematomas with a persistent
communication to a leaking artery, rupture within
adventitia
Aneurysm → ↑ Risk of Dissection
Dissection → ↑Risk of Aneurysm

Marfan Syndrome
Etiology
o Mutation of Fibrillin Gene → ↓Elasticity of the vessel
walls→ ↑ Risk Aneurysm and ↑ Risk of Dissection
Clinical Features
o Cardiovascular Disorders: mitral valve prolapse, aortic
aneurysm, and dissection
o Musculoskeletal Disorders: tall stature with
disproportionately long extremities, joint hypermobility
o Eyes Disorders: subluxation of the lens of the eye

Fibrillin= A glycoprotein that forms a supportive sheath

around Elastin

Ehlers-Danlos Syndrome(EDS)
Etiology
o Mutation of Collagen Gene→ ↓Resilience of the blood
vessels →↑ Risk Aneurysm and ↑ Risk of Dissection
Clinical Features
o Cardiovascular Disorders: mitral valve prolapse, aortic
aneurysm, and dissection
o Musculoskeletal Disorders: Joint Hypermobility
o Skin Disorders : Skin hyperextensibility, Easy
Bleeding , Tendency to bruise easily

(2) Bicuspid Aortic Valve

One of the most common types of congenital heart
disease
Genetic Disorder→ 2 valve cusps fuse together →
Bicuspid Aortic Valve
↑ Risk of
o Aortic Stenosis (Most Common)
o Aortic Regurgitation
o Hypertension
o Aortic Aneurysms (unknown Mechanism)
o Aortic Dissections( unknown Mechanism)
(Potential) Mechanism Figure 4. Congenital Causes of Aortic Dissection
o Bicuspid aortic Valve → Left Ventricle Hypertrophy →
HTN → Work harder to push blood out→↑ Risk Aortic
Dissection , ↑ Risk Aneurysm

Aortic Dissection CARDIOVASCULAR PATHOLOGY: Note #6. 3 of 8

 III) PATHOPHYSIOLOGY Narrowing / Occlusion of a branching vessel
(due to forming Hematoma) → Malperfusion
Tear in the aortic intima → blood enters the media of the Syndromes
aorta and forms a false lumen in the intima-media Intramural (Intraluminal) Thrombosis →
space→ 4 Possible Scenarios: Forming hematoma at the tear site
Reentry of the blood into the True lumen
↑ pressure within the aortic wall → Rupture

Figure 5. Pathophysiology of Aortic Dissection

IV) CLINICAL FEATURES

Table 2. Clinical Features of Aortic Dissection
Affected Structure Mechanism Clinical Features
Blood moves between the New Aortic Regurgitation murmur
Aortic Valve intima and media into the
valve leaflet
Malperfusion of Coronary Acute Coronary Syndrome
Coronary Arteries
arteries (mostly right) MI (STEMI, NSTEMI)
Coronary arteries rupture Cardiac Tamponade
into the pericardium
Pericardium (Classic signs of Beck's triad: low blood pressure, distension of the
jugular veins and decreased or muffled heart sounds)

Brachiocephalic, Syncope
Occlusion →↓ blood flow to
common carotid, Cerebral Vascular incidents (Stroke)
the brain
or left subclavian arteries

Upper extremity pulselessness

↓ BP on the Left upper Extremities (A considerable variation (>20
mmHg) in systolic blood pressure may be seen when comparing the
Occlusion of the Left blood pressure in the arms.)
Subclavian Artery and no Acute limb Ischemia
Left Subclavian Artery
occlusion of the Right o Pulselessness
Subclavian Artery o Pain
o Losing color (Pallor)
o Weak muscle → Paralysis
o Cold (Poikilothermia)

↓Urine output
Dynamic Obstruction and Acute kidney Injury
Renal artery Malperfusion of the Renal o ↑Creatinine
Artery o ↑BUN
o ↓GFR
Occlusion Anterior Spinal Artery Syndrome
o Paraplegia of lower extremities
Artery of Adamkiewicz o Loss of Sensations
o Incontinence

Dynamic Obstruction Acute Mesenteric Ischemia

Celiac or mesenteric Abdominal pain
arteries Bloody Diarrhea
Nausea and vomiting

Pulselessness of LLE
↓BP compared to RLE
If Occlusion of the Left Weakness
Common Iliac artery Acute Limb Ischemia
Common iliac artery o Pulselessness
→↓Blood flow to the Left
Lower Extremities LLE o Pain
o Losing color (Pallor)
o Weak muscle →Paralysis
o Cold (Poikilothermia

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 (2) EKG
V) DIAGNOSIS o Indication:
(1) Aortic Involvement  Initial evaluation of patients with chest pain
 Rule Out → Acute MI
Tearing Ripping pain → • less helpful in dissection leads to coronary
o Anterior chest pain →Dissections involving the ischemia
Ascending Aorta o Findings may include:
o Neck and Jaw Pain → Dissections involving the  Normal
Aortic Arch and its branches→ e.g., Carotid arteries  ST Elevation (Coronary Artery Occlusion)
o Interscapular Pain → Dissections involving the  ST Depression
Descending Aorta (Beyond Left Subclavian artery) o Troponin may be POSITIVE
Most Common Location for Aortic Dissection =
Ascending Aorta (2.2cm of Aortic Valve)

Figure 7 ST-Elevation [from the 12 leads of EKG lecture]

Figure 6. Aortic Involved site Associated Pain

Figure 8. EKG of STEMI

(3) Chest Xray

(4) TEE, Trans Esophageal Echocardiography
Advantage → Rapid
TEE
To Rule Out
Can be Performed at the bedside
o Pneumothorax
Indications:
o pleural effusion
o Hemodynamically unstable patients
o Pneumonia
o Severely low GFR
Finding:  Contrast Induced Nephropathy
o Mediastinal widening→ ≥ 8cm → Suspicious for
Rule out → Cardiac Tamponade
Aortic Dissection (Suspicious not Diagnostic!)
Findings:
o Intimal Flap
o False Lumen

Figure 9. Widened Mediastinum on a Chest Xray

Figure 10. Aortic Dissection TEE.

Aortic Dissection CARDIOVASCULAR PATHOLOGY: Note #6. 5 of 8

(5) CTA; CT Angiography (6) MRA; Magnetic Resonance Angiography
CTA → GOLD STANDARD Time Consuming
Indications: Indications:
o Hemodynamically Stable patients o Hemodynamically Stable patients
o Surgical Planning o Contradiction to CTA
Findings: Findings:
o Intimal Flap o Similar to CTA
o False lumen Table 3. Imaging Techniques Comparison
o Leak / rupture Imaging
Advantages
o Aortic Hematoma Modalities Disadvantages
Poor
CXR Rapid, Bedside Sensitivity

Rapid, Bedside Invasive

No radiation exposure May not be
TEE readily
Sensitive and Specific
available

Cannot be
performed at
Gold standard: Very the bedside
CTA high sensitivity and Radiation
specificity exposure
Operative Planning Contrast
Figure 11. Aortic Dissection CTA.
exposure
Cannot be
Very high sensitivity performed at
MRA and specificity the bedside
No radiation exposure Time
Consuming

VI) TREATMENT
Type of Dissection Determination
(B) MEDICAL TREATMENT
Aortic dissection classification systems
o The DeBakey System (1) Hypotensive Patients
o The Stanford System (Preferred) Goal → Mean Arterial Pressure ≥70mmhg
Stanford Classification IV Fluid
o Stanford A o IV Fluid →↑ Blood Volume →↑Blood Pressure
 Involves Ascending Aorta Vasopressor
Emergency → Surgical Therapy o →↑SVR →↑Blood Pressure
o Stanford B o Norepinephrine
 Beyond Left Subclavian Artery → Involves o Phenylephrine (Pure Alpha-1 vasoconstrictor)
Descending Aorta
 Medical Therapy BUT you may need Surgical Blood Transfusion
Intervention o →↑ Blood Volume →↑Blood Pressure
 Complications → may need Surgery Evaluate 3 Scenarios and fix them
• Medical Treatment Failure o Rupture→ repair the rupture
• Rupture o Cardiac Tamponade → Pericardial Fluid Drainage
• Propagation of dissection o Severe Aortic insufficiency → Valve Repair
• Expanding intramural Hematoma
(2) Hypertensive Patients
(A) SURGICAL TREATMENT Goal:
Open Surgery → replacement of the dissection with a o Systolic Blood Pressure 100-120mmhg
polyester graft implantation o Heart Rate < 60bpm
a. Type A Dissections
Endovascular Stent Placement Beta Blockers (Alpha and Beta blocker activity)
a. Type B Dissections o Esmolol
o Labetalol
o Mechanism:
 Blocking Beta receptors on AV/SA nodes→ ↓Heart
Rate
 Blocking Alpha-1 → Vasodilation → ↓SVR → ↓BP
o Beta Blockers are given first to prevent Reflex
Tachycardia
Vasodilators
o Vasodilators → Low Blood Pressure → Stimulate
Cardiac Acceleratory Center in the brain →↑Heart
rate and contractility (Reflex tachycardia)
Figure 12. Aortic Dissection Surgical Treatment. o Sodium Nitroprusside
 Vasodilation → ↓SVR → ↓BP

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 Figure 13. Aortic Dissection Medical Treatment.

VII) APPENDIX

Figure 14. Aortic Dissection Etiology, Pathophysiology, Diagnosis and treatment.

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 VIII) REVIEW QUESTIONS
1) Best Diagnostic test in Hemodynamically stable
patients with suspected aortic dissection:
a) ECG
b) CTA
c) CXR
d) TEE

2) Best Diagnostic test in Hemodynamically unstable

patients with suspected aortic dissection:
a) ECG
b) CTA
c) MRA
d) TEE

3) Which Statement is True?

a) Type B dissections involves the ascending aorta.
b) Type A dissections can be treated medically.
c) Type A dissections are surgical emergencies, Type
B are still emergencies but can often be treated
medically.
d) All patients with Type B dissections should have
surgery.

4) Which one is not a High-Risk condition associate

with Aortic Dissection?
a) Athletic Lifestyle
b) Cocaine Use
c) Hypertension
d) Preexisting Aortic Aneurysm
5) Acute Mesenteric Ischemia may happen as a result
of
a) Dynamic Obstruction of common Iliac Artery
b) Dynamic Obstruction of Celiac and mesenteric
arteries
c) Dynamic Obstruction of Anterior Spinal Artery
d) Dynamic Obstruction of Renal Artery

6) Treatment of Type B Aortic Dissection in a patient

with Hypertension:
a) Sodium Nitroprusside → Esmolol
b) Polyester Graft Implantation → Norepinephrine
c) Labetalol → Sodium Nitroprusside
d) IV Fluids → Phenylephrine

IX) REFRENCES
● AMBOSS: medical knowledge platform for doctors and students.
(n.d.). Amboss. Retrieved 2021, from https://www.amboss.com/us/
● UpToDate: Evidence-based Clinical Decision Support. (n.d.).
UpToDate.Com. Retrieved 2021, from
https://www.wolterskluwer.com/en/solutions/uptodate
● Le, T., Bhushan, V., & Sochat, M. (2021). First Aid for the
USMLE Step 1 2021, Thirty First Edition (31st ed.). McGraw-Hill
Education / Medical.
● Gabriel, D. (2019). USMLE Step 2 CK: A Student-to-student
Guide (Clinical Knowledge) (10th ed.). Independently published.
● Papadakis, M., McPhee, S., & Rabow, M. (2019). CURRENT
Medical Diagnosis and Treatment 2020 (59th ed.). McGraw-Hill
Education / Medical.

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