Aneurysms & Dissection Flashcards
(19 cards)
What is an Aortic Dissection?
- it is an INTIMAL tear with dissection of blood thorugh media of the aortic wall (tear in intima)
- remember blood vessel wall is intima, media, adventitia
- the intimal tear creates a false lumen with intramural hematoma
- the blood that is dissected can move up or down the aorta, blood dissecting up around the great vessels can close off the carotids, and blood dissecting down to coronaries can shut them off
Where does an Aortic Dissection occur?
- it occurs in the proximal 10cm of the Aorta (high stress region) and with preexisting weakness of the media
What are 2 common reaosns for Aortic Dissection to occur?
- most common cause is Hypertension
- inherested defects of connective tissue
What are inhereted defects of connective tissue?
- Marfan Syndrome (defect in elastic tissue Fibrillin)
- symptoms: hyperextensible joints, chromosome 15, Fibrillin-1 (FBN1), flat feet, tall/thin stature, myopia - Ehlers-Danlos Syndrome: defect in collagen
What symptoms does Aortic Dissection present with?
- sharp, tearing chest pain
- pain radiates to the back
- acute onset pain
- pulse deficit, hypotension
What are the Complications associated with Aortic Dissection?
- Pericardial Tamponade (most common cause of death): Step-by-Step Explanation:
What is Aortic Dissection?- A tear in the intimal layer of the aorta causes blood to flow between the layers of the aortic wall (intima and media).
- This creates a false lumen — a second “channel” for blood within the aortic wall.
- If the dissection occurs in the ascending aorta (Type A dissection):
- It’s very close to the heart, and especially to the pericardial sac (the sac surrounding the heart).
- Rupture into Pericardial Cavity:
- The dissection can rupture through the outer wall (adventitia) into the pericardial space.
- Blood fills the pericardial sac → this is called hemopericardium.
- Pericardial Tamponade Happens:
- The pericardial sac cannot stretch quickly, so the accumulating blood compresses the heart.
- This prevents proper filling of the heart chambers, especially the right atrium and ventricle.
- → Severe drop in cardiac output
- → Cardiogenic shock
- → Sudden death if untreated
🚑 Clinical Consequence:
* A Type A dissection is a surgical emergency primarily because of the risk of tamponade.
* Patients may present with:
* Severe chest pain radiating to the back
* Pulsus paradoxus
* Hypotension
* Muffled heart sounds (Beck’s triad)
- Rupture with fatal hemorrhage
- Obstruction of branching arteries (eg. coronary or renal) which results in end-organ ischemia: 🔁 The dissection creates a false lumen inside the aortic wall.
As blood tears through the intima, it enters the media and forms a false channel (false lumen), running alongside the true lumen.
⛔ This can block blood flow to major branches of the aorta:
* Renal arteries
* Mesenteric arteries
* Coronary arteries
* Carotids
* Spinal arteries
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🧠 How does that cause renal ischemia or infarction?
* The renal artery comes off the abdominal aorta.
* If the false lumen compresses the true lumen near the renal artery origin:
* ↓ Blood to the kidney → renal ischemia or infarction
* OR, the dissection flap may extend into the renal artery itself and block it.
How does blood “dissect through the media”?
🧬 The aortic wall has 3 layers:
1. Intima (inner, thin)
2. Media (thick muscular elastic layer)
3. Adventitia (outer)
⸻
🔨 Dissection starts with:
* A tear in the intima (from hypertension, connective tissue disorders like Marfan, trauma, etc.)
* Blood enters the media under high pressure and splits it apart — this is the dissection.
* The high-pressure blood creates a false channel within the media.
⸻
🧪 Why the media?
* The media is rich in elastic fibers, but under chronic stress (like hypertension), it degenerates (called cystic medial necrosis).
* This makes it easier for blood to push between the layers and spread the dissection.
⸻
⚠️ The dissection can:
* Extend forward or backward along the aorta
* Rupture outward → hemothorax, hemopericardium
* Block branch arteries → end-organ damage (kidney, gut, brain, etc.)
What is a type A and type B Aortic Dissection?
- Stanford Labeling System
Type A: aortic dissection in ascending aorta
Type B: aortic dissection anywhere else
How does the blood flow in an Aortic Dissection?
🔪 What is a dissection flap?
Think of the aorta like a 3-layer hose:
1. Intima (inner lining)
2. Media (middle muscle layer)
3. Adventitia (outer tough coat)
⸻
🧨 In a dissection:
* A tear happens in the intima.
* Blood rushes in and splits the media layer apart.
* This creates:
* A true lumen = the normal channel
* A false lumen = a new tunnel inside the wall
⸻
📌 The “flap” is:
* The layer of intima and part of media that separates the true and false lumens.
* It’s like a loose flap of wallpaper peeling off the wall, flapping between two layers.
* It can move or flutter with blood flow — and even block side branches!
⸻
🔁 How can a dissection go backward?
This is called retrograde dissection.
Blood doesn’t care about direction — it follows pressure:
* After the intimal tear, high-pressure blood enters the wall.
* The dissection can spread:
* Forward (antegrade) — toward the lower body
* Backward (retrograde) — toward the heart and arch vessels
⸻
🔴 Why is retrograde dissection dangerous?
* It can reach:
* The aortic root → block coronary arteries → heart attack
* The pericardial sac → rupture → cardiac tamponade
* The brain arteries (like carotids) → stroke
What is an Aneurysm?
- balloon-like dialtion of a blood vessel
- An aneurysm is a focal dilation of a blood vessel (usually an artery) due to weakening of the wall.
What are the common locations for Aneurysms?
🟥 1. Abdominal Aortic Aneurysm (AAA)
* Most common type
* Location: Below renal arteries (infrarenal aorta)
* Risk factors: Atherosclerosis, smoking, old age, male sex
* Presents with:
* Pulsatile abdominal mass
* Can rupture → severe abdominal/back pain, hypotension
⸻
🟥 2. Thoracic Aortic Aneurysm (TAA)
* Location: Above diaphragm, especially near the aortic arch
* Associated with:
* Hypertension
* Marfan syndrome
* Bicuspid aortic valve
* Tertiary syphilis (affects vasa vasorum of aorta)
* Can compress nearby structures:
* Recurrent laryngeal nerve → hoarseness
* Esophagus → dysphagia
* Trachea → cough/dyspnea
⸻
🧠 3. Cerebral (Berry) Aneurysms
* Location: Circle of Willis
* Most often at bifurcations:
* Anterior communicating artery (ACoA)
* Posterior communicating artery (PCoA)
* Risk factors:
* Polycystic kidney disease (PKD)
* Ehlers-Danlos
* Smoking, hypertension
* Rupture → Subarachnoid hemorrhage (thunderclap headache)
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💢 4. Ventricular Aneurysm (Post-MI)
* Location: Left ventricular wall after transmural MI
* Risk: Heart wall thins and bulges
* Can lead to:
* Heart failure
* Arrhythmia
* Mural thrombus (clot forms inside the aneurysm)
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🧬 5. Mycotic Aneurysm
* Location: Anywhere, often at arterial bifurcations
* Caused by infection of the vessel wall
* e.g. from bacterial endocarditis
* Rare but dangerous → prone to rupture
What is Syphillitic Aneurysm?
1️⃣ Syphilitic Aneurysm – Ascending Aorta
💉 Cause:
* happens in Tertiary stage of syphilis (Treponema Pallidum), usually affects men 40-55 years old
* Infects the vasa vasorum causing inflammation (tiny blood vessels that nourish the aortic wall)
🧬 What happens:
* Obliterative endarteritis → ↓ blood supply to tunica media
* Leads to weakening and scarring of the media
* Results in “tree-bark” appearance and aneurysmal dilation
* can see calcification and dilation of the ascending aorta
📍 Location:
* Classically in the ascending thoracic aorta
🚨 Complications:
* Aortic valve insufficiency (from aortic root dilation):This means the aortic valve is leaky — it doesn’t close properly, so some blood flows backward from the aorta into the left ventricle during diastole (when the heart relaxes). 🔁 What happens in the heart?
* Blood regurgitates back into the left ventricle
* This causes volume overload
* The LV becomes dilated and hypertrophied over time
* Eventually → heart failure
* Compression of adjacent structures in the mediastinum like the airway and esophagus
* Rare today due to antibiotics, but thrombosis and embolism can occur
What is an Aortic Dissection in the Ascending Aorta?
2️⃣ Aortic Dissection – Ascending Aorta
💣 Cause:
* Hypertension (most common)
* Marfan syndrome, Ehlers-Danlos (connective tissue disorders)
* Cystic medial necrosis
📍 Location:
* Type A (Stanford): Involves ascending aorta (life-threatening!)
* Type B: Starts after the left subclavian artery
🚨 Risk:
* Dissection can extend to aortic root, cause:
* Coronary artery occlusion
* Pericardial tamponade
* Stroke, renal ischemia
Where does Abdominal Aortic Aneurysm usually occur?
- it usually arises below the renal arteries, but above the aortic bifurcation
What demographic is usually impacted by Abdominal Aortic Aneurysms?
- classicially seen in male smokers over 60 years old with hypertension
- atherosclerosis causes thickening of the intima wall and less O2, leading to atrophy and weakness
🩺 How Atherosclerosis Leads to AAA
🧱 Step-by-step breakdown:
1. Atherosclerosis thickens the intima:
* The intima is the innermost layer of the blood vessel.
* Plaques (cholesterol, inflammatory cells, etc.) build up here.
2. Oxygen supply to the vessel wall decreases:
* The media (middle muscular layer) of large arteries like the aorta gets oxygen from small vessels called the vasa vasorum.
* In the abdominal aorta, these vessels are sparse.
* So when the intima thickens from atherosclerosis, oxygen diffusion is impaired.
3. Media layer undergoes atrophy:
* The muscle cells (smooth muscle) in the media weaken or die.
* Elastic fibers degrade due to inflammation and enzymes like matrix metalloproteinases (MMPs).
4. Wall becomes thin and weak:
* No structural support → wall balloons outward under pressure
* This is what forms an aneurysm
- abdominal aorta is a vessel very commonly impacted by atherosclerosis
What is the presentation of Abdominal Aortic Aneurysms?
- pulsatile abdominal mass
- grows with time
What is a major complication of Abdominal Aortic Aneurysm Rupture?
** rupture is more common when it is larger than 5cm in diameter (> 5cm)
- it presentd with a triad of Hypotension, Pulsatile Abdominal Mass and Flank Pain
- there can be compression of local structures (like the Ureter)
- thrombosis/embolism may occur
What is a Berry Aneurysm?
- these are small spherical aneurysms most commonly located at the bifurcation of cerebral vessels where hemodynamic stress is highest
- berry aneurysms are exactly located in the Circle of Willis, which is the main arterial circle at the base of the brain.
- increased intravascular pressure and weakness in arterial wall leads to their formation
- they can rupture and lead to Subarachnoid Hemorrhage
What results in a Tree-Bark appearance of the Aorta?
- syphillitic aneurysm (cardiovascular manifestation of tertiary syphilis due to Treponema Pallidum and involves the Ascending Aorta)
