Disease of the Aorta Flashcards
Why is the aorta prone to injury and disease?
due to it’s constant exposure to high pulsatile pressure and shear stress
What are the 3 layers of the aorta?
- Intima- the thin inner layer
- Media- the thick middle layer that gives the aorta strength, elasticity and distensibility
- Adventitia- the thin outer layer
What are the two anatomical divisions of the aorta?
- The thoracic aorta- within the thoracic cavity.
2. The Abdominal aorta- the section below the diaphragm.
what are the 3 distinct segments of the thoracic aorta?
ascending aorta
aortic arch
descending aorta
what are the two distinct segments of the ascending aorta?
aortic root
ascending aorta
Ascending aorta begins where?
what else is found here?
Begins at the level of the aortic valve
- Supports the aortic valve leaflets
- Extends into the sinotubular junction
- Area where right and left main coronaries arise
Where does the descending thoracic travel too?
runs distally to the diaphragm
What is the aortic isthmus and why is it important?
The point at which the aortic arch joins the descending aorta
This is the point at which the aorta is vulnerable to trauma due to its fixation to other structures within the chest cavity
Where does the Abdominal aorta start and what are their 2 segments
Extends from the thoracic aorta at the level of the diaphragm to the bifurcation of the right and left common iliac arteries
Consists of two segments:
Suprarenal- the segment above the renal arteries
Infrarenal- the segment below the renal arteries
What happens to the aorta as we age?
Elasticity and distensibility decreases with age
These changes occur earlier and more rapidly in men than in women
Loss of elasticity is accelerated in patients with HTN, Hypercholesterolemia and coronary artery disease
what is the definition of aortic aneurysms?
Pathologic dilation of the aorta that can occur anywhere along the course of the aorta
What are the two types of aneurysms?
Fusiform
Saccular
what is the definition of a sccular aneurysm?
involves only a portion of the circumference (outpouching of a vessel)
what is the definition of a fusiform aneurysm?
Fusiform- affects the entire circumference of a segment of a vessel
how are aneurysms classified?
by location
Abdominal- below diaphragm
Thoracic- above diaphragm
Thoracolumbar- involves the descending thoracic aorta and abdominal aorta
what are the complications with aneurysms?
dissection
acute rupture
what is the average growth of thoracic aneurysms?
0.1-0.2cm/year
Those with marfans syndrome expand at a greater rate
The risk of aneurysm is related to what?
size and presence of symptoms
what is the most common cause of ascending aortic aneurysms?
Cystic medial necrosis is most common cause
What is the most common cause of aortic arch and descending thoracic aneurysms?
Aortic arch and descending thoracic aneurysms
Atherosclerosis is the most common cause
what are the risk factors for thoracic aneurysms?
Atherosclerosis
Connective tissue disorders such as Marfan’s and Ehlers-Danlos syndrome
Hypertension
Familial thoracic aortic aneurysm syndromes
Infections: Syphilis (rare), tuberculosis
Vasculitis (ex. Takayasu’s arteritis, giant cell arteritis)
Trauma (penetrating or non-penetrating)
What are the signs and symptoms of thoracic aortic aneurysms
most are asymptomatic and found on routine physical exam or chest X-ray
If symptoms are present they coincide with the size and loctation of aneurysms
Aortic root: CHF, aortic regurgitation
Aortic arch: may compress the trachea (deviation, cough) or hoarness
Descending aortic: dysphagia
chest and back pain which is steady and deep
Thoracic aortic aneurysms imaging diagnosis
Imaging/Diagnosis:
-CT scan: Modality of choice
-CXR:
Widening of mediastinum, displacement or compression of the trachea, calcifications of the outline of the aorta, large aortic knob
-Transesophageal echocardiogram (TEE):
can assess the proximal ascending aorta and descending thoracic aorta
MRI and Aortography
Both sensitive and specific test
what is the Tx for aortic aneurysms?
Surgery
Aortic arch/ascending aorta: open surgery required
Descending: endovascular stent grafting
Medical Management
what are the surgery indications for: thoracic Ascending aortic aneurysms? thoracic Descending aortic aneurysms? Aneurysms that have increased? Marfan’s syndrome patients and patients with bicuspid aortic valve:
Symptomatic patients
Ascending aortic aneurysms >5.5-6.0cm
Descending aortic aneurysms >6.5-7.0cm
Aneurysms that have increased >1.0cm/year
Marfan’s syndrome patients and patients with bicuspid aortic valve: ascending aortic aneurysm >5.0cm
what are surgical complications with thoracic aortic aneurysms?
Higher morbidity and mortality than AAA
Paraplegia (4-10% rate following endovascular repair)
Stroke
what are the medical management options for thoracic aneurysms?
Indications:
Asymptomatic patients with aneurysms too small to justify surgery
Beta Blockers:
decrease mortality and slow the rate of dilation
ACE-I/ARB’s:
Studies are showing these reduce the rate of expansion in patients with Marfan’s syndrome
what is the prognosis for thoracic aneurysms?
Survival rate of those not undergoing repair is 20% at 5 years
Less than ½ of the patients with an acute rupture arrive to the hospital alive
what is the definition of a AAA
Defined as an aneurysm measuring ≥3.0cm
who is most at risk of AAA
Male to female ratio is 4:1
AAA are commonly caused by?
90% of AAA >4.0cm are related to atherosclerosis
where are most AAA located?
90% are infrarenal in location
what is the risk of rupture for AAA
5.0cm: 5 year risk if 20-40%
what is the mortality rate if AAA rupture
80%
Approximately 60% of patients with acute rupture die before receiving medical attention
Operative mortality for those reaching hospital is 50%
AAA risk factors
Atherosclerosis- most common HTN Smoking Hypercholesterolemia Peripheral vascular disease Age (incidence increases rapidly at 55 yr in men and 70 yr in women) Male gender Genetics (1st degree relatives)
AAA signs and symptoms?
mostly asymptomatic
usually detected on exam as a palpable, pulsatile, non-tender mass or seen incidentally on imaging studies ordered for an unrelated symptoms
As aneurysms expands, patients may feel abdominal or lower back pain
pain is usually sign of impending rupture
what is the gold standard for AAA diagnosis
abdominal ultrasound
AAA diagnosis/imaging
Pulsatile mass noted from the xiphoid process to the umbilicus
- X-ray- may show the calcified outline of the aneurysm (25% are not calcified)
- Computed Tomography-Can diagnose and size aneurysm, though w/ contrast it is more expensive and a risk of allergic reaction
- Contrast Aortography- Invasive and requires contrast
- MR angiography-uses contrast, extremely accurate, used to plan for surgical repair.
AAA treatment
Surgery
The definitive treatment!
AAA medical management
Smoking Cessation
Aggressive control of HTN and hyperlipidemia
Beta blockers: reduce expansion and rupture
Serial imaging q6months to monitor size and rate of expansion for aneurysms >4.0cm or greater
AAA prognosis
If treated surgically 5 year survival after tx: 60% MI is leading cause of death If no surgery 12% annual risk of rupture if >6.0cm 25% annual risk of rupture if >7.0cm
AAA prevention/screening
Treat risk factors (HTN, hyperlipidemia)
Smoking Cessation
Screening indications:
All men age 65-75 years who have ever smoked
Siblings or offspring of people w/ thoracic aortic or peripheral arterial aneurysms
aortic dissection definition
Tear of the intima that results in the formation of a false channel w/in the media layer
what are the common sites of aortic dissection
Right lateral wall of the ascending aorta (shear stress is highest)
Descending thoracic aorta just below the ligamentum arteriosum
When are aortic dissections most common and in who?
Peak incidence in the 6th and 7th decades of life
Men are at twice the risk as women
Aortic Dissection RF
HTN (present in 70% of pts w/ dissection)
Age (50-60’s)
Bicuspid aortic valve
Marfan’s syndrome and Ehlers Danlos syndrome
Inflammatory aortitis (Takayasu’s arteritis, giant cell arteritis)
Pregnancy (normal women in 3rd trimester
1/2 of all aortic dissections in females occur in women <40 years of age)
Blunt trauma to aorta
what is the debakey classification
type I
type II
type III
Type I- Originates in ascending aorta, continues to the aortic arch and many times beyond the arch distally
Type II- Originates and is confined to the ascending aorta
Type III- Originates in the descending aorta with extension distally
Stanford Classification:
Type A- all dissections involving the ascending aorta
Type B- all dissections not involving the ascending aorta
aortic dissection symptoms
Severe pain most common initial symptom
Pain described as “tearing”, “ripping” and “sharp”
May be localized to the front or back of chest, lower back
Migrates as it progresses
Ascending dissection: neck, throat, jaw pain
Descending dissection: interscapular pain
Less common symptoms: Dyspnea, syncope, weakness, CHF, CVA, paraplegia, cardiac arrest
aortic dissection signs
Hypertension or Hypotension Aortic regurgitation murmur Asymmetric or loss of pulses Pulmonary edema Neuro findings d/t carotid artery obstruction (hemiplegia, hemianesthesia) Paraplegia (spinal cord ischemia)
aortic dissection imaging/diagnosis
CT, echocardiogram and MRI are diagnostic
What is the medical therapy for aortic dissection?
Medical therapy:
Blood pressure control is essential
Beta blocker unless contraindicated to get HR down to 60bpm
Sodium nitruprusside to lower SBP <120 mmHg
CCC if BB and nitroprusside is contraindicated
Pain management (morphine)
Used alone for uncomplicated and stable distal dissections w/ follow up imaging q 6-12 months
what are surgical Tx for aortic dissection?
Superior to medical tx in acute proximal dissections
Involves incising the intimal flap, obliterating the false lumen and placing a graft
what are the indications for surgery for aortic dissection
Indications:
Acute distal dissections w/ vital organ compromise, rupture or impending rupture
Dissections in Marfan’s syndrome or
Continued pain
what are the indications for AAA surgery
Indications
Any size that is symptomatic
Any aneurysm that is rapidly expanding (≥ 0.5cm/yr)
Diameter >5.5cm
what are the surgical procedures done to fix a AAA?
Procedures Insertion of a prosthetic graft (open procedure) Mortality rate 1-5% Endovascular stent graft Mortality rate 0.5-2%
