Thoracic aortic disease study

Question 1

How are aortic aneurysms classified

Answer 1

true aneurysm– outpouching of all 3 layers of vessel wall
false aneurysm–thrombus contained by adventitia and surrounding tissues

shape–saccular or fusiform
etiology- athersclerotic, dissecting, or mycotic
location–ascending, arch, or descending

Question 2

Describe crawford classification of thoraco-abdominal aortic aneurysms

Answer 2

Type I: most of the descending thoracic aorta (just beyond the left subclavian to the suprarenal abdominal aorta.
Type II: Just beyond the left subclavian artery to the intrarenal abdominal aorta
Type III: lower descending aorta (below the 6th rib) into the abdomen
Type IV: below the diaphragm (abdominal aortic aneursym)
Type V: mid-desecending thoracic aorta above the diaphram (new addition to the classification…)

Question 3

What is natural history of thoracic aortic aneurysms

Answer 3

Carry the risk of rupture, dissection and death
Expansion of thoracic aneursysm occurs at a faster rate in larger aneurysms (0.3cm/year in aneurysms < 5cm) compared to 0.8cm/year in aneurysms > 5 cm) as per Laplace’s Law
The risk of rupture increases as the size of the aneurysm increaes (0.3%/year for aneurysms 4-5cm compared to 3.6% for aneurysms > 6 cm).
The median size for rupture is 6 cm for the ascending and 7 cam for the descending thoracic aortic aneurysms.

Question 4

What is pathophysiology of aortic aneurysm formation

Answer 4

The media normally contains elastin, collagen, smooth muscle cells, and ground matrix
Aneurysms form after loss of smooth muscle cells and fragmentation of elastin fibers (a process known as cystic medial degeneration) which results in loss of elasticity and tensile strength of the media

Question 5

What are predisposing factors for a thoracic aortic aneurysm

Answer 5

Age, Atherosclerosis
Bicuspid aortic valve (associated with fibrillin loss)
High blood pressure
Connective tissues disorders (Marfan, Ehler-Danlos, Loez-Dietz
Dissection, degenerative
Trauma, Aortitis, infection, syphilis
medical degeneration

Question 6

What is Marfan Syndrome

Answer 6

Autosomal dominant condition association with mutation of the fibrillin gene on chromosme 15

Many different genetic mutations and this results in many different phenotypes

Question 7

Diagnosis of Marfan syndrome (Ghent Criteria)

Answer 7

Tall thin pt–arm span greater than height
Arachnodactyly- long tapered fingers
High arched palate
scoliosis, pectus excavatum, protusic acetabulae
hypermobility of joints with skin laxity
spontaneous pneumothorax with apical bullae
eye signs–ectopia lentis (upward dislocation of lens), myopia, retinal detachment
mitral regurgitation
aortopathy

Question 8

What is Ehlers-Danlos syndrome

Answer 8

Autosomial dominant condition
Type IV results in a structural defect of type III collagen and subsequent aortopathy
less common then marfan syndrome

Question 9

Clinical features of patients with thoracic aortic aneurysms

Answer 9

Asmptomatic
Pain (typically interscapular)
Compression of nearby structures (hoarseness of voice–recurrent laryngeal, dyspagia–esophagus, stridor–trache.
Fistula–resulting in heamatemesis or hemoptysis

Question 10

5 indications for replacing the aortic root

Answer 10

Annulo-aortic ectasia–dilation of aortic root. similar recommendations based on same size criteria as ascending aorta
Aneurysms of sinus of Valsalva (most frequently in the non-coronary sinus, then the right coronary sinus, and less likely the left.
Aortic root abscess
Stanford Type A thoracic aortic dissection extending into the aortic root
Small aortic root if root sparing techniques are not possible

Question 11

What are operative choices for an aortic root replacement

Answer 11

1) David reimplantation procedure: The commisural pillars are reimplanted within a Dacron interposition tube graft and the coronar buttons are re-anastomosed.
The dacron tube diameter is equal to the average length of the free margin of the 3 leaflets
2) Yacoub remodelling procedure: ascending aorta and sinuses are replaced with a dacron interposition tube graft that is scalloped to incorporate the aortic valve commissural pillars.
3) Classical Bentall procedure (inclusion techqnique) valved conduit is placed within the aneurysmal aortic root
4) modified btnall procedure
5) Cabrol procedure
6) Homograft aortic root replacement-a cadaveric human aorti root is implantated
7) Ross procedure

Question 12

What is acute aortic syndrome

Answer 12

Defined as a group of life-threatening thoracic aortic pathologies that includes aortic dissection, penetrating aortic ulcer, intramural hematoma, and leaking aortic aneurysm.

Question 13

What is an intramural hematoma and penetrating aortic ulcer

Answer 13

IMH–blood that enters media without the presence of an intimal tear
-rupture of the vasa vasorum of the media
- hemorrhage within an atherosclerotic plaque
- progression from a penetrating aortic ulcer
Resolves spontaneously or progress over time.

Penetrating aortic ulcers
- focal intimal defects occurring at the site of atherosclerotic plaques
- progressive intimal erosion eventually resulting in pulsatile blood entering the media and hence penetrating ulcers may lead to IMH, dissection, and rupture.
Surgery indicated when diameter >20 mm and depth >10mm or when located in ascending aorta

Question 14

How are thoracic aortic dissections classified

Answer 14

acute (<14 days)
sub-acute (14 days to 2 months)
Chronic (>2 months)

Question 15

What is debakey classification–be able to draw it.

Answer 15

Type 1: while aorta involved
Type 2: only ascending aorta
Type 3a: Only descending aorta involved
Type 3b: descending and abdominal aorta involved

Question 16

Where are entry tears usually located in acute throacic aortic dissection

Answer 16

Ascending aorta (65%) approximately 2cm above the non-coronary sinus
Descending aorta (20%) proximally on the left anteriorlateral wall
Aortic Arch (10%) opposite the innominate artery on the lesser curve

Question 17

What are complications from endovascular repair of thoracic aorta

Answer 17

Stent complication (endoleak or migration---10-15%
Local vascular complications 5- 10% 
Mortality 5- 10% 
aortic trauma 5%
stroke or paraplegia 5%

Question 18

Describe the classification of endoleaks that occur after stenting

Answer 18

Type 1: leak at the junction of the aorta and the stent graft due to an inadquate seal
Type 2: back bleeding within the aneurysmal sac
Type 3: leak though the defect in the stent graft prosthesis (graft failure) graft to graft
Type 4 leak through the pores of the stent graft fabric (graft porosity)

Question 19

What are histological changes of aorta with age

Answer 19

Elastin fragmentation
Fibrosis with increased collagen
Medial Degeneration: generally causes diffuse fusiform dilation

Question 20

Define IMH

Answer 20

Ruptured vaso vasorum and bleeding into the medial wall layers without intimal rupture and classical flap formation

Question 21

What is rate of IMH progressing to type A dissection

Answer 21

.

Question 22

Penetrating atherosclerotic ulcers

Answer 22

represent rupture of an athersclerotic plaque, with penetration into the internal elastic lamina of the aorta and maybe associated with proximal and distal progression of an IMH

Question 23

What is 5 year rate of thoracic aneursym rupture

Answer 23

about 30%
For small aneursyms rate/year is 2%
3% for aneursyms 5.0 to 5.9
6.9% for aneursyms of 6.0 cm and larger

Question 24

What are mortality, paraplegia, and five year survival rates for thoracic aneursyms

Answer 24

5-10% mortality
3 to16% paraplegia
60 to 80% 5 year survival

Question 25

What are stanford group survival outcomes for Type B dissections treated medically

Answer 25

for all patients

1 year 70%, 5 year = 60%, 10 year = 35%, and 15 year = 17%

Question 26

What are common locations of thoracic aortic trauma

Answer 26

aortic isthmus = 36 to 54%
ascending aorta = 8 to 27 %
descending aorta = 11 to 21 %

only 20% of pts survive to hospital
mortality after admission is 39 to 73%

Question 27

What is pathophysiology of aortic dissection

Answer 27

occur in the medial layer separating the intima from the adventitia; blood flows through the true aortic lumen and through on or more false lumen channels that can form at variou potins along the aorta.

Question 28

Describe the anatomical layers of the thoracic aorta

Answer 28

Intima layer (inner layer of aorta) consists of endothelial cells, a subendothelial layer of connective tissue and an elastic membrane

Media layer (middle layer of the aorta) consists of elastin, collagen, smooth muscle cells and ground matrix

Adventitia (strong outer layer covering of the aorta) consists of connective tissue, collagen and elastic fibers