Thoracic aortic disease study Flashcards
How are aortic aneurysms classified
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
Describe crawford classification of thoraco-abdominal aortic aneurysms
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…)
What is natural history of thoracic aortic aneurysms
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.
What is pathophysiology of aortic aneurysm formation
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
What are predisposing factors for a thoracic aortic aneurysm
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
What is Marfan Syndrome
Autosomal dominant condition association with mutation of the fibrillin gene on chromosme 15
Many different genetic mutations and this results in many different phenotypes
Diagnosis of Marfan syndrome (Ghent Criteria)
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
What is Ehlers-Danlos syndrome
Autosomial dominant condition
Type IV results in a structural defect of type III collagen and subsequent aortopathy
less common then marfan syndrome
Clinical features of patients with thoracic aortic aneurysms
Asmptomatic
Pain (typically interscapular)
Compression of nearby structures (hoarseness of voice–recurrent laryngeal, dyspagia–esophagus, stridor–trache.
Fistula–resulting in heamatemesis or hemoptysis
5 indications for replacing the aortic root
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
What are operative choices for an aortic root replacement
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
What is acute aortic syndrome
Defined as a group of life-threatening thoracic aortic pathologies that includes aortic dissection, penetrating aortic ulcer, intramural hematoma, and leaking aortic aneurysm.
What is an intramural hematoma and penetrating aortic ulcer
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
How are thoracic aortic dissections classified
acute (<14 days)
sub-acute (14 days to 2 months)
Chronic (>2 months)
What is debakey classification–be able to draw it.
Type 1: while aorta involved
Type 2: only ascending aorta
Type 3a: Only descending aorta involved
Type 3b: descending and abdominal aorta involved
Where are entry tears usually located in acute throacic aortic dissection
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
What are complications from endovascular repair of thoracic aorta
Stent complication (endoleak or migration---10-15% Local vascular complications 5- 10% Mortality 5- 10% aortic trauma 5% stroke or paraplegia 5%
Describe the classification of endoleaks that occur after stenting
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)
What are histological changes of aorta with age
Elastin fragmentation
Fibrosis with increased collagen
Medial Degeneration: generally causes diffuse fusiform dilation
Define IMH
Ruptured vaso vasorum and bleeding into the medial wall layers without intimal rupture and classical flap formation
What is rate of IMH progressing to type A dissection
.
Penetrating atherosclerotic ulcers
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
What is 5 year rate of thoracic aneursym rupture
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
What are mortality, paraplegia, and five year survival rates for thoracic aneursyms
5-10% mortality
3 to16% paraplegia
60 to 80% 5 year survival
What are stanford group survival outcomes for Type B dissections treated medically
for all patients
1 year 70%, 5 year = 60%, 10 year = 35%, and 15 year = 17%
What are common locations of thoracic aortic trauma
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%
What is pathophysiology of aortic dissection
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.
Describe the anatomical layers of the thoracic aorta
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
