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==Overview==
==Overview==
[[Aortic]] dissection begins as a tear in the aortic wall in > 95% of patients. The tear is usually transverse, extends through the [[intima]] and halfway through the [[media]] and involves ~50% of the aortic circumference. Two thirds of dissections originate in the ascending aorta, and 20% are in the proximal [[descending aorta]].
[[Aortic]] dissection begins as a tear in the [[aortic]] wall in > 95% of patients. The tear is usually transverse, extends through the [[intima]] and halfway through the [[tunica media|media]] and involves ~50% of the [[aortic]] circumference. Two thirds of dissections originate in the [[ascending aorta]], and 20% are in the [[proximal]] [[descending aorta]].
==Pathophysiology==
===Normal Anatomy of the Aorta===
As with all other [[artery|arteries]], the [[aorta]] is made up of three layers. The layer that is in direct contact with the flow of blood is the [[tunica intima]], commonly called the [[intima]]. This layer is made up of mainly [[endothelial cell]]s. Just deep to this layer is the [[tunica media]], known as the [[tunica media|media]]. This middle layer is made up of [[smooth muscle]] cells and [[elastic tissue]]. The outermost layer (furthest from the flow of blood) is known as the [[tunica adventitia]] or the [[adventitia]]. This layer is composed of [[connective tissue]].[[Image:AoDissect Schema 01a.png|left|thumb|Blood penetrates the [[intima]] and enters the [[tunica media|media]] layer.]]


==Normal Anatomy of the Aorta==
===Pathogenesis===
As with all other [[artery|arteries]], the [[aorta]] is made up of three layers. The layer that is in direct contact with the flow of blood is the ''[[tunica intima]]'', commonly called the ''intima''.  This layer is made up of mainly [[endothelial cell]]s.  Just deep to this layer is the ''[[tunica media]]'', known as the ''media''.  This "middle layer" is made up of [[smooth muscle]] cells and elastic tissue.  The outermost layer (furthest from the flow of blood) is known as the ''[[tunica adventitia]]'' or the ''adventitia''. This layer is composed of [[connective tissue]].[[Image:AoDissect Schema 01a.png|left|thumb|Blood penetrates the ''intima'' and enters the ''media'' layer.]]
====Initial Intimal Tear====
 
* [[Aortic]] dissection begins as a tear in the [[aortic]] wall in > 95% of patients.
*It is usually transverse, extends through the [[intima]] and halfway through the [[tunica media|media]] and involves ~50% of the [[aortic]] circumference.
 
====Location of Dissections====


==Location of Aortic Dissections==
* Aortic dissection begins as a tear in the aortic wall in > 95% of patients.
*It is usually transverse, extends through the [[intima]] and halfway through the [[media]] and involves ~50% of the aortic circumference. 
* Location of dissections:
:*The initial tear is usually within 100 mm of the [[aortic valve]].
:*The initial tear is usually within 100 mm of the [[aortic valve]].
:*65% of dissections originate in the [[ascending aorta]], distal to the [[aortic valve]] and [[coronary ostia]]
:*65% of dissections originate in the [[ascending aorta]], distal to the [[aortic valve]] and [[coronary]] [[ostium|ostia]]
:*10% arise in the [[transverse aortic arch]]
:*10% arise in the [[transverse aortic arch]]
:*20% in the proximal [[descending aorta]]
:*20% in the [[proximal]] [[descending aorta]]
:*5% in the more distal [[descending aorta]]
:*5% in the more [[distal]] [[descending aorta]]
 
====Propagation of the Intimal Tear====
In an [[aortic]] dissection, blood penetrates the ''[[intima]]'' and enters the ''[[tunica media|media]]'' layer. The high pressure rips the [[biological tissue|tissue]] of the ''[[tunica media|media]]'' apart, allowing more blood to enter. This can propagate along the length of the aorta for a variable distance, dissecting either towards or away from the [[heart]] or both.


==Propagation of the Tear==
Once a tear develops, blood then passes into the [[tunica media|media]], and a [[false lumen]] is dissected in the outer layer of [[aortic]] [[tunica media|media]] involving ~50% of the [[aortic]] circumference. This [[false lumen]] can enlarge, and compress the true [[lumen]], as well as extend [[proximal]]ly or [[distal]]ly and occlude [[aortic]] branches. For some unknown reason, the right [[lateral]] wall of the [[ascending aorta]] is the most common site for dissection. The [[right coronary artery]] can become occluded as a result of this propagation.
In an aortic dissection, blood penetrates the ''intima'' and enters the ''media'' layer. The high pressure rips the [[biological tissue|tissue]] of the ''media'' apart, allowing more blood to enter. This can propagate along the length of the aorta for a variable distance, dissecting either towards or away from the [[heart]] or both.
Once a tear develops, blood then passes into the [[media]], and a [[false lumen]] is dissected in the outer layer of aortic [[media]] involving ~50% of the aortic circumference. This [[false lumen]] can enlarge, and compress the true lumen, as well as extend proximally or distally and occlude aortic branches. For some unknown reason, the right lateral wall of the ascending aorta is the most common site for dissection. The [[right coronary artery]] can become occluded as a result of this propagation.


Separating the [[false lumen]] from the true lumen is a layer of intimal tissue. This tissue is known as the '''intimal flap'''. As blood flows down the [[false lumen]], it may cause secondary tears in the [[intima]]. Through these secondary tears, the blood can re-enter the true lumen.
Separating the [[false lumen]] from the true [[lumen]] is a layer of [[intima]]l [[tissue]]. This [[tissue]] is known as the ''[[intima]]l flap''. As blood flows down the [[false lumen]], it may cause secondary tears in the [[intima]]. Through these secondary tears, the blood can re-enter the true [[lumen]].


==Risk Factors for an Intimal Tear==
====Aortic Dissection in the Absence of an Intimal Tear====
While it is not always clear why an intimal tear may occur, quite often it involves degeneration of the [[collagen]] and [[elastin]] that make up the media.  This is known as ''[[cystic medial necrosis]]'' and is most commonly associated with [[Marfan syndrome]] and is also associated with [[Ehlers-Danlos syndrome]]. [[Aging]], [[atherosclerosis]], [[diabetes]], [[hypertension]] and [[trauma]] are common risk factors for aortic dissection. Uncommon risk factors include [[Bicuspid aortic valve]], [[cocaine]], [[Coarctation of the aorta]], [[Cystic medial necrosis]], [[Ehlers-Danlos syndrome]], [[Giant cell arteritis]], [[Heart surgery]], [[Marfan’s syndrome]], [[Pseudoxanthoma elasticum]], [[Turner's syndrome]], [[Tertiary syphilis]] and the [[third trimester of pregnancy]].
In about 13% of [[aortic]] dissections, there is no evidence of an [[intima]]l tear. It is believed that in these cases the inciting event is an intramural [[hematoma]] (caused by [[hemorrhage]] within the [[tunica media|media]]). Since there is no direct connection between the true [[lumen]] and the [[false lumen]] in these cases, it is difficult to diagnose an [[aortic]] dissection by [[aortography]] if the [[etiology]] is an intramural [[hematoma]]. An [[aortic]] dissection secondary to an intramural [[hematoma]] should be treated the same as one caused by an [[intimal]] tear.


==Aortic Dissection in the Absence of an Intimal Tear==
An [[aortic]] intramural [[hematoma]] can form when the [[vasa vasorum]] ruptures into the [[aortic]] wall. This is distinguished from dissection by the lack of an [[intima]]l tear. This disorder parallels [[aortic]] dissection in terms of [[prognosis]] when the [[ascending aorta]] or [[aortic arch]] is involved, and rapid [[surgery|surgical]] intervention is indicated. Involvement of the [[descending aorta]], however, carries a better [[prognosis]] than dissection, and outcome tends to be similar with medical or [[surgery|surgical]] [[therapy]].
In about 13% of aortic dissections, there is no evidence of an intimal tear. It is believed that in these cases the inciting event is an intramural [[hematoma]] (caused by [[hemorrhage]] within the [[media]]). Since there is no direct connection between the true lumen and the [[false lumen]] in these cases, it is difficult to diagnose an aortic dissection by [[aortography]] if the [[etiology]] is an [[intramural hematoma]].  An aortic dissection secondary to an intramural [[hematoma]] should be treated the same as one caused by an [[intimal]] tear.
An aortic intramural hematoma can form when the vaso vasorum ruptures into the aortic wall. This is distinguished from dissection by the lack of an intimal tear. This disorder parallels aortic dissection in terms of prognosis when the ascending aorta or aortic arch is involved, and rapid surgical intervention is indicated. Involvement of the descending aorta, however, carries a better prognosis than dissection, and outcome tends to be similar with medical or surgical therapy.


==Gross Pathology Images==
==Genetics==
[[Genes]] involved in the [[pathogenesis]] of aortic dissection include:<ref name="PinardJones2019">{{cite journal|last1=Pinard|first1=Amélie|last2=Jones|first2=Gregory T.|last3=Milewicz|first3=Dianna M.|title=Genetics of Thoracic and Abdominal Aortic Diseases|journal=Circulation Research|volume=124|issue=4|year=2019|pages=588–606|issn=0009-7330|doi=10.1161/CIRCRESAHA.118.312436}}</ref><ref name="VerhagenKempers2018">{{cite journal|last1=Verhagen|first1=Judith M.A.|last2=Kempers|first2=Marlies|last3=Cozijnsen|first3=Luc|last4=Bouma|first4=Berto J.|last5=Duijnhouwer|first5=Anthonie L.|last6=Post|first6=Jan G.|last7=Hilhorst-Hofstee|first7=Yvonne|last8=Bekkers|first8=Sebastiaan C.A.M.|last9=Kerstjens-Frederikse|first9=Wilhelmina S.|last10=van Brakel|first10=Thomas J.|last11=Lambermon|first11=Eric|last12=Wessels|first12=Marja W.|last13=Loeys|first13=Bart L.|last14=Roos-Hesselink|first14=Jolien W.|last15=van de Laar|first15=Ingrid M.B.H.|title=Expert consensus recommendations on the cardiogenetic care for patients with thoracic aortic disease and their first-degree relatives|journal=International Journal of Cardiology|volume=258|year=2018|pages=243–248|issn=01675273|doi=10.1016/j.ijcard.2018.01.145}}</ref>
*[[FBN1]] ([[fibrillin-1]])
*[[Lysyl oxidase|LOX]] ([[lysyl oxidase]])
*[[MYH11]] (smooth muscle myosin heavy chain 11)
*[[ACTA2]] (smooth muscle α-actin 2)
*[[MYLK]] (myosin light chain kinase)
*[[PRKG1]] (protein kinase cGMP-dependent type 1)
*[[COL3A1]] (α-1 procollagen, type III)
*[[TGFBR1]] (TGF-β receptor type I)
*[[TGFBR2]] (TGF-β receptor type II)
*TGFB2
*[[SMAD3]] (mothers against decapentaplegic drosophila homolog 3)
==Associated Conditions==
[[Conditions]] associated with aortic dissection include:<ref name="PinardJones2019">{{cite journal|last1=Pinard|first1=Amélie|last2=Jones|first2=Gregory T.|last3=Milewicz|first3=Dianna M.|title=Genetics of Thoracic and Abdominal Aortic Diseases|journal=Circulation Research|volume=124|issue=4|year=2019|pages=588–606|issn=0009-7330|doi=10.1161/CIRCRESAHA.118.312436}}</ref>
*[[Aortic aneurysm]]
*Smooth muscle dysfunction syndrome
*[[Marfan syndrome]]
*[[Vascular Ehlers-Danlos syndrome]]
*[[Loeys-Dietz syndrome|Loeys-Dietz syndromes]]
==Gross Pathology==
[http://www.peir.net Images shown below are courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]
[http://www.peir.net Images shown below are courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]
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Image:Aortic dissection 1.jpg|Dissecting Aneurysm: Gross fixed tissue external view of heart aortic arch and descending aorta showing dilated first and second portion of arch from anterior projection.
Image:Aortic dissection 1.jpg|Dissecting [[Aneurysm]]: Gross fixed tissue external view of heart [[aortic arch]] and [[descending aorta]] showing dilated first and second portion of arch from [[anterior]] projection.
Image:Aortic aneurysm 8.jpg|Dissecting Aneurysm: Gross, a very good example of dissection beginning just above aortic ring.
Image:Aortic aneurysm 8.jpg|Dissecting [[Aneurysm]]: Gross, a very good example of dissection beginning just above [[aortic]] ring.
Image:Aortic aneurysm 24.jpg|Dissecting Aneurysm: Gross dissection first portion of arch fixed specimen (a good example).
Image:Aortic aneurysm 24.jpg|Dissecting [[Aneurysm]]: Gross dissection first portion of arch fixed [[specimen]] (a good example).
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Image:Aortic aneurysm 1.jpg|Dissecting Aneurysm: Gross very good example dissected channel has been opened.
Image:Aortic aneurysm 1.jpg|Dissecting [[Aneurysm]]: Gross very good example dissected channel has been opened.
Image:Aortic aneurysm 2.jpg|Dissecting Aneurysm: Gross external view good appearance from adventitia.
Image:Aortic aneurysm 2.jpg|Dissecting [[Aneurysm]]: Gross external view good appearance from [[adventitia]].
Image:Aortic aneurysm 3.jpg|Dissecting Aneurysm: Gross opened false channel.
Image:Aortic aneurysm 3.jpg|Dissecting [[Aneurysm]]: Gross opened false channel.
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Image:Aortic aneurysm 4.jpg|Dissecting Aneurysm: Gross good example dissection beginning at third portion aortic arch.
Image:Aortic aneurysm 4.jpg|Dissecting [[Aneurysm]]: Gross good example dissection beginning at third portion [[aortic arch]].
Image:Aortic aneurysm 5.jpg|Dissecting Aneurysm: Gross cross sections showing thrombus in false lumen true lumen has been opened longitudinally.
Image:Aortic aneurysm 5.jpg|Dissecting [[Aneurysm]]: Gross cross sections showing [[thrombus]] in [[false lumen]]. True [[lumen]] has been opened longitudinally.
Image:Aortic aneurysm 6.jpg|Dissecting Aneurysm: Gross shows origin just above aortic valve false channel shown in descending thoracic aorta (very good example).
Image:Aortic aneurysm 6.jpg|Dissecting [[Aneurysm]]: Gross shows origin just above [[aortic valve]] false channel shown in [[descending aorta|descending]] [[thoracic aorta]] (very good example).
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Image:Aortic aneurysm 10.jpg|Dissecting Aneurysm: Gross, an excellent example, starting just above the aortic valve with reflection of aorta to show the dissection tract and some thrombus  
Image:Aortic aneurysm 10.jpg|Dissecting [[Aneurysm]]: Gross, an excellent example, starting just above the [[aortic valve]] with reflection of [[aorta]] to show the dissection tract and some [[thrombus]]
Image:Aortic aneurysm 11.jpg|Dissecting Aneurysm: Gross shows dilated aorta with extensive atherosclerosis dissection is seen, a small abdominal aorta atherosclerotic aneurysm is present good for association of dilation with dissection  
Image:Aortic aneurysm 11.jpg|Dissecting [[Aneurysm]]: Gross shows dilated [[aorta]] with extensive [[atherosclerosis]] dissection is seen, a small [[abdominal aorta]] [[atherosclerotic]] [[aneurysm]] is present good for association of [[dilation]] with dissection  
Image:Aortic aneurysm 12.jpg|Dissecting Aneurysm: Gross arrow points to start of dissection in first portion aortic arch good but not the best example shows dilation  
Image:Aortic aneurysm 12.jpg|Dissecting [[Aneurysm]]: Gross arrow points to start of dissection in first portion [[aortic arch]] good but not the best example shows [[dilation]]
Image:Aortic aneurysm 13.jpg|Dissecting [[Aneurysm]]: Gross, very good to show start of dissection above [[aortic valve]] and blood in false channel.
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Image:Aortic aneurysm 13.jpg|Dissecting Aneurysm: Gross, very good to show start of dissection above aortic valve and blood in false channel.
Image:Aortic aneurysm 14.jpg|Dissecting [[Aneurysm]]: Gross, heart with root of [[aorta]] to show [[hemorrhage]] into [[pericardium]] (a very good example).
Image:Aortic aneurysm 14.jpg|Dissecting Aneurysm: Gross, heart with root of aorta to show hemorrhage into pericardium (a very good example).
Image:Aortic aneurysm 15.jpg|Dissecting [[Aneurysm]]: Gross, of heart and [[aorta]] with dissection and large false channel (a good example).
Image:Aortic aneurysm 15.jpg|Dissecting Aneurysm: Gross, of heart and aorta with dissection and large false channel (a good example).
Image:Aortic aneurysm 16.jpg|Dissecting [[Aneurysm]]: Gross cross section of [[aorta]] with two channels (a good example).
Image:Aortic aneurysm 19.jpg|Dissecting [[Aneurysm]]: Gross good example angular tear above [[aortic valve]].
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Image:Aortic aneurysm 16.jpg|Dissecting Aneurysm: Gross cross section of aorta with two channels (a good example).
Image:Aortic aneurysm 18.jpg|Dissecting [[Aneurysm]]: Gross good example of typical angular tear above [[aortic valve]].
Image:Aortic aneurysm 19.jpg|Dissecting Aneurysm: Gross good example angular tear above aortic valve.
Image:Aortic aneurysm 25.jpg|Dissecting [[Aneurysm]]: Gross, rather well shown dissection in first portion of the [[aortic arch]]
Image:Aortic aneurysm 18.jpg|Dissecting Aneurysm: Gross good example of typical angular tear above aortic valve.
Image:Aortic aneurysm 26.jpg|Dissecting [[Aneurysm]]: Gross, rather well shown dissection in first portion of the [[aortic arch]]
Image:Aortic aneurysm 27.jpg|Dissecting [[Aneurysm]]: Gross, an excellent example of type I [[lesion]]
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Image:Aortic aneurysm 25.jpg|Dissecting Aneurysm: Gross, rather well shown dissection in first portion of the aortic arch
Image:Aortic aneurysm 28.jpg|Dissecting [[Aneurysm]]: Gross, external view, an excellent example
Image:Aortic aneurysm 26.jpg|Dissecting Aneurysm: Gross, rather well shown dissection in first portion of the aortic arch
Image:Aortic aneurysm 29.jpg|Dissecting [[Aneurysm]]: Gross, Type I shows false channel
Image:Aortic aneurysm 27.jpg|Dissecting Aneurysm: Gross, an excellent example of type I lesion
Image:Aortic aneurysm 30.jpg|Dissecting [[Aneurysm]]: Gross, opened to show false channel (good example)
Image:Aortic aneurysm 36.jpg|Dissecting [[Aneurysm]]: Gross, large tear in first portion of [[aortic arch]], [[annuloaortic ectasia]]
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Image:Aortic aneurysm 28.jpg|Dissecting Aneurysm: Gross, external view, an excellent example
Image:Aortic aneurysm 32.jpg|Dissecting [[Aneurysm]]: Gross, coagulum of blood in false channel
Image:Aortic aneurysm 29.jpg|Dissecting Aneurysm: Gross, Type I shows false channel
Image:Aortic aneurysm 33.jpg|Dissecting [[Aneurysm]]: Gross, [[aortic valve]] area dissection (well shown, typical lesion)
Image:Aortic aneurysm 30.jpg|Dissecting Aneurysm: Gross, opened to show false channel (good example)
Image:Aortic aneurysm 37.jpg|Dissecting [[Aneurysm]]: Gross, external view of heart and first portion of [[aortic arch]], [[annuloaortic ectasia]], [[hemorrhage]] beneath [[adventitia]] is evidence of dissection
Image:Aortic aneurysm 41.jpg|Dissecting [[Aneurysm]] in a patient with [[Marfan's syndrome]]
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Image:Aortic aneurysm 36.jpg|Dissecting Aneurysm: Gross, large tear in first portion of aortic arch, annuloaortic ectasis
Image:Aortic aneurysm 32.jpg|Dissecting Aneurysm: Gross, coagulum of blood in false channel
Image:Aortic aneurysm 33.jpg|Dissecting Aneurysm: Gross, aortic valve area dissection (well shown, typical lesion)
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Image:Aortic aneurysm 37.jpg|Dissecting Aneurysm: Gross, external view of heart and first portion of aortic arch, annuloaortic ectasia, hemorrhage beneath adventitia is evidence of dissection
Image:Aortic aneurysm 41.jpg|Dissecting Aneurysm in a patient with [[Marfan's syndrome]]
Image:Aortic aneurysm 44.jpg|Dissecting Aneurysm: Gross, fixed tissue, descending thoracic segment dissection opened to show the false channel. The true surface is also visible
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Image:Aortic aneurysm 48.jpg|Dissecting Aneurysm: Gross natural color descending aorta opened into false channel
Image:Aortic aneurysm 44.jpg|Dissecting [[Aneurysm]]: Gross, fixed tissue, [[descending aorta|descending]] [[thoracic aorta|thoracic]] segment dissection opened to show the false channel. The true surface is also visible
Image:Aortic aneurysm 59.jpg|Dissecting Aneurysm: Gross natural color close-up view of aortic valve and proximal aortic arch with ruptured intima rather good illustration of this lesion
Image:Aortic aneurysm 48.jpg|Dissecting [[Aneurysm]]: Gross natural color [[descending aorta]] opened into false channel
Image:Aortic aneurysm 62.jpg|Dissecting Aneurysm Chronic: Gross natural color first portion of aortic arch with intimal rent well shown with healed margins and view into false channel that shows a surface looking like atherosclerosis which is known to develop in a chronic dissection
Image:Aortic aneurysm 59.jpg|Dissecting [[Aneurysm]]: Gross natural color close-up view of [[aortic valve]] and [[proximal]] [[aortic arch]] with ruptured [[intima]] rather good illustration of this [[lesion]]
Image:Aortic aneurysm 63.jpg|Dissecting Aneurysm Chronic: Gross, natural color, closer view of the previous one (a very good example)  
Image:Aortic aneurysm 62.jpg|Dissecting [[Aneurysm]] [[Chronic]]: Gross natural color first portion of [[aortic arch]] with [[intima]]l rent well shown with healed margins and view into false channel that shows a surface looking like [[atherosclerosis]] which is known to develop in a [[chronic]] dissection
Image:Aortic aneurysm 63.jpg|Dissecting [[Aneurysm]] [[Chronic]]: Gross, natural color, closer view of the previous one (a very good example)  
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==Microscopic Pathology==
{| align="left"
|[[File:Aortic dissection (2).jpg|thumb|none|200px|<ref>Case courtesy of Wikimedia Commons</ref>]]
|}


== References ==
== References ==
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Latest revision as of 18:07, 21 January 2020

Aortic dissection Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Aortic dissection from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Study of Choice

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

X-ray

Echocardiography and Ultrasound

CT scan

MRI

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Special Scenarios

Management during Pregnancy

Case Studies

Case #1


Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2] Sahar Memar Montazerin, M.D.[3]

Overview

Aortic dissection begins as a tear in the aortic wall in > 95% of patients. The tear is usually transverse, extends through the intima and halfway through the media and involves ~50% of the aortic circumference. Two thirds of dissections originate in the ascending aorta, and 20% are in the proximal descending aorta.

Pathophysiology

Normal Anatomy of the Aorta

As with all other arteries, the aorta is made up of three layers. The layer that is in direct contact with the flow of blood is the tunica intima, commonly called the intima. This layer is made up of mainly endothelial cells. Just deep to this layer is the tunica media, known as the media. This middle layer is made up of smooth muscle cells and elastic tissue. The outermost layer (furthest from the flow of blood) is known as the tunica adventitia or the adventitia. This layer is composed of connective tissue.
Blood penetrates the intima and enters the media layer.

Pathogenesis

Initial Intimal Tear

  • Aortic dissection begins as a tear in the aortic wall in > 95% of patients.
  • It is usually transverse, extends through the intima and halfway through the media and involves ~50% of the aortic circumference.

Location of Dissections

Propagation of the Intimal Tear

In an aortic dissection, blood penetrates the intima and enters the media layer. The high pressure rips the tissue of the media apart, allowing more blood to enter. This can propagate along the length of the aorta for a variable distance, dissecting either towards or away from the heart or both.

Once a tear develops, blood then passes into the media, and a false lumen is dissected in the outer layer of aortic media involving ~50% of the aortic circumference. This false lumen can enlarge, and compress the true lumen, as well as extend proximally or distally and occlude aortic branches. For some unknown reason, the right lateral wall of the ascending aorta is the most common site for dissection. The right coronary artery can become occluded as a result of this propagation.

Separating the false lumen from the true lumen is a layer of intimal tissue. This tissue is known as the intimal flap. As blood flows down the false lumen, it may cause secondary tears in the intima. Through these secondary tears, the blood can re-enter the true lumen.

Aortic Dissection in the Absence of an Intimal Tear

In about 13% of aortic dissections, there is no evidence of an intimal tear. It is believed that in these cases the inciting event is an intramural hematoma (caused by hemorrhage within the media). Since there is no direct connection between the true lumen and the false lumen in these cases, it is difficult to diagnose an aortic dissection by aortography if the etiology is an intramural hematoma. An aortic dissection secondary to an intramural hematoma should be treated the same as one caused by an intimal tear.

An aortic intramural hematoma can form when the vasa vasorum ruptures into the aortic wall. This is distinguished from dissection by the lack of an intimal tear. This disorder parallels aortic dissection in terms of prognosis when the ascending aorta or aortic arch is involved, and rapid surgical intervention is indicated. Involvement of the descending aorta, however, carries a better prognosis than dissection, and outcome tends to be similar with medical or surgical therapy.

Genetics

Genes involved in the pathogenesis of aortic dissection include:[1][2]

Associated Conditions

Conditions associated with aortic dissection include:[1]

Gross Pathology

Images shown below are courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

  • Dissecting Aneurysm: Gross very good example dissected channel has been opened.

    Dissecting Aneurysm: Gross very good example dissected channel has been opened.

  • Dissecting Aneurysm: Gross external view good appearance from adventitia.

    Dissecting Aneurysm: Gross external view good appearance from adventitia.

  • Dissecting Aneurysm: Gross opened false channel.

    Dissecting Aneurysm: Gross opened false channel.

Microscopic Pathology

[3]

References

  1. ↑ 1.0 1.1 Pinard, Amélie; Jones, Gregory T.; Milewicz, Dianna M. (2019). "Genetics of Thoracic and Abdominal Aortic Diseases". Circulation Research. 124 (4): 588–606. doi:10.1161/CIRCRESAHA.118.312436. ISSN 0009-7330.
  2. ↑ Verhagen, Judith M.A.; Kempers, Marlies; Cozijnsen, Luc; Bouma, Berto J.; Duijnhouwer, Anthonie L.; Post, Jan G.; Hilhorst-Hofstee, Yvonne; Bekkers, Sebastiaan C.A.M.; Kerstjens-Frederikse, Wilhelmina S.; van Brakel, Thomas J.; Lambermon, Eric; Wessels, Marja W.; Loeys, Bart L.; Roos-Hesselink, Jolien W.; van de Laar, Ingrid M.B.H. (2018). "Expert consensus recommendations on the cardiogenetic care for patients with thoracic aortic disease and their first-degree relatives". International Journal of Cardiology. 258: 243–248. doi:10.1016/j.ijcard.2018.01.145. ISSN 0167-5273.
  3. ↑ Case courtesy of Wikimedia Commons

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