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| {{Template:Aortic dissection}}
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| {{SI}}
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| {{CMG}}
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| '''Associate Editor-In-Chief:''' {{CZ}}
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| {{Editor Help}}
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| ==Overview==
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| == Epidemiology and Demographics ==
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| * Approximately 2000 cases in the US per year
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| * Accounts for 3-4% of [[sudden deaths]]
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| * 2:1 male:female predominance in all types of dissection.
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| * Peak incidence in the sixth and seventh decades.
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| **Patients with type I dissection present approximately 6 years younger than those with type II or type II dissection.
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| * 67% present with acute symptoms (<2 weeks), and 33% with chronic symptoms (>= 2 weeks).
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| **Chronic dissection is almost twice as common in patients with type III (45%) when compared with type I (24%) and type II (27%).
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| == Risk Factors ==
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| * [[Hypertension]] is seen in 71-86% of patients, occurring most frequently in those with type III dissection.
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| * [[Bicuspid aortic valve]] is the next most common risk factor, seen in approximately 7%.
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| * [[Marfan’s syndrome]] was seen in 6%.
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| * Other uncommon associations include:
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| **[[Giant cell arteritis]]
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| **[[Cystic medial necrosis]]
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| **[[Coarctation of the aorta]]
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| * Deceleration [[trauma]] most commonly causes aortic rupture, not dissection.
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| * Risk factors for [[atherosclerosis]] are also commonly seen, including tobacco use in 67%, and insulin dependent [[diabetes]] mellitus (IDDM) in 6%.
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| == Pathophysiology==
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| [[Image:AoDissect Schema 01a.png|left|thumb|Blood penetrates the ''intima'' and enters the ''media'' layer.]]
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| 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]].
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| 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. The initial tear is usually within 100 mm of the [[aortic valve]].
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| The risk in aortic dissection is that the aorta may rupture, leading to massive blood loss resulting in death.
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| The initiating event in an aortic dissection is a tear in the intimal lining of the [[aorta]]. Due to the high [[blood pressure|pressures]] in the aorta, blood enters the media at the point of the tear. The force of the blood entering the media causes the tear to extend. It may extend proximally (closer to the heart) or distally (away from the heart) or both. The blood will travel through the media, creating a ''false lumen'' (the ''true lumen'' is the normal conduit of blood in the aorta). Separating the false lumen from the true lumen is a layer of intimal tissue. This tissue is known as the '''intimal flap'''.
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| The vast majority of aortic dissections originate with an intimal tear in either the [[ascending aorta]] (65%), the [[aortic arch]] (10%), or just distal to the [[ligamentum arteriosum]] in the [[Descending aorta|descending thoracic aorta]] (20%).
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| 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.
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| 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]].
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| 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.
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| * 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.
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| * Location of dissections:
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| :*65% of dissections originate in the ascending aorta, distal to the aortic valve and coronary ostia.
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| :*10% arise in the transverse aortic arch
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| :*20% in the proximal descending aorta
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| :*5% in the more distal descending aorta.
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| Once a tear develops, blood then passes into the media, and a false leumen is dissected distally in the outer layer of aortic media involving ~50% of the aortic circumference. This false leumen can enlarge, and compress the true leumen, 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.
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| ::* 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.
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| ===Aneurysm vs Dissection:===
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| An aortic aneurysm is not synonymous with aortic dissection. Aneurysms are defined as a localized permanent dilation of the aorta to a diameter > 50% of normal. Cystic medial necrosis is the most common risk factor for the development of ascending aneurysms, and atherosclerosis is the commonest risk factor for descending aneurysms.
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| :* The natural history of thoracic aneurysms depends on the size. Rupture is the most common cause of death, and the frequency of rupture is much higher in dissecting aneurysms than in non-dissecting ones.
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| :* Thoracic aneurysms enlarge at a more rapid rate than abdominal aneurysms (0.42 vs. 0.28 cm/yr), with aneurysms of the aortic arch growing at ~ 0.56 cm/yr. Aneurysms that are 5-6cm in diameter have a faster rate of growth and a greater tendency to rupture than smaller ones.
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| ==Etiology==
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| Aortic dissection is associated with [[hypertension]] (high blood pressure) and many [[connective tissue]] disorders. [[Vasculitis]] ([[inflammation]] of an artery) is rarely associated with aortic dissection. It can also be the result of chest trauma. 72 to 80% of individuals who present with an aortic dissection have a previous history of hypertension.
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| The highest incidence of aortic dissection is in individuals who are 50 to 70 years old. The incidence is twice as high in males as in females (male-to-female ratio is 2:1). Half of dissections in females before age 40 occur during [[pregnancy]] (typically in the 3rd trimester or early [[postpartum]] period).
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| A [[bicuspid aortic valve]] (a type of [[congenital heart disease]] involving the [[aortic valve]]) is found in 7-14% of individuals who have an aortic dissection. These individuals are prone to dissection in the ascending aorta. The risk of dissection in individuals with bicuspid aortic valve is not associated with the degree of [[aortic stenosis|stenosis]] of the valve.
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| [[Marfan syndrome]] is noted in 5-9% of individuals who suffer from aortic dissection. In this subset, there is an increased incidence in young individuals. Individuals with Marfan syndrome tend to have aneurysms of the aorta and are more prone to proximal dissections of the aorta.
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| [[Turner syndrome]] also increases the risk of aortic dissection, by aortic root dilatation<ref>[http://www.ncbi.nlm.nih.gov/sites/entrez?Db=PubMed&Cmd=ShowDetailView&TermToSearch=17055808&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Increased maternal cardiovascular mortality associated with pregnancy in women with Turner syndrome.]</ref>.
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| Chest trauma leading to aortic dissection can be divided into two groups based on etiology: blunt chest trauma (commonly seen in car accidents) and [[iatrogenic]]. Iatrogenic causes include trauma during [[cardiac catheterization]] or due to an [[intra-aortic balloon pump]].
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| Aortic dissection may be a late sequalae of [[cardiac surgery]]. 18% of individuals who present with an acute aortic dissection have a history of open heart surgery. Individuals who have undergone aortic valve replacement for [[aortic insufficiency]] are at particularly high risk. This is because aortic insufficiency causes increased blood flow in the ascending aorta. This can cause dilatation and weakening of the walls of the ascending aorta.
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| ==Classification systems==
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| Several different classification systems have been used to describe aortic dissections. The systems commonly in use are either based on the anatomy of the dissection or the duration of onset of symptoms prior to presentation.
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| ===DeBakey classification system===
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| The DeBakey system is an anatomical description of the aortic dissection. It categorizes the dissection based on where the original intimal tear is located and the extent of the dissection (localized to either the ascending aorta or descending aorta, or involves both the ascending and descending aorta.<ref>DeBakey ME, Henly WS, Cooley DA, Morris GC Jr, Crawford ES, Beall AC Jr. Surgical management of dissecting aneurysms of the aorta. ''J Thorac Cardiovasc Surg'' 1965;49:130-49. PMID 14261867.</ref>
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| *'''Type I''' - Originates in ascending aorta, propagates at least to the aortic arch and often beyond it distally.
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| *'''Type II''' – Originates in and is confined to the ascending aorta.
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| *'''Type III''' – Originates in descending aorta, rarely extends proximally.
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| {| border="1" cellspacing="0" style="width:320px;float:Center;margin-left:0.5em;border-collapse:collapse" | |
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| |valign="top"|
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| |[[Image:AoDissect DeBakey1.png|90px]]
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| |[[Image:AoDissect DeBakey2.png|90px]]
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| |[[Image:AoDissect DeBakey3.png|90px]]
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| |-
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| |bgcolor="#DCDCDC"|Percentage
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| |align="center" bgcolor="#DCDCDC"|60 %
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| |align="center" bgcolor="#DCDCDC"|10-15 %
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| |align="center" bgcolor="#DCDCDC"|25-30 %
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| |style="border-bottom:white"|Type
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| |align="center" border="0"|DeBakey I
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| |align="center" |DeBakey II
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| |align="center" |DeBakey III
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| |-
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| |style="border-bottom:white"|
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| | colspan=2 align="center" |Stanford A
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| |align="center" |Stanford B
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| |-
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| | colspan=2 align="center" |Proximal
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| |align="center" |Distal
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| |- | | |- |
| | colspan=4 bgcolor="#ABCDEF" | <small>Classification of aortic dissection</small> | | | [[File:Siren.gif|30px|link=Aortic dissection resident survival guide]]|| <br> || <br> |
| | | [[Aortic dissection resident survival guide|'''Resident'''<br>'''Survival'''<br>'''Guide''']] |
| |} | | |} |
| | {{Template:Aortic dissection}} |
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| ===Stanford classification system===
| | '''For patient information, click [[Aortic_dissection_(patient_information)|here]]''' |
| Divided into 2 groups; A and B depending on whether the ascending aorta is involved.<ref>Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. ''Ann Thorac Surg'' 1970;10:237-47. PMID 5458238.</ref>
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| *'''A''' = '''Type I''' and '''II''' DeBakey
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| *'''B''' = '''Type III''' Debakey
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| [[Image:AoDissekt scheme StanfordB.png|left|thumb|Dissection of the aorta descendens (3), which starts from the left subclavian artery, reaching to the abdominal aorta (4). Aorta ascendens (1) and aortic arch (2) are not involved.]]
| | {{CMG}}; '''Associate Editor-In-Chief:''' {{CZ}} {{Sahar}} {{Laith}} |
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| {{-}} | | {{SK}} Leaking aneurysm; dissecting aortic aneurysm; aneurysm, dissecting, aorta; aortic aneurysm - dissecting |
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| == Natural History == | | ==[[Aortic dissection overview|Overview]]== |
| If the patient remains untreated, the mortality is:
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| * 1% per hour during the first day
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| * 75% at 2 weeks
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| * 90% at 1 year
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| ==Differential diagnosis of entities to distinguish from aortic dissection== | | ==[[Aortic dissection historical perspective|Historical Perspective]]== |
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| * [[Aortic Regurgitation]]
| | ==[[Aortic dissection classification|Classification]]== |
| * [[Aortic Stenosis]]
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| * [[Cardiac Tamponade]]
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| * [[Cardiogenic Shock]]
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| * [[Gastroenteritis]]
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| * [[Hemorrhagic Shock]]
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| * [[Hernias]]
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| * [[Hypertensive Emergencies]]
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| * [[Hypovolemic Shock]]
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| * [[Mechanical Back Pain]]
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| * [[Myocardial Infarction]]
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| * [[Myocarditis]]
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| * [[Myopathies]]
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| * [[Pancreatitis]]
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| * [[Pericarditis]]
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| * [[Peripheral Vascular Injuries]]
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| * [[Pleural Effusion]]
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| * [[Pulmonary Embolism]]
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| * [[Thoracic Outlet Syndrome]]
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| == Diagnosis == | | ==[[Aortic dissection pathophysiology|Pathophysiology]]== |
| In a study by Spittell et.al. at the Mayo, the initial clinical impression of dissection (after history, physical, chest x-ray and echocardiography) was made in 62% of patients. A correct diagnosis was more commonly made in patients with type I or type II dissections. The differential is quite broad and depends upon the location of dissection, aortic root / coronary involvement, and obstruction of aortic or aortic branch blood flow.
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| === History and Symptoms === | | ==[[Aortic dissection causes|Causes]]== |
| About 96% of individuals with aortic dissection present with severe pain that had a sudden onset. It may be described as tearing in nature, or stabbing or sharp in character. 17% of individuals will feel the pain migrate as the dissection extends down the aorta. The location of pain is associated with the location of the dissection. [[Anterior]] chest pain is associated with dissections involving the ascending aorta, while intrascapular (back) pain is associated with descending aortic dissections. If the pain is pleuritic in nature, it may suggest acute [[pericarditis]] due to hemorrhage into the pericardial sac.
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| While the pain may be confused with the pain of a [[myocardial infarction]] (heart attack), aortic dissection is usually not associated with the other signs that suggest myocardial infarction, including heart failure, and [[ECG]] changes. Also, individuals suffering from an aortic dissection usually do not present with [[diaphoresis]] (profuse sweating).
| | ==[[Aortic dissection differential diagnosis|Differentiating Aortic Dissection from other Diseases]]== |
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| Individuals with aortic dissection who do not present with pain have chronic dissection.
| | ==[[Aortic dissection epidemiology and demographics|Epidemiology and Demographics]]== |
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| Less common symptoms that may be seen in the setting of aortic dissection include [[congestive heart failure]] (7%), [[fainting|syncope]] (9%), [[cerebrovascular accident]] (3-6%), ischemic peripheral neuropathy, [[paraplegia]], [[cardiac arrest]], and sudden death. If the individual had a [[syncope|syncopal]] episode, about half the time it is due to hemorrhage into the pericardium leading to [[pericardial tamponade]].
| | ==[[Aortic dissection risk factors|Risk Factors]]== |
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| Neurologic complications of aortic dissection (i.e., [[cerebrovascular accident]] (CVA) and [[paralysis]]) are due to involvement of one or more arteries supplying portions of the [[central nervous system]].
| | ==[[Aortic dissection screening|Screening]]== |
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| If the aortic dissection involves the abdominal aorta, compromise of the branches of the abdominal aorta are possible. In abdominal aortic dissections, compromise of one or both [[renal artery|renal arteries]] occurs in 5-8% of cases, while mesenteric [[ischemia]] (ischemia of the [[large intestine]]s) occurs 3-5% of the time.<ref>Saner, H.E., et al., Aortic dissection presenting as Pericarditis. Chest, 1987. 91(1): p. 71-4. PMID 3792088</ref> <ref>Rosman, H.S., et al., Quality of history taking in patients with aortic dissection. Chest, 1998. 114(3): p. 793-5. PMID 9743168</ref> <ref>Hagan, P.G., et al., The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA, 2000. 283(7): p. 897-903. PMID 10685714</ref> <ref>von Kodolitsch, Y., A.G. Schwartz, and C.A. Nienaber, Clinical prediction of acute aortic dissection. Arch Intern Med, 2000. 160(19): p. 2977-82. PMID 11041906</ref>
| | ==[[Aortic dissection natural history|Natural History, Complications and Prognosis]]== |
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| ====Blood pressure changes==== | | ==Diagnosis== |
| While many patients with an aortic dissection have a history of [[arterial hypertension|hypertension]], the blood pressure is quite variable at presentation with acute aortic dissection, and tends to be higher in individuals with a distal dissection. In individuals with a proximal aortic dissection, 36% present with [[arterial hypertension|hypertension]], while 25% present with [[hypotension]]. In those that present with distal aortic dissections, 70% present with hypertension while 4% present with hypotension.
| | [[Aortic dissection history and symptoms|History and Symptoms]] | [[Aortic dissection physical examination|Physical Examination]] | [[Aortic dissection laboratory findings|Laboratory Findings]] | [[Aortic dissection electrocardiogram|Electrocardiogram]] | [[Aortic dissection imaging in acute aortic dissection|Imaging in Aortic Dissection]] | [[Aortic dissection chest x ray|Chest X Ray]] | [[Aortic dissection CT|CT]] | [[Aortic dissection MRI|MRI]] | [[Aortic dissection echocardiography|Echocardiography]] | [[Aortic dissection aortography|Aortography]] | [[Aortic dissection coronary angiography|Coronary Angiography]] | [[Aortic dissection other diagnostic studies|Other Diagnostic Studies]] |
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| Severe hypotension at presentation is a grave prognostic indicator. It is usually associated with [[pericardial tamponade]], severe [[aortic insufficiency]], or rupture of the aorta. Accurate measurement of the blood pressure is important. ''Pseudohypotension'' (falsely low blood pressure measurement) may occur due to involvement of the [[brachiocephalic artery]] (supplying the right arm) or the [[left subclavian artery]] (supplying the left arm).
| | ==Treatment== |
| | [[Aortic dissection medical therapy|Medical Therapy]] | [[Aortic dissection surgery|Surgery]] | [[Aortic dissection secondary prevention|Secondary Prevention]] | |
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| ====Aortic insufficiency==== | | ==Special Scenarios== |
| [[Aortic insufficiency]] (AI) occurs in 1/2 to 2/3 of ascending aortic dissections, and the [[heart sounds|murmur]] of aortic insufficiency is audible in about 32% of proximal dissections. The intensity (loudness) of the murmur is dependent on the blood pressure and may be inaudible in the event of [[hypotension]]. | | [[Aortic dissection management during pregnancy|Management During Pregnancy]] |
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| There are multiple etiologies for AI in the setting of ascending aortic dissection. The dissection may dilate the annulus of the [[aortic valve]], so that the leaflets of the valve cannot coapt. Another mechanism is that the dissection may extend into the aortic root and detach the aortic valve leaflets. The third mechanism is that if there was an extensive intimal tear, the intimal flap may prolapse into the LV outflow tract, causing intimal [[intussusception]] into the aortic valve preventing proper valve closure.
| | ==Case Studies== |
| | [[Aortic dissection case study one|Case #1]] |
| | ==Related Chapters== |
| | *[[Acute aortic syndrome]] |
| | *[[Penetrating atherosclerotic aortic ulcer]] |
| | *[[Aortic intramural hematoma]] |
| | *[[Aortic rupture]] |
| | *[[Abdominal aortic aneurysm]] |
| | *[[Thoracic aortic aneurysm]] |
| | *[[Aorta]] |
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| ====Myocardial infarction====
| | {{WikiDoc Help Menu}} |
| [[Myocardial infarction]] (heart attack) occurs in 1-2% of aortic dissections. The etiology of the infarction is involvement of the [[coronary artery|coronary arteries]] (the [[artery|arteries]] that supply the heart) in the dissection. The right coronary artery is involved more commonly than the left coronary artery. If the myocardial infarction is treated with [[thrombolytic]] therapy, the mortality increases to over 70%, mostly due to hemorrhage into the pericardial sac causing [[pericardial tamponade]].
| | {{WikiDoc Sources}} |
| | | [[CME Category::Cardiology]] |
| Because aortic dissection may present to the [[emergency room]] [[physician]] similar to a myocardial infarction, the physician must be careful to make the proper diagnosis prior to initiating treatment for myocardial infarction, since the treatment regimen for myocardial infarction can be lethal to an individual presenting with aortic dissection.
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| ====Pleural effusion====
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| A [[pleural effusion]] (fluid collection in the space between the [[lung]]s and the chest wall or [[diaphragm (anatomy)|diaphragm]]) can be due to either blood from a transient rupture of the aorta or fluid due to an inflammatory reaction around the aorta. If a pleural effusion were to develop due to an aortic dissection, it is more commonly in the left hemithorax rather than the right hemithorax.
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| * 74% of patients who survive the initial tear typically present with the sudden onset of severe tearing pain. 92% of patients with anterior chest pain as their major source of pain have either type I or type II dissections, and only 8% have type III. Neck, throat, jaw, and unilateral face pain are also seen more commonly in those with type I or type II dissection. 52% of patients with type III dissection have the majority of their pain in the back, and 67% of these patients have some degree of back pain.
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| * Up to 15 – 55 % of patients can have painless dissection. Dissection should therefore be included in the differential in patients with unexplained syncope, stroke or congestive heart failure (CHF).
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| * 4% of patients present with out of hospital cardiac arrest.
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| * Unusual symptoms include:
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| :* Hoarseness
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| :* Hemoptysis
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| :* Claudication
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| :* Superior vena cava (SVC) syndrome
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| :* Upper gastrointestinal (UGI) bleed
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| :* Upper airway obstruction.
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| === Physical Examination ===
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| * Cardiac tamponade, hemothorax, Horner syndrome, and hoarseness (due to compression of the left recurrent laryngeal nerve) can also be seen.
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| * Descending dissection can lead to splanchnic ischemia, renal insufficiency
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| ==== Heart ====
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| * [[Aortic regurgitation]] is present in approximately 40 – 66 % of patients and is almost always seen in those with type I or type II dissection. The murmur of [[aortic insufficiency]] ([[AI]]) due to aortic dissection is best heard at the R 2nd intercostal space (ICS), as compared with the lower left sternal border for [[AI]] due to primary aortic valvular disease.
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| ==== Lungs ====
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| [[Rales]] may be present due to [[cardiogenic pulmonary edema]]
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| ==== Extremities ====
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| Diminution or absence of pulses is found in up to 40% of patients, and occurs due to occlusion of a major aortic branch. For this reason it is critical to assess the pulse and blood pressure in both arms.
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| ==== Neurologic ====
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| * Neurologic deficits such as [[coma]], altered mental status, [[Ddx:Cerebrovascular Accident|Cerebrovascular accident]] (CVA) and [[vagal episodes]] are seen in up to 20%.
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| *There can also be focal neurologic signs due to occlusion of a [[Anterior spinal artery|spinal artery]]. This condition is known as [[Anterior spinal artery syndrome]] or [[Anterior spinal artery syndrome|"Beck's syndrome"]].
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| === Laboratory Findings ===
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| ==== Electrolyte and Biomarker Studies ====
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| * Routine blood work is usually not helpful, although one can see evidence of hemolysis from the blood in the false leumen. There has been one report using a smooth muscle myosin heavy chain immunoassay to help diagnose aortic dissection. They report that a level > 10 ng/ml within the first 12h is 90% sensitive and 97% specific. This needs to be confirmed in other trials however.
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| *The presence of an elevated CK MB may indicate the presence of concomitant MI (often an right coronary artery occlusion due to occlusion of the ostium of the RCA by the dissection).
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| ==== Electrocardiogram ====
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| [[ST elevation myocardial infarction]] ([[MI]]) due to occlusion by the dissection of the coronary artery at its ostium may be present. The [[right coronary artery]] tends to be involved more frequently than the [[left coronary artery]].
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| ==== Chest X Ray ====
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| * Chest X-Ray Abnormalities:
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| *:* An increased aortic diameter is the most common CXR finding, seen in up to 84% of patients.
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| *:* A widened mediastinum is the next most common finding, seen in 15-20%.
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| *:* Normal in 17%.
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| *:* Pleural effusion (hemothorax) in the absence of CHF can also be another clue to dissection.
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| ====Computed tomography angiography====
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| <div align="left">
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| <gallery heights="175" widths="175">
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| Image:AoDiss CT A-Diss.jpg|Aortic dissection Type Stanford A
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| Image:AoDiss CT A-Diss01.jpg|Aortic dissection Type Stanford A - '1'' Aorta ascendens, true Lumen - ''2'' false Lumen - ''3'' [[Pulmonary artery]] - ''4'' Aorta descendens - ''5'' thoracic vertebra
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| Image:Type-a-dissection-ct.jpg|Another example of Stanford A type dissection
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| </gallery>
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| </div>
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| [[Computed tomography angiography]] is a fast non-invasive test that will give an accurate three-dimensional view of the aorta. These images are produced by taking rapid thin cut slices of the chest and abdomen, and combining them in the computer to create cross-sectional slices. In order to delineate the aorta to the accuracy necessary to make the proper diagnosis, an iodinated contrast material is injected into a peripheral vein. Contrast is injected and the scan performed using a [[Bolus Tracking]] method. This is a type of scan timed to an injection, in order to capture the contrast as it enters the aorta. The scan will then follow the contrast as it flows though the vessel.
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| It has a sensitivity of 96 - 100% and a specificity of 96 to 100%. Disadvantages include the need for iodinated contrast material and the inability to diagnose the site of the intimal tear.
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| CT scanning with contrast has a reported sensitivity of 94% and a specificity of 87%. Unfortunately, the intimal flap is seen in < 75% of cases. Additionally, one can not assess the coronary arteries or for the presence of AI. Over the past few years, spiral CT and ultrafast CT (electron beam CT) have substantially improved the accuracy in the diagnosis of aortic dissection.
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| '''Differentiating a true lumen from the false lumen'''
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| *Beak sign: In the false lumen, there will be an acute angle between the dissection flap and the arterial wall.
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| *Aortic cobwebs: In the false lumen, there may be fibroelastic bands.
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| *Size: False lumen is usually larger than the true lumen.
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| *Diplaced intimal calcification: Usually faces the true lumen.
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| '''Labeled CT images shown below are courtesy of Radswiki and copylefted:'''
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| <div align="left">
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| <gallery heights="175" widths="175">
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| Image:Aortic dissection type B 001.jpg
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| Image:Aortic dissection type B 002.jpg
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| Image:Aortic dissection type B 003.jpg
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| </gallery>
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| </div>
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| <gallery heights="175" widths="175">
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| Image:Aortic dissection type B 004.jpg
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| Image:Aortic dissection type B 005.jpg
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| </gallery>
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| </div>
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| <div align="left">
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| <gallery heights="175" widths="175">
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| Image:Aortic dissection type B 006.jpg
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| Image:Aortic dissection type B 007.jpg
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| </gallery>
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| </div>
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| ==== MRI ====
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| [[Magnetic resonance imaging]] (MRI) is currently the [[gold standard (test)|gold standard test]] for the detection and assessment of aortic dissection, with a sensitivity of 98% and a specificity of 98%. An MRI examination of the aorta will produce a three-dimensional reconstruction of the aorta, allowing the physician to determine the location of the intimal tear, the involvement of branch vessels, and locate any secondary tears. It is a non-invasive test, does not require the use of iodinated contrast material, and can detect and quantitate the degree of [[aortic insufficiency]].
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| The disadvantage of the MRI scan in the face of aortic dissection is that it has limited availability and is often located only in the larger hospitals, and the scan is relatively time consuming. Due to the high intensity of the magnetic waves used during MRI, an MRI scan is contraindicated in individuals with metallic implants. In addition, many individuals succumb to [[claustrophobia]] while in the MRI scanning tube.
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| <div align="left">
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| <gallery heights="125" widths="125">
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| Image:AoDiss MRT.jpg|[[Magnetic resonance imaging|MRI]] of an aortic dissection. ''1'' Aorta descendens with dissection. ''2'' Aortic isthmus.
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| </gallery>
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| </div>
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| ==== Echocardiography ====
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| The [[transesophageal echocardiogram]] (TEE) is a relatively good test in the diagnosis of aortic dissection, with a sensitivity of up to 98% and a specificity of up to 97%. It is a relatively [[non-invasive (medical)|non-invasive test]], requiring the individual to swallow the echocardiography probe. It is especially good in the evaluation of AI in the setting of ascending aortic dissection, and to determine whether the ostia (origins) of the coronary arteries are involved. While many institutions give sedation during transesophageal echocardiography for added patient-comfort, it can be performed in cooperative individuals without the use of sedation. Disadvantages of the TEE include the inability to visualize the distal ascending aorta (the beginning of the [[aortic arch]]), and the descending abdominal aorta that lies bellow the [[stomach]]. A TEE may be technically difficult to perform in individuals with esophageal strictures or [[varices]].
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| Transthoracic (TTE) unfortunately does not provide pretty pictures of the distal ascending, transverse and descending aorta in a small number of patients. Its use is limited to assess cardiac complications of dissection including AI, tamponade and LV function.
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| Transesophageal (TEE), however, is a portable technique that can be brought to the emergency department and establish a diagnosis in < 5 minutes of starting the test. It can identify true and false lumens, the intimal flap, thrombosis in the false lumen, pericardial effusion, AI, and the proximal coronaries. Although monoplane TEE has a sensitivity of 98%, its specificity is only 77%. This can be increased to a sensitivity and specificity of 99% and 98% respectively with combined use of TTE and TEE. Biplane and multiplane imagine however have been shown to be 98% sensitive and 95% specific for aortic dissection.
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| In general, it is recommended to perform bedside multiplane TEE in patients with acute symptoms or clinically unstable, and MRI in patients with a more chronic presentation if they are hemodynamically stable.
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| CT angio is reserved for patients whom TEE or MRI is unavailable or contraindicated. Aortography is required if the tests listed above are non-diagnostic.
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| [[Image:Aortic dissection - Echocardiogram - Longitudinal view.jpg|420px|thumb|left|Echocardiogram of an aortic dissection]]
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| {{-}}
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| [[Image:Aortic dissection - Echocardiogram - Longitudinal view - Color.jpg|420px|thumb|left|Echocardiogram of an aortic dissection]]
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| {{-}}
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| <youtube v=nD8DrZCPFBI/>
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| {{-}}
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| Aortic Dissection Type A Example 1
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| <googlevideo>-1580944144837691434&hl=en </googlevideo>
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| {{-}}
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| Aortic Dissection Type A Example 2
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| <googlevideo>-3610218405615821421&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type A Example 3
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| <googlevideo>-8461290621229660122&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type A Example 4
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| <googlevideo>-8561147882050584609&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type A Example 5
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| <googlevideo>2157100999251300976&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type A Example 6
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| <googlevideo>698950344523479477&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type B Example 1
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| <googlevideo>3238725821918795498&hl=en</googlevideo>
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| {{-}}
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| Aortic Dissection Type B Example 2
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| <googlevideo>197658671308723787&hl=en</googlevideo>
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| {{-}} | |
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| ==== Other Imaging Findings ====
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| ====Aortogram====
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| An aortogram involves placement of a [[catheter]] in the [[aorta]] and injection of contrast material while taking x-rays of the aorta. The diagnosis of aortic dissection can be made by visualization of the intimal flap and flow of contrast material in both the true lumen and the false lumen.
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| The aortogram was previously considered the [[gold standard (test)|gold standard test]] for the diagnosis of aortic dissection, with a sensitivity of up to 88% and a specificity of about 94%. It is especially poor in the diagnosis of cases where the dissection is due to hemorrhage within the media without any initiating intimal tear.
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| The advantage of the aortogram in the diagnosis of aortic dissection is that it can delineate the extent of involvement of the aorta and branch vessels and can diagnose [[aortic insufficiency]].
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| The disadvantages of the aortogram are that it is an invasive procedure and it requires the use of iodinated contrast material.
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| Although aortography has a sensitivity of 88% and a specificity of 94% in experienced hands, it has largely been replaced by noninvasive diagnostic techniques. It is helpful however, in determining the site of dissection, the relationship of the dissection the major aortic branches, as well as identifying the true and false lumens. Additionally, coronary angiography can be preformed at the same time. False negatives occur if the false leumen is already thrombosed, or when there is simultaneous opacification of both lumens.
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| <googlevideo>-1291385681032114503&hl=en</googlevideo>
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| ==Aorta: Dissection, Cystic Medial Degeneration==
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| <youtube v=t9WVLNi7zXk/>
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| == Treatment ==
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| The risk of death due to aortic dissection is highest in the first few hours after the dissection begins, and decreases afterwards. Because of this, the therapeutic strategies differ for treatment of an acute dissection compared to a chronic dissection. An acute dissection is one in which the individual presents within the first two weeks. If the individual has managed to survive this window period, his prognosis is improved. About 66% of all dissections present in the acute phase.
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| In all individuals with aortic dissections, medication should be used to control [[hypertension|high blood pressure]], if present.
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| In the case of an acute dissection, once diagnosis has been confirmed, the choice of treatment depends on the location of the dissection. For ascending aortic dissection, surgical management is superior to medical management. On the other hand, in the case of an uncomplicated distal aortic dissections (including abdominal aortic dissections), medical management is preferred over surgical treatment <ref>{{cite journal | author = Suzuki T, Mehta RR, Ince H, Nagai R, Sakomura Y, Weber F, Sumiyoshi T, Bossone E, Trimarchi S, Cooper J, Smith D, Isselbacher E, Eagle K, Nienaber C | title = Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). | journal = Circulation | volume = 108 Suppl 1 | issue = | pages = II312-7 | year = | id = PMID 12970252}}</ref>
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| Individuals who present two weeks after the onset of the dissection are said to have chronic aortic dissections. These individuals have been self-selected as survivors of the acute episode, and can be treated with medical therapy as long as they are stable.
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| Medical management is appropriate in individuals with an uncomplicated distal dissection, a stable dissection isolated to the aortic arch, and stable chronic dissections. Patient selection for medical management is very important. Stable individuals who present with an acute distal dissection (typically treated with medical management) still have an 8 percent 30 day mortality.
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| [http://videos.med.wisc.edu/videoInfo.php?videoid=264 VIDEO - What is New in the Treatment of Type B Aortic Dissection?], Girma Tefera, MD, speaks at the University of Wisconsin School of Medicine and Public Health. | |
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| === Medical management ===
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| The prime consideration in the medical management of aortic dissection is strict blood pressure control. The target blood pressure should be a [[mean arterial pressure]] (MAP) of 60 to 75 mmHg. Another factor is to reduce the shear-force dP/dt (force of ejection of blood from the [[left ventricle]]).
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| To reduce the shear stress, a vasodilator such as [[sodium nitroprusside]] should be used with a [[beta blocker]], such as [[esmolol]], [[propranolol]], or [[labetalol]]. The alpha-blocking properties of [[labetalol]] make it especially attractive in this situation.
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| [[Calcium channel blocker]]s can be used in the treatment of aortic dissection, particularly if there is a contraindication to the use of beta blockers. The calcium channel blockers typically used are [[verapamil]] and [[diltiazem]], because of their combined vasodilator and negative [[inotropic]] effects.
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| If the individual has refractory hypertension (persistent hypertension on the maximum doses of three different classes of antihypertensive agents), involvement of the renal arteries in the aortic dissection plane should be considered.
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| === Surgical management ===
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| Indications for the surgical treatment of aortic dissection include an acute proximal aortic dissection and an acute distal aortic dissection with one or more complications. Complications include compromise of a vital organ, rupture or impending rupture of the aorta, retrograde dissection into the ascending aorta, and a history of [[Marfan's syndrome]].
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| The objective in the surgical management of aortic dissection is to resect (remove) the most severely damaged segments of the aorta, and to obliterate the entry of blood into the false lumen (both at the initial intimal tear and any secondary tears along the vessel). While excision of the intimal tear may be performed, it does not significantly change mortality.
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| Some methods of repair are:
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| * Replacement of the damaged section with a tube graft (often made of dacron) when there is no damage to the [[aortic valve]].
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| * [[Bentall procedure]] - Replacement of the damaged section of aorta and replacement of the aortic valve.
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| * [[David procedure]] - Replacement of the damaged section of aorta and reimplantation of the aortic valve.
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| A number of comorbid conditions increase the surgical risk of repair of an aortic dissection. These include:
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| * Prolonged pre-op evaluation (increased length of time prior to surgery)
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| * Advanced age
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| * Comorbid disease states (e.g.: [[coronary artery disease]])
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| * Aneurysm leakage
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| * [[Cardiac tamponade]]
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| * [[Shock (medical)|Shock]]
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| * Past history of [[myocardial infarction]] or [[cerebrovascular accident|CVA]]
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| * History of [[renal failure]] (either acute or chronic renal failure)
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| === Long term follow-up ===
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| The long term follow-up in individuals who survive aortic dissection involves strict blood pressure control. The relative risk of late rupture of an [[aortic aneurysm]] is 10 times higher in individuals who have uncontrolled [[hypertension]], compared to individuals with a systolic pressure below 130 mmHg.
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| The risk of death is highest in the first two years after the acute event, and individuals should be followed closely during this time period. 29% of late deaths following surgery are due to rupture of either the dissecting aneurysm or another aneurysm. In additions, there is a 17 to 25% incidence of new aneurysm formation. This is typically due to dilatation of the residual false lumen. These new aneurysms are more likely to rupture, due to their thinner walls.
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| Serial imaging of the aorta is suggested, with [[MRI]] being the preferred imaging technique.
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| *DeBakey and Cooley reported the first successful operation for resection and graft replacement of the ascending aorta using cardiopulmonary bypass in 1956.
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| *Any dissection that involves the ascending aorta is considered a surgical emergency. Without surgery, there is a 90% 3-month mortality. These patients can rapidly develop acute aortic insufficiency (AI), tamponade or myocardial infarction (MI). Even acute MI in the setting of dissection is not a surgical contraindication. Acute hemorrhagic stroke is, however, a relative contraindication, due to the necessity of intraoperative heparinization.
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| :*Operative mortality for ascending dissections is surgeon dependant, and averages ~ 5 – 20 %. This however, is well below the 50% mortality when these cases are managed with medical therapy.
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| :*Factors that increase surgical risk include renal insufficiency, visceral ischemia, tamponade and underlying pulmonary disease.
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| :*Surgical therapy involves excision of the intimal tear, obliteration of the proximal entry site into the false leumen, and reconstitution of the aorta with placement of a synthetic graft. AI can be corrected by resuspension of the native valve, or by aortic valve replacement (AVR).
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| :*Dissections involving the descending aorta only can be managed medically unless there is progression or continued hemorrhage into the pleural or retroperitoneal space. The major surgical complication in descending dissections is spinal cord ischemia and paralysis.
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| :*Medical management centers around blood pressure control and decreasing the velocity of left ventricular contraction with the goal of decreasing aortic shear stress. Pain control with morphine is also extremely important. For patients with DeBakey III or Daily B dissections, medical therapy offers an > 80% survival rate.
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| :*The systolic blood pressure is kept at the lowest level tolerated. Initial treatment usually involves either Labetalol (20mg bolus f/b 20-80mg q10min to a total dose of 300mg, or as an infusion of 0.5 – 2 mg/min) or Propranolol (1 – 10 mg load f/b 3mg/hr) with the goal heart rate ~ 60 BPM. Lopressor and Verapamil can also be used.
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| :*If the heart rate is controlled, and the systolic blood pressure (SBP) is > 100 mmHg with adequate mentation and urine output, Sodium Nitroprusside is added (0.25 – 0.5 ug/kg/min). Nitroprusside should never be used prior to beta blockade, as the hypotension can result in a reflex tachycardia.
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| :*All patients should have an arterial line in the arm with the higher BP for accurate monitoring.
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| ==Pathological Findings==
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| <div align="left">
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| <gallery heights="225" widths="225">
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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. <br> <small> [http://www.peir.net Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology] </small>
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| </gallery>
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| </div>
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| == References ==
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| {{Reflist|2}}
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| == Acknowledgements ==
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| The content on this page was first contributed by: David Feller-Kopman, MD and [[C. Michael Gibson]] M.S., M.D.
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| {{Circulatory system pathology}}
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