Aortic dissection overview: Difference between revisions
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==Overview== | ==Overview== | ||
[[Aortic]] dissection is a tear in the wall of the [[aorta]] that causes [[blood]] to flow between the layers of the wall of the [[aorta]] and force the layers apart. [[Aortic]] dissection is a [[medical emergency]] and can quickly lead to death, even with optimal treatment. If the dissection tears the [[aorta]] completely open (through all three layers) massive and rapid blood loss occurs. [[Aortic]] dissections resulting in rupture have a 90% [[mortality]] rate even if intervention is timely. | [[Aortic]] dissection is a tear in the wall of the [[aorta]] that causes [[blood]] to flow between the layers of the wall of the [[aorta]] and force the layers apart. [[Aortic]] dissection is a [[medical emergency]] and can quickly lead to death, even with optimal treatment. If the dissection tears the [[aorta]] completely open (through all three layers) massive and rapid blood loss occurs. [[Aortic]] dissections resulting in rupture have a 90% [[mortality]] rate even if intervention is timely. | ||
[[Acute]] [[aortic]] dissection is the most common fatal condition that involves the [[aorta]]. The [[mortality]] rate has been estimated to be as high as 1% per hour during the first 48 hours. Because of the diverse clinical manifestations of [[aortic]] dissection, one needs to maintain a high index of suspicion in patients with not just [[Ddx:Chest Pain|chest pain]], but also those with [[stroke]], [[congestive heart failure]], [[hoarseness]], [[hemoptysis]], [[claudication]], [[superior vena cava (SVC) syndrome]], or upper airway obstruction. Despite the fact that a noninvasive [[diagnosis]] can be made in up to 90% of cases, the correct antemortem [[diagnosis]] is made less than 50% of the time. Recognition of the condition and vigorous pre-operative management are critical to survival. | |||
==Historical Perspective== | ==Historical Perspective== | ||
DeBakey and Cooley reported the first successful operation for resection and [[graft]] replacement of the [[ascending aorta]] using [[cardiopulmonary bypass]] in 1956. | DeBakey and Cooley reported the first successful operation for resection and [[graft]] replacement of the [[ascending aorta]] using [[cardiopulmonary bypass]] in 1956. | ||
==Classification== | ==Classification== | ||
Several different classification systems have been used to describe [[aortic]] dissections. The systems commonly in use are either based on either the [[anatomy]] of the dissection ([[proximal]], [[distal]]) or the duration of onset of [[symptom]]s ([[acute]], [[chronic]]) prior to presentation. | Several different classification systems have been used to describe [[aortic]] dissections. The systems commonly in use are either based on either the [[anatomy]] of the dissection ([[proximal]], [[distal]]) or the duration of onset of [[symptom]]s ([[acute]], [[chronic]]) prior to presentation. | ||
==Pathophysiology== | ==Pathophysiology== | ||
[[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]]. | [[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]]. | ||
==Causes== | ==Causes== | ||
Age related changes due to [[atherosclerosis]] and [[hypertension]] are associated with spontaneous dissection, while blunt trauma injury and sudden deceleration in a motor vehicle accident is a major cause of [[aortic]] dissection. | Age related changes due to [[atherosclerosis]] and [[hypertension]] are associated with spontaneous dissection, while blunt trauma injury and sudden deceleration in a motor vehicle accident is a major cause of [[aortic]] dissection. | ||
==Differentiating Aortic Dissection from other Diseases== | ==Differentiating Aortic Dissection from other Diseases== | ||
[[Aortic]] dissection is a life threatening entity that must be distinguished from other life threatening entities such as [[cardiac tamponade]], [[cardiogenic shock]], [[myocardial infarction]], and [[pulmonary embolism]]. An [[aortic aneurysm]] is not synonymous with [[aortic]] dissection. [[Aneurysm]]s are defined as a localized permanent [[dilation]] of the [[aorta]] to a diameter > 50% of normal. | [[Aortic]] dissection is a life threatening entity that must be distinguished from other life threatening entities such as [[cardiac tamponade]], [[cardiogenic shock]], [[myocardial infarction]], and [[pulmonary embolism]]. An [[aortic aneurysm]] is not synonymous with [[aortic]] dissection. [[Aneurysm]]s are defined as a localized permanent [[dilation]] of the [[aorta]] to a diameter > 50% of normal. | ||
==Epidemiology and Demographics== | ==Epidemiology and Demographics== | ||
There are approximately 2,000 cases of [[aortic]] dissection in the US per year, and [[aortic]] dissection accounts for 3-4% of [[sudden deaths]]. The peak [[incidence]] is in the sixth and seventh decades, and males predominate 2:1. | There are approximately 2,000 cases of [[aortic]] dissection in the US per year, and [[aortic]] dissection accounts for 3-4% of [[sudden deaths]]. The peak [[incidence]] is in the sixth and seventh decades, and males predominate 2:1. | ||
== Risk Factors == | == Risk Factors == | ||
[[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]]. | [[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]]. | ||
==Screening== | ==Screening== | ||
Screening guidelines state that an [[EKG]] should be obtained for all patients who present with symptoms suspicious for aortic dissection. A chest x ray should be obtained for patients determined to be in low-risk, and moderate-risk categories, and for patients in high-risk categories, [[TEE]], [[CT]] or [[MRI]] should be obtained. | Screening guidelines state that an [[EKG]] should be obtained for all patients who present with symptoms suspicious for aortic dissection. A chest x ray should be obtained for patients determined to be in low-risk, and moderate-risk categories, and for patients in high-risk categories, [[TEE]], [[CT]] or [[MRI]] should be obtained. | ||
==Natural History, Complications and Prognosis== | ==Natural History, Complications and Prognosis== | ||
[[Aortic]] dissection carries a very poor [[prognosis]]. 90% of patients who are untreated will be dead at one year. Type A dissection is associated with a worse [[prognosis]] than type B dissection. [[Aortic]] dissection can be complicated by extension to the [[coronary artery|coronary arteries]] resulting in [[myocardial infarction]], involvement of the [[aortic arch]] to cause [[stroke]], dilation of the route to cause [[aortic insufficiency]], extension into the [[pericardium]] to cause [[pericardial tamponade]], and [[heart failure]], and [[aortic rupture]]. | [[Aortic]] dissection carries a very poor [[prognosis]]. 90% of patients who are untreated will be dead at one year. Type A dissection is associated with a worse [[prognosis]] than type B dissection. [[Aortic]] dissection can be complicated by extension to the [[coronary artery|coronary arteries]] resulting in [[myocardial infarction]], involvement of the [[aortic arch]] to cause [[stroke]], dilation of the route to cause [[aortic insufficiency]], extension into the [[pericardium]] to cause [[pericardial tamponade]], and [[heart failure]], and [[aortic rupture]]. | ||
==Diagnosis== | ==Diagnosis== | ||
===History and Symptoms=== | ===History and Symptoms=== | ||
67% of patients with [[aortic]] dissection present with [[acute]] [[symptom]]s (<2 weeks), and 33% with [[chronic]] [[symptom]]s (>= 2 weeks). 74% of patients who survive the initial tear typically present with the sudden onset of severe tearing pain. | 67% of patients with [[aortic]] dissection present with [[acute]] [[symptom]]s (<2 weeks), and 33% with [[chronic]] [[symptom]]s (>= 2 weeks). 74% of patients who survive the initial tear typically present with the sudden onset of severe tearing pain. | ||
===Physical Examination=== | ===Physical Examination=== | ||
[[Aortic dissection]] is commonly associated with varying blood pressure (pseudohypotension or [[hypertension]] or [[hypotension]]), [[wide pulse pressure]] (if the [[aortic root]] is involved causing [[aortic insufficiency]]), [[tachycardia]], [[pulsus paradoxus]], [[swollen face]] due to [[superior vena cava]] compression ([[superior vena cava syndrome]]). In proximal dissections involving [[aortic root]], [[aortic insufficiency]] is a [[complication]], and on physical examination an early [[diastolic]] decrescendo [[murmur]], which is best heard in the right second [[intercostal space]] is noted. | [[Aortic dissection]] is commonly associated with varying blood pressure (pseudohypotension or [[hypertension]] or [[hypotension]]), [[wide pulse pressure]] (if the [[aortic root]] is involved causing [[aortic insufficiency]]), [[tachycardia]], [[pulsus paradoxus]], [[swollen face]] due to [[superior vena cava]] compression ([[superior vena cava syndrome]]). In proximal dissections involving [[aortic root]], [[aortic insufficiency]] is a [[complication]], and on physical examination an early [[diastolic]] decrescendo [[murmur]], which is best heard in the right second [[intercostal space]] is noted. | ||
===Laboratory Findings=== | ===Laboratory Findings=== | ||
Routine blood work is usually not helpful and should not delay definitive [[diagnosis|diagnostic studies]] such as a [[CT]] scan and treatment. [[Hemolysis]] can be present as a result of blood in the [[false lumen]]. The presence of an elevated [[CK MB]] may indicate the presence of concomitant [[acute myocardial infarction]] (often a [[right coronary artery]] occlusion due to occlusion of the [[ostium]] of the [[RCA]] by the dissection). [[Hematuria]] may be present and may indicate the presence of [[renal infarction]]. | Routine blood work is usually not helpful and should not delay definitive [[diagnosis|diagnostic studies]] such as a [[CT]] scan and treatment. [[Hemolysis]] can be present as a result of blood in the [[false lumen]]. The presence of an elevated [[CK MB]] may indicate the presence of concomitant [[acute myocardial infarction]] (often a [[right coronary artery]] occlusion due to occlusion of the [[ostium]] of the [[RCA]] by the dissection). [[Hematuria]] may be present and may indicate the presence of [[renal infarction]]. | ||
===Electrocardiogram=== | ===Electrocardiogram=== | ||
[[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]]. [[Electrical alternans]] may be present in the setting of a [[pericardial effusion]] should the dissection have extended into the [[pericardium]]. | [[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]]. [[Electrical alternans]] may be present in the setting of a [[pericardial effusion]] should the dissection have extended into the [[pericardium]]. | ||
===Imaging in Acute Aortic Dissection=== | ===Imaging in Acute Aortic Dissection=== | ||
There are a wide variety of imaging studies that can be used to [[diagnose]] [[aortic]] dissection, but in general, [[Transesophageal echocardiography (TEE)|transesophageal imaging]] is the imaging modality of choice in the [[acute]]ly ill patient and [[MRI]] is the imaging modality of choice in the assessment of longstanding [[aortic]] disease in a patient who has [[chronic]] [[chest pain]] who is [[hemodynamic]]ally stable or for the evaluation of a [[chronic]] dissection. | There are a wide variety of imaging studies that can be used to [[diagnose]] [[aortic]] dissection, but in general, [[Transesophageal echocardiography (TEE)|transesophageal imaging]] is the imaging modality of choice in the [[acute]]ly ill patient and [[MRI]] is the imaging modality of choice in the assessment of longstanding [[aortic]] disease in a patient who has [[chronic]] [[chest pain]] who is [[hemodynamic]]ally stable or for the evaluation of a [[chronic]] dissection. | ||
===Chest X-ray=== | ===Chest X-ray=== | ||
An increased [[aortic]] diameter is the most common finding on chest [[X ray]], and is observed in up to 84% of patients. A [[widened mediastinum]] is the next most common finding, and is observed in 15-20% of patients. The chest X-Ray is normal in 17% of patients. A [[pleural effusion]] ([[hemothorax]]) in the absence of [[congestive heart failure]] can be another sign of [[aortic]] dissection. | An increased [[aortic]] diameter is the most common finding on chest [[X ray]], and is observed in up to 84% of patients. A [[widened mediastinum]] is the next most common finding, and is observed in 15-20% of patients. The chest X-Ray is normal in 17% of patients. A [[pleural effusion]] ([[hemothorax]]) in the absence of [[congestive heart failure]] can be another sign of [[aortic]] dissection. | ||
===CT=== | ===CT=== | ||
A [[CT scan]] can be used to [[diagnosis|diagnose]] [[aortic]] dissection if neither a [[TEE]] nor [[MRI]] is available in a timely fashion, or if there is a contraindication to their performance. An example would be after hours in an emergency room setting. If the results of the [[CT]] scan are non-[[diagnostic]], then [[TEE]] or [[MRI]] should be performed to confirm the [[diagnosis]]. | A [[CT scan]] can be used to [[diagnosis|diagnose]] [[aortic]] dissection if neither a [[TEE]] nor [[MRI]] is available in a timely fashion, or if there is a contraindication to their performance. An example would be after hours in an emergency room setting. If the results of the [[CT]] scan are non-[[diagnostic]], then [[TEE]] or [[MRI]] should be performed to confirm the [[diagnosis]]. | ||
===MRI=== | ===MRI=== | ||
[[MRI]] is the imaging modality of choice in the assessment of longstanding [[aortic]] disease in a patient who has [[chronic]] [[chest pain]] who is [[hemodynamic]]ally stable or for the evaluation of a [[chronic]] dissection. | [[MRI]] is the imaging modality of choice in the assessment of longstanding [[aortic]] disease in a patient who has [[chronic]] [[chest pain]] who is [[hemodynamic]]ally stable or for the evaluation of a [[chronic]] dissection. | ||
===Echocardiography=== | ===Echocardiography=== | ||
In the management of the [[acute]] patient with suspected [[aortic]] dissection, a [[TEE|transesophageal echo]] performed [[acute]]ly in the emergency room is the preferred approach. If the patient is [[hemodynamic]]ally unstable, then a [[TEE|transesophageal echo]] can be performed in the operating room as the patient after the patient has been induced and is being prepared for [[surgery]]. | In the management of the [[acute]] patient with suspected [[aortic]] dissection, a [[TEE|transesophageal echo]] performed [[acute]]ly in the emergency room is the preferred approach. If the patient is [[hemodynamic]]ally unstable, then a [[TEE|transesophageal echo]] can be performed in the operating room as the patient after the patient has been induced and is being prepared for [[surgery]]. | ||
===Aortography=== | ===Aortography=== | ||
[[Aortography]] is rarely used in the modern era. It can be used of the other imaging modalities are not available or are inconclusive. | [[Aortography]] is rarely used in the modern era. It can be used of the other imaging modalities are not available or are inconclusive. | ||
===Coronary Angiography=== | ===Coronary Angiography=== | ||
Pre-operative [[angiography]] has not been associated with improved outcomes in [[retrospective]] analyses. | Pre-operative [[angiography]] has not been associated with improved outcomes in [[retrospective]] analyses. | ||
==Treatment== | ==Treatment== | ||
===Medical Therapy=== | ===Medical Therapy=== | ||
Type A dissections of the [[proximal]] [[aorta]] are generally managed with operative repair whereas Type B dissections of the [[descending aorta]] are generally managed medically. Even patients who are undergoing operative repair require optimal medical management. The two goals in the medical management of [[aortic]] dissection are to reduce [[blood pressure]] and to reduce the oscillatory shear on the wall of the aorta (the shear-force dP/dt or force of ejection of blood from the [[left ventricle]]). The target [[blood pressure]] should be a [[mean arterial pressure|mean arterial pressure (MAP)]] of 60 to 75 mmHg. | Type A dissections of the [[proximal]] [[aorta]] are generally managed with operative repair whereas Type B dissections of the [[descending aorta]] are generally managed medically. Even patients who are undergoing operative repair require optimal medical management. The two goals in the medical management of [[aortic]] dissection are to reduce [[blood pressure]] and to reduce the oscillatory shear on the wall of the aorta (the shear-force dP/dt or force of ejection of blood from the [[left ventricle]]). The target [[blood pressure]] should be a [[mean arterial pressure|mean arterial pressure (MAP)]] of 60 to 75 mmHg. | ||
===Surgery=== | ===Surgery=== | ||
Any dissection that involves the [[ascending aorta]] is considered a [[surgery|surgical]] emergency, and urgent [[surgery|surgical]] consultation is recommended. There is a 90% 3-month [[mortality]] among patients with a [[proximal]] [[aortic]] dissection who do not undergo [[surgery]]. These patients can rapidly develop [[acute]] [[aortic insufficiency]] ([[AI]]), [[tamponade]] or [[myocardial infarction]] ([[MI]]). | Any dissection that involves the [[ascending aorta]] is considered a [[surgery|surgical]] emergency, and urgent [[surgery|surgical]] consultation is recommended. There is a 90% 3-month [[mortality]] among patients with a [[proximal]] [[aortic]] dissection who do not undergo [[surgery]]. These patients can rapidly develop [[acute]] [[aortic insufficiency]] ([[AI]]), [[tamponade]] or [[myocardial infarction]] ([[MI]]). | ||
===Secondary Prevention=== | ===Secondary Prevention=== | ||
Proper treatment and control of hardening of the [[artery|arteries]] ([[atherosclerosis]]) and high [[blood pressure]] may reduce risk of [[aortic]] dissection. It is very important for patients at risk for dissection to tightly control their [[blood pressure]]. Taking safety precautions to prevent injuries can help prevent dissections. Many cases of aortic dissection cannot be prevented. If diagnosed with [[Marfan syndrome|Marfan]] or [[Ehlers-Danlos syndrome]], regular follow-up is advisable. | Proper treatment and control of hardening of the [[artery|arteries]] ([[atherosclerosis]]) and high [[blood pressure]] may reduce risk of [[aortic]] dissection. It is very important for patients at risk for dissection to tightly control their [[blood pressure]]. Taking safety precautions to prevent injuries can help prevent dissections. Many cases of aortic dissection cannot be prevented. If diagnosed with [[Marfan syndrome|Marfan]] or [[Ehlers-Danlos syndrome]], regular follow-up is advisable. | ||
== References == | == References == | ||
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[[Category:Up-To-Date cardiology]] | [[Category:Up-To-Date cardiology]] | ||
{{WH}} | {{WH}} | ||
{{WS}} | {{WS}} | ||
Revision as of 13:35, 12 August 2013
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Aortic dissection Microchapters |
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Treatment |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]
Overview
Aortic dissection is a tear in the wall of the aorta that causes blood to flow between the layers of the wall of the aorta and force the layers apart. Aortic dissection is a medical emergency and can quickly lead to death, even with optimal treatment. If the dissection tears the aorta completely open (through all three layers) massive and rapid blood loss occurs. Aortic dissections resulting in rupture have a 90% mortality rate even if intervention is timely.
Acute aortic dissection is the most common fatal condition that involves the aorta. The mortality rate has been estimated to be as high as 1% per hour during the first 48 hours. Because of the diverse clinical manifestations of aortic dissection, one needs to maintain a high index of suspicion in patients with not just chest pain, but also those with stroke, congestive heart failure, hoarseness, hemoptysis, claudication, superior vena cava (SVC) syndrome, or upper airway obstruction. Despite the fact that a noninvasive diagnosis can be made in up to 90% of cases, the correct antemortem diagnosis is made less than 50% of the time. Recognition of the condition and vigorous pre-operative management are critical to survival.
Historical Perspective
DeBakey and Cooley reported the first successful operation for resection and graft replacement of the ascending aorta using cardiopulmonary bypass in 1956.
Classification
Several different classification systems have been used to describe aortic dissections. The systems commonly in use are either based on either the anatomy of the dissection (proximal, distal) or the duration of onset of symptoms (acute, chronic) prior to presentation.
Pathophysiology
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.
Causes
Age related changes due to atherosclerosis and hypertension are associated with spontaneous dissection, while blunt trauma injury and sudden deceleration in a motor vehicle accident is a major cause of aortic dissection.
Differentiating Aortic Dissection from other Diseases
Aortic dissection is a life threatening entity that must be distinguished from other life threatening entities such as cardiac tamponade, cardiogenic shock, myocardial infarction, and pulmonary embolism. 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.
Epidemiology and Demographics
There are approximately 2,000 cases of aortic dissection in the US per year, and aortic dissection accounts for 3-4% of sudden deaths. The peak incidence is in the sixth and seventh decades, and males predominate 2:1.
Risk Factors
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.
Screening
Screening guidelines state that an EKG should be obtained for all patients who present with symptoms suspicious for aortic dissection. A chest x ray should be obtained for patients determined to be in low-risk, and moderate-risk categories, and for patients in high-risk categories, TEE, CT or MRI should be obtained.
Natural History, Complications and Prognosis
Aortic dissection carries a very poor prognosis. 90% of patients who are untreated will be dead at one year. Type A dissection is associated with a worse prognosis than type B dissection. Aortic dissection can be complicated by extension to the coronary arteries resulting in myocardial infarction, involvement of the aortic arch to cause stroke, dilation of the route to cause aortic insufficiency, extension into the pericardium to cause pericardial tamponade, and heart failure, and aortic rupture.
Diagnosis
History and Symptoms
67% of patients with aortic dissection present with acute symptoms (<2 weeks), and 33% with chronic symptoms (>= 2 weeks). 74% of patients who survive the initial tear typically present with the sudden onset of severe tearing pain.
Physical Examination
Aortic dissection is commonly associated with varying blood pressure (pseudohypotension or hypertension or hypotension), wide pulse pressure (if the aortic root is involved causing aortic insufficiency), tachycardia, pulsus paradoxus, swollen face due to superior vena cava compression (superior vena cava syndrome). In proximal dissections involving aortic root, aortic insufficiency is a complication, and on physical examination an early diastolic decrescendo murmur, which is best heard in the right second intercostal space is noted.
Laboratory Findings
Routine blood work is usually not helpful and should not delay definitive diagnostic studies such as a CT scan and treatment. Hemolysis can be present as a result of blood in the false lumen. The presence of an elevated CK MB may indicate the presence of concomitant acute myocardial infarction (often a right coronary artery occlusion due to occlusion of the ostium of the RCA by the dissection). Hematuria may be present and may indicate the presence of renal infarction.
Electrocardiogram
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. Electrical alternans may be present in the setting of a pericardial effusion should the dissection have extended into the pericardium.
Imaging in Acute Aortic Dissection
There are a wide variety of imaging studies that can be used to diagnose aortic dissection, but in general, transesophageal imaging is the imaging modality of choice in the acutely ill patient and MRI is the imaging modality of choice in the assessment of longstanding aortic disease in a patient who has chronic chest pain who is hemodynamically stable or for the evaluation of a chronic dissection.
Chest X-ray
An increased aortic diameter is the most common finding on chest X ray, and is observed in up to 84% of patients. A widened mediastinum is the next most common finding, and is observed in 15-20% of patients. The chest X-Ray is normal in 17% of patients. A pleural effusion (hemothorax) in the absence of congestive heart failure can be another sign of aortic dissection.
CT
A CT scan can be used to diagnose aortic dissection if neither a TEE nor MRI is available in a timely fashion, or if there is a contraindication to their performance. An example would be after hours in an emergency room setting. If the results of the CT scan are non-diagnostic, then TEE or MRI should be performed to confirm the diagnosis.
MRI
MRI is the imaging modality of choice in the assessment of longstanding aortic disease in a patient who has chronic chest pain who is hemodynamically stable or for the evaluation of a chronic dissection.
Echocardiography
In the management of the acute patient with suspected aortic dissection, a transesophageal echo performed acutely in the emergency room is the preferred approach. If the patient is hemodynamically unstable, then a transesophageal echo can be performed in the operating room as the patient after the patient has been induced and is being prepared for surgery.
Aortography
Aortography is rarely used in the modern era. It can be used of the other imaging modalities are not available or are inconclusive.
Coronary Angiography
Pre-operative angiography has not been associated with improved outcomes in retrospective analyses.
Treatment
Medical Therapy
Type A dissections of the proximal aorta are generally managed with operative repair whereas Type B dissections of the descending aorta are generally managed medically. Even patients who are undergoing operative repair require optimal medical management. The two goals in the medical management of aortic dissection are to reduce blood pressure and to reduce the oscillatory shear on the wall of the aorta (the shear-force dP/dt or force of ejection of blood from the left ventricle). The target blood pressure should be a mean arterial pressure (MAP) of 60 to 75 mmHg.
Surgery
Any dissection that involves the ascending aorta is considered a surgical emergency, and urgent surgical consultation is recommended. There is a 90% 3-month mortality among patients with a proximal aortic dissection who do not undergo surgery. These patients can rapidly develop acute aortic insufficiency (AI), tamponade or myocardial infarction (MI).
Secondary Prevention
Proper treatment and control of hardening of the arteries (atherosclerosis) and high blood pressure may reduce risk of aortic dissection. It is very important for patients at risk for dissection to tightly control their blood pressure. Taking safety precautions to prevent injuries can help prevent dissections. Many cases of aortic dissection cannot be prevented. If diagnosed with Marfan or Ehlers-Danlos syndrome, regular follow-up is advisable.