Dr. M. SOFI MD; FRCP (London); FRCPEdin; FRCSEdin AORTIC DISSECTION Dr. M. SOFI MD; FRCP (London); FRCPEdin; FRCSEdin

AORTIC DISSECTION Aortic dissection is defined as separation of the layers within the aortic wall. The primary event in aortic dissection is a tear in the aortic intima. Degeneration of the aortic media, or cystic medial necrosis, is felt to be a prerequisite for the development of nontraumatic aortic dissection. Blood passes into the aortic media through the tear, separating the intima from the surrounding media and/or adventitia, and creating a false lumen. Mortality is still high despite advances in diagnostic and therapeutic modalities

Dissection site can be: Ascending aorta Aortic arch Descending aorta Abdominal aorta Dissection of the descending part of the aorta (3), which starts from the left subclavian artery and extends to the abdominal aorta (4). The ascending aorta (1) and aortic arch (2) are not involved.

Signs and symptoms Aortic dissection can be rapidly fatal, with many patients dying before reaching ED or before diagnosis is made in the ED. Neck or jaw pain: with aortic arch involvement and extension into the great vessels Tearing or ripping intrascapular pain: May indicate dissection involving the descending aorta No pain in about 10% of patients Syncope Sudden onset of severe chest pain that often has a tearing or ripping quality Chest pain may be mild Anterior chest pain: Usually associated with anterior arch or aortic root dissection

Signs and symptoms CVA symptoms: hemianesthesia, and hemiparesis, hemiplegia) Altered mental status Numbness and tingling, pain, or weakness in the extremities Horner syndrome (ptosis, miosis, anhidrosis) Dyspnea Hemoptysis Dysphagia Flank pain (with renal artery involvement Abdominal pain (with abdominal aorta involvement) Fever Anxiety and premonitions of death

Possible physical examination findings include the following: Hypertension Hypotension Interarm blood pressure differential greater than 20 mm Hg Signs of aortic regurgitation (bounding pulses, wide pulse pressure, diastolic murmurs) Findings suggestive of cardiac tamponade (muffled heart sounds, hypotension, pulsus paradoxus, jugular venous distention, Kussmaul sign) Neurologic deficits (e.g., syncope, altered mental status) Peripheral paresthesias Horner syndrome New diastolic murmur Asymmetrical pulses (e.g., carotid, brachial, femoral) Progression or development of bruits

Possible laboratory study findings include the following: Leukocytosis: Stress state Decreases in hemoglobin and hematocrit values: Leaking or rupture of the dissection Elevation of the blood urea nitrogen and creatinine levels: Renal artery involvement or prerenal azotemia Elevation of the myocardial muscle creatine kinase isoenzyme, myoglobin, and troponin I and T levels: Myocardial ischemia from coronary artery involvement Lactate dehydrogenase elevation: Hemolysis in the false lumen

Possible laboratory study findings include the following: Lactate dehydrogenase elevation: Hemolysis in the false lumen Smooth muscle myosin heavy-chain assay: Increased levels in the first 24 hours are 90% sensitive and 97% specific for aortic dissection Fibrin degradation product (FDP) elevation: In symptomatic patients, a plasma FDP of 12.6 μg/mL or higher suggests possible aortic dissection with a patent false lumen. FDP level of 5.6 μg/mL or higher suggests the possibility of dissection with complete thrombosis of the false lumen

Causes Turner’s syndrome also increases the risk of aortic dissection, by aortic root dilatation. Chest trauma can be divided into two groups based on etiology: blunt chest trauma seen in car accidents. Iatrogenic causes include trauma during cardiac catheterization or due to an intra-aortic balloon pump. Aortic dissection may be a late sequela of cardiac surgery. 18% of individuals who present have a history of open heart surgery. Aortic dissection is associated with hypertension Chest trauma. 72 to 80% of individuals have a previous history of hypertension. A bicuspid aortic valve (a type of congenital heart disease involving the aortic valve) is found in 7–14%. Risk is not associated with the degree of stenosis of the valve. Marfan syndrome is noted in 5–9%. Individuals with Marfan syndrome tend to have aneurysms of the aorta and are more prone to proximal dissections of the aorta.

Pathophysiology Blood penetrates the intima and enters the media layer. The high pressure rips the tissue of the media apart along the laminated plane splitting the inner 2/3 and the outer 1/3 of the media apart. This can propagate along the length of the aorta for a variable distance forward or backwards Aorta is made up of three layers, the intima, the media, and the adventitia. The intima is in direct contact with blood and consists of a layer of endothelial cells on a basement membrane. Media contains connective and muscle tissue Adventitia, comprising connective tissue outer layer

Pathophysiology The blood traveling through the media, creating a false lumen separating from the true lumen is a layer of intimal tissue. This tissue is known as the intimal flap. The majority of dissection are in ascending aorta (65%) aortic arch (10%), descending thoracic aorta (20%). The initiating event is a tear in the intimal lining of the aorta. High pressure blood enters the media at the point of the tear. The force of the blood causes the tear to extend. May extend proximally or distally or both.

A U T O P S Y H E R Dissection media as well outer media

Pathophysiology: The aortic dissections originate with an intimal tear in:  Ascending aorta (65%) Aortic arch (10%) Descending thoracic aorta (20%) No evidence of tear (13%) Histopathological image of dissecting aneurysm of thoracic aorta in a patient without evidence of Marfan syndrome. Vic Blood penetrates the intima and enters the media layer.

Rupture Aortic Aneurysm: Rupture of an aortic aneurysm should not be confused with aortic dissection. It will cause chest pain that may be indistinguishable from acute myocardial infarction (MI). Hemoptysis may occur. If bleeding occurs into the mediastinum, it can cause cardiac tamponade and rapidly be fatal. The patient will probably never reach hospital alive and the diagnosis is made post-mortem Figure A shows a normal aorta. Figure B shows a thoracic aortic aneurysm (which is located behind the heart). Figure C shows an abdominal aortic aneurysm located below the arteries that supply blood to the kidneys

Diagnosis The diagnosis of acute aortic dissection requires a high index of suspicion and involves the following: History and physical examination Imaging studies Chest X-Ray CT with contrast MRI Aortoraphy Electrocardiography Complete blood count, serum chemistry studies, cardiac marker assays

Imaging studies Chest radiography: Initial imaging technique if it is readily available at the bedside Widening of the mediastinum is the classic finding Hemothorax may be evident if the dissection has ruptured CT with contrast: The definitive test in most patients with suspicion of aortic dissection Useful only in hemodynamically stable patients Findings help determine whether hypothermic circulatory arrest is necessary for surgery

Imaging studies Echocardiography: Transesophageal echocardiography (TEE) is more accurate than transthoracic echocardiography (TTE) TTE is most useful in ascending aortic dissections TEE is as sensitive and specific as CT scanning and magnetic resonance imaging TEE is strongly dependent on operator experience MRI: The most sensitive method for diagnosing aortic dissection Specificity is similar to that of CT scanning Aortography: Has been the diagnostic criterion standard study for aortic dissection Is being replaced by newer, safer imaging modalities

Electrocardiogram of a patient presenting to the ED with chest pain; this patient was diagnosed with aortic dissection.

Chest X-Ray Widening of the mediastinum on an CXR has moderate sensitivity in an ascending aortic dissection. However, it has low specificity. The calcium sign on CXR suggests aortic dissection. It is the separation of the intimal calcification from the outer aortic soft tissue border by 10 mm. Pleural effusions may be seen on CXR. Commonly in descending aortic dissections. If seen, they are typically in the left hemithorax. Obliteration of the aortic knob, depression of the left mainstem bronchus, loss of the paratracheal stripe, and tracheal deviation. About 12 to 20% of individuals presenting with an aortic dissection have a "normal" chest x-ray

Chest radiograph demonstrating widened mediastinum and calcium sign in a patient with aortic dissection.

Computed Tomography CT is a fast non-invasive test that will give an accurate three-dimensional view of the aorta. Contrast is injected and the scan performed using a Bolus Tracking method. This is a type of scan timed to an injection to capture the contrast as it enters the aorta. The scan will then follow the contrast as it flows though the vessel. It has a sensitivity of 96 to 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. CT with contrast demonstrating aneurysmal dilation and a dissection of the ascending aorta (Type A Stanford)

Aortic dissection. Intimal flap and left pleural effusion.

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 has become the preferred imaging modality for suspected aortic dissection. An echocardiogram displaying the true lumen and false lumen of an aortic dissection. In the image to the left, the intimal flap can be seen separating the two lumens. In the image to the right, color flow during ventricular systole suggests that the upper lumen is the true lumen

(MRI) is currently the 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. MRI of an aortic dissection 1 Aorta descendens with dissection 2 Aorta isthmus

Classification Type I – Originates in ascending aorta, propagates at least to the aortic arch and often beyond it distally. It is most often seen in patients less than 65 years of age and is the most lethal form of the disease. Type II – Originates in ascending aorta and is confined to the ascending aorta. Type III – Originates in descending aorta, rarely extends proximally but will extend distally. It most often occurs in elderly patients with atherosclerosis and hypertension. Percentage 60% 10 -15% 25 – 30 % Type DeBakey I Stanford A (Proximal) Stanford B Distal

Classification: Image A represents a Stanford A or a DeBakey type 1 dissection. Image B represents a Stanford A or DeBakey type II dissection. Image C represents a Stanford type B or a DeBakey type III dissection. Image D is classified in a manner similar to A but contains an additional entry tear in the descending thoracic aorta. Note that a primary arch dissection does not fit neatly into either classification.

Management: The management is medical /surgical. In surgical treatment, the area of the aorta with the intimal tear is usually resected and replaced with a Dacron graft. Endovascular repair is emerging as the preferred treatment for descending aortic dissection. Medical management includes the following: Decreasing the blood pressure and the shearing forces of myocardial contractility Antihypertensive therapy, including beta blockers, is the treatment of choice for all stable chronic aortic dissections Pain management: Narcotics and opiates are the preferred agents Emergency surgical correction is the preferred treatment for the following: Stanford type A (DeBakey type I and II) ascending aortic dissection Complicated Stanford type B (DeBakey type III) aortic dissections with specific clinical or radiologic evidence

Management In acute dissection treatment choice depends on its location. Stanford type A dissection, surgical management is superior to medical management. Stanford type B dissections medical management is preferred over surgical. The risk of death due to aortic dissection is highest in the first few hours Acute dissection is one in which the individual presents within the first two weeks. About 66% of all dissections present in the acute phase. Those who present two weeks after the onset of the dissection are said to have chronic aortic dissections. Can be treated with medically Beta blockers are first line treatment for acute and chronic In acute dissection, rapidly acting, titratable parenteral agents (such as esmolol, or labetalol) Vasodilators such as sodium nitroprusside  for ongoing hypertension, but they should never be used alone. Calcium channel blockers can be used if there is a contraindication to the use of beta blockers. The calcium channel blockers typically used are verapamil and diltiazem, for their combined vasodilator and negative inotropic effects.

Surgical Treatment Indications for the surgical treatment include: Acute proximal aortic dissection Acute distal aortic dissection with complications. Complications include: Risk of a vital organ damage Impending rupture of the aorta, Retrograde dissection in A/A Marfan syndrome Ehlers-Danlos Syndrome The objective in the surgical Rx resect the most severely damaged segments of the aorta Obliterate blood into false lumen The treatment depends on the segment or segments of aorta involved. Some treatments are Open Aortic  surgery with replacement of the damaged section of aorta with a dacron tube graft when there is no damage to the aortic valve. Bentall procedure — Replacement of the damaged section of aorta and replacement of the aortic valve. David procedure — Replacement of the damaged section of aorta and reimplantation of the aortic valve. Endovascular repair via stent graft (covered stent),

Epidemiology & Prognosis It has been difficult to establish because many cases are only diagnosed after death. It is estimated that aortic dissection affects 2–3.5 people out of every 100,000 every year. Studies from Sweden suggest that the incidence of aortic dissection may be rising. Men are more commonly affected than women: 65% of all people with aortic dissection are male. The mean age at diagnosis is 63 years.  In females before the age of 40, half of all aortic dissections occur during pregnancy (typically in the 3rd trimester or early post partum period). Of all people with aortic dissection, 40% die almost straight away and do not reach hospital. Of the remainder, 1% die every hour, making prompt diagnosis and treatment a priority. Even after diagnosis, 5–20% die during surgery or in the immediate postoperative period. In ascending aortic dissection, if there is a decision that surgery is not appropriate, 75% die within 2 weeks. With aggressive treatment 30-day survival for thoracic dissections may be as high as 90%