Aortic dissection resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Chetan Lokhande, M.B.B.S [2]

Overview

A tear in the layers of the aorta especially in the intima leading to bleeding and separation of the layers of the aorta from within which creates a false lumen. Aortic dissection can be further defined as:

1. Acute aortic dissection- Dissection occurring within 2 weeks of onset of pain
2. Subacute aortic dissection-Dissection occurring witin 2-6 weeks of onset of pain
3. Chronic aortic dissection- Dissection occurring within 6 weeks of pain.

Classification

Aortic dissection can be classified into four types. DeBakey and Daily (Stanford) systems are the commonly used systems used to classify aortic dissection.

• Stanford system classifies dissection into the following two types based on whether ascending aorta is involved or not.

1. Ascending aortic dissection or type A
2. All other dissections or type B

• DeBakey system classifies dissection according to location of the tear.

1. Type I- Starts at ascending aorta and extension upto the aortic arch
2. Type II- Starts and is limited till the ascending aorta
3. Type III- Starts in the descending aorta and progresses proximally or distally
   1. Type III A - Restricted till the descending thoracic aorta
   2. Type III B - Dissection extending below the diaphragm

• The third type of classification divides aortic dissection according to the proximity

1. Proximal- Ascending aortic involvement
2. Distal- Descending aortic involvement distal to left subclavian artery

Causes

Life Threatening Causes

Aortic dissection is a life-threatening condition and must be treated as such irrespective of the causes. Life-threatening conditions may result in death or permanent disability within 24 hours if left untreated.

Common Causes

• Atherosclerosis
• Complication of cardiac procedures
• Chest trauma
• Connective tissue disorders
• Hypertension
• Vasculitis

Do's

History and Examination

• For pre-test risk determination include information about:
  • Medical History
  • Family history and ask specifically for family history of aortic dissection or thoracic aneurysm
  • Pain history
• Do a detailed physical examination to identify findings for certain high risk conditions like: (class I, level of evidence B)
  • Marfans'syndrome
  • Loey's-Dietz syndrome
  • Ehler's Danlos syndrome
  • Turner's syndrome
  • Connective tissue disorder
• Check for genetic mutations predisposing to dissection: (class I, level of evidence B)
  • FBN1
  • TGFBR1
  • TGFBR2
  • ACTA2
  • MYHH11
• Any recent aortic or surgical or catheter manipulation. (class I, level of evidence C)
• Ask in detail about the pain. Include the following: (class I, level of evidence B)
  • Onset of pain whether abrupt or instantaneous
  • Severity of pain
  • Quality of pain whether ripping, tearing,stabbing or sharp.
• Check for the following features on examination: (class I, level of evidence B)
  • Pulse deficits
  • Blood pressure (systolic) difference of above 20 mm of hg in limbs
  • New aortic regurgitation features
  • Focal neurological deficit
• Patients less than 40 years of age and presenting with sudden chest, abdominal or back pain should be evaluated for high risk conditions.
• Patients presenting with features of syncope along with features of dissection should have a detailed neurological examination and cardiovascular examination to rule out pericardial tamponade and other neurological deficits. (class I, level of evidence C)

Screening Tests

• Do an EKG on all patients with dissection symptoms. (class I, level of evidence B)
• If ST elevation is present in EKG then treat the patient as an acute cardiac event unless the patient has high risk factors for acute dissection.
• If EKG shows ST elevation with no dissection features then perform a coronary angiography and then do a thrombolysis or percutaneous coronary intervention.
• Do a X-ray for all patients with intermediate risk and low risk to rule out alternate diagnosis. (class I, level of evidence C)
• High risk patients should be evaluated by transesophageal echocardiogram, computed tomography or magnetic resonance imaging to rule out dissection. (class I, level of evidence B)
• Obtain a secondary imaging study if there is high cinical suscpicion even if the initial aortic imaging studies are negative. class III, level of evidence C

Initial Management

• Medical management should be aimed at decreasing aortic wall stress. (class I, level of evidence C)
• Titrate Beta blocker to maintain heart rate of 60 beats/ minute. (class I, level of evidence C)
• If beta blockers are contra indicated then use nondihyropyridine calcium channel blockers to control rate. (class I, level of evidence C)
• If BP remains above 120 mm of hg even after medical treatment then use angiotensin converting enzyme and other vasodilators to maintain end organ perfusion. (class I, level of evidence C)

Definitive Management

• Do a surgical consultation for all patients once diagnosed with aortic dissection. This applies to patients presenting with dissection at any location. (class I, level of evidence C)
• Do an emergent repair in acute dissection of ascending aorta to prevent complications like rupture. (class I, level of evidence C)
• Treat all descending aorta medically unless complicated by life threatening conditions like perfusion deficit, dissection enlargement, aneurysmal enlargement or blood pressure refractory to treatment. (class I, level of evidence C)
• Do a definitive aortic imaging study as soon as Chest X-ray suggests widened mediastinum.
• Goal should be to maintain heart rate less than 60 beats / minute and blood pressure between 100 and 120 mm hg.
• Use Esmolol if asthma, congestive heart failure or chronic obstructive pulmonary disease.
• Use Labetalol to maintain heart rate and blood pressure, it prevents usage of another vasodilator.
• Do pericardiocentes for pericardial bleeding and dissection related hemopericardium.
• Do a plasma smooth muscle myosin heavy chain protein, D-dimer and high sensitive C-reactive protein to rule out alternate diagnosis.

Dont's

• Don't use beta blocker in patients having aortic regurgitation as they may block the tachycardia caused by compensation.
• Don't use vasodilator before heart rate is controlled otherwise there would be reflex tachycardia which would increase the stress on aorta and worsening the dissection.
• Use Sodium nitroprusside as the first line for treating hypertension. Nicardipine, nitroglycerin and fenoldopam are other drugs used to treat hypertension.
• Don't delay aortic imaging even if chest x-ray is negative. (class III, level of evidence C).