Aortic Dissection

KEY FEATURES

Essentials of Diagnosis

• Sudden searing chest pain with radiation to back, abdomen, or neck in a hypertensive patient

• Widened mediastinum on chest radiograph

• Pulse discrepancy in the extremities

• Acute aortic regurgitation may develop

General Considerations

• Occurs when a spontaneous intimal tear develops and blood dissects into the media of the aorta

• Tear can result from repetitive torque applied to ascending and proximal descending aorta during the cardiac cycle

• Blood entering the intimal tear may extend the dissection into the

  • Abdominal aorta

  • Lower extremities

  • Carotid arteries

  • Subclavian arteries (less commonly)

• Hypertension is important component

• Abnormalities of smooth muscle, elastic tissue, or collagen are more common in patients without hypertension

• Both absolute pressure levels and the pulse pressure are important in propagation of dissection

• Dissections are classified by the entry point and distal extent

• Type A dissection

  • Involves the arch proximal to the left subclavian artery

  • Death may occur within hours, due to rupture of dissection into pericardial sac or dissection into the coronary arteries, resulting in myocardial infarction

  • Rupture into plural cavity also possible

  • Flap of aortic wall created by the dissection may occlude major aortic branches, resulting in ischemia of brain, intestines, kidney, or extremities

• Type B dissection typically occurs in the proximal descending thoracic aorta just beyond the left subclavian artery

• Conditions associated with increased risk of dissection

  • Pregnancy

  • Bicuspid aortic valve

  • Coarctation

CLINICAL FINDINGS

Symptoms and Signs

• Sudden onset of severe persistent chest pain

  • Characteristically radiates down the back or possibly into the anterior chest

  • May also radiate into the neck

• Dissections may occur with minimal pain

• Hypertension

• Syncope

• Hemiplegia

• Paralysis of lower extremities

• Mesenteric ischemia or kidney injury

• Peripheral pulses may be diminished or unequal

• A diastolic murmur may develop due to dissection in the ascending aorta close to the aortic valve, causing valvular regurgitation, heart failure, and cardiac tamponade

Differential Diagnosis

• Myocardial infarction

• Pulmonary embolism

• Arterial embolism

DIAGNOSIS

Imaging Studies

• Multiplanar CT scan with contrast enhancement

  • Immediate diagnostic imaging modality of choice

  • Low threshold for obtaining this study in any hypertensive patient with chest pain and equivocal findings on ECG

  • Should include the chest, abdomen, and pelvis to fully delineate the extent of the dissected aorta

• MRI

  • Excellent imaging modality for chronic dissections

  • The longer imaging time and the difficulty of monitoring patients in the scanner make CT scanning preferable in acute situations

• Chest radiographs may reveal

  • An abnormal aortic contour

  • Widened superior mediastinum

• Transesophageal echocardiography

  • An excellent diagnostic imaging method

  • However, it is generally not readily available in the acute setting

Diagnostic Procedures

• ECG findings

  • May be normal ...