Aortic Dissection 

The extensively dissected media filled with blood is apparent in this photo.

This section with elastic-trichrome green stain shows blood in the dissected media.  Cystic medial degeneration can be readily identified in the media.

A probe marks the site of external rupture in this case of aortic dissection resulting in sudden death due to cardiac tamponade. When aortic dissection leads to rupture the results are catastrophic. Rupture can occur into the mediastinum or thoracic cavity with severe loss of blood. Not uncommonly, however, the dissection spreads in a retrograde manner as well as in an antegrade direction and rupture occurs into the pericardial sac causing hemopericardium. Since the blood is under pressure, the result is cardiac tamponade. In this condition filling of the cardiac chambers is markedly impaired resulting in shock and often in sudden death.

The intimal tear is readily identified in this case of aortic dissection with bicuspid aortic valve. This association is common.

This photo shows cross-sections of an iliac artery into which dissection had extended from the aorta.  Note blood filling the false lumen in the split media. The true lumen is compressed.

This high magnification photo shows cystic medial degeneration in a case of aortic dissection.

Aortic dissection occurs when blood enters the wall of aorta, separating its layers, and creating a blood filled cavity. Most common in men between 40-60 years of age with history of hypertension. Those younger than 40 often have connective tissue disorders such as Marfan syndrome. Although rare, it can also result from a complication secondary to diagnostic catherization. Intimal tear often precedes the dissection. When intimal tear is present, hypertension can enhance hematoma progression. Cystic medial degeneration (CMD), which results in elastin fragments in the aortic media may play a role in the development of dissection. The exact trigger for intimal tear and intramural aortic hemorrhage is unknown in most cases. Patients present with a sudden onset of excruciating pain beginning in the chest, radiating to the back and downwards. Other associated symptoms include: diaphoresis, palpitation, hypertension (hypotension can also occur), aortic regurgitation and/or focal neurological signs. The classic presentation of aortic dissection is not always apparent, and can be mistaken for MI (i.e., thrombolytics have fatal consequences in aortic dissection, therefore make sure to distinguish aortic dissection from MI). CXR will show widened mediastinum. CT and/or transesophageal echocardigraphy (TEE) can diagnose aortic dissection. Aortic angiography can also be performed for detailed view of the dissection. Type A (proximal) aortic dissection must undergo surgical repair to prevent aortic insufficiency. Type B (distal) dissections can be managed medically. Heart rate and BP pressure should be reduced with IV beta-blockers (e.g., esmolol) and IV sodium nitroprusside.

Contributed by: Dr. Lorraine Potocki and Dr. Charles Kuhn