Aortic Aneurysm Dissections Ruptures

Fritz J. Baumgartner

GENERAL CLASSIFICATION

The topic of aortic aneurysms, dissections and ruptures is a difficult one in terms of the classification and management. First, the common misconception that the thoracic aortic aneurysm is the same as a dissection should be dispelled. These are different entities and their management is different with one exception. When an aortic dissection has persisted for a long period of time, it becomes a chronic aortic dissection which should actually be classified under the term chronic aortic aneurysm. There is no such thing as an acute aortic aneurysm. There is, however, such a thing as an acute aortic dissection. Table 7.1 classifies the etiology, indications for surgery and technique of surgery for acute aortic dissection and chronic aortic aneurysm. Figure 7.1a-c provides a diagrammatic summary of the aortic pathologies and repair techniques.

AORTIC DISSECTION

Etiologies of acute aortic dissection include Marfan's syndrome, cystic medial necrosis, and hypertension. The presence of a bicuspid aortic valve has a high coincidence with aortic dissection. Acute aortic dissection arises from separation of the aorta within the media. The media and adventitia of the aorta literally dissect away from the intima and the inner portion of the media. Controlling the patient's hypertension is essential in slowing or halting the progression of the aortic dissection. There is always an intimal tear associated with the aortic dissection which permits blood to dissect into the media, and the location of this intimal tear is critical for planning surgical management. The tear is propagated simply by the pulsatile effect of cardiac contraction. Although the progression of the aortic dissection varies, usual locations are the right anterior portion of the ascending aorta, greater curvature of the transverse arch, and left anterolateral wall of the descending aorta.

Patients with acute aortic dissection typically present with a tearing sensation in the back which is different in quality and location than the pain of angina. Nonetheless, the pain of acute aortic dissection may mimic other disorders in-

Table 7.1.

Etiology

Acute Aortic Marfan's (#1 etiology) Dissection Cystic Medial Necrosis

Bicuspid Aortic Valve

Chronic

Aortic

Aneurysm

Atherosclerotic Disease (#1 Etiology) Chronic Dissection Marfan's

Cystic Medial Necrosis Aortitis (syphilis or granuloma)

Aortic Blunt Deceleration

Transection

Indications for Surgery

Type A-mere presence

Type B-complications (rupture, visceral or limb ischemia, persistent pain)

Ascending or Descending: > 6 cm

Transverse or Thoracoabd:

Recent \ in size or symptoms

Mere presence

Technique

Ascending-50% have AI which must be managed by resuspension or AVR; can do Bentall, Cabrol, or separate AVR/ ascending graft replacement.

Descending-Tube graft replacement; as with ascending type, can leave false lumen distally; may use LA-fem or fem-fem bypass to protect spine.

Thoracoabdominal -Need LA-fem or fem-fem bypass to protect the spine.

/If aneurysm prox to innominate a., clamp and cannula may be applied to aorta.

Ascending

^^ If distal to innominate a., RA-fem a. bypass then circ arrest. Use interposition or inclusion method; may need AVR by Bentall, Cabrol, or separate AVR/ascending graft.

Transverse: RA-fem a. bypass then circ arrest.

Descending Thoracic: 5th-7th interspace; LA ^ fem or fem-fem bypass. Thoracoabdominal: 7-9th interspace; again use LA-fem a. bypass or fem-fem bypass.

/If no prox extension, "clamp & go" if repair < 30 min otherwise LA-fem a. bypass. At ligamentum arteriosum (Left thoracotomy)

^ If prox extension, LA ^ fem bypass, cool & circ arrest.

Ascending Aorta (Median sternotomy)

RA-fem a. bypass; clamp prox to innominate a. if possible but if not, need circ. arrest.

Stanford A

Stanford A

Stanford B

Stanford B

Ascending

Ascending

Transverse

Descending Thoracic Thoracoabdominal

Transverse

Descending Thoracic Thoracoabdominal

Trans ver: Ascending

Trans ver: Ascending

Descending

Descending

Fig. 7.1. Types of aortic pathologies and techniques of repair. (a) Acute Dissection. Stanford A: RA-femoral a. bypass with circulatory arrest; If need to replace aortic valve, need Bentall/Cabrol or separate supraannular graft placement. Stanford B: surgery for medical failures; LA-femoral a. or fem-fem bypass to protect spinal cord. (b) Chronic Aneurysm. Ascending: Standard CPB (cannulas in RA and aorta); Transverse: RA-femoral a. CPB with hypothermic circ arrest (inclusion technique of graft placement; Descending Thoracic and Thoracoabdominal-LA-fem a. or fem. fem. bypass; circ arrest is an alternative. (c) Traumatic Rupture. Transverse RA-femoral a. bypass and circ. arrest; Ascending-Standard CPB; Descending-"clamp and go" or additional protection with LA-fem bypass; If tear in descending aorta goes proximally into arch, need fem-fem bypass and circ. arrest.

cluding angina, heartburn, or pneumothorax. The patient may present with the signs and symptoms of cardiac tamponade if rupture has occurred into the pericardium.

Figure 7.2 shows the types of aortic dissection based on the location. A dissection involving the ascending, transverse, and descending aorta is a De Bakey type I dissection; that involving only the ascending aorta is a De Bakey type II; a dissection only involving the descending thoracic aorta is a De Bakey type III dissection. This has been simplified in the Stanford classification, where one simply asks the question whether or not there is a component of an ascending aortic dissection. If the dissection does involve the ascending aorta, i.e. a De Bakey Class I or II, then this is a Stanford A dissection. If, however, only the descending thoracic aorta is involved (De Bakey III) then this is Stanford B. This is a simpler and clinically more useful classification because the management is exactly related to whether it is a type A or type B dissection. Type A dissections are managed with surgery and

Classification Aortic Dissection
Fig. 7.2. Classification of aortic dissection.
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