Aortic dissection is one of the true surgical emergencies that still exists in the field of cardiac surgery. Any busy practice can say that there are patients frequently turning up in the emergency department with acute and chronic aortic dissection. Smaller practices may not get as much exposure to this type of pathology. In speaking to the emergency department and to transferring hospitals, I have come to understand that there is some confusion among the medical community in general, and perhaps even in the cardiac surgery community, regarding the appropriate classification of aortic dissection. I thought a brief primer in classification might be a useful review.
Aortic dissections can involve the ascending aorta, the descending aorta, or both. Ascending dissections are more common, and are often life threatening. They can be spontaneous, iatrogenic, or traumatic in nature. They can be caused by genetic collagen disorders such as Elhers-Danlos or Marfans, or can be secondary to having an aortic aneurysm or bicuspid aortic valve. They are also seen after cardiac surgery or cardiac catheterization. Uncontrolled hypertension is a common finding in patients with aortic dissection. The two primary systems for classification of aortic dissection are the Stanford classification and the DeBakey classification. While the Stanford classification is the more commonly used system, the DeBakey classification gives more information about the dissection, and surgeons who specialize in aortic surgery often use this system. For this reason, it is important to understand both systems of classification.
The Stanford classification breaks dissection down to Type A and Type B. Type A dissections are located in the ascending aorta and may progress into the arch or beyond. These dissections originate proximal to the left subclavian artery and require surgical intervention. Type B dissections are those that are distal to the left subclavian artery. They are managed differently. Generally, medical management with blood pressure control with or without the addition of aortic stenting in the form of TEVAR (thoracic endovascular aortic repair) are the treatment of choice for this type of dissection.
The DeBakey classification is based on the site of origin of the dissection. Type I dissections originate in the ascending and progress at least to the arch. This type can include the descending as well. Type II dissections originate in the ascending aorta and are confined only to the ascending. Type III dissections originate in the descending aorta (distal to the left subclavian artery) and extend distally and/or proximally. This type is further broken down to IIIa which extends distally and proximally and remains above the diaphragm, and IIIb which extends distally and extends below the diaphragm. Again, Type I and II dissections are managed surgically, and Type III dissections are often managed medically with or without stent graft placement. I read something one time that used the pneumonic BAD as a way to remember the DeBakey classification: B (both ascending and descending), A (ascending only), D (descending).
This was just a brief primer on an incredibly complicated subject. Details on management and treatment of aortic dissection would require volumes to fully explain. But in starting with the basics, we at least ensure that we can communicate effectively with our surgeons, and maybe even help educate those not in the cardiac surgery community to facilitate discussions about our patients.