Types of Aortic Dissection
Aortic dissections are primarily classified using two systems: the Stanford classification and the DeBakey classification, with the Stanford system being more clinically practical as it directly guides management decisions between surgical and medical approaches. 1
Stanford Classification System
Type A: Involves the ascending aorta regardless of the site of origin. These dissections typically require immediate surgical intervention due to high risk of complications including rupture, tamponade, and aortic valve insufficiency. 2, 1
Type B: Does not involve the ascending aorta. These dissections are usually managed medically unless complications occur. Note that involvement of the aortic arch without ascending aorta involvement is classified as Type B. 2
DeBakey Classification System
This system categorizes dissections based on the origin of the intimal tear and the extent of the dissection:
Type I: Dissection originates in the ascending aorta and propagates distally to include at least the aortic arch and typically the descending aorta (surgery usually recommended). 2, 1
Type II: Dissection originates in and is confined to the ascending aorta (surgery usually recommended). 2, 1
Type III: Dissection originates in the descending aorta and propagates most often distally (nonsurgical treatment usually recommended). 2
Relationship Between Classifications
Stanford Type A corresponds to DeBakey Types I and II, while Stanford Type B corresponds to DeBakey Type III. 1
The Stanford system simplifies the DeBakey classification by focusing on therapeutic implications rather than detailed anatomy. 1
Clinical Implications and Management
Type A dissections (Stanford) have high mortality rates, increasing by 1% per hour if untreated, highlighting the importance of immediate surgical intervention. 1, 3
Type B dissections (Stanford) are often managed medically with antihypertensive medications to reduce blood pressure and heart rate, unless complications such as malperfusion, rupture, or persistent pain occur. 4
With the advancement of thoracic endovascular aortic repair (TEVAR), this procedure has been extended to treat selected patients with Type B dissections, showing promising results with early mortality rates from 10% to 20%. 4
Controversies in Classification
There is some controversy regarding aortic arch dissections (between the innominate and left subclavian arteries) that are not clearly accounted for in the Stanford classification. 5
Some radiologists tend to categorize arch dissections as Type A lesions (indicating surgery), but this interpretation is not always supported by standard dissection classification or current clinical management practices. 5
Some clinicians prefer a more pragmatic approach, referring to dissections as either proximal or distal to the left subclavian artery. 2
Newer Classification Systems
A newer TEM classification system has been proposed that extends the Stanford classification by adding:
- Type of dissection (A, B, or non-A non-B)
- Entry tear location (E0-E3)
- Malperfusion status (M0-M3, with + for clinical and - for radiological findings) 6
This system aims to provide more clarity regarding the extent of disease, enhance awareness of the disease mechanism, aid in decision-making about repair extent, and help predict outcomes. 6