Current management of type B aortic dissection Adventitia Intima Media Aortic Wall Figure 1 Layers of aortic wall. department (ED), 7% of patients presenting with AAD were younger than 40 years of age. Compared to the typical AAD patients, these younger patients were more likely to have Marfan syndrome, bicuspid aortic valve, Ehlers-Danlos syndrome, Loeys-Dietz syndrome and a history prior cardiac surgery. In the evaluation of acute chest pain syndrome in the younger patients, suspicious chest pain with the above characteristics should raise the index of suspicion for acute aortic dissection. Table 1 summarizes the distinguishing features in these two patient populations.8 Vascular staging and classiﬁcation Aortic dissection is categorized as acute or chronic depending on the onset of symptoms or dissection. If the symptoms or dis- section occur within last 14 days, the dissection is termed acute aortic dissection (AAD). If the symptoms or dissection occur outside of the 14 days, the dissection is termed chronic aortic dissection. AAD is further classiﬁed depending on the location Vascular Health and Risk Management 2009:5 Vaso Vasorum of the dissection. In the DeBakey classiﬁcation (Figure 3A), type I refers to dissections that propagate from the ascending aorta, extend to the aortic arch, and commonly, beyond the arch distally. Type II refers to dissections that are conﬁned to the ascending portion of the aorta. Type III dissections are limited to the descending aorta. Class III also includes the dissections that start in the descending aorta that extend proximally to the arch and ascending aorta. In the more commonly used Stanford classiﬁcation system (Figure 3B), type A refers to dissections that involve the ascending and transverse aorta regardless of the site of origin. Type B refers to dissections that involve only the descending aorta. Rarely, dissections that start in the descending aorta can also extend proximally into the aortic arch and the ascending aorta. This is a special case of type B dissection, and should be called retro-A dissection. The term “complicated” type B AAD is used for patients who present with, or during the hospital course, develop the following: rupture, malperfusion syndromes, 55