**2. Classification**

The Stanford classification (1970) is the most commonly used system (**Figure 1**) [4]. It does not classify the site of tear. It is more of a clinically useful classification

### **Figure 1.**

*Stanford and DeBakey classification.*

to guide acute management. Stanford type A involves ascending aorta proximal to innominate artery, irrespective of involvement of aortic arch or descending aorta. Stanford type B dissection involves only the thoracic aorta distal to the left subclavian artery [5]. Intimal tears originating distal to left subclavian artery but dissecting retrogradely into ascending aorta will be type A. Intimal tears starting in the aortic arch and extending into ascending aorta are type A and extending into descending aorta are type B. If the intimal tear is restricted to aortic arch, then it is type non-A non-B.

The DeBakey type I involves ascending aorta and extends beyond the innominate artery. Type II involves only the ascending aorta. Type III involves thoracic aorta distal to left subclavian artery. It is more useful for long-term follow-up as it differentiates between proximal and distal aortic dissection extent (**Figure 1**) [4].

The Penn classification is a recently introduced method of classifying based on clinical presentation [6]. Class Aa—absence of branch vessel malperfusion or circulatory collapse; Class Ab—symptoms or signs of localised organ ischemia; Class Ac—circulatory collapse with or without cardiac involvement; Class Abc combined localised and generalised ischemia.
