“…The University of Pennsylvania group 13,18 introduced this classification system and categorized 221 AADA patients (mean age, 62 years, treated between 1993 and 2004) into four groups as follows: Aa (58%), Ab (18%), Ac (15%), Abc (9%). The Karolinska group 14 categorized 360 AAAD patients (mean age, 60 years, treated between 1990 and 2009) into Aa (61%), Ab (14%), Ac (18%) and Abc (7%). Distribution of the Penn classes in our study (Aa 48%, Ab 19%, Ac 9%, Abc 24%) showed a higher number of patients with both branch vessel malperfusion and circulatory collapse.…”