Objective: The risk of acute type B aortic dissection is thought to increase with descending thoracic aortic diameter. Currently, elective repair of the descending thoracic aorta is indicated for an aortic diameter of 5.5 cm or greater. We sought to investigate the relationship between aortic diameter and acute type B aortic dissection, and the utility of aortic diameter as a predictor of acute type B aortic dissection. Methods: We examined the descending aortic diameter at presentation of 613 patients with acute type B aortic dissection who were enrolled in the International Registry of Acute Aortic Dissection between 1996 and 2009, and analyzed the subset of patients with acute type B aortic dissection with an aortic diameter less than 5.5 cm. Results: The median aortic diameter at the level of acute type B aortic dissection was 4.1 cm (range 2.1-13.0 cm). Only 18.4% of patients with acute type B aortic dissection in the International Registry of Acute Aortic Dissection had an aortic diameter of 5.5 cm or greater. Patients with Marfan syndrome represented 4.3% and had a slightly larger aortic diameter than patients without Marfan syndrome (4.68 vs 4.32 cm, P = .121). Complicated acute type B aortic dissection was more common among patients with an aortic diameter of 5.5 cm or greater (52.2% vs 35.6%, P < .001), and the in-hospital mortality for patients with an aortic diameter less than 5.5 cm and 5.5 cm or greater was 6.6% and 23.0% (P < .001), respectively. Conclusions: The majority of patients with acute type B aortic dissection present with a descending aortic diameter less than 5.5 cm before dissection and are not within the guidelines for elective descending thoracic aortic repair. Aortic diameter measurements do not seem to be a useful parameter to prevent aortic dissection, and other methods are needed to identify patients at risk for acute type B aortic dissection.
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The majority of patients with ABAD present with a descending aortic diameter less than 5.5 cm and miss the threshold for elective descending thoracic aortic repair. The findings of the present study suggest that descending aortic diameter is not a useful parameter to predict acute type B dissection. To prevent ABAD, further natural history studies are needed, as well as research on genetic predisposition for thoracic aortic disease. These may reveal other risk factors for aortic dissection in addition to increasing aortic diameter, resulting in better medical and interventional criteria for prophylactic thoracic aortic repair. Appendix 1 IRAD co-principal investigators: Kim A. Eagle, MD, University of Michigan, Ann Arbor, Mich; Eric M. Isselbacher, MD, Massachusetts General Hospital, Boston, Mass; Christoph A. Nienaber, MD, University of Rostock, Rostock, Germany. IRAD co-investigators: Eduardo Bossone, MD, National Research Council, Lecce, Italy; Alan Braverman, MD, Washington University School of Medicine, St Louis, Mo; Stefanos Demertzis, MD, Cardiocentro Ticino, Lugano, Switzerland; Giuseppe DiBenedetto, MD, San Giovanni e Ruggi, Salerno, Italy; Mark Ehrlich, MD, University of Vienna, Vienna, Austria; Arturo Evangelista, MD, Hospital General Universitari Vall d’Hebron, Barcelona, Spain; Rossella Fattori, MD, University Hospital S. Orsola, Bologna, Italy; James Froehlich, MD, and Thomas Tsai, MD, University of Michigan, Ann Arbor, Mich; Dan Gilon, MD, Hadassah University Hospital, Jerusalem, Israel; Alan Hirsch, MD, and Kevin Harris, MD, Minneapolis Heart Institute, Minneapolis, Minn; G. Chad Hughes, MD, Duke University, Durham, NC; Stuart Hutchison, MD, St Michael’s Hospital, Toronto, Ontario, Canada; James L. Januzzi, MD, Massachusetts General Hospital, Boston, Mass; Alfredo Llovet, MD, Hospital Universitario 12 de Octubre, Madrid, Spain; Truls Myrmel, MD, Tromsø University Hospital, Tromsø, Norway; Peter Oberwalder, MD, Medical School Graz, Graz, Austria; Patrick O’Gara, MD, and Joshua Beckman, MD, Brigham and Women’s Hospital, Boston, Mass; Jae K. Oh, MD, Mayo Clinic, Rochester, Minn; Linda A. Pape, MD, University of Massachusetts Hospital, Worcester, Mass; Reed Pyeritz, MD, University of Pennsylvania School of Medicine, Philadelphia, Pa; Udo Sechtem, MD, and Gabriel Meinhardt, MD, Robert-Bosch Krankenhaus, Stuttgart, Germany; P. Gabriel Steg, MD, Hôpital Bichat, Paris, France; Toru Suzuki, MD, University of Tokyo, Tokyo, Japan; Santi Trimarchi, MD, IRCCS Policlinico San Donato, San Donato, Italy. Data management and biostatistical support: Daniel Montgomery, MS, and Elise Woznicki, University of Michigan, Ann Arbor, Mich.