Is the aortic size all that matters in predicting the risk of type A dissection?

Background: According to the current ESC guidelines, elective ascending aortic replacement is recommended to prevent acute type A aortic dissection when any segment of the proximal aorta is greater than 5.5 cm in patients with tricuspid aortic valve while lower thresholds are proposed for the bicuspid valve and the Marfan disease. Increased dimension of the aortic root and proximal aorta is considered a significant risk factor for catastrophic events that involve the ascending aorta. However, in the International Registry of Acute Aortic Dissection (IRAD) 40% of patients with bicuspid valve and acute type A aortic presented with aortic diameters <5 cm and 60% patients with tricuspid valve presented aortic diameters <5,5 cm. These findings motivated the present study in order to better understand the relationship between aortic diameter and type A dissection. Methods: We studied retrospectively all consecutives patients from two different centers in Belgium between 2002 and 2012 (mean age of 65,5) hospitalized with a diagnostic of acute type A aortic dissection. We have excluded the patients with a traumatic or an iatrogenic aortic dissection and the patients with a history of cardiac surgery. The maximum aortic diameters were obtained by a careful examination of the CT scan and compared with the transthoracic and transoeophageal echocardiographic measurements. The largest aortic diameter was used. Results: We examined 41 patients. The majority of patients presented with acute type A aortic dissection and tricuspid aortic valve (75,60%) and without systemic disease (100%). In this category 80,64% of patients had an aortic diameter of less than 55 mm at admission. The patients with bicuspid valve (21,95% of patients) had an aortic diameter of less than 50 mm in 55,55% of cases. All cause mortality was appreciated at 31%, which corresponds to the rate of mortality found in the literature. An important biological finding is the presence in all cases of D dimers elevation >500pg/ml. Conclusions: The majority of patients with tricuspid aortic valve or bicuspid aortic valve and acute type A aortic dissection present with aortic diameters of <55 cm and respectively <50 cm and thus do not fall within current guidelines for elective aneurysm surgery. Methods other than size measurement of the ascending aorta are needed to identify patients at risk for dissection.