Root Dilatation Is More Malignant Than Ascending Aortic Dilation

Background Data from the International Registry of Acute Aortic Dissection indicate that the guideline criterion of 5.5 cm for ascending aortic intervention misses many dissections occurring at smaller dimensions. Furthermore, studies of natural behavior have generally treated the aortic root and the ascending aorta as 1 unit despite embryological, anatomical, and functional differences. This study aims to disentangle the natural histories of the aforementioned aortic segments, allowing natural behavior to define specific intervention criteria for root and ascending segments of the aorta. Methods and Results Diameters of the aortic root and mid-ascending segment were measured separately. Long-term complications (dissection, rupture, and death) were analyzed retrospectively for 1162 patients with ascending thoracic aortic aneurysm. Cox regression analysis suggested that aortic root dilatation (P=0.017) is more significant in predicting adverse events than mid-ascending aortic dilatation (P=0.087). Short stature posed as a serious risk factor. The dedicated risk curves for the aortic root and the mid-ascending aorta revealed hinge points at 5.0 and 5.25 cm, respectively. Conclusions The natural histories of the aortic root and mid-ascending aorta are uniquely different. Dilation of the aortic root imparts a significant higher risk of adverse events. A diameter shift for intervention to 5.0 cm for the aortic root and to 5.25 cm for the mid-ascending aorta should be considered at expert centers.