Longitudinal Mapping of True Lumen Morphology for Accurate Endograft Oversizing in Patients with Type B Aortic Dissections

When planning thoracic endovascular aortic repair (TEVAR), proper selection of endograft size is important to achieve adequate seal in landing zones and avoid complications. This study maps preoperative aortic morphology and incorporates device specifications to analyze longitudinal oversizing variation using two different methods. Computed tomography angiograms of patients before and after TEVAR of type B aortic dissection were used to construct geometric models of the aorta, endograft, and arch branch vessels. Using the left common carotid artery as a fiducial marker, the endograft-covered aortic segment was indexed to the pre-TEVAR anatomy. In this region, true lumen major diameter, as well as diameter derived from circumference, were measured. Longitudinally mapped oversizing was defined along the whole length using the localized measured diameter and the endograft device diameter specification (Fig). Two-tailed, paired t tests were used to compare between the two methods, as well as between longitudinal regions. Twenty patients with type B aortic dissection (62.8 ± 9.9 years; 15.0% female) were treated with TEVAR with one or two endografts (W. L. Gore & Associates, Newark, DE). Length-averaged oversizing was lower in the proximal landing zone compared with the distal landing zone and the whole stented region irrespective of methods (P < .05), except for whole stented region versus proximal landing zone using the major diameter method (P = .07). Length-averaged oversizing differed significantly between methods in all regions (P < .05) (Table). Oversizing increases distally as the proximal landing zone is in the nondissected aorta and the true lumen tends to taper. Therefore, tapered devices may be preferable to avoid excessive distal oversizing. The fact that both methods had significantly different oversizing levels in all comparisons confirms the theoretical difference for the methods. For a circular cross-section, the methods are identical, while the discrepancy increases with eccentricity. Since the circumference-based method accounts for irregular cross-sections accurately, it is superior for sizing for dissection morphology. Consensus on the definition of oversizing and levels are important to minimize complications through intervention planning and device development.TableComputed length-averaged oversizing in the whole stented region prethoracic endovascular aortic repair (TEVAR; matching the endograft segment post-TEVAR) and landing zones, for circumference and major diameter methodsOversizing (%) based onWhole stented regionProximal landing zone (20 mm)Distal landing zone (25 mm)Circumference45 ± 27a,b,d18 ± 19a,c,d70 ± 44b,c,dMajor diameter17 ± 17b,d10 ± 13c,d33 ± 29b,c,daSignificant difference between whole stented region and proximal landing zone (P < .05).bSignificant difference between whole stented region and distal landing zone (P < .05).cSignificant difference between proximal and distal landing zone (P < .05).dSignificant difference between methods (P < .05). Open table in a new tab