Differences in Aortic Diameter Measurements with Intravascular Ultrasound and Computed Tomography After Blunt Traumatic Aortic Injury

Abstract

Intravascular ultrasound (IVUS) has been recommended as an adjunct to thoracic endovascular aortic repair (TEVAR) as computed tomography (CT) in injured patients may inaccurately determine the true aortic diameter. We hypothesize that CT and IVUS offer discordant measurements of aortic diameter in trauma patients and that each modality may result in different graft size estimates for TEVAR. Patients treated by TEVAR for blunt aortic injury from June 2011 to 2016 were reviewed. Cases where IVUS was not used and those without complete CT and IVUS images were excluded. Three-dimensional reconstructions were used to derive centerline diameters of the aorta, proximal and distal to the injury. IVUS diameters were taken from the flow lumen, not including the aortic wall itself. Measurements were made by an investigator blinded to the graft implanted. Descriptive statistics were used to compare patients with concordant diameter (group 1) with patients with discordant diameters (group 2). A total of 24 blunt thoracic aortic injuries were repaired with TEVAR during the study period; complete data were available for 16. The mean age of the patients was 43 (±18), and 12 of the patients were men. The median time from injury to CT was 2.5hr (0.9-8.5) and to TEVAR was 18 (3-48) hr. Stent graft diameter for implantation based on CT and IVUS imaging was the same in 5 cases (group 1). In 11 cases, the graft diameter for implantation based on IVUS was differently sized compared with that determined by CT (group 2). Ten diameters were 1 size larger, and 1 diameter was 1 size smaller by IVUS. There were no significant differences in the mean lowest systolic blood pressure (98 vs. 92, P=0.53), median fluid resuscitation in the first 24hr (4.9 vs. 5.0L, P=0.97), or median 24-hr transfusion requirements (130 vs. 1311mL, P=0.11) between the groups 1 and 2, respectively. In group 2, the graft size chosen for surgery correlated more with measurements obtained from the CT than from IVUS (9 vs. 2). The TEVAR has become the standard therapy for blunt aortic injury, despite a dearth of long-term outcome data. The preoperative CT frequently underestimates aortic diameter compared with intraoperative IVUS. The implications of placing thoracic endografts and whether excessive oversizing results in long-term aortic dilation need to be the focus of long-term studies in these relatively young patients.