Critical evaluation of chest computed tomography scans for blunt descending thoracic aortic injury

Although aortography has been the long-held "gold standard" for diagnosis of traumatic blunt aortic injury, advances in imaging technology offer less-invasive, more-rapid, and potentially more cost-effective evaluation. The purpose of this study was to review this hospital's experience with the screening and diagnosis of blunt aortic injury with emphasis on the critical evaluation of computed tomography (CT) scans for defining descending thoracic aortic injury.

A retrospective single-center analysis of all patients undergoing aortography to evaluate for blunt aortic injury between January 1, 1997, and August 31, 2004, was performed. A policy of relying on CT scans to definitively diagnose blunt aortic injury was not in force, and all patients with positive, equivocal, and negative screening CT scans with significant injury mechanism underwent subsequent aortography; this contributed to an unbiased analysis. A subgroup of patients imaged with the latest generation multislice CT scanners (July 1, 2003, to August 31, 2004) was separately analyzed with rapid three-dimensional reconstruction.

Of 856 aortograms, 206 (24.1%) were preceded by chest CT scan. Of 31 patients with confirmed aortic injury, 20 had undergone CT scan with 16 positive for definite injury, 3 positive for possible injury, and 1 false-negative study. Of the 206 patients scanned, 114 (55.3%) showed possible injury, 76 (36.9%) were negative, and 16 (7.8%) were positive. Only 3 of the 114 with possible injury (2.6%) were true positives whereas 1 of the 76 negative scans (1.3%) was a false negative and all 16 positive scans were true positives. These data for CT scan imaging result in a sensitivity of 95%, a specificity of 40%, a positive predictive value of 15%, and a negative predictive value of 99%.

Chest CT is an acceptable screening tool based on prerequisite high sensitivity and ease of performance in the trauma patient suspected of having a descending thoracic aortic injury. Although the excellent negative predictive value resulted in an algorithm change at this institution, there were a significant number of equivocal scans that required subsequent aortography. Three-dimensional software reconstruction of the aorta can aid in diagnosing blunt aortic injury when findings are equivocal, but there will continue to be artifacts and limitations that require aortography for clarification.