Background: Thoracic aortic injury (TAI) is a devastating condition in which prompt recognition can obviate morbidity and mortality. It is a long-held belief that TAI is more likely when there is a “major mechanism of injury.” The purposes of this prospective study were to determine mechanism characteristics that are predictive of TAI and to evaluate chest computed tomography (CT) as a screening tool for TAI.
Methods: Over a 5 1/2 year period, blunt chest trauma patients at two Level I trauma centers were evaluated for potential TAI. Patients were assigned mechanism and radiograph scores from 1 (low suspicion for TAI) to 5 (very high suspicion for TAI). Immediate aortography was obtained when suspicion for TAI was very high. The remaining patients were evaluated with contrast-enhanced chest CT. Confirmatory aortography was obtained on all positive chest CT scans and on all patients with mechanism scores of 4 or 5 even if the CT was negative. Mechanism and radiographic data were correlated with the results of aortic imaging.
Results: Of the 1,561 patients evaluated for TAI, 30 aortic injuries were found. The assessment of mechanism was imperfect with a reliance on often incomplete and subjective data. The subjective mechanism score proved to be the most useful predictor of TAI. Radiographic scores were useful but insensitive for intimal injuries. Computed tomography was found to have 100% and 100% NPV for TAI.
Conclusion: Considering the inherent difficulties in identifying patients at risk for TAI and the effectiveness of chest CT as a screening tool for aortic injury, we recommend liberal use of chest CT in blunt chest trauma. Guidelines for determining the need for aortic imaging are outlined.
Thoracic aortic injury (TAI) is a devastating injury that requires early recognition to minimize morbidity and obviate mortality. With prompt diagnosis, TAI can be treated with Beta-blocking/antihypertensive agents and operative repair, resulting in survival rates approaching 90%. 1–4 The challenge is to identify the population at risk and develop a rapid, safe, and widely available screening test.
It is a long held belief that TAI is more likely when there is a “major mechanism of injury.” Several series have attempted to characterize the mechanisms associated with TAI, which fundamentally represent “sudden and violent deceleration”. 5,6 Undisputed risk factors for TAI include high-speed motor vehicle crashes, involving frontal and side impacts or occupant ejection, and motorcycle crashes. 5–8 However, the injury has also been observed in patients involved in auto-pedestrian collisions, falls, crush injuries, and other mechanisms. 5,7 Despite the enormous transfer of energy, there are few physical findings in TAI; less than half of patients have visible signs of chest wall injury. 9–11 Although the chest radiograph is sensitive for mediastinal hemorrhage, it has a low positive predictive value for TAI. 9,12,13 Of even greater concern are the reports of normal chest radiographs in 2 to 7% of patients with TAI. 1,14
Aortography has been the gold standard for the diagnosis of TAI. Although safe, it is time-consuming, costly, invasive, and resource-intensive. Because of the lack of specific clinical indicators for TAI, a large number of negative aortograms are done. In recent years, computed tomography has been promoted as an effective screening tool for TAI. Computed tomography is widely available and trauma patients at risk for TAI often require other computed tomography examinations, e.g., head and abdomen. The frequent presence of computed tomography technologists in-house 24 hours per day has also increased the accessibility of computed tomography. 15 Most importantly, computed tomography has been reported to be an accurate screening tool for TAI with the ability to decrease the need for aortography. 16–23 The purposes of this prospective study were to determine objective and subjective mechanism characteristics that are predictive of TAI and to evaluate the utility of chest computed tomography as a definitive screening tool for TAI.