G. Vasileiou1, S. Qian1, H. Al-ghamdi1, D. Pace1, R. Rattan1, G. D. Pust1, M. Mulder1, N. Namias1, D. D. Yeh1 1University Of Miami,Surgery,Miami, FL, USA
Introduction: It is commonly taught that a widened mediastinum (WM) on CXR is a marker for aortic injury (AI). We sought to describe the epidemiology of injuries for all patients with WM and compare their CXR to those of patients with confirmed AI.
Methods: Adults (age≥ 18) sustaining blunt traumatic injuries from 1/17-6/17 with both CXR (supine, anterior-posterior [AP]) and chest CT were included. We excluded those whose CT preceded CXR and those with missing data. Basic demographic information, injury characteristics, mediastinal width (MW), mediastinal-to-thoracic width ratio (MTR), and all thoracic imaging findings were analyzed. MW >8cm was considered “widened”. We also queried our registry for all AI patients over a 4 yr period. The sensitivity (Sn), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and accuracy of WM on CXR for AI were calculated for the 6-month period. Mann-Whitney U test was used as appropriate to compare patients with WM, and patients with confirmed AI. Multivariate logistic regression was performed to identify factors associated with positive traumatic findings.
Results: Of 749 included subjects, 502 (67%) had a MW > 8 cm: mean age was 48 ±20 yrs, 381 (76%) were men, and mean BMI was 28 ± 5 kg/m2. Mechanism of injury was: motor vehicle crash (MVC) in 335 (67%); fall in 113 (23%); assault in 31 (6%), other (jet-ski accidents, etc.) in 17 (3%), and unknown in 6 (1%). Only 128 (26%) of WM patients had positive findings on CT, with the most common [80 (16%)] being non-traumatic findings (thymic tissue, lymph nodes, etc.), followed by hemo/pneumomediastinum [32 (6%)], sternal fractures [18 (4%)], multiple findings [15 (3%)], and vertebral fractures [6 (1%)]. Only 2 (1%) had AI. The Sn was 100%, Sp was 33%, PPV was 0.4%, NPV was 100%, and accuracy was 33%. From 2013-2017, 38 patients had AI: mean age was 46 ± 19 yrs, 26 (68%) were men, and mean BMI was 28 ±4 kg/m2. MVC was the most common mechanism (n=34 (89%)), followed by ‘other’ trauma mechanism in 2 (5%), fall in 1 (3%), and assault in 1 (3%). On univariate analysis, compared to all patients with WM, AI patients had significantly greater MW (9.5 [8.8-10.4] vs 10.2 [9.1-11.1]; p= 0.042) and MTR (0.31 [0.28-0.34] vs 0.32 [0.31-0.37]; p=0.001), though the actual differences were not clinically significant. Regression analysis did not identify any factors associated with traumatic CXR findings (Table).
Conclusion: Most blunt mechanism injured adults have a WM and the majority of those have either no findings or non-traumatic findings. The PPV of a WM for AI is <1%. WM on supine AP CXR is non-specific and inaccurate for diagnosing traumatic injuries, especially AI.
