Computed tomography improves the differentiation of infectious mediastinitis from normal postoperative changes after sternotomy in cardiac surgery

Abstract

Objectives: To identify CT parameters independently associated with infectious mediastinitis after cardiac surgery and to improve the discrimination of patients with acute infection from those with normal postoperative changes.

Methods: In this single-center, retrospective, observational cohort study, we evaluated thoracic CT scans of poststernotomy cardiac surgery patients. Inclusion criteria were clinically suspected mediastinitis, unclear CT signs (e.g., retrosternal mass), and subsequent deep revision surgery. Revision surgery and microbiological samples determined the mediastinitis status. Overall, 22 qualitative and quantitative CT imaging parameters were assessed and associated with infectious mediastinitis in univariate and multivariate regression models. Discriminative capacity and incremental value of the CT features to available clinical parameters were determined by AUC and likelihood-ratio tests, respectively.

Results: Overall 105 patients (82% men; 67.0 ± 10.3 years) underwent CT and deep revision surgery. Mediastinitis was confirmed in 83/105 (79%) patients. Among available clinical parameters, only C-reactive protein (CRP) was independently associated with infectious mediastinitis (multivariate odds ratio (OR) (per standard deviation) = 2.3; p < 0.001). In the CT, the presence of free gas, pleural effusions, and brachiocephalic lymph node size were independently associated with mediastinitis (multivariate ORs = 1.3-6.3; p < 0.001-0.039). Addition of these CT parameters to CRP increased the model fit significantly (X² = 17.9; p < 0.001; AUC, 0.83 vs. 0.73).

Conclusion: The presence of free gas, pleural effusions, and brachiocephalic lymph node size in CT is independently associated with infectious mediastinitis in poststernotomy patients with retrosternal mass. These imaging features may help to differentiate mediastinitis from normal postoperative changes beyond traditional clinical parameters such as CRP.

Key points: • Presence of free gas, pleural effusions, and brachiocephalic lymph node size on CT are associated independently with infectious mediastinitis. • Combination of these CT parameters increases the discriminatory capacity of clinical parameters such as CRP.

Keywords: Cardiac surgery; Mediastinitis; Multidetector computed tomography; Sternotomy.