Patient Selection, data collection, and endpoints
This was a systematic retrospective cohort study of consecutive patients undergoing surgical management of deep sternal wound infection following cardiac surgery between January 2006 and December 2016. The Institutional Review Board of the University of Southern California Health Sciences Campus approved this study (HS-17-00053) and waived the requirement for patient consent.
Patients were treated for DSWI at a single center (Keck Hospital of USC), however, patients transferred from other institutions were included. All patients were required to have undergone cardiac surgery via a full sternotomy. Partial sternotomies, other less invasive approaches, and sternotomies for non-cardiac surgery were not included. No time limit was placed on the interval between previous sternotomy and diagnosis of deep sternal wound infection. Patients with sterile sternal wound dehiscence who only required sternal rewiring were excluded. The follow-up period closed April 30th, 2017.
Deep sternal wound infection was defined according to the mediastinitis category as reported in the Centers for Disease Control and Prevention Guidelines[12]. The diagnosis of deep sternal wound infection required one of the following: positive cultures from the mediastinal area, evidence of infection during surgical exploration, or one of the following signs or symptoms with no other recognized cause: fever, chest pain or sternal instability, and either purulent drainage from the mediastinal area, positive cultures in blood or the mediastinal area, or mediastinal widening on chest x-ray[12].
The cohort was divided into two groups based on the timing of onset of deep sternal wound infection after the index cardiac procedure. An early infection was defined as those occurring less than 30 days from the index procedure, while a late infection was defined as those occurring greater than or equal to 30 days from the index procedure.
Patient baseline demographics, operative characteristics for the index cardiac procedure and all procedures related to the DSWI, and perioperative outcomes were identified through the USC Cardiothoracic Surgery Database and The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database. All medical records from our electronic medical record were reviewed. Mortality was confirmed through clinical follow-up, direct patient (or family) or direct provider contact. Follow-up was 100% complete. The primary endpoint was mortality.