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.