Overall cohort
A total of 64 patients with a deep sternal wound infection after a previous cardiac procedure were identified during the study period. Baseline and index operative, and operative characteristics of the DSWI procedures are shown in Tables 1, 2, and 3 . In general, the overall cohort was predominantly older men (mean 60 ± 12 years) who were borderline obese (30.2 ± 7.1 kg/m2), hypertensive, diabetic, and had coronary artery disease. Almost half were transferred to our center from another institution for management of the DSWI after a cardiac procedure elsewhere. The most common index cardiac procedure was a coronary artery bypass grafting, followed by a valve repair or replacement. DSWI after an aortic procedure or ventricular assist device were less common in this cohort.
The median time to diagnosis of DSWI was 30 days (Interquartile Range (IQR) 13.5 – 67 days). Positive wound cultures were documented in 54 (84%) with Gram-positive organisms being the most common. Twenty-one (33%) patients had an attempt at medical management with antibiotics alone, however, all eventually underwent surgical therapy as per study design. A total of 135 operative procedures for treatment of the DSWI were performed on these 64 patients. Surgical management was debridement and wound therapy alone in 13 (20%), while 51 (80%) underwent flap coverage as either a primary or secondary procedure.
Mean follow up was 34.1 ± 32.3 months. Overall survival was 93.9, 85.1, and 80.8% at 1, 3, and 5 years respectively (Figure 1 ). Univariate Cox proportional hazard modelling showed only a history of hypertension was associated with overall mortality (hazard ratio (HR), 0.21, 95% confidence intervals, 0.05-0.96, p=0.44, see Supplemental Table 1). A multivariable model of mortality with those variables with univariate p valves <0.2 (infection diagnosed more than 30 days after index operation, male gender, history of hypertension, and attempted medical management) showed infection diagnosed within 30 day of index cardiac procedure and attempted initial medical management were strongly associate with overall mortality (hazard ratios 25.0 and 9.9, respectively), while the absence of hypertension was protective (hazard ratio 0.10, Table 4) .