Comparison of cohorts based on timing of DSWI diagnosis
As time of diagnosis of the DSWI in relation to the index procedure was significant for mortality on adjusted multivariable Cox proportional hazard modeling, we divided the cohort into two groups: those in which the diagnosis of DSWI was made within 30 days of the index cardiac procedures (33 patients, early onset), and those in which it was made 30 days or more after the index cardiac procedure (31 patient, late onset).
Baseline and index operative, and operative characteristics of the DSWI procedures of the two cohorts are shown in Tables 1, 2, and 3 . Those with early diagnosis of DSWI were less likely to be female, more likely to be smokers, and more likely to have an elevated glycated hemoglobin. The early DSWI group also had longer lengths of stay after the index hospital procedure.
The median time to infection was 14 days in the early onset group and 76 days in the late onset group. Fifty-four patients (84%) had positive wound cultures, and a positive wound culture was more common in the early DSWI group. Types of organisms did not differ between groups. Equal numbers of patients had an initial attempt at medical management, however all eventually underwent surgical therapy as per study design. The initial DSWI operation was performed urgently after diagnosis more commonly in the late diagnosis group, and electively in the early group. Initial flap coverage was performed in similar numbers of in the early diagnosis group, while delayed flap coverage was more common in the delayed infection group.
Mean follow up was slightly longer in the late DSWI group (32.0±28.6 versus 36.1±35.8 months, p=0.03). Overall survival was 88.1, 77.0, 70.6 and 100, 94.0 and 94.0% at 1,3, and 5 years in the early and late DSWI groups, respectively (Log-rank = 0.074).