Association between QTc interval prolongation and outcomes of diabetic foot ulcers: Data from a 4-year follow-up study in China

Abstract

ObjectivesTo examine whether QTc interval prolongation is an independent risk factor of outcomes in patients with diabetic foot ulcers (DFU). Research design and methods331 patients with type 2 diabetes and DFU hospitalized in a Chinese tertiary hospital were recruited.ECG was done at baseline and QTc interval was calculated through Bazett's formula. Participants were classified into 2 groups according to the QTc interval as prolonged (≥440 ms) or not (<440 ms). These patients were followed-up for an average of 48 months to observe the outcomes, including ulcer healing, ulcer recurrence, nonfatal cerebral or cardiovascular events (NCCVE), cerebral cardiovascular death, cardiac death and all-cause death. The associations between the risk of outcomes and QTc interval prolongation, as well as per 1-SD increase in QTc interval were analyzed by Cox proportional-hazards models. ResultsIn terms of the univariate Cox proportional hazard models, patients with QTc interval prolongation had a higher all-cause mortality (HR = 1.621, 95%CI: 1.040–2.526, P = .013), higher cardiac mortality (HR = 2.011 95%CI: 1.106–3.657, P = .019), higher cerebral cardiovascular mortality (HR = 1.525, 95%CI: 0.8151–2.852, P = .045). The multivariate analysis showed that QTc prolongation was an independent risk factor for cardiac death (HR = 5.465, 95%CI: 2.818–8.112, P = .039). Similar results were obtained when QTc interval was used as a continue variable, a 1-SD increase in QTc interval was associated with an 5.883 times risk for cardiac mortality (HR = 6.883, 95%CI: 4.153–9.613, P = .012). The association between QTc interval prolongation with ulcer healing, recurrence and NCCVE were not observed either in univariate or multivariate analysis (P > .05). ConclusionQTc interval prolongation was a plausible predictor for cardiac death in DFU patients, but it cannot accurately predict ulcer healing or recurrence.