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

OBJECTIVES: To examine whether QTc interval prolongation is an independent risk factor of outcomes in patients with diabetic foot ulcers (DFU). RESEARCH DESIGN AND METHODS: 331 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. RESULTS: In 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). CONCLUSION: QTc interval prolongation was a plausible predictor for cardiac death in DFU patients, but it cannot accurately predict ulcer healing or recurrence.