Chromium supplementation shortens QTc interval duration in patients with type 2 diabetes mellitus

Background We investigated the potential effects of chromium supplementation on QTc interval duration in type 2 diabetic patients. Methods Of 60 patients with type 2 diabetes mellitus, 30 were randomly assigned to group A, and 30 to group B. Group A received 1000 mu g of chromium picolinate (CrPic) daily for 3 months, followed by placebo in the next 3 months; group B was treated with placebo for the first 3 months and CrPic in the next 3 months. At each visit, QT interval was measured on a standard electrocardiogram by averaging 3 consecutive beats in leads II and V4 and corrected for heart rate with Bazett formula. Results Although baseline QTc interval was similar in both groups (422 +/- 34 milliseconds in group A vs 425 +/- 24 milliseconds in group B, P = .77), QTc interval at 3 months was shorter in group A (406 +/- 35 milliseconds) than in group B (431 +/- 26 milliseconds, P = .01). In the following 3 months, QTc interval shortened in group B but not in group A, which resulted in a comparable QTc interval duration of both groups at the end of the study (414 +/- 28 milliseconds in group A vs 409 +/- 22 milliseconds in group B, P = .50). Apart from body mass index (31.4 +/- 4.2 kg/m(2) in patients with QTc shortening vs 28.7 +/- 4.2 kg/m(2) in patients without QTc shortening, P = .03), none of the clinical and laboratory variables predicted QTc interval shortening in our patient cohort. Conclusions Short-term chromium supplementation shortens QTc interval in patients with type 2 diabetes mellitus.