Chromium supplementation shortens QTc interval duration in patients with type 2 diabetes mellitus Matjaz Vrtovec, MD, a Bojan Vrtovec, MD, PhD, a Alenka Briski, PhD, a Andreja Kocijancic, MD, PhD, a Richard A. Anderson, PhD, b and Branislav Radovancevic, MD, c Ljubljana, Slovenia, Beltsville, Md, and Houston, Tex 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 Ag 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 F 34 milliseconds in group A vs 425 F 24 milliseconds in group B, P = .77), QTc interval at 3 months was shorter in group A (406 F 35 milliseconds) than in group B (431 F 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 F 28 milliseconds in group A vs 409 F 22 milliseconds in group B, P = .50). Apart from body mass index (31.4 F 4.2 kg/m 2 in patients with QTc shortening vs 28.7 F 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. (Am Heart J 2005;149:632- 6.) QTc interval prolongation has been shown to be a powerful predictor of total mortality, cardiac death, and future stroke in patients with type 2 diabetes mellitus. 1,2,3 The predictive value of prolonged QTc in diabetic patients is independent of other cardiovas- cular risk factors and appears to be related to impaired glucose homeostasis. Accordingly, QTc interval duration has been shown to correlate with fasting plasma insulin levels and inversely relate to insulin sensitivity in type 2 diabetic subjects. 4 Experimental and clinical studies suggest that chro- mium supplementation improves insulin sensitivity, lowers plasma insulin levels, and improves glucose homeostasis. 5,6 Because these factors have potential roles in the development of atherosclerosis and cardio- vascular events, 7 chromium deficiency may represent a primary risk factor for cardiovascular disease in type 2 diabetic patients. 8 Because both QTc interval prolongation and chromi- um deficiency appear to be related to altered insulin sensitivity, impaired glucose homeostasis, and increased cardiovascular morbidity in type 2 diabetes mellitus, we sought to investigate the potential effects of chromium supplementation on QTc interval duration in this patient cohort. Methods Patients We performed a double-blind, randomized, placebo- controlled crossover trial enrolling 60 diet-treated patients with type 2 diabetes mellitus. Patients with hepatic or renal dysfunction, history of heart failure, coronary artery disease, or cerebrovascular disease were not included in the study. In addition, we did not enroll the patients taking medications, which could potentially alter glucose homeostasis or QTc interval duration (thiazides, corticosteroids, phenothiazines, estrogens, sympathomimetics, type I and type II antiarrhyth- mic drugs). The study protocol was approved by the National Ethics Committee, and all patients gave their informed consent before entering the study. From the a Ljubljana University Medical Centre, Ljubljana, Slovenia, b Nutrient Require- ments and Functions Laboratory, Beltsville Human Nutrition Research Center, Beltsville, Md, and c Division of Cardiopulmonary Transplantation, Texas Heart Institute, Houston, Tex. Submitted February 21, 2004; accepted July 27, 2004. Reprint requests: Bojan Vrtovec, MD, PhD, Department of Cardiology, Ljubljana University Medical Centre, MC 1000 Ljubljana, Slovenia. E-mail: bovrtovec@yahoo.com 0002-8703/$ - see front matter n 2005, Elsevier Inc. All rights reserved. doi:10.1016/j.ahj.2004.07.021