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(Circulation. 1999;100:e149.)
© 1999 American Heart Association, Inc.

Circulation Electronic Pages

QTc Dispersion, Hyperglycemia, and Hyperinsulinemia

Raffaele Marfella, MD; Francesco Rossi, MD; Dario Giugliano, MD

Department of Geriatrics and Metabolic Diseases and Institute of Pharmacology, Second University of Naples, Piazza Miraglia, Naples, Italy

	Introduction

 
To the Editor:

QTc dispersion is an important predictor of cardiac mortality. In the Rotterdam Study,¹ persons in the highest tertile (>60 ms) relative to the lowest tertile (<39 ms) of QTc dispersion had a 2-fold risk of cardiac death. The Rotterdam Study also confirms that QTc dispersion is larger in diabetic than in nondiabetic persons. QTc duration and QTc dispersion are associated with plasma glucose and insulin levels,² but their relative contributions to each are still unclear. We evaluated the effect of acute hyperglycemia, with or without the accompanying hyperinsulinemia, on QTc duration and QTc dispersion in normal subjects.

We studied 27 healthy volunteers (17 men and 15 women) aged 49±6 years (mean±SD). All subjects were given a hyperglycemic glucose clamp in which plasma glucose concentrations were acutely raised with a bolus injection of 0.33 g/kg glucose (50% solution) followed by a 30% glucose infusion to achieve steady-state plasma glucose levels of 15 mmol/L for 120 minutes. On another occasion, which was separated from the first by at least a 3-day interval and in random order, the subjects underwent the same hyperglycemic clamp plus octreotide administration (25 µg as IV bolus followed by a 0.5 µg/min infusion) to block the release of endogenous insulin. All tests were made with the aid of an artificial pancreas (Biostator). Electrocardiograms were recorded with a standard resting 12-lead ECG at 50 mm/s. QT interval analysis was done by a cardiologist who was blinded regarding other information. QT intervals were corrected with Bazett’s formula . . . [Full Text of this Article]

Martine C. de Bruyne; Jacqueline M. Dekker

Julius Centre for Patient-Oriented Research Utrecht, The Netherlands