The effect of acute hyperglycaemia on QTc duration in healthy man

Aims/hypothesis. Prolongation of heart rate-adjusted QT (QTc) is associated with an increased risk of coronary heart disease and sudden death. The obj ective of this study was to investigate whether acute increases of plasma g lucose concentrations in healthy subjects could influence QTc and QTc dispe rsion. Methods. Plasma glucose concentrations were quickly raised to 15 mmol/l in 20 healthy subjects (10 men/10 women) and maintained for 2 h. On another oc casion, and in random order, all subjects underwent the same hyperglycaemic clamp as above and an infusion of the somatostatin analogue octreotide (25 mu g as iv bolus followed by a 0.5 g/min infusion) to block the release of endogenous insulin. Results. Systolic and diastolic blood pressures, heart rate and plasma cate cholamine concentrations showed significant increases (p < 0.05) starting a fter 60 min of hyperglycaemia. QTc, QTc dispersion and PR interval also sho wed significant increments at 120 min of the hyperglycaemic clamp. The infu sion of octreotide did not influence QTc duration, QTc dispersion, PR inter val and the haemodynamic effects of acute hyperglycaemia. Conclusion/interpretation. The results show that acute hyperglycaemia produ ces significant increments of QTc and QTc dispersion in normal subjects. In this context, endogenously released insulin during acute hyperglycaemia se ems to play a minor part.