ALTERED VENTRICULAR REPOLARIZATION DURING HYPOGLYCEMIA IN PATIENTS WITH DIABETES

There is circumstantial evidence implicating hypoglycaemia in the sudd en overnight death of young patients with insulin-dependent (Type 1) d iabetes mellitus (IDDM), the mechanism of which is unknown. We have in vestigated the effects of hypoglycaemia on the electrocardiogram in 15 patients with diabetes (8 with IDDM and 7 with NIDDM) using a high re solution computer-based system. Patients were randomized to either 2h of euglycaemia or hypoglycaemia (at around 3 mmol l(-1)) during the af ternoon, using hyperinsulinaemic glucose clamps, the two visits separa ted by a period of at least 9 weeks. Corrected QT interval (QTc), plas ma potassium, and adrenaline were measured at baseline and at 0, 60, a nd 120 min. The degree of QTc lengthening (from baseline) during clamp ed hypoglycaemia was greater compared to the euglycaemic control perio d in patients with IDDM (median{range} at 60 min, 156{8 to 258} vs 6{- 3 to 28} ms, p < 0.02) and NIDDM (120 rain, 128{16 to 166} vs 4{-3 to 169} ms, p < 0.05). The fall in plasma potassium was greater during cl amped hypoglycaemia compared to euglycaemic in those with NIDDM (p < 0 .03) but not in those with IDDM (p > 0.06). The rise in plasma adrenal ine was greater during clamped hypoglycaemia in both groups (IDDM p < 0.02, NIDDM p < 0.02) and there tvas a strong relationship between the rise in adrenaline and increase in QTc (r = 0.73, p < 0.0001). These data demonstrate alteration of ventricular repolarization with lengthe ning of the QT interval during hypoglycaemia and suggest a possible me chanism by which hypoglycaemia could cause ventricular arrhythmias. (C ) 1997 by John Wiley & Sons, Ltd.