Hypoglycaemia and Cardiac Arrhythmias in Patients with Type 2 Diabetes Mellitus

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Abstract
Improved blood glucose control by insulin treatment in patients with Type 2 (non-insulin dependent) diabetes mellitus increases the risk for hypoglycaemic episodes. Our objective was to investigate if hypoglycaemia causes electrocardiographic changes and cardiac arrhythmias in patients with Type 2 diabetes. Six insulin-treated patients with Type 2 diabetes and no known cardiac disease took part in the study. Hypoglycaemia was induced by insulin infusion aiming at a plasma glucose ≥ 2.0 mmol I−1 or hypoglycaemic symptoms. All patients experienced hypoglycaemic symptoms. The median lowest arterial plasma glucose was 2.0 mmol I−1. Arterial plasma adrenaline concentration increased from 0.4 ± 0.1 (mean ± SE) to 6.9 ±0.3 nmol I−1 (p < 0.001) while serum potassium was lowered from 4.1 ± 0.3 mmol I−1 to 3.5 ± 0.2 mmol I−1 (p < 0.001). The heart rate increased significantly during hypoglycaemia except in one patient who developed hypoglycaemic symptoms and a severe bradyarrhythmia at a plasma glucose of 4.4 mmol I−1. One patient developed frequent ventricular ectopic beats during hypoglycaemia while four patients showed no arrhythmia. ST-depression in ECG leads V2 and V6 was observed during hypoglycaemia in five patients (p < 0.05) and four patients developed flattening of the T-wave. In conclusion, the study supports the hypothesis that hypoglycaemia in patients with Type 2 diabetes may be hazardous by causing cardiac arrhythmias.