Severe hypoglycemia-induced lethal cardiac arrhythmias are mediated by sympathoadrenal activation
Candace M Reno1, Dorit Daphna-Iken, Y Stefanie Chen
1Division of Endocrinology, Metabolism, & Lipid Research, Department of Medicine, Washington University, St. Louis, Missouri.
Abstract:
For people with insulin-treated diabetes, severe hypoglycemia can be lethal, though potential mechanisms involved are poorly understood. To investigate how severe hypoglycemia can be fatal, hyperinsulinemic, severe hypoglycemic (10-15 mg/dL) clamps were performed in Sprague-Dawley rats with simultaneous electrocardiogram monitoring. With goals of reducing hypoglycemia-induced mortality, the hypotheses tested were that: 1) antecedent glycemic control impacts mortality associated with severe hypoglycemia; 2) with limitation of hypokalemia, potassium supplementation could limit hypoglycemia-associated deaths; 3) with prevention of central neuroglycopenia, brain glucose infusion could prevent hypoglycemia-associated arrhythmias and deaths; and 4) with limitation of sympathoadrenal activation, adrenergic blockers could prevent hypoglycemia-induced arrhythmic deaths. Severe hypoglycemia-induced mortality was noted to be worsened by diabetes, but recurrent antecedent hypoglycemia markedly improved the ability to survive an episode of severe hypoglycemia. Potassium supplementation tended to reduce mortality. Severe hypoglycemia caused numerous cardiac arrhythmias including premature ventricular contractions, tachycardia, and high-degree heart block. Intracerebroventricular glucose infusion reduced severe hypoglycemia-induced arrhythmias and overall mortality. β-Adrenergic blockade markedly reduced cardiac arrhythmias and completely abrogated deaths due to severe hypoglycemia. Under conditions studied, sudden deaths caused by insulin-induced severe hypoglycemia were mediated by lethal cardiac arrhythmias triggered by brain neuroglycopenia and the marked sympathoadrenal response.
Insights
Severe hypoglycemia can be fatal in insulin-treated diabetes. Preventing brain glucose depletion and blocking beta-adrenergic responses significantly reduces lethal cardiac arrhythmias and mortality in rats.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Metabolic Disorders
Background:
- Severe hypoglycemia is a life-threatening complication of insulin-treated diabetes.
- The precise mechanisms underlying hypoglycemia-induced mortality remain poorly understood.
- Understanding these mechanisms is crucial for developing effective preventative strategies.
Purpose of the Study:
- To investigate the mechanisms by which severe hypoglycemia leads to mortality.
- To test the efficacy of interventions aimed at reducing hypoglycemia-induced mortality.
- To explore the roles of antecedent glycemic control, potassium, brain glucose, and sympathoadrenal activation.
Main Methods:
- Hyperinsulinemic, severe hypoglycemic clamps (10-15 mg/dL) were performed in Sprague-Dawley rats.
- Simultaneous electrocardiogram (ECG) monitoring was employed.
- Interventions included antecedent glycemic control, potassium supplementation, intracerebroventricular glucose infusion, and beta-adrenergic blockade.
Main Results:
- Diabetes worsened mortality from severe hypoglycemia, while recurrent antecedent hypoglycemia improved survival.
- Potassium supplementation showed a trend towards reducing mortality.
- Severe hypoglycemia induced various cardiac arrhythmias (PVCs, tachycardia, heart block).
- Intracerebroventricular glucose infusion and beta-adrenergic blockade significantly reduced arrhythmias and mortality.
- Beta-adrenergic blockade completely prevented deaths.
Conclusions:
- Sudden deaths from insulin-induced severe hypoglycemia are mediated by lethal cardiac arrhythmias.
- These arrhythmias are triggered by central neuroglycopenia and sympathoadrenal activation.
- Targeting brain glucose levels and the sympathoadrenal response can prevent fatal outcomes.
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