Severe hypoglycemia-induced sudden death is mediated by both cardiac arrhythmias and seizures

We previously demonstrated that insulin-induced severe hypoglycemia-associated sudden death is largely mediated by fatal cardiac arrhythmias. In the current study, a pharmacological approach was taken to explore the potential contribution of hypoglycemic seizures and the sympathoadrenergic system in mediating severe hypoglycemia-associated sudden death. Adult Sprague-Dawley rats were randomized into one of four treatment groups: 1) saline (SAL), 2) anti-arrhythmic ( ₁ blocker atenolol), 3) antiseizure (levetiracetam), and 4) combination antiarrhythmic and antiseizure ( ₁ BlockerLevetiracetam). All rats underwent hyperinsulinemic severe hypoglycemic clamps for 3.5 h. When administered individually during severe hypoglycemia,  ₁ blocker reduced 2nd and 3rd degree heart block by 7.7-and 1.6-fold, respectively, and levetiracetam reduced seizures 2.7-fold, but mortality in these groups did not decrease. However, it was combined treatment with both  ₁ blocker and levetiracetam that remarkably reduced seizures and completely prevented respiratory arrest, while also eliminating 2nd and 3rd degree heart block, leading to 100% survival. These novel findings demonstrate that, in mediating sudden death, hypoglycemia elicits two distinct pathways (seizure-associated respiratory arrest and arrhythmia-associated cardiac arrest), and therefore, prevention of both seizures and cardiac arrhythmias is necessary to prevent severe hypoglycemia-induced mortality.