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Wednesday, April 23, 2014

One of the causes of mortality in subjects with epilepsy is SUDEP (Sudden Unexpected Death with Epilepsy). A reason why this could be the case is that subjects with epilepsy can have cardiac dysfunction as well.

  • The heart and the central nervous system do not work independently; in fact, there is much cross-talk between the two systems.

  • The heart is regulated by the autonomic nervous system, so it is not surprising that seizures can transiently influence cardiac function. In addition, disorders of the cardiovascular system, and treatments meant to alleviate, them can precipitate new seizures or influence the management of existing seizures.

  • Despite some speculations, the mechanism behind cardiac dysfunction in subjects with epilepsy is not yet known. One obvious place to look would be to examine something that is common to both the nervous system and the heart. One convergence between the two systems is the HCN (Hyperpolarization-activated cyclic nucleotide-gated) channels.

  • HCN channels are present in the membrane of heart and brain cells and modulate the flow of positive ions (cations) into the cell. Since HCN channels give rise to rhythmic activity between groups of brain or heart cells, they are also known as “pacemaker channels.”

To examine the mechanism behind cardiac dysfunction in epilepsy, a recent study used animal models of epilepsy and looked at cardiac function and HCN channel expression.

Two rat models of epilepsy were used. The first was a model for generalized absence seizures (Genetic Absence Epilepsy Rats from Strasbourg; GAERS model); the second was a model for acquired temporal lobe epilepsy (post–status epilepticus; SE model). These are the findings:

  • Rats from both models of epilepsy (i.e. GAERS and post-SE) showed cardiac dysfunction.

  • There was a reduction in HCN expression in the hearts of these rats.

Hence, these results show that a dysfunction in HCN channels could potentially underlie cardiac dysfunction in epilepsy.

Authored by: Sloka Iyengar PhD on 4/2014
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