Epilepsy is one of the most common diseases of the nervous system. One in 10 people has an epileptic seizure sometime during their life that causes them to lose consciousness or lose control of all or part of their body. Luckily, drugs can treat people with epilepsy so effectively that the disease is not usually dangerous.
Unfortunately, people with epilepsy still do not feel totally secure, because sudden fluctuation in heart rate – becoming either very slow or very fast – can be fatal, causing sudden unexpected death in epilepsy, often during sleep. Now Danish researchers have come closer to understanding how these fatal heart attacks occur.
The researchers more closely examined ictal tachycardia: a sudden and large increase in heart rate since it is not clear why the baroceptor reflex that normally reduces the heart rate is suddenly inhibited during this type of heart attack.
The vagus nerve is considered important for baroreflex mediation. The researchers therefore induced a controlled heart attack in 10 pigs using the drug pentylenetetrazole. The pigs were closely monitored during the heart attack through electrocardiography, blood pressure and especially the vagus nerve activity.
During the heart attacks, the researchers observed that vagus nerve activity rose initially, suddenly fell and then rose again once the heart attack ended. The lack of vagus nerve activity during the heart attack might explain why the normal baroreflex reduction of the heart rate was temporarily inhibited.
This research is an important step in understanding the mechanisms of the body during a heart attack. Ictal tachycardia is not abnormal, even among people without epilepsy, but is usually harmless. However, it can lead to more serious heart diseases such as atrial fibrillation and sudden unexpected death in epilepsy during sleep.
The results are especially interesting because vagus nerve stimulators are already used to reduce the number, length and severity of epileptic seizures. These pacemaker-like devices deliver electrical impulses through a major nerve to the brain. Many people with epilepsy also have epilepsy alarms, both bed seizure alarms and wristband alarms. Globally, about 40 million people have epilepsy.
“Changes in vagus nerve activity associated with ictal tachycardia in pigs” has been published in Epilepsy Research. In 2013, the Novo Nordisk Foundation awarded an Exploratory Pre-Seed Grant to Johannes J. Struijk for the project ARTONOS – Determining Aortic Pulse Wave Velocity.