Sudden unexpected death in epilepsy (SUDEP) accounts for about 500 deaths in the UK every year. Post-mortem examinations typically reveal no specific cause of death, but most deaths are thought to occur because breathing and heart function are compromised during or as a result of a seizure. Breathing is often affected during seizures and there is some recent evidence that seizures can on rare occasions cause a fatal interruption to the normal functioning of the heart.

Although preventing seizures with treatment is considered to be the best protection against SUDEP, it's also known that anti-epileptic medication can affect the electrical activity of the heart. Further, there are certain types of epilepsy caused by genetic alterations to ion channels in cells; these alterations affect both brain and heart tissue, so in these cases, we might expect to see heart abnormalities in addition to epilepsy, though for the moment this is only a theory.

We know that people who died from SUDEP tend to have several of the following features of their condition:

• uncontrolled seizures (this is the most important factor)
• young adults
• generalised tonic-clonic seizures
• learning disability
• found dead in bed, indicating seizures during sleep
• unwitnessed seizures
• treatment factors, such as a history of not complying with treatment, and frequent changes of drug and dosage.

Studying people who have epilepsy with these features may point to underlying clinical conditions which might predispose them to dying in a seizure.

Dr Sanjiv Petkar and colleagues from the Manchester Royal Infirmary therefore investigated heart function in 128 patients from the David Lewis Centre in Cheshire. All patients had severe epilepsy and learning difficulties, and all had seizures that did not respond to treatment with anti-epileptic drugs. The researchers investigated heart function in these patients by carrying out electrocardiograms (ECGs).

An ECG measures the electrical activity of the heart, including the rate and regularity of the heartbeats. Carrying out an ECG involves attaching a number of electrodes to the arm, leg and chest of a seated patient. The test is painless.

In their preliminary report, which they presented at the World Congress of Cardiology 2006 in Barcelona, Spain, Dr Petkar and his colleagues said that 60% of patients in the study had some sort of abnormality on their ECG. The majority of these abnormalities were very mild, and none were severe enough to disrupt normal heart function. However this finding may be an indication that heart problems of various kinds may be more common in patients with this type of epilepsy. This is interesting because overly-low and overly-high heart rates are both preventable with medication. Might a proportion of SUDEP deaths be preventable?

Dr Petkar and his colleagues will now carry out more studies on the same group of patients to get more detailed information about the types of heart abnormalities seen. They will also study a group of people with epilepsy living in the community and compare their heart rhythms to those of the first group.