A pacemaker for the stomach

By Lynley Hargreaves 05/11/2014

Dr Peng Du at the clinic in Kentucky
Dr Peng Du at the clinic in Kentucky

After no solid food for 16 months, an elderly man in Louisville, Kentucky, ate a peanut butter and jelly sandwich. A temporary pacemaker device fitted to his stomach had resuscitated the bioelectrical waves that govern digestion. Auckland University’s Dr Peng Du tells us from Kentucky how his Fast-Start Marsden grant can help explain what these waves mean, and what happens when things go wrong.

Does the stomach beat like a heart, and can you feel it?

They are similar. Your heart beat is governed by a bioelectrical impulse, and so is your stomach. The bioelectrical waves generated by the stomach’s network of pacemaker cells are very low in amplitude compared to the heart, making them a challenge to record. After a meal, the stomach works hard and contracts around three beats a minute to grind, mix, and empty its contents, but you do not feel the bioelectrical events associated with these contractions at all.

Why does the stomach stop working?

Once the pacemaker cells (called the interstitial cells of Cajal) in the stomach become degraded, particularly as result of diabetes, the bioelectrical activity can become dysrhythmic. We have devised recording techniques to show that prolonged periods of dysrhythmia can result in the inability to digest meals properly, leading to a condition called gastroparesis, or ‘paralysis of stomach’. Around 20% of type 1 diabetes patients may develop gastroparesis at some point.

When this happens to people, how much help can the medical system provide?

One of our overall goals is to establish the link between the stomach tissue structure and bioelectrical activity, and then test what happens to the bioelectrical activity when the structures are damaged. We have developed the ability to use hundreds of electrodes to record and generate an accurate ‘map’ of the stomach bioelectrical activation sequence. Then, in turn, we are interested in using this technique to pinpoint the source of the problem in many digestive diseases. To facilitate this process, we have also been using mathematical simulations to predict the conditions under which dysrhythmia will become sustained.

What are you doing in Kentucky?

Our collaborators here are running a world-class programme by fitting patients with medical pacemaker devices. Some patients respond well, like the aforementioned elderly man. With our detailed recording of stomach bioelectrical waves we hope to inform the clinicians on the change in the profile of these waves in response to the pacemaker device.

What’s next?

The next stage is helping people to lead a more healthy lifestyle. An issue is that we don’t quite understand the details contributing to the bioelectrical waves in the intact stomach. Many studies are done in isolated ‘in vitro’ tissue preparations in a tissue-bath, and that makes it difficult to draw conclusions of how the same tissue actually functions inside the body, i.e., in-vivo. We’re trying to work from an integrative multi-scale approach, and get a better understanding of the fundamental science.

Watch normal stomach activity in blue, unhealthy re-entry characteristics in red, and see the location of the electrodes on the stomach (on the right).

These interviews showcase researchers supported by the Marsden Fund which, since 1994, has been supporting fundamental, investigator-led research in New Zealand.