Pacemaker power: All in a heartbeat

Medical Tribune December 2008 P8
David Brill

Pacemakers could one day be powered by the beating of the heart, allowing for the development of more advanced features without the need for larger batteries, a British study suggests.

The team at Southampton University Hospital demonstrated that a prototype device, implanted into a pig, was able to successfully generate electricity solely from the contractions of the cardiac chambers.

At present the energy produced is just 17 percent of that needed to power a contemporary pacemaker but refinements of the model could increase this output to 100 percent, the researchers say.

“This study has proved the concept that it’s possible to harvest the energy of cardiac motion using a device that could be part of a standard pacemaker or ICD lead,” said Dr. Paul Roberts, a consultant electrophysiologist who led the study.

“We think that this study may represent a major advance in pacemaker and ICD technology. We don’t envisage that this would be a stand-alone device – we think that it would … augment current pacemaker and ICD batteries so in effect the heart would be continuing to charge the pacemaker battery.

“This may therefore allow for the development of additional device functions that had previously been limited by power constraints,” he said.

The so-called self-energizing implantable medical microsystem (SIMM) is presently hampered by the size of the lead, which has a maximum diameter of around 6mm. The researchers are now looking to bring this into line with current pacemakers by reducing the diameter to around 2 or 3 mm, Roberts said.

He added that it is likely to be several years before the device could be ready for use in humans.

The prototype, which has already attracted commercial interest and UK government funding, was inserted using the standard techniques for pacemaker implantation. The procedure was uneventful and took around 2 or 3 minutes, Roberts said.

The SIMM comprises two pressure-sensitive bladders placed in the right atrium and ventricle. As the heart contracts and relaxes the pressure pushes a magnet back and forth through the connecting lead, thereby generating electricity from a series of coils embedded in the lead.

At rest the system produced 4.3 μJ of energy and a voltage of 0.2 per heartbeat. The energy output increased to 9.6 μJ/beat during pharmacologically-induced tachycardia and dropped to 3.0 and 1.5 μJ/beat during bradycardia and atrial fibrillation, respectively.