Gentle beams of light could replace electric shocks in treatment of heart disorders

Using high-tech human heart models and mouse experiments, scientists at Johns Hopkins University in the USA and Germany's University of Bonn have shown that beams of light could replace electric shocks in patients reeling from a deadly heart rhythm disorder.

The new findings could pave the way for a new type of implantable defibrillators. Current devices deliver pulses of electricity that are extremely painful and can damage heart tissue. Light-based treatment should provide a safer and gentler remedy for patients at high risk of arrhythmia, an irregular heartbeat that can cause sudden cardiac death within minutes.

This idea springs from advances in the field of optogenetics, in which light-sensitive proteins are embedded in living tissue, enabling the use of light sources to modify electrical activity in cells.

"We are working towards optical defibrillation of the heart, where light will be given to a patient who is experiencing cardiac arrest, and we will be able to restore the normal functioning of the heart in a gentle and painless manner," said research supervisor Professor Natalia Trayanova.

To move the new heart treatment closer to reality, the scientists at the University of Bonn and Johns Hopkins focused on two different types of research.

The Bonn team conducted tests on beating mouse hearts whose cells had been genetically engineered to express proteins that react to light and alter electrical activity within the organ. When the Bonn researchers triggered ventricular fibrillation in the mouse heart, a light pulse of one second applied to the heart was enough to restore normal rhythm.

Light based treatment for arrhythmia safer and gentler than electric shocks

"This is a very important result," said Tobias Bruegmann, one of the lead authors of the journal article. "It shows for the first time experimentally that light can be used for defibrillation of cardiac arrhythmia."

To find out if this technique could help human patients, Trayanova's team at Johns Hopkins performed an analogous experiment within a detailed computer model of a human heart, one derived from MRI scans taken of a patient who had experienced a heart attack and was now at risk of arrhythmia.

"Our simulations show that a light pulse to the heart could stop the cardiac arrhythmia in this patient," said Professor Patrick M. Boyle, who was also a lead author of the journal article.

To do so, however, the method from the University of Bonn had to be tweaked for the human heart by using red light to stimulate the heart cells, instead of the blue light used in mice. Professor Boyle explained that the blue light used in the much smaller mouse hearts was not powerful enough to fully penetrate human heart tissue. The red light, which has a longer wavelength, was more effective in the virtual human tests.

"In addition to demonstrating the feasibility of optogenetic defibrillation in a virtual heart of a patient, the simulations revealed the precise ways in which light alters the collective electrical behaviour of the cells in the heart to achieve the desired arrhythmia termination," Professor Trayanova said.

Professor Boyle added that this aspect of the study highlighted the important role that computational modelling can play in guiding and accelerating the development of therapeutic applications for cardiac optogenetics, a technology that is still in its infancy. However, more time and research will be needed before the light treatment can become a commonplace medical procedure.

The findings are published online in The Journal of Clinical Investigation.

Any form of disturbance to the heart's normal regular beat Full medical glossary
Relating to the heart Full medical glossary
The basic unit of all living organisms. Full medical glossary
Giving a controlled electric shock to restore normal heart rhythm in cases of cardiac arrest. Full medical glossary
A device used for defibrillation, which involves giving a controlled electric shock to restore normal heart rhythm in cases of cardiac arrest. Full medical glossary
Devices used for defibrillation, which involves giving a controlled electric shock to restore normal heart rhythm in cases of cardiac arrest. Full medical glossary
Abnormally fast and uneven contractions of the heart muscle, so that blood cannot be pumped efficiently Full medical glossary
The basic unit of genetic material carried on chromosomes. Full medical glossary
Relating to the genes, the basic units of genetic material. Full medical glossary
The death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. Full medical glossary
A large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. Full medical glossary
An abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field. Full medical glossary
Compounds that form the structure of muscles and other tissues in the body, as well as comprising enzymes and hormones. Full medical glossary
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A group of cells with a similar structure and a specialised function. Full medical glossary
Relating to a ventricle (either in the brain or the heart) Full medical glossary