Gentle light beams may treat lethal heart condition: study

Scientists have shown that beams of light could replace harsh electric shocks to treat patients reeling from arrhythmia - a deadly heart rhythm disorder.
Researchers from the Johns Hopkins University in the US and University of Bonn in Germany said that light-based treatment should provide a safer and gentler remedy for patients at high risk of arrhythmia - irregular heartbeat that can cause sudden cardiac death within minutes.
Current devices deliver electric pulses that are extremely painful and can damage heart tissue, researchers said.
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 Natalia Trayanova, from Johns Hopkins University.
Researchers 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 they triggered ventricular fibrillation in a mouse heart, a light pulse of one second applied to the heart was enough to restore normal rhythm.

"This is a very important result," said Tobias Bruegmann, from University of Bonn.
"It shows for the first time experimentally that light can be used for defibrillation of cardiac arrhythmia," said Bruegmann.
To find if this technique could help human patients, researchers 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 Patrick M Boyle, a Johns Hopkins research professor.

To do so, however, the method 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.
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," Trayanova said.

The study appears in the Journal of Clinical Investigation.