Researchers have found a way to restore a normal heartbeat in people who have atrial fibrillation (AF) using a beam of light, rather than electricity, to shock the patient’s heart back into rhythm. Their findings were presented at the European Society of Cardiology's recent meeting Frontiers in CardioVascular Biology 2014 in Barcelona, Spain.
The study is the first to demonstrate the use of light-induced, shockless defibrillation as a painless method of treating AF, the most common kind of heart rhythm disorder, or arrhythmia. Currently, the quickest way to bring a patient out of AF is to give him or her an electric shock. However, this technique can be painful and requires giving the patient anesthesia, which can also cause negative side effects, said study author Dr. Brian Bingen in a press release.
“In the future we might be able to terminate cardiac arrhythmias directly without resorting to electric shocks,” Bingen told Healthline. “One method to do so is through inserting ion channels in the heart that are activated by energy forms other than electricity that are less likely to trigger a pain response, such as light, followed by their activation—illumination with blue light in our case.”
The Importance of Treating AF
AF causes the heart’s two upper chambers to beat irregularly and out of sync with the heart’s lower chambers, resulting in poor blood flow to the body. Symptoms can include chest pain, heart failure, and an increased risk of stroke, according to the National Heart, Lung, and Blood Institute (NHLBI).
“Atrial fibrillation significantly contributes to morbidity and mortality, for instance, through its causality in...stroke,” Bingen said.
AF can last anywhere from a few minutes to several days, or become “an ongoing, long-term heart problem that lasts for years,” according to NHLBI.
“AF causes structural changes to the atrium, which makes patients more prone to subsequent induction of AF,” Bingen said in a press release. “That's another reason to get patients back into sinus rhythm as soon as possible.”
Shining a Light on AF
In order to restore normal cardiac rhythms in patients with AF without using electricity, Bingen and his team tried optogenetics, a method in which light is used to control the activity of light-sensitive cells in living tissue. Researchers change the cells on a genetic level to make them react by turning on or off in the presence of light.
“The theory was that we could just turn a light switch on and depolarise the entire [heart muscle] without needing a shock,” Bingen said. “In theory, the patient could be given an implantable device with a mesh of light emitting diodes (LEDs) and when AF occurs you turn the light on and the AF stops.”
However, because the heart is a three-dimensional structure, testing this theory was a challenge, Bingen told Healthline.
“We essentially made two-dimensional hearts by isolating cardiomyocytes, the main contractile cells in the heart, from complete hearts, and allowing these single cardiomyocytes to reattach to a petri dish,” he said. “The cardiomyocytes then reestablish their intercellular connections (i.e. they think they form a complete heart again) and start contracting simultaneously again, forming a functional 2D heart.”
Bingen and his team then induced arrhythmias in 31 of these 2D hearts by stimulating the cardiomyocytes with multiple electrical pulses per second.
“We made the cells sensitive to light by genetic modification, which allowed us to test the possibility to terminate the arrhythmias by light, thus without shock,” he said. “Then it was just a matter of switching on the light and seeing what happened."
“We found that in all 31 of these 2D hearts we were able to achieve the 2D equivalent of [a return to] sinus rhythm. The mechanism we saw was a bit different than the normal defibrillation, but was equally effective,” he said.
Shockless Therapy in 3D
While the study was a success, there are still many hurdles to overcome, and it may be more than 20 years before this therapy can be implemented in patients in the real world, Bingen said.
“The next step is to try our shockless defibrillation protocol in vivo (in a living organism),” he said. “Hence, we still have to find out whether or not the 3D structure of the heart itself does not preclude light-induced arrhythmia termination.”
“Moreover," he added, "we want to see whether patterned illumination or illumination of certain anatomical—areas that are associated with the initiation or promote maintenance of atrial fibrillation in the heart—allow more effective light induced arrhythmia termination.”