Researchers created a computer model that simulates the heart’s electrical circuits to study how different voltage fields affect various scenarios of fibrillation and defibrillation. Their findings revealed that significantly less energy is necessary compared to what is currently used in advanced defibrillation methods. By utilizing an adjoint optimization approach, they learned that adjusting both the duration and the gradual change in the voltage delivered by defibrillation devices can dramatically lower the energy required to end fibrillation, by a factor of a thousand.
In a recent paper published in Chaos by AIP Publishing, a team from Sergio Arboleda University in Bogotá, Colombia, and the Georgia Institute of Technology in Atlanta employed an electrophysiological computer model to analyze how the applied voltage field influences various fibrillation-defibrillation situations. They found that much less energy is essential compared to that used in today’s top defibrillation practices.
“The findings were completely unexpected. We discovered that the rationale for ultra-low-energy defibrillation isn’t linked to the synchronization of excitation waves as we initially thought. Instead, it’s about whether these waves can travel through tissue regions that have not fully recovered from prior excitations,” said author Roman Grigoriev. “Our goal was to determine the optimal timing variation of the applied electric field over an extended period. Since the duration wasn’t pre-determined, we adjusted it until we achieved a workable defibrillating protocol.”
The researchers implemented an adjoint optimization method, which seeks to attain a specific outcome—defibrillation in this context—by solving the electrophysiological model for a specific voltage input and then methodically working backward in time to adjust the voltage profile that would effectively restore normal heart activity while minimizing energy usage.
Reducing energy consumption in defibrillation devices is an important focus of ongoing research. Although defibrillators effectively terminate harmful arrhythmias, they can be painful and may damage heart tissue.
“Current low-energy defibrillation techniques only moderately lessen tissue damage and pain,” Grigoriev highlighted. “Our research indicates that these issues could be entirely resolved. Traditional methods require significant power for implantable cardioverter-defibrillators (ICDs), and the subsequent replacement surgeries pose serious health risks.”
In a regular heartbeat, electrochemical signals initiated by pacemaker cells at the top of the atria spread through the heart, causing coordinated contractions. However, during arrhythmias like fibrillation, these excitation waves start to whirl instead of propagating normally through the tissue.
“Certain conditions determine whether an excitation wave can travel through the tissue. This critical moment is referred to as the ‘vulnerable window,'” Grigoriev explained. “The outcome hinges on minuscule variations in the timing of the excitation wave or slight external disturbances.”
“The ultra-low-energy defibrillation method we identified takes advantage of this sensitivity. By altering the electrical field profile over a longer timeframe, we can inhibit the propagation of the rotating excitation waves through the sensitive tissue areas, effectively halting the irregular electrical activity in the heart.”
