Rotating spiral waves in live human hearts
Washington, US: Electrical signals cause the heart to beat and can cause severe cardiac events like tachycardia and fibrillation as they spiral outward in spiral waves. The first high-resolution images of steady spiral waves in human ventricles are helping researchers get a fresh understanding of these complex circumstances.
According to School of Physics Professor Flavio Fenton, "Clinicians have known for decades that spiral waves of electrical activity can occur in the heart and researchers have done studies in animal and human hearts before." The formation of rather stable spiral waves of voltage and calcium in the ventricles of human hearts, however, has never before been mapped with such fine spatial and temporal resolution.
Studying live hearts from heart transplant recipients offers a unique perspective into the heart's intricate functioning amid challenging-to-treat diseases like fibrillation. As a result, medical professionals will have a better grasp of how spiral waves start and continue, which may result in the development of novel treatments.
The Georgia Tech School of Physics and the Emory School of Medicine have worked together for ten years on the current project. "Direct observation of a stable spiral wave reentry in ventricles of a whole human heart using optical mapping for voltage and calcium" and "Spiral wave breakup: Optical mapping in an explanted human heart shows the transition from ventricular tachycardia to ventricular fibrillation and self-termination" are the most recent findings that the researchers have made, respectively, in the journals Heart Rhythm and Heart Rhythm.
The researchers used timed electric shocks to the heart to create the conditions for spiral waves. Then, they introduced fluorescent calcium and voltage dyes into the artificial blood that keeps the heart beating in order to see and record the spiral waves. They are able to capture signals across the heart tissue via optical mapping, a process made possible by variations in light intensity.
According to Ilija Uzelac, a physics research scientist at Georgia Tech, "by monitoring the changes in light intensity as direct changes in calcium and voltage in the cardiac cells, we can view simultaneously the calcium and electrical waves in the heart." The great thing about this method is that we can monitor voltage and calcium at very high spatial and temporal resolutions using a high-resolution camera that is not even achievable with thousands of recording electrodes all over the heart.
Researchers may study the dynamics of spiral waves with various types and severity of disease since each heart has a little distinct ailment that necessitates a transplant.
For more than 20 years, Fenton's team has been researching spiral waves in the heart. Spiral waves are a strong contender for the physics topic of nonlinear dynamics, where seemingly unpredictable systems are actually chaotic rather than random. As Fenton's group theoretically demonstrated earlier this year, techniques can be devised to manage and terminate spiral waves to cease fibrillation with little energy.
The team has previously worked with hearts from certain mammalian species, fish, reptiles, and amphibians. However, as a result of their collaboration with Emory, they were able to investigate 10 human hearts from recipients of recent heart transplants.
To conduct these tests, Emory and Georgia Tech have a solid relationship, which Fenton described as being quite lucky. Very few doctors desire to work with physicists to investigate arrhythmias in addition to treating patients.
Medically speaking, the research has also been eye-opening.
Shahriar Iravanian, an Emory cardiologist who was part of the study, said, "I had a simplistic view of ventricular fibrillation based on what I see in the clinic and what I have read. But actually looking at ventricular fibrillation directly through these experiments gives a different perspective of the complexity and of what's going on with their dynamics.
Dr. Andre G. Kleber, Professor of Pathology in the Disease Biophysics Group at the A. Paulson School of Engineering and Applied Sciences, Harvard, stated that "mapping electrical and chemical waves simultaneously in the isolated human heart offers a unique opportunity to investigate mechanisms of sudden cardiac death at a new functional level and to associate the dynamic electrical changes characterising malignant arrhythmias to the specific and individual pathology of patients."
The goal of the ongoing research on explanted hearts is to better understand how they function and to develop remedies. For instance, most arrhythmias are treated with electric shocks or ablation, which involves burning the substrate of malfunctioning circuits. This research may allow for more precise and even individualised ablation and ablation treatments. Such developments may have a significant impact on how cardiac arrhythmias, a leading cause of death in the US, are treated in the future.
Because of patient instability and signal complexity, mapping ventricular fibrillation is challenging, according to Neal Bhatia, an associate professor of medicine at Emory University and a team member. "There could be serious clinical ramifications from our research. We can better understand spiral wave dynamics through precise mapping, which will help us decide if and when to use more effective catheter ablation techniques to treat the heart.
