Electrical signals tell the heart to contract, but when the signals form spiral waves, they can lead to dangerous cardiac events such as tachycardia and fibrillation. Researchers at the Georgia Institute of Technology and clinicians at the Emory University School of Medicine are bringing new understanding to these complex conditions with the first high-resolution imaging of standing spiral waves in human ventricles.
“Clinicians have known for decades that spiral waves of electrical activity can occur in the heartand researchers have performed experiments on animal and human hearts before,” said School of Physics Professor Flavia Fenton. “However, this is the first time that the evolution of relatively stable spiral waves of voltage and calcium in the ventricles of human hearts has been mapped at very high spatial and temporary permit.”
Studying living hearts from heart transplant patients provides a rare window into the detailed behavior of the heart during conditions that are difficult to treat, such as fibrillation. As a result, doctors may better understand how spiral waves are generated and sustained, which could lead to new treatments.
This work was part of a decade-long collaboration between the Georgia Tech School of Physics and the Emory School of Medicine. The researchers published their latest findings: “Direct observation of a stable spiral wave returning to the ventricles of an intact human heart using voltage-calcium optical imaging” and “Spiral wave decay: optical imaging in the explanted human heart reveals transition from ventricular tachycardia.” to Ventricular Fibrillation and Self-Termination,” in Journal Heart rhythm.
Reflection of the heart
To create conditions for spiral waves to occur, researchers applied timed electric shocks to the heart. Then, to visualize and record the spiral waves, they injected fluorescent voltage dyes and calcium into the blood substitute that supports the heart. Changes in light intensity allow them to record signals through heart tissue, a method known as optical reflection.
“In this way, we can simultaneously visualize calcium and electrical waves in the heart, measuring changes in light intensity as direct changes in calcium content and voltage in cardiac cells,” said Ilya Uzelak, a physics researcher at Georgia Tech. “The amazing thing about this technique is that with a high-resolution camera, we can get measurements of voltage and calcium. with very high spatial and temporal resolution, which is not possible even with the use of thousands of recording electrodes around the heart.”
Each heart has a slightly different condition that leads to the need for a transplant, so researchers can study spiral wave dynamics in different types and severities of disease.
Collaborates with clinicians
Fenton’s group has studied spiral waves in hearts for more than two decades. Spiral waves are a good candidate for the field of nonlinear dynamics physics, where seemingly unpredictable systems are not random but chaotic. Methods to control and stop spiral waves can be developed to stop fibrillation with a small amount of energy, like Fenton’s group demonstrated theoretically earlier this year.
The group previously worked with the hearts of fish, reptiles, amphibians and some mammals. However, thanks to a partnership with Emory, they were able to study 10 human hearts from transplant patients who received a new heart last year.
“We are very fortunate to have a collaboration between Emory and Georgia Tech to conduct these experiments,” Fenton said. “There are very few doctors who, in addition to treating patients, want to collaborate with physicists in the study of arrhythmias.”
The study was also eye-opening from a medical perspective.
“I had a simplistic view of ventricular fibrillation based on what I saw in the clinic and what I read, but actually looking at ventricular fibrillation directly through these experiments gives a different picture of the complexity and what’s going on with their dynamics,” said Shahryar Iravanian, an Emory cardiologist on the team.
“Simultaneous imaging of electrical and chemical waves in the isolated human heart provides a unique opportunity to investigate the mechanisms of sudden cardiac death at a new functional level and to relate the dynamic electrical changes that characterize malignant arrhythmias to the specific and individual pathology of patients,” said Dr. Andre G. Kleber, Professor of Pathology in the Biophysics of Disease Group at Harvard University’s A. Paulson School of Engineering and Applied Sciences.
Researchers continue to study the explanted hearts and hope to set up experiments not only for basic science, but also to improve treatments. For example, most arrhythmias are treated by ablation, burning the substrate of the faulty circuits or electric shock, and this research could make such treatments more targeted and even personalized. Such progress could have huge implications for the future of treatment for cardiac arrhythmias, the leading cause of death in the United States
“It is difficult to make a map ventricular fibrillation because of patient instability and signal complexity,” said Neil Bhatia, an Emory associate professor of medicine and a member of the collaboration. “This study has the potential to have significant clinical complications. By mapping spiral wave dynamics in detail, we can better understand their evolution and ultimately determine when and how the heart can be treated with better catheter ablation strategies.”
Iliya Uzelats and others. Direct observation of the stable spiral wave returning to the ventricles of the whole human heart using voltage-calcium optical imaging, Heart rhythm (2022). DOI: 10.1016/j.hrthm.2022.06.015
Ilija Uzelac et al, Spiral wave breakup: Optical imaging in the explanted human heart reveals transition from ventricular tachycardia to ventricular fibrillation and self-completion, Heart rhythm (2022). DOI: 10.1016/j.hrthm.2022.07.013
Georgia Institute of Technology
Citation: Researchers image rotating spiral waves in living human hearts (2022, September 8) Retrieved September 8, 2022, from https://medicalxpress.com/news/2022-09-rotating-spiral-human-hearts.html
This document is subject to copyright. Except in good faith for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.