An international team of researchers from the George Washington University, U.S., and the Moscow Institute of Physics and Technology, Russia, has created an open-source solution for multiparametric optical mapping of the heart’s electrical activity. The method requires monitoring numerous parameters simultaneously—for instance, both electrical excitation and the variations in the intracellular calcium concentration. This method is a beneficial tool for improving one’s understanding of the mechanisms involved in cardiac arrhythmias. The 3D models of the mapping system parts and the source code for data analysis are freely available, allowing other study groups to gain from the new solution. The research was reported in Scientific Reports.
Cardiac excitation-contraction contains many interacting phenomena, mainly electrical excitation and the disparity in calcium concentration. Usually, excitation is started by a group of cells in the right atrium, known as the sinoatrial node, and spreads via the cardiac conduction system to the atria and ventricles. Irregularities in propagation, called arrhythmias, are a leading reason for mortality in Russia and other developed nations.
Optical mapping is presently the leading method for examining the mechanisms behind arrhythmias. This method is founded on perfusing ex vivo whole heart or a portion of cardiac tissue with fluorescent dyes. Many intracellular parameter changes could be monitored this way using high-speed cameras. The equipment’s high cost and the technical challenges of tracking several parameters of the sample simultaneously and processing the related signals prevent more extensive use of optical mapping in the biological setting.
To look into this, the researchers came up with an open-source and expansible system that concurrently monitors cardiac electrical excitation and intracellular calcium dynamics. Every system constituent, other than the lenses, cameras, and pumps, was 3D-printed. Since the designs of all components are currently openly available, any laboratory can reconstruct an analogous tool. The researchers deliberated that this could help other scientists save up to $20,000, compared with commercially available products. Together with the designs, the researchers open-sourced the code of their Matlab-based RHYTHM software for signal processing.
We made it a priority that physiologists would have access to the software, because they may lack the programming skills needed to code in C++, for example. The current version of the software has a number of modules for analyzing the action potential and calcium transients. But the architecture allows one to add a new module to enable simultaneous measurement of metabolic changes (NADH concentration), for example. Although the excitation propagation in the heart muscle is associated with an interaction between multiple complex phenomena, it is usually the case that researchers can only measure one parameter. Studies using multiparametric mapping are still uncommon.
Roman Syunyaev, Study Co-Author and Researcher, Human Physiology Lab, MIPT.
“Our laboratory maintains an open data policy,” says Professor Igor Efimov of the George Washington University, who also heads the Human Physiology Lab at MIPT. “Not many research teams nowadays can afford the expensive equipment for optical mapping. Now they can use our designs to recreate an affordable system just like the one we used. And they can process the data with RHYTHM. A further advantage of our tool is that it offers the freedom to design new experiments on diverse samples.”