An Open-Source Platform for Multimodal Electrical and Optical Mapping of Ex Vivo Hearts

The heart is a pump, but it is also an electrical machine. For a heartbeat to occur, a wave of electricity must travel smoothly through the muscle, telling the cells when to squeeze. When this electrical signal gets tangled or blocked, the heart can beat too fast, too slow, or in a chaotic rhythm known as an arrhythmia. Doctors treat these dangerous rhythms by mapping the heart's electrical activity, trying to find the exact spot where the signal goes wrong so they can fix it with a catheter. However, the electrical signals doctors see on the surface are often a blurred version of what is actually happening deep inside the muscle. It is like trying to understand the movement of a crowd by watching only the shadows they cast on a wall; the shape is there, but the details are lost. To truly understand how these dangerous rhythms start and how to stop them, scientists need to see the electrical activity and the heart's physical structure at the same time, with perfect clarity.

A team of researchers has built a new, open-source platform that allows scientists to do exactly this: watch the heart's electrical signals and its physical structure simultaneously in a perfused organ outside the body. Published in a recent study, this system is designed to work with hearts of different sizes, from small rabbits to large pigs and even human hearts that were not suitable for transplant. The researchers created a setup that combines three different ways of looking at the heart. First, they use high-speed cameras and special dyes to see the electrical waves moving across the heart muscle in real time, creating a detailed map of the activation. Second, they use tiny electrodes that touch the heart's surface to record the electrical signals exactly as they would be measured during a patient's procedure. Third, they place the heart in a tank filled with a conductive liquid that mimics the human body, allowing them to record the electrical field from a distance, just as a doctor would see it on a patient's skin. By synchronizing all these measurements, the team can compare what is happening on the surface, deep inside the muscle, and far away in the surrounding fluid, all during the same heartbeat.

The platform was tested in three different configurations to handle the unique challenges of different heart sizes. For small hearts, like those from rabbits, the team used a setup that captured the entire organ from multiple angles. They placed the heart in a tank and used three cameras to get a panoramic view of the surface while electrodes touched the heart and sensors in the tank recorded the distant signals. This allowed them to see how the electrical wave moved across the whole heart and how that movement translated into the signals recorded by the electrodes and the tank. For larger hearts, such as those from pigs and humans, the researchers adapted the system to fit the bigger organs while keeping them intact. In the large-heart whole-organ configuration, they used transparent electrode interfaces that allowed cameras to see through the tank walls to capture optical data and electrical potentials from the surrounding fluid simultaneously. In a separate large-heart configuration, the researchers split the heart to look at the inner and outer surfaces at the same time, something that is impossible to do in a living patient. This setup revealed that the electrical patterns on the inside of the heart can look very different from those on the outside, especially during chaotic rhythms like fibrillation.

The researchers demonstrated that their system works by recording the hearts in various states, including normal rhythm, rapid beating, and chaotic fibrillation. They found that the different methods of measuring the heart's electricity do not always tell the same story. For example, the high-resolution camera view showed a smooth, continuous wave of activation, while the electrodes, which only touch specific points, showed a more scattered picture that required computer interpolation to connect the dots. The signals recorded from the tank, which represent the electrical field after it has traveled through the fluid, looked even more different, showing how the complex patterns of the heart muscle are smoothed out and altered before they reach the body's surface. These differences are not errors; they are real physical phenomena that occur because each method measures a different aspect of the electrical activity. The platform allows scientists to see these differences side by side, helping them understand why a treatment that looks good on a map might not work as expected in a patient.

What makes this work particularly significant is that the researchers have made the entire system available to the public. They have shared the software, the electronic designs, and the mechanical blueprints so that other laboratories can build their own versions of this platform. This is a departure from the usual practice where such complex equipment is kept proprietary or built only by a single team. By providing a reproducible framework, the authors hope to accelerate the study of heart rhythms and improve the methods doctors use to diagnose and treat them. The system is not a magic solution that instantly cures heart disease, but it provides a powerful new tool for understanding the complex relationship between the heart's physical structure and its electrical signals. It bridges the gap between the high-resolution images scientists can see in a lab and the electrical signals doctors see in a clinic, offering a clearer picture of how the heart's electrical system works when it goes wrong.

The study also included a method to create a three-dimensional model of the heart's shape after the experiments were done. By taking pictures of the heart from every angle as it was slowly rotated, the team could build a digital mesh that matched the exact shape of the organ used in the experiment. This model helps researchers place their electrical and optical maps onto a realistic shape, making it easier to visualize where the signals are coming from. While this model only shows the outside of the heart and cannot see inside the muscle or into hidden crevices, it provides a crucial link between the data and the physical reality of the organ. The researchers emphasized that this platform is a foundation for future studies, allowing scientists to test new mapping techniques and better understand how electrical signals travel through different types of heart tissue.

In the end, this work is about bringing different ways of looking at the heart together. For years, scientists have had to choose between seeing the heart in high detail with cameras or measuring the electrical signals that doctors use with electrodes. This new platform removes that choice, allowing both to happen at once. It shows that the electrical signals recorded on the surface are a complex reflection of what is happening inside the muscle, and that understanding this relationship is key to developing better treatments for heart rhythm disorders. By making this technology open and adaptable, the researchers have created a shared resource that can help the entire scientific community move closer to solving the mysteries of cardiac arrhythmias. The heart remains a complex and vital organ, but with tools like this, we are beginning to see its electrical life with a clarity that was previously out of reach.