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Sudden cardiac death: regular cyclones in the heart


Göttingen cardiac researchers are developing new, promising ultrasound diagnostics for cardiac arrhythmias
Germany alone dies every five minutes of sudden cardiac death. Cardiac arrest is caused by ventricular fibrillation - a severe cardiac arrhythmia. To this day, doctors do not understand in detail what exactly happens in the heart. So far, it has not been possible for doctors to make the dynamic processes in the flickering heart muscle visible. A new research project was able to reveal astonishing knowledge for the first time.

In today's publication of Nature magazine, an international team of researchers led by Jan Christoph and Stefan Luther from the Max Planck Institute for Dynamics and Self-Organization and Gerd Hasenfuß from the Heart Center of the University Medical Center Göttingen shows for the first time how vortex-like rotating contractions that underlie life-threatening cardiac fibrillation Inside of the heart can be observed. To do this, they use a new imaging method for which ultrasound devices that are established in medicine can be used. This will enable doctors to better examine cardiac arrhythmias, but also other heart diseases, and to develop new treatment methods.

To the heart of ventricular fibrillation: Max Planck researchers use ultrasound images (left) to reconstruct how the heart muscle contracts in a vortex shape in the event of a cardiac arrhythmia (center). You can also locate the filaments (right) that form the cores of the vertebrae. These insights provide starting points for improved therapies.

If the heart muscle no longer contracts in a coordinated manner, but only flickers, it becomes life-threatening. Doctors speak of fibrillation. If the main chambers of the heart twitch in this disorderly way, there is only one salvation: the heart muscle must be defibrillated within a few minutes with a strong current surge, which is very painful and can damage the heart tissue. Flickering in the atrium, on the other hand, does not lead directly to death, but can have fatal consequences if left untreated. "The key to a better understanding of fibrillation lies in new high-resolution imaging, which can also be used to observe the processes inside the heart muscle," says Stefan Luther, head of the "Biomedical Physics" research group at the Max Planck Institute for Dynamics and Self-organization and professor at the University Medical Center Göttingen.

"The mechanical movement of the heart muscle in fibrillation is highly complex, but at the same time it is very characteristic - almost like a fingerprint of fibrillation," says Jan Christoph, researcher at the Max Planck Institute for Dynamics and Self-Organization and at the German Center for cardiovascular research in Göttingen and lead author of the study. Together with Stefan Luther and an international team of researchers, the physicist is now presenting a diagnostic method with which the flickering of the heart muscle can be examined in a time-resolved manner in three dimensions using a conventional ultrasound device, and thus much more precisely than was previously possible in the patient.

Helpful for diagnosis and therapy of myocardial weakness

3D ultrasound measurements of mechanical filaments in the fibrillating heart

The new diagnostic method will help make ventricular fibrillation and possibly atrial fibrillation therapy more effective. The better understanding of fibrillation that can be achieved with the method should help to advance the development of low-energy defibrillation. Weaker, but much more targeted current surges are supposed to end ventricular fibrillation than with the painful defibrillation with high-energy electric shocks that is common today. With the new form of ultrasound diagnostics, physicians can find out how they have to set the current surges with lower energy in order to get the heart back on track.

The Göttingen researchers are also further developing the method so that it also makes the complex excitation dynamics of atrial fibrillation visible. In the future, cardiologists will be able to see where they should ablate pathological areas of excitement through ablation. The new ultrasound method should also be helpful for researching, diagnosing and treating cardiac muscle weakness. The heart muscle cells work ineffectively because their coordinated contraction is disturbed. Physicians could investigate the causes of this with detailed ultrasound examinations so that they can identify heart failure earlier and treat it more effectively.

Electrical stimulation causes mechanical contractions of the heart

Computer simulation of an electromechanical vertebra in the heart muscle tissue

Computer simulation of an electromechanical vertebra in the heart muscle tissue
Every heartbeat is triggered by electrical excitation waves that shoot through the heart muscle at high speed and cause the heart muscle cells to contract. If these excitation waves get mixed up, cardiac arrhythmias arise. Doctors have known for a long time that in the event of cardiac arrhythmias, the electrical stimulation travels through the heart muscle in a vortex shape. So far, they have focused on these electrical vertebrae when studying cardiac arrhythmias. However, they could not get a complete picture of the dynamics in everyday medical practice. The Max Planck researchers took a different approach and instead looked at the twitching contractions of the flickering heart muscle instead of electrical stimulation. “So far, the analysis of muscle contractions and deformations during fibrillation has been of little importance. In our measurements, however, we saw that the electrical vortices always occur with corresponding vortex-shaped mechanical deformations, ”says physicist Jan Christoph.

In order to depict the trembling movements inside the heart muscle in three dimensions and to connect them with the electrical excitation of the heart, the researchers developed new, high-resolution ultrasound measurement methods. They also demonstrated that these methods can be used in high-performance ultrasound machines that are already routinely used in many cardiology facilities. By analyzing the image data of the muscle contractions, they were able to follow in a flickering heart exactly how areas of contracted and relaxed muscle cells move in a vortex-shaped manner through the heart muscle. They also observed filament-like structures that were previously only known to physicists in theory and from computer simulations. Such a filament-like structure resembles a thread and marks the eye of the cyclone that moves through the heart muscle. Localizing the centers of the vertebrae inside the muscle is now possible for the first time.

In parallel to the ultrasound images, the researchers used high-speed cameras and fluorescent dyes, which make the electrophysiological processes in the heart muscle visible. The recordings made confirm that the mechanical vortices reflect the electrical vortices very well.

Potential to revolutionize cardiac arrhythmia treatment

Electrical vortices on the surface of the heart

According to the Göttingen researchers, ultrasound technology has undergone tremendous development in recent years in terms of image quality and recording speeds - the potential of modern ultrasound technology has not yet been fully exploited. "Together with the immensely increased computing power of modern computers and the rapid developments in computer graphics and digital image processing, completely new measurement and visualization options open up in the heart. We can use these developments in medicine today, ”says Jan Christoph.

The study is an example of successful interdisciplinary collaboration between physicists and doctors in the German Center for Cardiovascular Research. “This development has the potential to revolutionize the treatment options for patients with cardiac arrhythmias. We will use the new technology in our patients as early as 2018 in order to better diagnose and treat both cardiac arrhythmias and cardiac muscle diseases, ”says Gerd Hasenfuß, co-author of the study, chairman of the cardiac research center Göttingen and the cardiac center of the University Medical Center Göttingen. Stefan Luther is certain: "A deep look into the inner dynamics of the heart is a milestone in heart research and will shape the understanding and treatment of heart diseases in the future." MPIDS / PH

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