Enhanced Lesion Depth and Preserved Deep Thermal Safety of Sequential Radiofrequency and Pulsed Field Ablation: An Ex Vivo Porcine Heart Study
This ex vivo porcine heart study demonstrates that sequential radiofrequency and pulsed field ablation, particularly when radiofrequency precedes pulsed field delivery, creates significantly deeper myocardial lesions than either modality alone while maintaining a safe thermal margin at 7 mm depth, thereby offering a promising strategy to balance ablation efficacy with the protection of adjacent structures.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
For decades, doctors have used a technique called catheter ablation to treat irregular heartbeats by creating tiny scars on the heart muscle. These scars stop the electrical signals that cause the heart to race. The most common way to make these scars is with heat, using a tool that burns the tissue just enough to kill the cells and form a barrier. However, this heat is a double-edged sword. While it is effective at creating a scar, it can accidentally burn nearby structures, such as the esophagus, which sits dangerously close to the back wall of the heart. On the other hand, a newer method uses powerful bursts of electricity to zap the cells without generating significant heat. This approach is much safer for surrounding organs, but the scars it creates are often too shallow to stop the problem in thicker parts of the heart. The challenge has been finding a way to get the depth of the old method with the safety of the new one.
Researchers at the First Affiliated Hospital of University of Science and Technology of China set out to test a solution that combines both approaches. They wanted to see if using the heat method first, followed immediately by the electricity method, or vice versa, could create deeper, more effective scars without causing dangerous temperature spikes deep inside the tissue. To do this, they worked with fresh pig hearts removed from the body, a model that allows for precise measurement of how deep the damage goes and how hot the tissue gets without the complications of a living animal's blood flow. They tested four different strategies: using only heat, using only electricity, using electricity then heat, and using heat then electricity.
The team carefully monitored the temperature deep within the heart muscle, placing sensors just three millimeters and seven millimeters below the surface where the ablation took place. They found that when they used only the heat method, the temperature rose significantly as they increased the energy, creating deep scars. When they used only the electricity method, the temperature rise was much smaller, and the scars were shallower. However, when they combined the two, the results were more complex. The combination of heat followed by electricity created the deepest scars of all, reaching a depth of nearly seven millimeters. This was deeper than what either method could achieve on its own.
Crucially, the researchers discovered that this extra depth did not come with a dangerous spike in temperature at the deeper levels. Even though the surface and shallow layers got hot, the temperature at seven millimeters deep remained very low, rising by less than one degree in almost every case. This suggests that the heat did not travel far enough to threaten the structures behind the heart. The order in which the energy was applied mattered greatly. When the heat was applied first, followed by the electricity, the tissue damage was primarily a result of the heat, with the electricity helping to extend the scar deeper. When the electricity was applied first, the tissue showed a mix of heat damage and a different type of cell death that looks more like a programmed self-destruction, but the resulting scars were slightly shallower than the heat-first approach.
The study also looked at how the cells died under a microscope. The heat method caused the cells to swell and burst, a classic sign of thermal injury. The electricity method caused the cells to shrink and their internal structures to condense, a sign of a different biological process. When the two were combined, the type of cell death depended on which came first. The heat-first approach resulted in a scar dominated by thermal damage, while the electricity-first approach kept some of the unique cellular changes associated with the electrical method.
These findings suggest that a sequential approach, starting with heat and finishing with electricity, offers a promising way to create deeper, more durable scars while keeping the temperature rise in deep tissue minimal. This balance is vital for treating the back wall of the heart, where the risk of damaging the esophagus is highest. While these results come from a model outside the body and do not yet prove how this will work in living patients, the data indicates that the order of energy delivery is a key factor. By applying heat first to warm the tissue and then electricity to deepen the effect, doctors may be able to treat difficult heart rhythms more effectively without increasing the risk of deep thermal injury. The research highlights that the sequence of treatment is not just a technical detail, but a fundamental variable that shapes both the safety and the success of the procedure.
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