Atrial fibrillation is a common heart condition characterized by a rapid, irregular heartbeat stemming from the heart’s upper chamber. It is a leading cause of stroke from clots that form in a small pouch of the heart called the left atrial appendage (LAA). While several treatment options exist, they have many drawbacks, and risks often remain. But now, researchers have developed a promising new treatment involving magnetic fluids. Their study, published in Nature, describes the new procedure and results from rat and pig studies.
Atrial fibrillation treatment options
Blood thinners are a common treatment for atrial fibrillation. However, some patients cannot take them due to an increased risk of bleeding. Another option is closing off the LAA with a device. This is referred to as left atrial appendage occlusion (LAAO). While the devices that are currently available reduce stroke risk, they can leave small leaks and attract clots on or around the device itself. One of these devices is the Watchman occluder—a metallic transcatheter LAAO device.
One reason blocking off the LAA is difficult is that its shape varies from patient to patient, and is often rather odd. Names of these strange and difficult-to-fill shapes include cauliflower, cactus, chicken wing and the most challenging type—the windsock. Some improvements have been made to attempt to fit these shapes better, but issues remain.
“To optimize metallic occluders, soft occluders such as transcatheter patches and silicone occluders based on 3D-printed molds have been developed to provide personalized treatments. However, to achieve full occlusion, these occluders are often designed to be oversized or overinflated. Extra stresses are placed on the surrounding anatomy of the LAA, resulting in undesirable hemodynamics at the ostium,” the study authors explain.
Because liquids or gels can fill up the difficult morphologies of the LAA, some liquid-based treatments have been attempted. However, these approaches either require curing temperatures that are too hot, or they get washed away by fast blood flow, posing risks of tissue damage or embolism.
Magnetic fluid for left atrial appendage occlusion
The team involved in a new study have proposed a different approach—a magnetic fluid that can be guided into the LAA using a magnet. Once the LAA is filled, the fluid hardens enough to stay in place, completely filling in gaps. Specialized bonding occurs and the gel begins to solidify in about 60 seconds, reaching a stable form in about 11 minutes.
The study authors write, “Once the LAA ostium was sealed by the collagen network after 7 days, the risk of magnetogel dislodgement was eliminated. The resilience of the magnetogel for long-term use was proven using cyclic compression tests.”
The magnetic material consists of neodymium–iron–boron (NdFeB) magnetic particles, which is combined with a polymer solution and poly(vinyl alcohol) to improve toughness and cell adhesion. During insertion with a catheter, the fluid is guided by a 50–200 mT magnetic field. The team were able to confirm that it resisted blood flow and stays in the LAA. Then, contact with blood water triggers a liquid–liquid phase separation into a solid gel.
Promising results in rats and pigs
The team has already conducted magnetic fluid trials in rats and pigs with impressive results. Data from both rat and pig studies showed preserved heart function with no systemic toxicity, inflammation, or particle migration to organs. Data from pigs in the study was taken for 10 months, and in that time there was no device-related thrombus or magnetogel leakage, no myocardial injury or crevices showing up between the gel and heart tissue.
The magnetic gel was also compared to the metal Watchman device in pigs. Pigs with the Watchman showed rough, incomplete endocardial coverage, leaks and clots on its surface. They also experienced injury in the heart tissue from anchoring barbs. Meanwhile, the pigs with the magnetogel had fully integrated gel in the LAA, with a smooth, firm, thrombus‑free endocardial lining and complete filling of the LAA.
The team writes, “Challenges posed by high-speed blood flow and cardiac contractions were effectively overcome under a sufficient magnetic field. The long-standing clinical issues of peri-device leak and DRT were solved, and the associated risks of postoperative stroke were reduced substantially based on our in vivo experiments across different animal models. The resilience and biocompatibility of the magnetogel can offer a promising clinical solution for the long-term thrombus-free LAAO.”
While the team is optimistic, they will need additional research before they can begin human trials. They hope to optimize the magnetofluid formulation to improve shelf life, handling time, and ease of use in clinical labs. And while MRIs are still possible with the implant, they do produce large artifacts that obscure the heart, limiting cardiac MR imaging in patients. Still, for some patients, the procedure may offer long-lasting stroke prevention in the future. https://medicalxpress.com/news/2026-03-safer-effective-atrial-fibrillation-treatment.html
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