UChicago cardiologist rethinks devices used to prevent stroke in patients with AFib

Approximately 10.5 million Americans have atrial fibrillation (AFib), a condition that causes an irregular, often too fast, heartbeat. AFib increases the risk of stroke four to five times more than normal because it can cause blood to pool in the atria, or upper chambers of the heart. This allows clots to form, which can travel to the brain and cause a stroke.

The standard treatment to prevent stroke for people with AFib is to prescribe blood thinners. However, this isn’t a great option for everyone. Blood thinners can be expensive for patients who don’t have insurance that covers their full costs, and up to 25% of people who are prescribed blood thinners don’t take them. They are also risky for people with active lifestyles or who do physical labor, because they can lead to bruising and internal bleeding from falls and hard contact.

One alternative for people who aren’t good candidates for blood thinners is to implant a left atrial appendage occlusion (LAAO) device in the heart. The left atrial appendage is a small, pouch-like structure attached to left atrium; when people have AFib, it’s one of the places where blood can pool and form clots. LAAO devices work like a plug that basically seals off the appendage to prevent this from happening.

Atman Shah, MD, is a cardiologist at the University of Chicago Medicine who has been implanting these devices to treat AFib for more than 12 years. “The left atrial appendage is a lot like the appendix in our gut. We're not really sure what it does in adults, but it can cause a lot of problems,” he said. “This device gives us a way to wall it off so clots can’t form. Then patients don’t have to take blood thinners, and their risk of stroke is lower.”

Evaluating devices in the real world

There are currently two FDA-approved LAAO devices on the market. The Boston Scientific Watchman was approved in 2015, and Abbott’s Amplatzer Amulet LAA Occluder was approved in 2021. Since then, Shah and his colleagues have been part of multiple studies evaluating the Amulet after its widespread use in patients. They used data from a large, national registry of all patients with the device that recorded major events like death, heart attack, or stroke, along with other details like how the device was implanted and what kinds of follow-up medications they were given.

In one study, published in Cardiovascular Revascularization Medicine, Shah and his colleagues looked at what kinds of medications patients were given to prevent clots from forming around the device after it was implanted. The standard of care is two different anticoagulants—aspirin and Plavix—but data from the registry showed that patients taking both medications had a higher risk of bleeding. Instead, those on just one had fewer bleeding events and no increase in clots, suggesting a simpler medication regimen could be enough.

A second study, published in JACC: Cardiovascular Interventions, looked at two different imaging tools used to help guide surgeons as they implant the device. The first, older, method called transesophageal echocardiography (TEE) requires the patient to swallow a probe, so it stays in the esophagus while it sends images to a monitor. The second, newer technique, intracardiac echocardiography, uses a catheter inserted through a vein into the heart. While TEE has been around longer, it is invasive and requires patients to go under general anesthesia. Intracardiac echocardiography is less invasive, but since it is newer, there is less safety data available. When Shah and his colleagues analyzed data from the LAAO registry, both imaging techniques are just as safe and effective. Intracardiac echocardiagraphy procedures took a little longer, but that time decreased as physicians gained more experience.

Shah said that it’s important to continue studying the performance of such devices in the general population, even though they already went through rigorous testing to gain FDA approval.

“It's critically important to have these large, real world registry trials to assess the safety and the efficacy of the device long-term and in different populations that may not have been included in the original trials,” he said.

Creating a new design

While both devices have helped thousands of patients, almost 20% of patients are not eligible for effective closure due to the fact they are round in shape — and human appendages are not. This can lead to more clots, leaks and strokes. The current devices also rely on sharp hooks for fixation in a very thin structure, which can also lead to bleeding.

Based on his extensive experience with these devices. Shah has launched Parasol, named after the French word for umbrella, to offer an alternative, personalized solution to patients who need left atrial appendage closure. Parasol has received support from the Polsky Center for Entrepreneurship and Innovation at UChicago to design a prototype and connect with a manufacturer. The goal is that the final device would cost a third of the currently available options.

“There's lower risk of trauma to the left atrial appendage, and there's lower risk of clots or leaks because you can get a more effective seal,” he said. “I'm very grateful to the university and its ecosystem at the Polsky Center, which has been instrumental in developing it and providing that culture of inquisitiveness to make the world a better place.”