Prevention and Treatment of Device-Related Thrombus: Interview With Madhu Reddy, MD, MBA, FACC, FHRS

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Interview by Jodie Elrod

EP Lab Digest talks with Madhu Reddy, MD, MBA, FACC, FHRS, about his presentation entitled "Prevention and Treatment of DRT” at Western AFib 2026.

Can you start with the brief introduction?

Thank you for having me. I’m Madhu Reddy, Chief of Electrophysiology at the University of Kansas Health System, where I’ve been practicing for the past 15 years. We have a large practice with 12 electrophysiologists and cover the full spectrum of EP care in a high-volume center. Over time, we’ve also evolved our practice in appendage closure, which we’ll discuss today.

What are the key clinical and mechanistic factors electrophysiologists should understand about device-related thrombus (DRT) in patients with atrial fibrillation (AF)?

The mechanistic implications of device-related thrombus are similar to those in patients who develop left atrial appendage thrombus without a device. The most common reasons patients develop thrombus on a device are the same underlying risk factors we already recognize: increasing age, a higher CHA₂DS₂-VASc score, and permanent atrial fibrillation. The main issue is platelet aggregation on the device, along with a greater propensity for thrombus formation due to stasis. When a device is implanted in a large left atrium, that stasis can persist. Additional factors—including procedural and patient-related considerations, as well as echocardiographic findings—can further increase the risk of DRT.

We have several risk scores to help identify patients at higher risk for DRT. While there are many, they generally fall into 3 main categories: patient-related clinical history, implant-related techniques, and echocardiographic findings. From an echocardiographic standpoint, factors such as prior thrombus, spontaneous echocontrast, or an enlarged left atrium—particularly beyond the typical 4–5 cm range—are associated with increased risk. Procedurally, device positioning is critical. If the device is implanted too deep into the appendage, it can create what we refer to as a pseudo-appendage, which increases the risk of stroke.

Another important consideration is the presence of periprocedural pericardial effusion. In these cases, anticoagulation is often stopped, which can further increase the risk of DRT and subsequent stroke.

What are the main challenges in preventing and detecting DRT after left atrial appendage occlusion, and have recent advances meaningfully changed management?

I would like to say it has, but unfortunately, we still continue to see DRT despite recent advances in device technology, as well as improvements in identifying and treating DRT earlier. For example, with the initial iteration of the WATCHMAN FLX device (Boston Scientific) compared with the original WATCHMAN 2.5, we observed nearly a 50% reduction in DRT—but it was not eliminated. So while device-related improvements have made an impact, we still see an incidence of around 2% with the Amulet (Abbott) and current-generation WATCHMAN.

Another important advancement has been the ability to identify patients at higher risk for DRT before the procedure. If we can recognize these patients and potentially avoid implantation, that may be one of the most effective ways to prevent DRT. 

In addition, rigorous follow-up with imaging has become essential. We know that among patients who develop DRT, about one-third will experience a stroke. Early on, there was a trend in which devices were implanted but follow-up TEEs were not consistently performed, which created risk—particularly if a thrombus developed and went unrecognized, leading to inappropriate discontinuation of anticoagulation. Frequent follow-up imaging, whether by TEE or CT, is therefore critical to detect DRT.

If no DRT is present and the WATCHMAN or Amulet device is well seated, anticoagulation can be safely discontinued. However, if DRT is detected, additional imaging—typically at least 2 or 3 follow-up studies—is needed. Many patients will develop a DRT, receive anticoagulation or other available therapies, and show thrombus resolution, but there remains up to a 50% risk of recurrence on the device. For this reason, these patients often require longer-term follow-up with sequential imaging.

How should evolving evidence on DRT prevention and treatment influence everyday AF practice and long-term stroke prevention strategies?

Many patients we identify as candidates for appendage closure are selected because they cannot tolerate long-term anticoagulation, but that represents a broad spectrum. It’s important to carefully assess why we are considering appendage closure in each patient, whether they can tolerate short-term anticoagulation, and to evaluate clinical risk factors—using available scoring systems—to determine which patients are at higher risk of DRT and whether they are appropriate candidates for the procedure.

For example, consider a patient with a large left atrium, permanent AF, a wide left atrial appendage, and spontaneous echocontrast who also cannot take anticoagulation. While this patient is clearly at high risk of stroke without a device, their risk of DRT is also very high. In such cases, if DRT develops, we may not be able to treat it effectively because they cannot tolerate anticoagulation afterward.

For this reason, we aim to be judicious in screening patients before offering this therapy. We generally avoid implanting devices in high-risk patients who cannot take anticoagulation. On the other hand, if a patient has a high risk of DRT but is able to take anticoagulation, it may still be reasonable to proceed—provided they understand that there is a possibility of thrombus formation on the device and that they may require anticoagulation, sometimes even lifelong. In fact, about one-third of patients who develop DRT ultimately remain on lifelong anticoagulation.

The transcripts were edited for clarity and length.