Cardioversion Without Anticoagulation Appears Safe in Patients With Watchman

Direct current cardioversion for symptomatic atrial fibrillation or flutter is feasible and safe in patients implanted with the Watchman left atrial appendage (LAA) occlusion device, even in the absence of oral anticoagulation, a small multicenter study suggests.

Sinus rhythm was restored in all such patients, with no thromboembolic events seen in the first 6 weeks after cardioversion. There were three TIAs, but they occurred after more than 3 months had elapsed and were deemed unrelated to the procedure.

Outcomes were similar regardless of whether oral anticoagulation was started after cardioversion, researchers report.

What to do regarding the use of cardioversion in patients with an LAA occlusion device is “uncharted territory” and that uncertainty has translated to variation in how the situation is managed, senior author Dhanunjaya Lakkireddy, MD (Kansas City Heart Rhythm Institute and Research Foundation, Overland Park, KS), told TCTMD. Some clinicians have chosen to start oral anticoagulation before the procedure, some have chosen to start it afterwards, and others have stuck with single or dual antiplatelet therapy.

“It’s important to do a transesophageal echo when you’re thinking of doing a cardioversion in somebody that has a device or any kind of closure. If you think that the appendage is closed, make sure you’ve confirmed the appendage is closed and there are no major leaks and there’s no thrombus in front of the device,” Lakkireddy said in describing his recommended approach.

“And then when you cardiovert these patients, continue the regimen that the patient is on at that given point in time, because a cardioversion may be needed at different phases of the maturation of the [LAA occlusion] device,” he continued. “If you’re doing it in the first 6 weeks [after implantation], make sure their anticoagulation is continued. If you’re doing it between 6 weeks and 6 months, make sure their dual antiplatelet therapy is continued. And if you’re doing it after 6 months, then make sure their single antiplatelet therapy is continued.”

Lakkireddy acknowledged, however, that larger studies—and ideally randomized trials—are needed to definitively resolve whether it’s safe to forgo anticoagulation in these patients.

Anil Gehi, MD (UNC School of Medicine, Chapel Hill, NC), who wasn’t involved in the study, echoed that assessment. A study of this size—148 patients—"is not going to give you complete confidence in the safety,” he said, “but it’s good to know that there’s not even a signal of risk in this group.”

Because of the low overall risk of stroke after cardioversion, Gehi explained, “if you want to really demonstrate adequate safety, you’d need really large numbers of patients who had a Watchman and then had a cardioversion without any kind of anticoagulation after it.” That said, he continued, “it’s nice to have some data. I don’t think it would give me complete comfort, but it gives me some comfort that this may be a safe option.”

The study, with lead author Sharan Prakash Sharma, MD (Kansas City Heart Rhythm Institute and Research Foundation), was published online ahead of the November 5, 2019, issue of the Journal of the American College of Cardiology.

No Guideline Recommendations

Direct current cardioversion has the potential to cause LAA stunning, a temporary loss of contractility that increases the risk of thrombus formation, Lakkireddy said. To mitigate that risk, many clinicians choose to perform a transesophageal echocardiogram (TEE) to ensure the absence of a clot and then put the patient on oral anticoagulation after cardioversion.

International guidelines currently recommend starting anticoagulation 3 weeks before cardioversion and then continuing therapy for at least 4 weeks afterwards. However, there’s no specific guidance for patients with LAA occlusion devices and no long-term data to inform practice.

To fill that gap, the investigators performed a multicenter, retrospective study of 148 consecutive patients with a Watchman device (Boston Scientific) who underwent elective cardioversion for symptomatic atrial fibrillation or flutter (mean age 72 years; 59% men). All patients received the standard post-Watchman antithrombotic regimen that starts with aspirin plus oral anticoagulation then switches to aspirin plus clopidogrel and eventually aspirin monotherapy.

Every patient underwent TEE before cardioversion to assess LAA occlusion device apposition, the presence of device-related thrombus, and peridevice leak. Thrombus was seen in four patients (2.7%), all of whom were treated with oral anticoagulation and underwent cardioversion 6 to 8 weeks later.

In all patients, cardioversion successfully restored sinus rhythm. There were no cardioversion-related thromboembolic complications.

At the time of the procedure, 34% of patients were on oral anticoagulation, 30% were taking aspirin plus clopidogrel, and 36% were taking aspirin alone. Overall, 22% initiated oral anticoagulation after cardioversion. There was no difference in cardioversion-related complications based on the use of anticoagulation.

The three TIAs that were observed occurred 3 to 4 months after cardioversion in patients who were in sinus rhythm and taking aspirin monotherapy. “The cause of TIA in these patients could be most likely due to small-vessel disease given the presence of other risk factors such as diabetes, hypertension, and congestive heart failure,” the authors suggest.

Major bleeding occurred in four patients, all of whom were taking a direct oral anticoagulant after cardioversion. There were two minor bleeds, one in a patient treated with warfarin and the other in a patient not taking any oral anticoagulation.

During a median follow-up of 12.8 months, there were no cases of device/left atrial thrombosis, device dislodgement, or new device leak. One patient died from cancer.

Words of Caution

“Overarching claims cannot be made on how this should be done,” Lakkireddy said, citing the small sample size, “but at least the early observations show a signal that once the appendage is closed and there is no thrombus on the device, shocking them and putting them in normal sinus rhythm doesn’t really increase the risk of stroke.”

He said the findings have changed his practice in that he had been “overcautious” before, putting every patient on oral anticoagulation and continuing for 4 to 6 weeks after cardioversion. Now, “I feel comfortable that most of these people can be managed on their existing regimen in the course of their post-Watchman implantation [period],” Lakkireddy said, once again stressing that a TEE is needed before cardioversion to rule out device-related thrombus.

He said his group has just finished writing the protocol for a randomized trial that will evaluate whether patients with LAA occlusion devices require anticoagulation after undergoing cardioversion. The study still requires funding.

While awaiting additional data, Gehi said, “this analysis suggests that there’s not a large safety concern with doing cardioversion in patients who’ve had a Watchman device [implanted] and who are not being anticoagulated after their cardioversion. There still may be some increased risk with doing it without anticoagulation, but we would need a large data set to be able to establish the true safety profile.”

The lack of cardioversion-related thromboembolic events in this study “is reassuring,” he said, “but because the numbers are small I don’t think it could be something that we could say is perfectly safe.”

John Mandrola, MD (Baptist Health Louisville, KY), Gregory Y.H. Lip, MD (University of Birmingham, England), and Andrew Foy, MD (Penn State Health, Hershey, PA), and colleagues provide similar caveats in an accompanying editorial.

“We urge caution, not only for doing direct current cardioversion after left atrial appendage closure, but also for embracing nonpharmacological stroke prevention with LAA occlusion in the first place,” they write. “This paper should prompt us to stop and think about this technology.”