LAA Electrical Isolation Sparks Strokes, But Is Risk Manageable?

Patrice Wendling

August 23, 2019

New data underscore that electrical isolation of the left atrial appendage (LAA) during catheter ablation for atrial fibrillation (AF) is a man-made risk factor for stroke. They also suggest that optimal lifelong oral anticoagulation or placement of an LAA occlusion device may reduce that risk.

During 2.3 years of follow-up, 4.9% of 1854 consecutive patients experienced a stroke or transient ischemic attack (TIA) after pulmonary vein isolation with electrical LAA isolation.

Anticoagulation was discontinued in all patients who had normal LAA function at 6 months — irrespective of CHA2DS2-VASc risk score — and none experienced a stroke event.

Among patients with abnormal LAA function at 6 months, the stroke/TIA rate was 1.7% on anticoagulation and 16.7% off anticoagulation (P < .001). Thromboembolic events were reported across all CHA2DS2-VASc risk scores from 0 to 6.

"What we are showing is that if patients are properly counseled on blood thinners, we are not putting them into a dangerous situation," Andrea Natale, MD, Texas Cardiac Arrhythmia Institute, Austin, told | Medscape Cardiology.

Although studies have reported that electrical isolation of the appendage improves ablation success, concerns have been raised that the add-on therapy may be too aggressive and increases LAA thrombus formation and stroke.

"It's aggressive to a point," observed Natale. "We're seeing patients who sometimes come to us after six or seven failed ablations. So do you want to keep ablating things if it doesn't make a difference?

"We're not saying that you have to do it in everybody; we're saying you have to do it when it's needed. That's different."

The study, published online in the August 27 issue of the Journal of the American College of Cardiology, stresses that anticoagulation is crucial to reduce stroke risk, noting that 100% of patients who had a stroke on oral anticoagulation (OAC) had a subtherapeutic international normalized ratio or had discontinued therapy for a brief time.

"Some of these patients can get into trouble within 24 or 48 hours of stopping their blood thinner," Natale said. "So clearly, appendage isolation makes patients more dependent on their blood thinner."

"But we hope this [data] will move the field and that once we do that, the next step will be closing the appendage mechanically so we can bring these people back to being less dependent on blood thinner, and, in the majority of them, stopping it."

Among the subset of 90 patients with stroke/TIA, 84 went on to receive either the Lariat exclusion device (SentreHEART) or the Watchman occlusion device (Boston Scientific). After a median of 12.4 months, 98% of these patients were off continuous OAC and only one thromboembolic event occurred post-Watchman in a patient still on OAC.

"This data will make it easier for us to consider appendage closure with devices like the Watchman, even if the CHA2DS2-VASc is not above 2 or 3, which is the current indication," Natale said.

The data support use of LAA occlusion devices in patients who have undergone electrical isolation and are in line with their own recent study showing significantly fewer thromboembolic events with LAA closure than continued OAC, Boris Schmidt, MD, coauthor of a related editorial, told | Medscape Cardiology.

He noted that the present study is the largest to date in this particular population and reports success rates as high as 92% of patients being free from AF during follow-up.

Nevertheless, Schmidt urged caution regarding the suggestion that OAC can be safely stopped in patients whose LAA function is intact after electrical isolation, regardless of individual patient risk. There are no randomized trials showing the safety of systematically stopping OAC. Also, the most recent expert consensus statement recommends adherence to AF anticoagulation guidelines for patients who have undergone ablation, "regardless of the apparent success or failure of the procedure."

"If this strategy of LAA isolation is applied in a more generalized fashion we have to come up with appropriate stroke prevention strategies," Schmidt said. "The authors propose to just keep them on oral anticoagulation and that this is a manageable problem. But they also show that if patients stop the anticoagulation for just 1 or 2 days for another medical intervention or because they just forgot, they get strokes.

"If the therapeutic range is so narrow with oral anticoagulation between safety and stroke, then we need to come up with something different."

Both the editorialists and the authors agree that the safety of LAA electrical isolation (LAAEI) under optimal anticoagulation needs further evaluation in randomized trials.

"Additionally, discontinuation of OAC based on the LAA function irrespective of the CHA2DS2-VASc score in post-LAAEI patients is not a standard practice, and larger studies will be needed to verify the safety of this approach," the authors write.

Although not highlighted in the paper, an important part of the procedure is the need for experienced echocardiographers to assess appendage function, which isn't easy, observed Natale. The "biggest mistake" is in assessing flow velocity, where studies have shown significant overlap of flow velocities measured in isolated and nonisolated LAAs.

"We kind of learned it the hard way at the beginning and then we try to focus on the reading and who does the final reading because people without experience can make a mistake when they assess appendage function and say it's normal when it's not," he said. "The imaging part is a new thing. It was never an issue before we started doing this, but now it is."

Patients in the study had follow-up transesophageal echocardiography (TEE) at 6 months to assess LAA function based on three functional parameters: contractility, velocity, and consistent A-waves. At the 6-month TEE, 336 patients had normal LAA function and 1518 had impaired function.

Natale reported consulting for Baylis Medical, Boston Scientific, Biosense Webster, Bristol-Myers Squibb, St. Jude Medical, Biotronik, and Medtronic. Coauthor conflicts are listed in the paper. Schmidt reported consulting for and receiving speaker honoraria from Abbott and Boston Scientific. Coeditorialist Julian Chun, MD, reported consulting for and receiving speaker honoraria from Medtronic.

J Am Coll Cardiol. 2019;74:1019-1028. Abstract, Editorial

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