Need for TEE Before AF Ablation Questioned if DOACs on Board: Large Cohort Study

July 27, 2020

There's no need to double up on echo modalities before and during ablation for atrial fibrillation (AF) as long as the patient has been on uninterrupted therapy with a direct oral anticoagulant (DOAC), propose the researchers behind one the largest studies to explore the issue.

It saw only one case of stroke or transient ischemic attack (TIA) in more than 6000 such patients who were on a DOAC for at least a month and didn't undergo transesophageal echocardiography (TEE) before their AF ablation, which was guided by intracardiac echocardiography (ICE).

The study, which counted events only in the first 48 hours after the procedure, suggests that such anticoagulated patients can safely forego routine preablation TEE. The procedure can reveal or rule out potentially embolic thrombi in the left atrium or left atrial appendage (LAA), but comes with added risks and costs.

Its job was adeptly performed by ICE, which not only guided the transeptal catheter procedure, but also "ruled out LAA and left-atrial thrombus in all patients," says a report published July 15 in Heart Rhythm, with lead author Kavisha Patel, MD, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York.

TEE before AF ablation should represent merely an alternative, discretionary approach, rather than a recommended routine part of the procedure, senior author Luigi Di Biase, MD, PhD, from the same institution, told | Medscape Cardiology. "You can do it without TEE without having any problem."

But there's a caveat: all patients without TEE should have been on uninterrupted oral anticoagulation for the previous 4 weeks or longer. Assuming that's the case, atrial and LAA thrombi are unlikely and can be largely ruled out by ICE, Di Biase said.

In the warfarin age, patient compliance with oral anticoagulation was often confirmed by international normalized ratio (INR) results, he observed; the guidelines recommend preablation TEE if the INR is subtherapeutic.

But with DOACs, which have been overtaking vitamin K antagonists in use, it's up to patients to tell their physicians whether they have been nonadherent. "We need to rely on the patients. That's an important limitation."

Still, Di Biase said, even if a patient reports missing a dose in recent weeks, TEE isn't necessarily needed because ICE — already in place to guide the procedure's transeptal puncture and to cut down on fluoroscopy time — can sweep for any LAA thrombus. "Intracardiac echo, we have shown in our series, is as good as TEE."

The current study's population largely resembled candidates for AF ablation seen in clinical practice, except for perhaps a slight shortfall in paroxysmal AF, observed Christopher R. Ellis, MD, Vanderbilt University, Nashville, Tennessee, who isn't connected with the study.

Those with persistent or longstanding persistent AF made up about 82% of the cohort; paroxysmal AF accounted for the rest. Their average CHA2DS2-VASc score was 2.86.

"That means most of the people were probably on a blood thinner chronically. The chances of them walking in the door and having a clot in the appendage, if they're taking the medication appropriately, is really super low," Ellis, who directs his center's cardiac electrophysiology laboratory and LAA closure program, told | Medscape Cardiology.

"If you start with a population of patients who have a very high chance that they don't have a clot, really any imaging modality is going to look pretty good."

Ellis questioned the report's claim that ICE ruled out thrombus in all patients. "There's a lot of subjectivity to the ultrasound determination of a thrombus," he said, adding that the decision can be influenced by the probe's positioning, interpretation of the scans, and other variables.

Importantly, ICE images for fully 27% of the cohort were documented as showing spontaneous echo contrast, a marker of blood stasis considered a precursor to thrombus formation.

"When you're looking at the images you can ask, is that just heavy, spontaneous echo contrast or is there actually a clot there? It's a bit in the eye of the beholder," Ellis said.

"That's why all the ultrasound-guided methods are really subject to the bias of the person who's interpreting the ultrasound image." And if the team and the patient are already set up in the lab for an ablation, that could swing the interpretation away from any thrombus that might stop the procedure.

"The point is, they didn't use TEE at all and had a one in 6000 chance of having a stroke from AFib ablation. That means, realistically, they probably missed a few thrombi in the left atrial appendage."

The current analysis included patients undergoing AF ablation without TEE at predominantly one center who were on uninterrupted DOAC therapy for at least 4 weeks prior to undergoing catheter ablation. The 6186 patients were predominantly white and male, with a mean age of 69 years.

In addition to the CHA2DS2-VASc score of 2.86, their mean CHADS2 score was 1.65; it was at least 2.00 in half the cases.

Still on DOACs, overwhelmingly apixaban (Eliquis, Pfizer/Bristol-Myers Squibb) or rivaroxaban (Xarelto, Bayer), patients received an intraprocedural heparin bolus prior to transeptal puncture, followed by a continuous heparin infusion, the report notes.

There were no strokes and only one TIA, in a patient "with long-standing persistent AF, in the setting of a missed dose of rivaroxaban prior to ablation," write the authors.

"Patients with persistent AFib have a higher risk for thrombus, even if they have been anticoagulated," Ellis observed. For them, "I tend to do a TEE on the table to rule out thrombus before I do the case. Could I substitute that with ICE? Potentially."

But with ICE alone, the ultrasound probe would have to be in the left atrium for the best images, which would be after transeptal puncture. So it's easier "to abort the case and reschedule" if TEE sees a clot before the actual catheter procedure has started.

TEE may also have side benefits in some patients, Ellis said. While it's scanning for thrombus, it could be used to assess ejection fraction, valvular function, or the aorta for signs of cardiovascular risk. "There is information in certain patients that would heavily favor doing a TEE rather than ICE at the time of procedure."

Di Biase discloses consulting for Stereotaxis, Biosense Webster, Boston Scientific, and Abbott Medical; and receiving honoraria or travel reimbursement from Medtronic, Atricure, Bristol Myers Squibb, Pfizer, and Biotronik. Disclosures for the other authors are in the report. Ellis has previously disclosed receiving consulting fees from Boston Scientific, Abbott Medical, and Medtronic; and receiving research grants from Boston Scientific, Abbott Medical, and Medtronic.

Heart Rhythm. Published online July 15, 2020. Full text

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