Surgical Left Atrial Appendage Occlusion in AF Seen to Cut Thromboembolic Risk

January 25, 2018

CHICAGO — Patients with atrial fibrillation (AF) who underwent left atrial appendage occlusion (LAAO) during a cardiac surgery had a reduced 3-year risk for death or hospitalization for thromboembolism in an observational study of more than 10,000 patients.[1]

The apparent benefit in such patients aged 65 years or older compared with those not getting surgical LAAO during operations such as CABG or heart-valve repair or replacement "may have been primarily related to lower observed rates of thromboembolism in the substantial group of patients discharged without anticoagulation," according to a report in this week's JAMA.     

Only about a third of patients with AF undergoing cardiac surgeries in the United States get LAAO at the same session, senior author, Dr J Matthew Brennan (Duke University School of Medicine, Durham, NC) told theheart.org | Medscape Cardiology.

Usually, physicians planning the cases "just aren't convinced" with the available evidence that adding surgical LAAO will reduce thromboembolic risk. This is not surprising, Brennan said, given the "generally underpowered" evidence base supporting the approach.

In the only randomized trial of LAAO at cardiac surgery, the recently reported Left Atrial Appendage Closure During Open Heart Surgery (LAACS) study, the procedure in patients with or without a preoperative history of AF appeared to cut the risk for  magnetic resonance–confirmed stroke or transient ischemic attack (TIA) by 70% independent of baseline CHA2DS2-VASc score.

But LAACS was small and underpowered at only 187 patients, Brennan observed. With the new findings, "I would say that we've added enough weight to the literature that we should be moving toward a new standard of care, occluding these appendages when we can."

The pressing question that requires clinical trials, he said, is not "Do we occlude?" but "Once we occlude the appendage, is it safe to take our patients off the long-term oral anticoagulant?"

Most Underwent Surgical AF Ablation

In an interview, Dr Vinod Thourani (MedStar Washington Hospital Center, Washington, DC) pointed out that of the current cohort's 3892 patients who underwent surgical LAAO with their CABG, valve surgery, or both, 94% also underwent a maze surgical ablation for their AF. Only 12% of the 6632 patients not undergoing surgical LAAO had the maze procedure.

Thourani, chair of cardiac surgery at his center and a PARTNER 2A investigator, proposed that because surgical LAAO was so often paired with surgical ablation, it may have been the combination of those procedures that was associated with reduced thromboembolic risk. In other words, if most of the patients who had surgical AF ablation were in sinus rhythm by the end of the follow-up, that could at least partly explain the risk reduction, said Thourani, who isn't connected with the study.

"It shouldn't be misconstrued that just closing the left atrial appendage is all that is needed."

A conclusion that surgical LAAO was followed by a reduction in thromboembolic risk would carry more weight, Thourani said, if it could be shown that most patients were still in AF during the follow-up.

Their data don't shed light on the prevalence of postoperative AF, Brennan said; however, surgical AF ablation remains "underdeveloped." Whether it reduces AF over the long term "is still open for debate."

In addition, he said, propensity analysis in the study adjusted for the effect of surgical ablation. "It does not appear to be the ablation that's giving the benefit. It appears to be independent of the ablation, very clearly."

Given the current evidence base, all patients like those in the study should get surgical LAAO, Brennan said. Surgical AF ablation "may also have some benefit, but that's not been shown conclusively, and it's certainly not what we addressed here."

Benefit Independent of AF Type

The analysis looked at Medicare patients with AF undergoing a first cardiac surgery (CABG or aortic or mitral valve surgery with or without CABG) in the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database from 2011 to 2012.

Of the 10,524 patients, with a median age of 76 years, of whom 39% were women, 3892 or 37% underwent surgical LAAO.

Over a mean follow-up of 2.6 years, 20.5% of those undergoing surgical LAAO and 28.7% of those not receiving the procedure experienced the primary endpoint of readmission for thromboembolic events, including stroke, TIA, or systemic embolism. The rate of death from any cause was 17.3% and 23.9%, respectively; hemorrhagic strokes occurred in 0.9% of both groups.

The findings were independent of whether the AF was paroxysmal, persistent, or chronic, Brennan said.

Table. Adjusted Hazard Ratio for Outcomes, Surgical LAAO vs No LAAO, Overall and by Discharge Anticoagulation Strategya

Endpoints HR (95% CI), P Value
Overall No Anticoagulation at Discharge (n=3848) Discharged on Anticoagulation (n=6676)
Rehospitalization for thromboembolic stroke, TIA, or systemic embolism (primary endpoint) 0.67 (0.56–0.81), <0.001 0.26 (0.17–0.40), <0.001 0.88 (0.56–1.39), 0.59
Death from any cause 0.88 (0.79–0.97), 0.001 1.11 (0.75–1.65), 0.60 1.10 (0.85–1.41), 0.48
Death from any cause, rehospitalization for thromboembolism or hemorrhagic stroke 0.83 (0.76–0.91), <0.001 0.96 (0.66–1.39), 0.82 1.01 (0.81–1.26), 0.96
aBased on propensity scores accounting for demographic characteristics; type of AF; STS score; cardiovascular, cerebrovascular, and pulmonary disease diagnoses; renal function; warfarin use; aspects of the valve surgery; and other factors. HR = hazard ratio.

 

Of note, anticoagulation was prescribed to 68.9% of patients in the surgical LAAO group and 60.3% of those not getting surgical LAAO (P<0.001), the report says. Among patients not discharged on oral anticoagulants, those with surgical LAAO showed a reduced adjusted risk for the primary endpoint compared to those not getting the added LAAO procedure. But among patients discharged on oral anticoagulants, there was no such reduction.

Still, it doesn't follow that surgical LAAO would make oral anticoagulation unnecessary, according to Brennan.

Of those in the study not discharged on anticoagulation, "I'd expect every one of them, probably, would have had an absolute indication for anticoagulation."  Many were probably "patients who had problems with postoperative bleeding, or something that came up in the postoperative setting that kept them from being anticoagulated," he said.

"Our ability to predict who is going to be that patient who cannot be discharged on an anticoagulant is terrible."

So the way to maximize the benefits of surgical LAAO in patients like those in the study "is by treating everyone." Unless there is a clear contraindication, he said, closing the appendage should be the standard of care.

The analysis indeed supports the use of surgical LAAO for patients with AF undergoing cardiac surgery to prolong postoperative survival, writes Dr Victor A Ferraris (University of Kentucky, Lexington) in an accompanying editorial.[2]

He points the "strong signal" that surgical LAAO "may be equivalent to anticoagulation prophylaxis to avoid thromboembolism in certain patients." That "intriguing" possibility still suggests that surgical LAAO in such cases "may be as effective as anticoagulation and could potentially avoid the bleeding risks associated with anticoagulation," Ferraris writes.

"This somewhat novel hypothesis, if true, could avoid a significant morbidity associated with anticoagulation while providing adequate treatment for thromboembolic complications of AF."

Brennan agrees and proposed that a next step would be a randomized trial that, for example, compares added surgical LAAO without oral anticoagulation (but perhaps with aspirin) to a strategy of no LAAO followed by oral anticoagulation. That may be an option, he said, as could a trial in which everyone receives surgical LAAO followed by aspirin with vs without oral anticoagulation.

Brennan has received an Innovation in Regulatory Science Award from Burroughs Welcome Fund. Friedman discloses receiving grants from Boston Scientific and Abbott. Disclosures for the other authors are in the report. Ferraris and Thourani have disclosed no relevant financial relationships.

Follow Steve Stiles on Twitter: @SteveStiles2. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

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