LAA Closure Beneficial in AF Patients Undergoing Cardiac Surgery

May 24, 2018

Surgical occlusion of the left atrial appendage (LAA) in patients undergoing concurrent cardiac surgery was associated with a reduced risk for subsequent stroke and all-cause mortality, in a new propensity-matched cohort study.

However, LAA closure also appeared to be linked to an increased future burden of atrial fibrillation (AF).

When patients were stratified by history of AF at the time of surgery, results appeared to suggest more benefit from closing the LAA in patients with pre-existing AF than in those without the condition.

"In patients with previous AF, there was a marked reduction in stroke and mortality in those who had the LAA closed, while in patients without previous AF there was not a significant reduction in stroke or mortality associated with LAA occlusion," senior author Peter Noseworthy, MD, Mayo Clinic, Rochester, Minnesota, told Medscape Medical News. "In both groups the procedure was linked to an increased burden of AF as measured by utilization of healthcare resources for AF."

"Although the P value for interaction between the two groups is not significant, so we can't say for sure that the results are different in those with and without existing AF, I would say our results support the closure of LAA in patients with existing AF but they do not support this practice in the absence of AF," Noseworthy added.

A randomized controlled trial (Left Atrial Appendage Occlusion Study [LAAOS] III) is now underway to look at this issue further, he noted. "Until we have results from this randomized trial, I think our data from this study could be used to guide practice."

The study is published in the May 22/29 issue of JAMA.

In the paper, the researchers, led by Xiaoxi Yao, PhD, Mayo Clinic, Rochester, Minnesota, explain that more than 300,000 coronary artery bypass graft (CABG) and valve operations are performed annually in the United States and surgical occlusion of the LAA is sometimes performed during the surgery to reduce long-term risk for stroke.

They note that thrombi in the LAA account for a high percentage of cardioembolic strokes, particularly in patients with AF, so LAA closure is a common practice. However, there are limited data on the effectiveness of this procedure to guide evidence-based decision making.

For the current study, the researchers analyzed data from a large US administrative database (OptumLabs DataWarehouse), which contains data from patients with private insurance or Medicare Advantage of all ages and races and includes information on more than 75,000 adults who underwent CABG or valve surgery between 2009 and 2017.

One-to-one propensity score matching was used to balance patients on 76 dimensions to compare those with versus those without LAA occlusion, stratified by history of AF at the time of surgery.

The research team compared 4295 patients who underwent LAA closure with 4295 propensity-matched patients who did not undergo the surgical closure.

Results showed that LAA closure was associated with a reduced risk for stroke (hazard ratio [HR], 0.73; 95% CI, 0.56 - 0.96) and mortality (HR, 0.71; 95% CI, 0.60 - 0.84) in the overall population.

But LAA occlusion was also associated with higher rates of AF-related outpatient visits (rate ratio, 1.17; 95% CI, 1.10 - 1.24) and hospitalizations (rate ratio, 1.13; 95% CI, 1.05 - 1.21).

In patients with prior AF, who made up 75% of those studied, the risk for stroke was significantly reduced with LAA closure (HR, 0.68; 95% CI, 0.50 - 0.92), as was risk for death (HR, 0.67; 95% CI, 0.56 - 0.80).

But in patients without prior AF (25% of the study group), risks for stroke and death were similar in those with or without LAA occlusion, with the procedure having nonsignificant HRs of 0.95 for stroke and 0.92 for mortality.

However, the risk for postoperative AF was increased in patients who had the LAA closed (HR, 1.46; 95% CI, 1.22 - 1.73).

The interaction term between prior AF and LAA occlusion was not significant (P = .29 for stroke and P = .16 for mortality).

The authors note that to their knowledge this is the first study to investigate associations between LAA occlusion and clinical outcomes stratified by preexisting AF.

While the interaction between LAA occlusion and prior AF was not statistically significant, they point out that the absolute risk reduction for stroke and mortality associated with LAA closure was small in patients without pre-existing AF but the CIs were wide, "and thus, future studies with larger sample sizes will be needed to fully assess the interaction and the role of LAA occlusion in patients without prior AF."

They add that: "The consideration of preemptive LAA occlusion in patients without documented preoperative AF must be balanced against the fact that the majority of patients would not develop AF after the surgery and LAA occlusion may be associated with an increased risk of subsequent AF."

They suggest that LAA occlusion may be an option for patients with AF who have difficulty taking oral anticoagulant drugs and those who desire further risk reduction in addition to anticoagulation.

Noting that in the current study, the association between LAA occlusion and stroke was not significant among patients with AF who were taking oral anticoagulation, they suggest that this could be attributable to the small number of events and patients in that subgroup, as well as the possibility that oral anticoagulation already reduced the risk for stroke, and the additional risk reduction from LAA closure was smaller than that seen in patients who did not receive oral anticoagulation.

On the observation of a higher rate of AF-related health utilization after LAA occlusion, the authors note that this has been reported before, and the risk for subsequent AF needs to be discussed with patients during shared decision making.

Noseworthy suggested that mechanisms behind the possible increased risk for AF may include "the fact that the surgery may be longer if LAA closure is also performed, and the LAA can act as pressure reservoir and closure can make it more sensitive to stresses."

The researchers point out that their findings in patients with AF are consistent with those from another recent observational study, but the previous study was limited to patients age 65 years and older who had prior AF, whereas the current study included a large number of patients of all ages and races undergoing cardiac surgery at a diverse range of institutions across the US.

They further note that the ongoing randomized LAAOS III trial plans to enroll 4700 patients but is limited to high-risk patients with documented AF or atrial flutter undergoing CABG surgery and will not address the population without AF or those undergoing valve surgery.

This study was funded by the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery. The authors report no disclosures.

JAMA. Published online May 22, 2018. Abstract

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