Procedure Reduces Postop AF After Cardiac Surgery: PALACS

Susan Jeffrey

November 14, 2021

New randomized data suggest that posterior left pericardiotomy during surgery in patients undergoing coronary, aortic valve, and aortic surgical procedures is associated with a significant reduction in postoperative atrial fibrillation (AF).

Postoperative AF was seen in 17% of those who received posterior left pericardiotomy compared with 37% of those who did not, a 45% reduction.

"Not only is this intervention highly effective," lead investigator Mario Gaudino, MD, PhD, Stephen and Suzanne Weiss Professor in Cardiothoracic Surgery, Weill Cornell Medicine, New York City, said in an interview, but it adds only a few minutes of operative time, "without any added risk, and no side effects. So that is potentially a game changer for the prevention of atrial fibrillation."

Still, Gaudino cautioned, the trial was a single-center, proof-of-concept study in highly selected patients. The investigators are already planning a larger multicenter trial that will include a broader patient population and be powered to examine clinical outcomes.

Results of the PALACS (Posterior Left Pericardiotomy Reduces Postoperative Atrial Fibrillation After Cardiac Surgery) trial were presented November 14 at the American Heart Association (AHA) Scientific Sessions 2021 and published simultaneously in The Lancet.

Most Common Complication

AF is the most common complication after cardiac surgery, reported in 30% to 40% of patients, depending on the type of operation and the assessment method used, the authors write. Postop AF is associated with extended in-hospital stays and increased adverse outcomes, including death and stroke, they note. 

Pericardial effusion is common after cardiac surgery, although clinically evident postoperative effusion is uncommon. It's known from experimental studies that even a small amount of effusion may trigger AF, Gaudino said, probably via local inflammation and oxidative stress, "or even through simple mechanical compression on the atria."

Posterior left pericardiotomy is a simple surgical procedure in which a 4- to 5-cm incision is made to connect the pericardial sac with the left pleural space and to drains fluid and thrombi from the pericardial cavity during the postoperative period, he said.

Some small studies suggested an association between the procedure and lower postoperative AF, but the results were not consistent, Gaudino said. "So, as a result, the procedure is not widely adopted, but I would say also, not well known in the surgical community, and that was the rationale for performing our trial."

In PALACS, the researchers conducted an adaptive randomized controlled trial of adult patients undergoing elective interventions, including those on the coronary arteries, the aortic valve, the ascending aorta, or a combination of these done at their institution.

Eligible patients had no  history of AF or other arrhythmias and no contraindication to this intervention. They were randomly assigned to undergo the procedure or no intervention. Participants were stratified by the CHA2DS2-VASc score, which helps predict the risk for  postoperative AF after cardiac surgery, and according to a mixed block randomization approach, in block sizes of 4, 6, and 8. Patients and assessors were blinded to treatment assignment.

All patients received prophylactic β-blockers starting at postoperative day 1. 

The primary outcome was the incidence of AF during the postoperative in-hospital stay, assessed by using continuous cardiac monitoring, in the intention-to-treat population. AF was defined as an irregular heart rhythm, without detectable P waves, lasting more than 30 seconds.

Safety outcomes, assessed in the as-treated population, included operative mortality, postoperative major adverse events (defined as all-cause mortality, stroke, and myocardial infarction), and postoperative clinical or imaging evidence of left pleural or pericardial effusion.

Ultimately, 420 patients were randomly assigned: 212 in the pericardiotomy group and 208 in the no-intervention group. Median age was 61 years, 24% of patients were female, and the median CHA2DS2-VASc score was 2.0. The groups were balanced in terms of clinical and surgical characteristics, and no patient was lost to follow-up. Three patients in the intervention group did not receive the intervention.

The researchers found that in the intention-to-treat population, the incidence of postoperative AF was statistically significantly lower in the intervention group than in the no-intervention group.

Table. PALACS: Primary Endpoint

Endpoint Posterior Left Pericardiotomy (%) No Intervention (%) Odds Ratio Adjusted for Stratification Variable (95% CI) P Value
Postoperative AF 17 32 0.44 (0.27 - 0.70) .0005


Two patients died in the intervention group (1%) and 1 died in the no-intervention group (<1%)  within 30 days of hospital discharge.

The incidence of postoperative pericardial effusion was also lower among those in the posterior left pericardiotomy group, 12% vs 21% (relative risk, 0.58; 95% CI, 0.37 - 0.91).

Postoperative adverse events were seen in 6 (3%) patients in the intervention group vs 4 (2%) in the no-intervention group. There were no complications related to the procedure.

Gaudino said this procedure was first described in the 1980s by Gianni D. Angelini, MD, at the University of Bristol, United Kingdom, but has been examined only in small trials until now.

"It's just interesting how this old procedure, almost ignored for 40 years, is now at the center of everybody's interest because of the high efficacy and high safety, so I think it's just an interesting story in the history of cardiac surgery," Gaudino told | Medscape Cardiology.

When they got the PALACS results, he added, he contacted Angelini. "I was very, very happy to make that call, to reach out to him and say, 'You know what? You were right. Forty years later, I can tell you, you were right.'" 

A Recalcitrant Clinical Problem

Invited discussant for the presentation was Subodh Verma, MD, St. Michael's Hospital, Toronto, Ontario, Canada. Postoperative AF, Verma said, "remains a common, a recalcitrant clinical problem, and that's why we need new and novel solutions."

Strengths of the PALACS trial include that it tests just such a novel hypothesis and "provides the first surgical vs pharmacological approach to reducing postoperative atrial fibrillation after cardiac surgery."

The trial was well conducted and adequately powered for the primary outcome measure, Verma noted. "It is an incredibly safe strategy with no increased rates of pleural effusion."

The effect size is large, and the benefits were consistent across all subgroups studied, he said, "including those who received postoperative β-blockers."  

The relative risk reduction of 45% for postoperative AF is also "really quite marked" compared with other pharmacologic interventions that have been studied, including β-blockers, amiodarone, colchicine, or botulinum toxin.  

Some limitations include that only in-hospital AF was studied, although in a recent publication from their group, SEARCH AF, most AF was "front-loaded," with low rates out to day 30, he said. "Therefore, it's unclear whether this strategy has benefits with respect to subacute atrial fibrillation."  

The definition of AF was also "quite liberal" at 30 seconds or more, "and the question is, would a more clinically relevant or stringent definition be actually more important?" he said. It is also a single-center trial that needs to be confirmed.

Still, Verma concluded, "This is a well-conducted surgical trial that provides convincing proof-of-concept that a simple, inexpensive, generalizable surgical adjunctive procedure of pericardial drainage can safely reduce postoperative atrial fibrillation after cardiac surgery."

Jim Cheung, MD, also at Weill Cornell Medicine, and chair-elect of the American College of Cardiology's Electrophysiology Section, called the findings "notable."

"What's striking about these results is this was a randomized trial, and the treatment effect was really quite impressive," Cheung told | Medscape Cardiology. "The fact that 32% of the no-intervention group had postop Afib and only 17% in the group that had the pericardiotomy wound up having Afib is quite a significant effect," he said, and importantly, there were no apparent adverse outcomes.

The study was not powered to show changes in outcomes such as hospital stay, readmissions, and stroke, "but I think it's an important first step in terms of adding a potentially promising technique for repressing postoperative Afib after cardiac surgery, which is a significant problem facing a lot of surgeons and cardiologists who manage patients who undergo cardiac surgery," he concluded.

The trial received no funding. The researchers report no competing interests.  

American Heart Association (AHA) Scientific Sessions 2021. Presented November 14, 2021.

Lancet. Published online November 14, 2021. Abstract

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