Conference Coverage

Preop atrial fib in CABG patients spells trouble



– Preoperative atrial fibrillation is present in more than 10% of patients undergoing isolated coronary artery bypass graft (CABG) surgery, and if not subjected to concomitant surgical ablation it’s associated with increased perioperative and long-term major morbidity and mortality, S. Chris Malaisrie, MD, reported at the annual meeting of the Western Thoracic Surgical Association.

The increased early and late risks posed by preoperative atrial fibrillation (AF) that go unaddressed remain significant even after adjusting for the numerous comorbid conditions more prevalent in CABG patients with preoperative AF than in those without the arrhythmia, added Dr. Malaisrie, a cardiac surgeon at Northwestern University in Chicago.

 Dr. S. Chris Malaisrie a cardiac surgeon at Northwestern University in Chicago

Dr. S. Chris Malaisrie

He presented an analysis of the Society of Thoracic Surgeons database which utilized a validated linkage process to meld with Medicare data on mortality and major morbidity in 347,977 patients who underwent isolated CABG during 2006-2013, including 24,059 with preoperative AF that was not addressed during the cardiac surgery. Excluded from this part of the ongoing study were 13,161 CABG patients with preoperative AF who underwent concomitant surgical ablation.

The unadjusted operative mortality rate was 1.8% in the no-AF group and 4.0% in patients with preoperative AF. Unadjusted in-hospital rates of permanent stroke, prolonged ventilation, reoperation, and new renal failure were also significantly higher in the preoperative AF group.

Not surprisingly, the preoperative AF group was older. They also had significantly higher baseline rates of numerous comorbid conditions, including diabetes, peripheral vascular disease, renal failure, and prior stroke, as well as a lower mean left ventricular ejection fraction. However, after adjustment for the many comorbidities in multivariate regression analysis, the risks of all in-hospital adverse outcomes remained significantly higher in the preoperative AF group. For example, their adjusted risk of operative mortality was 1.5-fold greater than in the no-AF patients.

In the long-term follow-up analysis, the unadjusted risk of mortality in the first 5 years after CABG was 2.5-fold greater in the preoperative AF group. Their 5-year risk of stroke or systemic embolization was 1.5-fold greater, too. Upon adjustment for potentially confounding comorbid conditions, preoperative AF was associated with a 1.5-fold increased 5-year risk of mortality and a 1.2-fold increase in stroke or systemic embolism.

In an effort to identify a particularly high-risk group of CABG patients with preoperative AF, Dr. Malaisrie and his coinvestigators stratified the group’s long-term stroke and mortality risks by their CHA2DS2-VASc score at the time of surgery. The results were revealing: the unadjusted 5-year risk of stroke or systemic embolization was 7.9% in those with a CHA2DS2-VASc score of 1-3, 12.2% with a score of 4-6, and 15.4% with a score of 7-9. The 5-year survival rate was 74.8% with a score of 1-3, 56.5% with a score of 4-6, and 41.2% with a score of 7-9.

“That’s really a striking finding,” Dr. Malaisrie observed. “When you consider a patient who’s, say, 72-75 years old, who is undergoing isolated CABG with preoperative atrial fibrillation and who has a high CHA2DS2-VASc score of 7-9, 5-year survival is only 41%, with a 15% risk of stroke or systemic embolization.”

Discussant William T. Caine, MD, found the study results unsettling.

“I was surprised to see that in this day and age, fully two-thirds of the patients who had preoperative atrial fibrillation had no attempt at any ablation procedure to treat their atrial fibrillation,” declared Dr. Caine of Intermountain Medical Center in Salt Lake City.

In reply, Dr. Malaisrie noted that other, smaller studies have also found that only about 30% of CABG patients with preoperative AF undergo surgical AF ablation through a maze procedure or some other method.

“Probably most of us in this room would go ahead and perform surgical ablation, but the STS database represents all isolated CABG procedures done throughout the United States,” Dr. Malaisrie said. “I think this dataset should help convince the other 70% of surgeons out there that there is a high cost for preoperative AF – in particular, in patients with very high CHA2DS2-VASc scores. If you can identify a group of patients at increased risk for stroke and mortality, you’d certainly want to bend their survival curve.”

The maze procedure has been convincingly shown to be very safe, with no associated increased risk of perioperative morbidity and mortality. The downside is cost. But while it’s true that adding surgical ablation to an isolated CABG procedure boosts OR time and procedural costs, a successful ablation is likely to pay dividends through reduced downstream rates of major morbidity and mortality.

“I look forward to the second part of our analysis, where we’ll look at the comparative data for the patients who did in fact have surgical ablation. That dataset is pending from the Duke Clinical Research Institute,” according to Dr. Malaisrie.

He cited as study limitations the inability to complete linkage to the Medicare database in about 37% of CABG patients in the STS database, or more than 200,000 people. Also, the Medicare database is an administrative dataset reliant upon medical record coding. The mortality data are probably quite accurate, but the stroke and systemic embolization rates cited in this analysis likely underestimate the true rates.

He reported serving as a consultant to Edwards Lifesciences, Abbott Vascular, and Baxter, and serving on speakers’ bureaus for Bolton and Abiomed. However, the STS analysis was funded exclusively by philanthropy.

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