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HOUSTON -- Ablating atrial fibrillation (Afib) at the time of mitral valve surgery might eliminate the early survival disadvantage typically associated with the arrhythmia, analysis of a U.S. national registry suggested.

In an analysis of nearly 90,000 procedures, risk-adjusted in-hospital operative mortality was elevated with atrial fibrillation untreated at the time of cardiac surgery compared with patients who did not have arrhythmia (OR 1.15, 95% CI 1.04-1.27), , of West Virginia University in Morgantown, reported here at the Society of Thoracic Surgeons meeting.

But with ablation as part of the operation, that early mortality disadvantage shrank and became statistically insignificant (adjusted OR 1.08, 95% CI 0.96-1.21), Rankin reported.

For composite major morbidity, the elevated risk with atrial fibrillation remained significant whether treated or untreated with ablation during the surgery, albeit with a lower adjusted odds ratio (1.13 and 1.08, respectively, versus no Afib).

Neither outcome differed significantly between Afib patients who got ablation versus those who had the arrhythmia but were ablated.

The only significant difference when looking at specifics of the ablation procedure was an operative mortality advantage of cryoablation over radiofrequency ablation (adjusted OR 0.71, 95% CI 0.54-0.92).

Rankin's analysis of the STS Adult Cardiac Surgery database covered 88,765 patients with isolated mitral valve repair or replacement, including procedures in patients with associated coronary artery bypass grafting, atrial septal defect closure, and tricuspid valve repair, but not prior MitraClip procedures or surgical ablation of only the right atrium. The study findings were adjusted with established STS valve risk models.

Of the cohort, 60% had no Afib at the time of mitral valve surgery and thus did not get ablation, while 18% had Afib and got ablation as part of their surgery and another 12% had Afib that went untreated at surgery.

A further 9% had no Afib at the time of surgery but did get surgical ablation due to a history of Afib. This group was excluded from analysis due to uncertainty about that history.

Cause of death could not be determined from the STS database used. But as to mechanism Rankin suggested:

"From our practices we certainly agree that patients that have a post-operative pneumonia or other complications are better off if they're in sinus rhythm. They have better cardiac outputs, they're less likely to have other complications, there's a small incidence of thromboembolism postoperatively in atrial fibrillation. And probably the mortality benefits are related to just the physiologic effect of being in sinus rhythm as it effects all of the causes of mortality."

Study discussant , of St. Louis University, highlighted the potential for selection bias confounding the findings, given that guidelines support Afib ablation only if it does not add additional risk.

"The surgeons already decided not to add ablation to group three [Afib but no ablation]; can your current statistical analysis really overcome their selection bias?" he said, suggesting that propensity-matched analysis would have been a better choice.

He also noted the possibility of confounding from the heterogeneous group of surgeries included in the study.

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