Add Atrial Fibrillation to Pre-Noncardiac Surgery Risk Evaluation: New Support

June 20, 2022

Practice has gone back and forth on whether atrial fibrillation (AF) should be considered in the preoperative cardiovascular risk (CV) evaluation of patients slated for noncardiac surgery, and the Revised Cardiac Risk Index (RCRI), currently widely used as an assessment tool, doesn't include the arrhythmia.

But consideration of preexisting AF along with the RCRI predicted 30-day mortality more sharply than the RCRI alone in an analysis of data covering several million patients slated for such procedures.

Indeed, AF emerged as a significant, independent risk factor for a number of bad postoperative outcomes. Mortality within a month of the procedure climbed about 30% for patients with AF before the noncardiac surgery. Their 30-day risks for stroke and for heart failure hospitalization went up similarly.

The addition of AF to the RCRI significantly improved its ability to discriminate 30-day postoperative risk levels regardless of age, sex, and type of noncardiac surgery, Amgad Mentias, MD, Cleveland Clinic, Cleveland, Ohio, told | Medscape Cardiology. And "it was able to correctly up-classify patients to high risk, if AF was there, and it was able to down-classify some patients to lower risk if it wasn't there."

"I think [the findings] are convincing evidence that atrial fib should at least be part of the thought process for the surgical team and the medical team taking care of the patient," said Mentias, who is senior author on the study published today in the Journal of the American College of Cardiology, with lead author Sameer Prasada, MD, also of the Cleveland Clinic.

The results "call for incorporating AF as a risk factor in perioperative risk scores for cardiovascular morbidity and mortality," the published report states.

Supraventricular arrhythmias had been part of the Goldman Risk Index once widely used preoperatively to assess cardiac risk before practice adopted the RCRI in the past decade, observe Anne B. Curtis, MD, and Sai Krishna C. Korada, MD, University at Buffalo, Buffalo, New York, in an accompanying editorial.

The current findings "demonstrate improved prediction of adverse postsurgical outcomes" from supplementing the RCRI with AF, they write. Given associations between preexisting AF and serious cardiac events, "it is time to 're-revise' the RCRI and acknowledge the importance of AF in predicting adverse outcomes" after noncardiac surgery.

The new findings, however, aren't all straightforward. In one result that remains a bit of a head-scratcher, postoperative risk of myocardial infarction (MI) in patients with preexisting AF went in the opposite direction of risk for death and other CV outcomes, falling by almost 20%.

That is "hard to explain with the available data," the report states, but "the use of anticoagulation, whether oral or parenteral (as a bridge therapy in the perioperative period), is a plausible explanation" given the frequent role of thrombosis in triggering MIs.

Consistent with such a mechanism, the group argues, the MI risk reduction was seen primarily among patients with AF and a CHA2DS2-VASc score of 2 or higher — that is, those at highest risk for stroke and therefore most likely to be on oral anticoagulation. The MI risk reduction wasn't seen in such patients with a CHA2DS2-VASc score of 0 or 1.

"I think that's part of the explanation, that anticoagulation can reduce risk of MI. But it's not the whole explanation," Mentias said in an interview. If it were the sole mechanism, he said, then the same oral anticoagulation that protected against MI should have also cut the postoperative stroke risk. Yet that risk climbed 40% among patients with preexisting AF.

The analysis started with 8.6 million Medicare patients with planned noncardiac surgery, seen from 2015 to 2019, of whom 16.4% had preexisting AF. Propensity matching for demographics, urgency and type of surgery, CHA2DS2-VASc score, and RCRI index created two cohorts for comparison: 1.13 million patients with and 1.92 million without preexisting AF.  

Preexisting AF was associated with a higher 30-day risk for death from any cause, the primary endpoint: 8.3% vs 5.8% for those without such AF (P < .001), for an odds ratio (OR) of 1.31 (95% CI, 1.30 - 1.32).

Corresponding 30-day ORs for other events, all significant at P < .001, were  

  • 1.31 (95% CI, 1.30 - 1.33) for heart failure

  • 1.40 (95% CI, 1.37 - 1.43) for stroke

  • 1.59 (95% CI, 1.43 - 1.75) for systemic embolism

  • 1.14 (95% CI, 1.13 - 1.16) for major bleeding  

  • 0.81 (95% CI, 0.79 - 0.82) for MI

Those with preexisting AF also had longer hospitalizations at a median 5 days compared with 4 days for those without such AF (P < .001).

The study has the limitations of most any retrospective cohort analysis. Other limitations, the report notes, include lack of information on any antiarrhythmic meds given during hospitalization or type of AF.

For example, AF that is permanent — compared to paroxysmal or persistent — may be associated with more atrial fibrosis, greater atrial dilatation, "and probably higher pressures inside the heart," Mentias observed.

"That's not always the case, but that's the notion. So presumably people with persistent or permanent atrial fib would have more advanced heart disease, and that could imply more risk. But we did not have that kind of data."

Mentias and Prasada report no relevant financial relationships; disclosures for the other authors are in the report. Curtis discloses serving on advisory boards for Abbott, Janssen Pharmaceuticals, Sanofi, and Milestone Pharmaceuticals; receiving honoraria for speaking from Medtronic and Zoll; and serving on a data-monitoring board for Medtronic. Korada reports he has no relevant financial relationships.

J Am Coll Cardiol. Published online June 20, 2022. Abstract, Editorial

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