Postoperative atrial fibrillation after noncardiac surgery ups risk of stroke

New postoperative atrial fibrillation (AF) following noncardiac surgery appears to elevate the risk of stroke by 2.5 times, with the highest risk among patients undergoing nonthoracic noncardiac surgery, results of a systematic review and meta-analysis have shown.

“Given the efficacy of new oral anticoagulants (NOACs) for stroke prophylaxis, prospective studies are warranted to assess whether they can reduce the risk of stroke in patients with postoperative AF,” the investigators said.

Articles published up to May 2019 for studies of patients undergoing noncardiac surgery that reported incidence of new AF and stroke were searched in the databases of Medline, Cochrane and Embase. A random-effects model was used to pool risk ratios (RRs) as well as event rates from individual studies.

Fourteen studies comprising 3,536,291 patients undergoing noncardiac surgery met the eligibility criteria for the quantitative analysis (mean follow-up, 1.4 years). Of the studied patients, 26,046 (0.74 percent) developed new AF, with a higher incidence occurring after thoracic surgery. [Am J Med 2020;133:311-322.e5]

Stroke occurred in 279 (1.5 percent) patients with postoperative AF and in 6,199 (0.4 percent) without. Pooled analysis revealed a significant association between postoperative AF and increased risk of stroke (RR, 2.51, 95 percent confidence interval [CI], 1.76–3.59), with moderate heterogeneity. AF following nonthoracic, compared with thoracic, surgery was associated with significantly higher stroke risk (RR, 3.09 vs 1.95; p=0.01).

“Our study focused on a cohort of patients with AF after noncardiac surgery and included a larger cohort of patients from 14 studies,” the investigators said. “Further, we made a targeted effort to exclude studies of patients with pre-existing nonvalvular AF by rigorously appraising the methodology for ascertainment of AF.”

In other studies that assessed the risk of stroke after cardiac surgery, findings showed an even lower risk (RR, 1.36, 95 percent CI, 1.12–1.65). These differences in stroke risk across surgeries could have been driven by multiple factors. [J Am Heart Assoc 2017;doi:10.1161/JAHA.117.007558]

“Mechanistically, as AF in cardiac and thoracic surgery occurs following direct manipulation of the heart, pulmonary veins or the lung hilum, it is thought to be a direct and possibly short-lived trigger,” the investigators said. [Nat Rev Cardiol 2019;16:417-436; Europace 2012;14:159-174]

“In noncardiac surgery, however, exact reasons for AF occurrence are less clear, with some evidence suggesting that a pre-existing substrate may be accountable,” they added. [Ann R Coll Surg Engl 2007;89:91-95; Nat Rev Cardiol 2019;16:417-436]

This was supported by studies showing recurrence rates of AF following noncardiac surgery as high as 64 percent. [Circulation 2015;131:1648-1655]

Studies included in the present meta-analysis, however, did not thoroughly describe the burden of AF, symptoms and stroke timing, according to the investigators.

“Future studies with more effective surveillance for AF recurrence are warranted to better inform clinicians about the natural history of postoperative AF following noncardiac surgery,” they added.