Study Shows Post-Op and Non-Valvular AFib Carry Similar Thromboembolism Risk

A new study into the long-term risk of thromboembolism has uncovered new-onset postoperative atrial fibrillation(POAF) is associated with a similar risk of thromboembolism as nonsurgical, nonvalvular atrial fibrillation(NVAF).

After examining more than 700 patients with POAF, investigators concluded long-term risk was similar among POAF and NVAF patients and oral anticoagulation therapy resulted in a reduction in risk for thromboembolic events in both groups.

In an effort to evaluate whether patients who develop POAF after left-sided heart valve surgery had a similar long-term risk as those with NVAF, investigators designed a retrospective cohort study using Danish nationwide registries and the Eastern Danish Heart Surgery Database. For inclusion in the study, patients had to be at least 18 years of age, had no history of atrial fibrillation, developed POAF, had not redeemed any oral anticoagulant prescription in the 6 months prior to surgery, and had to be alive at discharge.

Investigators examined data available from 2000 until June, 30 2015 and identified a cohort of 1587 patients who underwent isolated left-sided heart valve surgery. Of this group, 741(46.7%) developed POAF during admission and 675 were matched and included in the final analysis. For their comparison, investigators matched these patients to patients with nonsurgical NVAF in a 1:3 ratio by age, sex, heart failure, hypertension, diabetes, a history of thromboembolism, ischemic heart disease, and year of diagnosis.

The primary outcome measures of the study were thromboembolism, a composite of ischemic stroke, transient cerebral ischemia, and thrombosis or embolism in peripheral arteries. Secondary outcomes included recurrent atrial fibrillation, which investigators defined as a hospital admission or outpatient visit with atrial fibrillation as a primary or secondary diagnosis code.

Of the patients included in analysis with POAF, the incidence rate was 46.8%(554 of 1184) after isolated aortic valve replacement, 48.5%(16 of 33) after isolated mitral valve replacement, 46.3%(158 of 341) after isolated mitral valve repair, and 44.8%(13 of 29) after combined aortic and mitral valve surgery. Investigators pointed out oral anticoagulation therapy was initiated within 30 days of discharge in 62.9%(420) of patients with POAF patients and 51.4%(1030) of patients with NVAF.

Analyses revealed crude incidence rates of thromboembolism were 21.9(95% CI, 17.4-27.6) and 17.7(95% CI, 15.2-20.6) events per 1000 person-years for patients with POAF and patients with NVAF, respectively. When adjusting for confounding factors, investigators found the long-term risk of thromboembolism was similar in patients with POAF and NVAF(HR 1.22; 95% CI, 0.88-1.68).

Additionally, oral anticoagulation therapy during the follow-up period was associated with a reduction in risk of thromboembolic events in patients with POAF(HR 0.45; 95% CI, 0.22-0.90) and NVAF(HR 0.63; 95% CI, 0.45-0.87)when compared to patients who did not receive anticoagulation therapy.

In an invited commentary published in JAMA Cardiology, Jonathan Piccini, MD, MHS, a clinical cardiac electrophysiologist and Associate Professor of Medicine at Duke University Medical Center, wrote the results of the study highlight the need for additional research into POAF.

“While many clinicians continue to argue that POAF is a transient phenomenon in which long-term therapy is not beneficial nor advisable, there is mounting observational evidence to suggest otherwise,” Piccini wrote. “Based on a wealth of data, POAF and NVAF appear to have similar risks and both appear to benefit from OAC therapy. However, only prospective data from randomized clinical trials can provide the certainty both clinicians and patients need.”

This study, “Long-term Thromboembolic Risk in Patients With Postoperative Atrial Fibrillation After Left-Sided Heart Valve Surgery,” is published in JAMA Cardiology.