Support for OAC Protection in Atrial Fib After Valve Surgery

October 24, 2019

Thromboembolic risk in two distinct types of atrial fibrillation (AF), and the potential for countering it with oral anticoagulation (OAC), may be more alike than clinical practice seems to recognize.

The risk for a thromboembolic event was about one in five over an average of 4 years for patients with new-onset AF after isolated aortic or mitral valve surgery and for a propensity-matched group of patients with nonvalvular AF unrelated to surgery in a Denmark-based registry study.

OAC, either with warfarin or one of the newer direct oral anticoagulants (DOACs), was associated with reduced thromboembolic risk in both AF groups, by 55% in patients with postoperative AF (POAF) and 37% in those with nonvalvular AF (NVAF).

"After adjustment for comorbidity, concomitant pharmacotherapy, and postdischarge OAC treatment, we found that new-onset POAF after left-sided heart valve surgery was associated with a similar risk of thromboembolism compared with NVAF," write the authors, led by Jawad Haider Butt, MD, Copenhagen University Hospital.

Moreover, "we found that OAC therapy during follow-up was associated with a comparably lower thromboembolic risk in both patients with POAF and patients with NVAF, suggesting a similar effectiveness of OAC for stroke prevention," they say in their report, published October 9 in JAMA Cardiology.

It may be tempting to conclude that OAC should be indicated in patients who develop POAF, similar to its use in NVAF. But as the authors emphasize, such a recommendation would require support from randomized trials.

Even after the advent of DOACs, "the optimal treatment approach for preventing stroke in patients with POAF remains unknown," writes Jonathan P. Piccini, MD, MHS, in an accompanying editorial.

The guidelines leave room for physician judgment in considering OAC in POAF, so "in the acute postoperative period, clinicians need to balance the benefits of stroke prevention against the risks of postoperative bleeding," says Piccini, from Duke University, Durham, North Carolina.

The current analysis, he writes, "advances the field by confirming the link between POAF and the long-term risks of recurrent AF and stroke. Additionally, these observations raise the hypothesis that long-term OAC therapy may reduce stroke and improve survival in patients with POAF."

Notably, the findings contrast somewhat with a similar analysis from 2018, by many of the same authors , in which long-term thromboembolic risk from new-onset AF after isolated coronary bypass surgery (CABG) was significantly lower than that from nonvalvular AF.

The current analysis was based on 741 adult patients with new-onset AF during hospitalization for isolated left-sided valve surgery, of whom 675 were propensity-matched to 2025 patients with primary NVAF and no history of cardiac surgery.

Their data covered the years 2000 through 2015. Propensity matching was based on age, sex, year of diagnosis, and whether they had a history of thromboembolism, heart failure (HF), hypertension, diabetes, or ischemic heart disease.

OAC, primarily warfarin, was started in the first month after discharge in 63% of patients with POAF and 51% of those with NVAF over the 16 years of data.

Thromboembolic events, defined as ischemic stroke, transient cerebral ischemia, or peripheral artery thrombosis or embolism, occurred at the rate of 21.9 per 1000 person-years in the POAF group and 17.7 per 1000 person-years in the NVAF group. The adjusted hazard ratio (HR) was not significantly increased, at 1.22 (95% CI, 0.88 - 1.68).

The HR for thromboembolic events on vs off OAC was 0.45 (95% CI, 0.22 - 0.90) for the POAF group and 0.63 (95% CI, 0.45 - 0.87) for patients with NVAF.

The risk for recurrent AF was significantly reduced in the POAF group, compared with the NVAF group (HR, 0.62; 95% CI, 0.56 - 0.70). The reduction was driven by a significant effect in patients who had aortic valve surgery; there was no such effect in those with mitral-valve procedures.

"It is time for a randomized clinical trial of OAC medications in patients with POAF. Fortunately, trials are underway," writes Piccini, singling out the Anticoagulation for New-Onset Post-Operative Atrial Fibrillation After CABG (PACES).

PACES, currently getting underway in Germany and North America, is comparing single antiplatelet therapy with vs without OAC on an open-label basis in an estimated 3200 adults with AF after isolated CABG.

The primary end point is a composite of death, stroke, transient ischemic attack, myocardial infarction, systemic arterial thromboembolism, and venous thromboembolism at 6 months.

Butt reports no conflicts. Disclosures for the other authors are in the report. Piccini discloses receiving research grants from Abbott, the American Heart Association, the Association for the Advancement of Medical Instrumentation, Bayer, Boston Scientific, the National Heart, Lung, and Blood Institute, and Philips; and serving as a consultant to Abbott, Allergan, ARCA Biopharma, Biotronik, Boston Scientific, LivaNova, Medtronic, Milestone, Sanofi, Philips, and Up-to-Date.

JAMA Cardiology. Published online October 9, 2019. Abstract, Editorial

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