Atrial fibrillation has been known to confer an increased risk for poor outcomes after transcatheter aortic valve replacement, but there’s been no evidence of how the etiology of AFib can influence post-TAVR outcomes.
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Now, a group of researchers from Bern (Switzerland) University are reporting that valvular AFib almost triples the risk of death or debilitating stroke, compared with patients with no AFib, and significantly increases the risk over nonvalvular AFib.*
“The present findings may have implications for risk stratification in patients undergoing TAVR,” wrote Taishi Okuno, MD, and colleagues in what they said is the first study “to appreciate the combined effect” of AFib and mitral stenosis in TAVR. “The identification of valvular AFib may refine the estimated risk for adverse clinical outcomes in patients undergoing TAVR,” they wrote in JACC: Cardiovascular Interventions.
“The fact that valvular AFib seems to confer a higher risk is an interesting finding,” Fred Welt, MD, professor of cardiology at the University of Utah, Salt Lake City, said in an interview. “I think it helps to a certain extent in prognostication because we can say to patients who have concomitant mitral valve disease that they are at higher risk.” Dr. Welt is also chair of the American College of Cardiology Interventional Council.
The analysis included 1,472 patients with aortic stenosis who had TAVR at Bern University Hospital between August 2007 and June 2018, 32% of whom (465) had atrial fibrillation, subcategorized as nonvalvular (26%, 376) and valvular (6%, 89). The primary endpoint, a composite of cardiovascular death or disabling stroke 1 year after TAVR, occurred in 9.3% of patients with no AFib, 14.5% of those with nonvalvular AFib and 24.2% of patients with valvular AFib.
In terms of hazard ratios, patients with nonvalvular AFib had a 57% greater risk of poor outcomes (P = .009) and those with valvular AFib had a 275% greater risk (P < .001), compared with patients with no AFib. Patients with valvular AFib had a 77% higher rate of cardiovascular death or stroke than those with nonvalvular AFib (P = .027).**
In their analysis, Dr. Okuno and colleagues acknowledged that the definition of valvular AFib used in guidelines and clinical trials isn’t uniform. Valvular atrial fibrillation was defined as AFib with mitral stenosis or a mitral valve prosthesis.
To account for the varying definitions of valvular and nonvalvular AFib, the researchers performed a sensitivity analysis of AFib patients with significant valve disease other than mitral stenosis; 42% of patients in the nonvalvular group fit this definition. Patients with AFib and valvular disease other than mitral stenosis had almost twice the risk of cardiovascular death or disabling stroke at 1 year, compared with patients who had AFib but no significant disease of any valve (20.1% vs. 10.9%, P = .03).
Furthermore, when they excluded patients with mild mitral stenosis from the valvular AFib group, “the effect of an increased risk for cardiovascular death or disabling stroke was no longer statistically significant.”
When the researchers separated out the two elements of the composite endpoint, they found valvular AFib carried a significantly higher risk of cardiovascular death – 21.1% (P < .002) vs. 7% for no AFib and 12.3% (P = .003) for nonvalvular AFib. However, the incidence of cardiovascular events – disabling stroke, nondisabling stroke and transient ischemic attack – showed no significant difference across the three groups, Dr. Okuno and colleagues noted. Specifically, the rates of disabling stroke were 3.8%, 3.7% and 5.7% in the no-AFib, nonvalvular-AFib, and valvular-AFib groups, respectively
In an invited editorial, Bernard Iung, MD, and Vincent Algalarrondo, MD, PhD, noted the problems with the definitions for valvular and nonvalvular AFib. “The term valvular AFib now frequently refers to patients with AFib associated with moderate or severe mitral stenosis or a mechanical heart valve,” they wrote. The definition is justified, they noted, because there’s little evidence on the use of non–vitamin K antagonist oral anticoagulants (NOACs) in patients with mitral stenosis.
They noted the term nonvalvular is “ambiguous” because it doesn’t exclude valvular disease but rather only a subset defined by the restrictive use of a class of anticoagulants. Hence, the definition of valvular AFib “is subject to criticisms and remains not standardized.”
“The individualization of valvular AFib in patients undergoing TAVR is debatable, and the definition used in the present study also included mild mitral stenosis and bioprostheses, thereby highlighting again the lack of a clear and uniform definition of the concept of valvular AFib,” they wrote.
While Dr. Welt said the findings may help in stratifying risk in patients with valvular AFib, he’s not certain how that would influence treatment decisions. “In most cases when we’re considering TAVR in these patients it’s because they have severe symptomatic aortic stenosis,” he said.
Surgery as an alternative is fraught with consequences, he said. “Would it be because you would want to repair the mitral valve as well?” he said. “And once you get into that territory, you’re talking about double-valve surgery, which is a much riskier operation than isolated aortic valve replacement.”
The study raises important questions about patients with valvular AFib, Dr. Welt added. “Why are these patients dying at higher rate? Is it some other arrhythmia or some other hemodynamic problem? Are there other things we can learn about these patients that would help us to better treat patients?”
But exploring these findings further with a randomized clinical trial may not be practical, he added. “The number of patients in whom this is an issue is in the scheme of things rather low: 6%,” he said.
Dr. Okuno has no relevant financial disclosures. Dr. Iung is a consultant for Edwards Lifesciences. Dr. Algalarrondo has been a consultant for Pfizer and Alnylam. Dr. Welt disclosed a relationship with Medtronic.
SOURCE: Okuno T et al. JACC Cardiovasc Interv. 2020 Sep 21. doi: 10.1016/j.jcin.2020.05.049.
Corrections, 9/29/20: An earlier version of this article misstated the increase in risk of (*) death or debilitating stroke and of (**) a poor outcome in those with valvular Afib.