DOACs Offered After Heart Valve Surgery Despite Absence of Data

Direct oral anticoagulants (DOACs) are used in about 1% of patients undergoing surgical mechanical aortic and mitral valve replacement, but in up to 6% of surgical bioprosthetic valve replacements, according to registry data presented at CRT 2021.

In an analysis of the Society of Thoracic Surgery (STS) registry during 2014–2017, DOAC use increased steadily among those undergoing surgical bioprosthetic valve replacement, reaching a number that is potentially clinically significant, according to Ankur Kalra, MD, an interventional cardiologist at Akron General Hospital who has an academic appointment at the Cleveland Clinic.

There was no increase in the use of DOACs observed among patients undergoing mechanical valve replacement, “but even if the number is 1%, they should probably not be used at all until we accrue more data,” Kalra said.

DOACs Discouraged in Patients With Mechanical or Bioprosthetic Valves

In Food and Drug Administration labeling, DOACs are contraindicated or not recommended. This can be traced to the randomized RE-ALIGN trial, which was stopped prematurely due to evidence of harm from a DOAC, according to Kalra.

In RE-ALIGN, which enrolled patients undergoing mechanical aortic or mitral valve replacement, dabigatran was associated not only with more bleeding events than warfarin, but also more thromboembolic events.

There are no randomized data comparing the factor Xa inhibitors rivaroxaban or apixaban to warfarin in heart valve surgery, but Kalra noted cautionary language is found in the labeling of both, “perhaps due to the RE-ALIGN data.”

Registry Shows Trends in Prescribing

In the STS registry data, 193 (1.1%) of the 18,142 patients undergoing mechanical aortic valve surgery, 139 (1.0%) of the 13,942 patients undergoing mechanical mitral valve surgery, 5,625 (4.7%) of the 116,203 patients undergoing aortic bioprosthetic aortic valve surgery, and 2,180 (5.9%) of the 39,243 patients undergoing bioprosthetic mitral valve surgery were on a DOAC at discharge.

Among those receiving a mechanical value and placed on a DOAC, about two-thirds were on a factor Xa inhibitor rather than dabigatran. For those receiving a bioprosthetic value, the proportion was greater than 80%. Kalra speculated that the RE-ALIGN trial might be the reason factor Xa inhibitors were favored.

In both types of valves, whether mechanical or bioprosthetic, more comorbidities predicted a greater likelihood of receiving a DOAC rather than warfarin. For those receiving mechanical values, the comorbidities with a significant association with greater DOAC use included hypertension (P = .003), dyslipidemia (P = .02), arrhythmia (P < .001), and peripheral arterial disease (P < 0.001).

The same factors were significant for predicting increased likelihood of a DOAC following bioprosthetic valve replacement, but there were additional factors, including atrial fibrillation independent of other types of arrhythmias (< .001), a factor not significant for mechanical valves, as well as diabetes (P < .001), cerebrovascular disease (< .001), dialysis (P < .001), and endocarditis (P < .001).

“This is probably intuitive, but patients who were on a factor Xa inhibitor before their valve replacement were also more likely to be discharged on a factor Xa inhibitor,” Kalra said at the virtual meeting, sponsored by MedStar Heart & Vascular Institute.

The year-to-year increase in DOAC use among those undergoing bioprosthetic valve replacement over the study period, which was a significant trend, was not observed among those undergoing mechanical valve replacement. Rather, the 1% proportion remained stable over the study period.

“We wanted to look at outcomes, but we found that the STS database, which only includes data out to 30 days, is not structured for this type of analysis,” Kalra said. He was also concerned about the limitations of a comparison in which 1% of the sample was being compared to 99%.

Expert: One Percent Is ‘Very Small Number’

David J. Cohen, MD, commented on the 1% figure, which was so low that a moderator questioned whether it could be due mostly to coding errors.

“This is a very, very small number so at some level it is reassuring that it is so low in the mechanical valves,” Cohen said. However, he was more circumspect about the larger number in bioprosthetic valves.

“I have always thought it was a bit strange there was a warning against using them in bioprosthetic valves, especially in the aortic position,” he said.

“The trials that established the benefits of DOACs were all in nonvalvular atrial fibrillation, but this did not mean non-aortic stenosis; it meant non-mitral valvular. There have been articles written about how that has been misinterpreted,” said Cohen, director of clinical and outcomes research at the Cardiovascular Research Foundation and director of academic affairs at St. Francis Hospital, Roslyn, N.Y.

For his part, Kalra reported that he does not consider DOACs in patients who have undergone a surgical mechanical valve replacement. For bioprosthetic valves, he “prefers” warfarin over DOACs.

Overall, the evidence from the registry led Kalra to suggest that physicians should continue to “exercise caution” in using DOACs instead of warfarin after any surgical valve replacement “until randomized clinical trials provide sufficient evidence” to make a judgment about relative efficacy and safety.

Results of the study were published online as a research letter in Jama Network Open after Kalra’s presentation. Kalra and Cohen report no potential conflicts of interest.

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