Larger TAVR Valves May Predispose to Clot, but Will Warfarin Help?

Larry Hand

September 12, 2016

ROME, ITALY — Larger valves may predispose patients to thrombosis after transcatheter aortic-valve replacement (TAVR), but treatment with warfarin may have a protective effect, according to new research[1].

Dr Nicaloj C Hansson (Aarhus University Hospital, Denmark) and colleagues analyzed data on 460 consecutive patients who underwent TAVR at their institution, of whom 405 (mean age 83, 54% female) underwent contrast-enhanced multidetector computed tomography (MDCT) and echocardiographic follow-up 1 to 3 months post-TAVR.

The results were published online August 28, 2016 in the Journal of the American College of Cardiology simultaneously with presentation at the European Society of Cardiology (ESC) 2016 Congress.

The researchers detected transcatheter-valve thrombosis in 27 (7%) of patients, observing no difference between patients who had TAVR with the Sapien XT or the Sapien 3 (Edwards Lifesciences). They observed a higher mean gradient at follow-up in transcatheter-valve-thrombosis patients compared with patients with no transcatheter-valve thrombosis.

Of the 27 thrombosis patients, one developed a stroke and three developed obstruction with heart failure. However, warfarin alone or in combination with antiplatelet therapy caused thrombosis regression as shown with MDCT.

Using multivariable analysis, the researchers found that a 29-mm transcatheter valve and no post-TAVR warfarin treatment, but not LVEF  less than 35% at discharge, predicted transcatheter-valve thrombosis.

The risk of transcatheter-valve thrombosis was 10.7% in patients not receiving warfarin, compared with 1.8% for patients receiving warfarin. Patients receiving non–antiplatelet therapy had a risk of 18.8%.

"Although often subclinical, transcatheter-valve thrombosis may have important clinical implications," the researchers conclude. "Future studies are warranted to assess whether tailored post-TAVR antithrombotic therapy can reduce the incidence of transcatheter-valve thrombosis."

Dr Robert O Bonow (Northwestern University Feinberg School of Medicine, Chicago, IL), who was not involved in the new study, told heartwire from Medscape that the study results are "further evidence that subclinical thrombosis after TAVR is real. It's a little more certainty about the likelihood and the prevalence of it occurring. And 7% is a real figure considering there are thousands of patients now getting a valve.

"It does lead to an impetus to do what's already being planned, and that's to do a prospective study, not only with the Sapien valves but all the other valves as well," he said.

"As far as whether one should give warfarin now based on this evidence, I think it's probably premature. In many patients getting a TAVR valve, there are comorbidities and bleeding risks, so I think it's premature to make a blanket statement for warfarin for all patients getting a TAVR procedure, based on this evidence. But it's something to keep in mind for any patient getting a prosthetic valve," he added.

"This is an important piece of evidence," Bonow concluded. "The patients were consecutive; they weren't selected."

Dr Howard C Herrmann (Perelman School of Medicine, University of Pennsylvania, Philadelphia) agrees regarding the warfarin issue. He told heartwire by email, "Interestingly, this study suggested a protective as well as a treatment effect with warfarin anticoagulation, but this must be confirmed in a prospective trial (such as GALILEO) before we start prescribing an agent that has a significant risk for bleeding without knowing that it works. Future studies will also be helpful to identify risk factors for this event (eg, increased gradient, atrial fibrillation, or others).

"This is the largest observational study to date of this recently described phenomenon. It demonstrates that there is a risk of valve and leaflet thrombosis after TAVR with balloon-expandable devices (probably also true with self-expanding and even surgical prostheses, though not part of this study)," he said.

"However," he concluded, "the overall incidence (7%) was lower than in previous smaller reports, and it was rarely associated with hemodynamic obstruction or stroke."

The authors reported no funding or relevant financial relationships.

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