Valve Thrombosis After TAVR Linked to Larger Device Size, Lack of Warfarin Therapy

ROME, Italy—Adding to what has been a somewhat muddled issue, a new single-center study has identified post-TAVR valve thrombosis in 7% of patients using multidetector CT. The vast majority of cases were asymptomatic.

Two factors independently associated with the complication were use of a 29-mm valve (RR 2.89; 95% CI 1.44-5.80) and the absence of warfarin therapy (RR 5.46; 95% CI 1.68-17.70), Nicolaj Hansson, MD (Aarhus University Hospital Skejby, Denmark), reported here at the European Society of Cardiology Congress 2016. The results were published simultaneously online in the Journal of the American College of Cardiology.

Previous studies evaluating transcatheter heart valve thrombosis using a variety of approaches have come up with wide-ranging results, from a low of 0.61% to a high of 40%, owing to a lack of standardization in the field, according to Nicolo Piazza, MD, PhD (McGill University, Montreal, Canada), who commented for TCTMD.

It’s difficult to pin down a firm estimate for transcatheter heart valve thrombosis, he said, because of differences across centers in terms of what valves are used, the type and quality of imaging that is used, when the assessments take place, the level of expertise of the physicians interpreting the images, and how thrombosis—or leaflet thickening—is defined and subsequently treated.

Surveys show that post-TAVR antithrombotic therapy can include single or dual antiplatelet therapy, single oral anticoagulant therapy, or a combination of antiplatelet and anticoagulant therapy, Piazza noted.

“It’s a real mess when it comes to the types of treatments these patients are getting and how we interpret all of the data,” he said.

Some overarching messages can be taken away from all of the research up to this point as the field awaits some standardization, Piazza said. First, “physicians have to realize that this happens in transcatheter aortic valves and it also happens with surgical aortic valves,” he said. “We can’t make this just a TAVR problem.” And second, Piazza noted, warfarin therapy has consistently been associated with a lower risk of developing valve thrombosis, as well as with greater resolution of the finding in those who already have it.

Thrombosis Mostly Asymptomatic

In the current study, Hansson and colleagues focused on 405 patients who underwent TAVR at Aarhus University Hospital between January 2011 and January 2016. All were evaluated with prospective ECG-gated multidetector CT, transthoracic echocardiography (TTE), and transesophageal echocardiography (TEE) 1 to 3 months after the procedure. All patients received a Sapien XT or Sapien 3 valve (Edwards Lifesciences).

Standard post-TAVR therapy included dual antiplatelet therapy with aspirin and clopidogrel in patients with A-fib and warfarin alone or in combination with either aspirin or clopidogrel according to physician discretion in patients with the arrhythmia.

TEE identified “leaflet thickening and/or restrictive leaflet movement” in 86% of the patients with CT-detected valve thrombosis. Obstructive thrombosis associated with symptoms was found in five patients; the rest were asymptomatic.

The overall rate of thrombosis was lower in patients with A-fib (3.2% vs 10.1%), but Hansson explained that that is the result of most patients with A-fib already taking warfarin. Indeed, the rate of the complication was only 1.8% in patients taking warfarin as part of their post-TAVR therapy and 10.7% in the rest.

Of the 28 patients with valve thrombosis detected by CT, 23 initiated warfarin with or without antiplatelet therapy, three who were already taking warfarin had their target INR increased to 2.5-3, and two continued on routine dual antiplatelet therapy. The vast majority of patients (85%) had complete thrombus resolution on CT and restored leaflet mobility. Among the five patients with obstructive thrombosis, heart valve function normalized in four.

Moving Forward

Hansson acknowledged during his presentation that the study cannot be used to determine the optimal approach to post-TAVR antithrombotic therapy, noting, too, that there are few data from other studies to inform the issue.

He pointed out that there are ongoing trials—GALILEO and POPular-TAVI—that are evaluating approaches to antithrombotic therapy after TAVR and may provide some guidance.

As for the possibility of using warfarin in a more systematic fashion based on the accumulated evidence so far, Hansson said, “I certainly don’t think that you should give these old comorbid patients warfarin without a very good reason.”

Piazza pointed out that the risk of thrombosis needs to be weighed against the risk of bleeding when considering how to treat patients after TAVR, noting that a recent study showed that cardiac event rates did not differ between patients taking dual antiplatelet therapy or warfarin but bleeding was higher with warfarin.

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