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Larger bioprosthetics were associated with more valve thrombosis after transcatheter aortic valve replacement (TAVR), a single-center study reported, but anticoagulation therapy appeared to lower that risk.

On multivariable analysis, thrombosis was more likely among patients who got a 29-mm bioprosthesis (11.8% vs 2.3% with a 23 mm valve, RR 2.89, 95% CI 1.44-5.80), , of Denmark's Aarhus University Hospital Skejby, and colleagues found.

The independent risk of valve thrombosis was 5.46-fold elevated for those who did not receive warfarin (Coumadin) after TAVR (10.7% versus 1.8%), according to in their study published online in the .

Contrast-enhanced multidetector CT detected device thrombosis after TAVR in 7% of cases, only one-fifth of which were clinically overt. The authors suggested: "Although often subclinical, transcatheter heart valve thrombosis may have important clinical implications."

"Treatment with warfarin effectively reverted transcatheter heart valve thrombosis and normalized transcatheter heart valve function in 85% of patients as documented by follow-up transesophageal echocardiography [TEE] and multidetector CT," Hansson and colleagues wrote.

"Taken together, these findings suggest that a front-line diagnostic strategy for thrombosis may consist of transthoracic echocardiography and leaflet morphology assessment by multidetector CT with supplementary TEE in cases of equivocal multidetector CT findings or contraindications to multidetector CT," they continued. "In our experience, multidetector CT offers several potential advantages over TEE with regard to detection of thrombosis; for example, it is less invasive, less operator-dependent, and it detected a few more cases of thrombosis in this study."

Of the 460 consecutive patients who got TAVR, Hansson and colleagues included the 405 who underwent contrast-enhanced multidetector CT in addition to transthoracic and transesophageal echocardiography after bioprosthesis placement. Patients received either the Sapien 3 or XT.

With regards to the limitations of the study, the authors pointed to the lack of long-term data in their observational study. Furthermore, they acknowledge that their findings may not be generalizable to other transcatheter heart valves.

"It seems logical that no warfarin therapy, an increase in the transvalvular gradient, increased cusp thickness, and abnormal cusp mobility are strong predictors and indicators of valve thrombosis," wrote , and , both of Erasmus Medical Centre in the Netherlands, in an accompanying editorial.

"It is not clear whether valve thrombosis and valve deterioration represent the same disease process at different points in time," they continued. "The late consequence of valve thrombosis may be fibrotic organization of the thrombus, with an increase in valvular gradient; thus, it could be labeled as valve failure."

Kappetein and Head called the 7% incidence found in the study by Hansson's group a high rate, emphasizing that "early detection of valve thrombosis is therefore key."

"Without knowing the optimal peri- and postprocedural antithrombotic regimens, clinicians should have an increased awareness of valve thrombosis after surgical aortic valve replacement [SAVR] and TAVR," they wrote.

"As always in medicine, it is better to prevent than to cure and points to the fact that antithrombotic therapy in the setting of TAVR has only been empirically determined," the editorialists added. "After TAVR, dual antiplatelet therapy with aspirin (80 to 325 mg/day) and clopidogrel ([Plavix] 75 mg/day) has been used in most centers and studies. However, the use of a loading dose of clopidogrel (300 to 600 mg) before TAVR is typically not specified, and the duration of clopidogrel therapy has varied among studies."

"The same applies for SAVR, in which it is still unclear whether aspirin alone is enough, or if a vitamin K antagonist or a new oral anticoagulant should be added for 3 to 6 months," according to Kappetein and Head.

"The optimal duration of warfarin therapy is also undetermined, but early discontinuation results in recurrence of valve thrombosis. Close echocardiographic follow-up is needed to evaluate the efficacy of the treatment. In cases of overt clinical symptoms and no resolution with anticoagulation therapy, SAVR should be considered."