May 09, 2018
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Best choice for antithrombotic therapy after TAVR depends on patient characteristics

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Transcatheter aortic valve replacement has revolutionized the management of aortic stenosis in recent years. Patients whose surgical risk factors have historically made doctors think twice before offering AVR are now able to receive this life-prolonging, symptom-alleviating procedure through minimally invasive techniques. Although this rapidly proliferating alternative to surgical AVR is highly beneficial, postprocedural stroke remains a major source of morbidity and mortality.

Currently available prostheses suitable for TAVR consist of bovine or porcine valves affixed to a balloon-expandable or self-expandable scaffold. As with surgically placed bioprosthetic valves, anticoagulation is currently not mandatory.

The 2017 American Heart Association/American College of Cardiology Focused Update of the 2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease and 2017 ACC Expert Consensus Decision Pathway for Transcatheter Aortic Valve Replacement in the Management of Adults With Aortic Stenosis suggest that anticoagulation may be considered for the first 3 months after TAVR. Low-dose aspirin (75 to 100 mg daily) is recommended indefinitely, regardless of the decision to anticoagulate. Unlike the ACC/AHA guidelines, the 2017 European Society of Cardiology/European Association for Cardio-Thoracic Surgery Guidelines for the Management of Valvular Heart Disease only recommend anticoagulation after TAVR in patients with other indications for anticoagulation. Guideline recommendations for antithrombotic regimens after TAVR are compared in Table 1.

Daniel Miller

The standard antithrombotic regimen in clinical trials in which TAVR was initially evaluated is distinct from surgical AVR in that dual antiplatelet therapy with aspirin and clopidogrel was used. Although still considered the standard of care, the practice of administering DAPT after TAVR has been challenged by recent evidence.

Evidence on DAPT

In patients with ACS and in those undergoing PCI, DAPT has been studied extensively. This body of evidence has consistently demonstrated increased bleeding risk with DAPT compared with single antiplatelet therapy. It is logical to believe that such a risk would be observed in patients undergoing TAVR. Furthermore, most patients undergoing TAVR are elderly with comorbidities such as hypertension and abnormal renal function further increasing the risk for major bleeding. What is yet to be fully elucidated is whether such a risk is justified by a reduction in thromboembolic events with DAPT compared with single antiplatelet therapy in the TAVR population. Several studies that have attempted to answer this question suggest that single antiplatelet therapy may be associated with a more favorable risk-benefit ratio (see Table 2). Unfortunately, these studies were underpowered.

Tables provided by: Daniel Miller, PharmD, BCPS.
Tables provided by: Daniel Miller, PharmD, BCPS.
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Anticoagulation may be option

Further complicating matters is the recent observation that 7% to 40% of patients have leaflet thickening or reduced leaflet motion observed on CT within 3 months after TAVR. In most patients, this resolved after anticoagulation with a vitamin K antagonist, suggesting the imaging findings represent thrombus. Multivariate analysis of 405 patients screened with multidetector CT and echocardiography identified larger valve size and lack of warfarin treatment as the only independent predictors of valve thrombosis. Among the 30 cases of structural valve dysfunction due to leaflet thrombosis reported in the FDA Manufacturer and User Facility Device Experience (MAUDE) database, 30% were managed by intensification of antithrombotic regimen. These data raise the question of whether anticoagulation should be the standard antithrombotic regimen after TAVR.

A recent prospective observational analysis associated use of apixaban (Eliquis, Bristol-Myers Squibb) with improved 30-day outcomes compared with warfarin in patients with atrial fibrillation after TAVR. Still, the effect of anticoagulation on clinical outcomes after TAVR in patients without other indications for anticoagulation has not been demonstrated. Several ongoing studies such as AUREA (DAPT vs. vitamin K antagonist), ATLANTIS (apixaban vs. vitamin K antagonist or antiplatelets), POPular TAVI (DAPT vs. single antiplatelet therapy vs. anticoagulant plus clopidogrel vs. anticoagulant) and GALILEO (rivaroxaban [Xarelto, Janssen] plus aspirin vs. DAPT) will provide insight as to whether routine anticoagulation after TAVR may be beneficial.

Patient specifics

As with nearly all situations encountered in clinical medicine, the best choice of antithrombotic regimen will depend on patient-specific characteristics. Patients with other conditions that warrant anticoagulation, such as AF or prior venous thromboembolism, are likely to benefit more from anticoagulation than those without such conditions. Other conditions that may increase the risk for thromboembolism such as left ventricular systolic dysfunction should also be considered. The data suggesting less bleeding without an increase in thromboembolic risk with single antiplatelet therapy compared with DAPT should reassure clinicians when making decisions for a patient at high risk for bleeding complications.

Disclosure: Miller reports no relevant financial disclosures.