Antithrombotic therapy following bioprosthetic aortic valve replacement

Non-vitamin K antagonist oral anticoagulants in atrial fibrillation patients with bioprosthetic valves

INTRODUCTION

The non-vitamin K antagonist oral anticoagulants (NOACs), which include dabigatran, apixaban, edoxaban and rivaroxaban, are preferred over vitamin K antagonists for stoke prevention in most patients with non-valvular atrial fibrillation. The NOACs are contraindicated in atrial fibrillation patients with rheumatic mitral stenosis or mechanical heart valves. There is evidence that bioprosthetic heart valves are less thrombogenic than mechanical heart valves, but it is unknown whether the risk of thromboembolism in atrial fibrillation patients with bioprosthetic valves differs from that in patients without such valves. Areas covered: The authors present a review of the efficacy and safety evidence surrounding the use of NOACs for stroke prevention in atrial fibrillation patients with bioprosthetic heart valves. Expert commentary: While the data is limited, there is no significant difference in thromboembolic, and bleeding outcomes in patients with AF and bioprosthetic heart valves treated with NOAC therapy. Future studies are required before definitive conclusions can be drawn regarding the safety and efficacy of NOAC therapy in AF patients bioprosthetic heart valves.

Oral anticoagulation, stroke and thromboembolism in patients with atrial fibrillation and valve bioprosthesis

Vitamin K antagonists are currently recommended in patients with ‘valvular’ atrial fibrillation (AF), e. g. those having mitral stenosis or artificial heart valves. We compared thromboembolic risk in patients with ‘non valvular’ AF and in those with AF and biological valve replacement (valve bioprosthesis). Among 8962 AF patients seen between 2000 and 2010, a diagnosis of ‘non-valvular AF’ was found in 8053 (94 %). Among patients with ‘valvular’ AF, 549 (6 %) had a biological prosthesis. The patients with bioprosthesis were older and had a higher CHA2DS2-VASc score than those with non valvular AF. After a follow-up of 876 é 1048 days (median 400 days, interquartile range 12–1483), the occurrence of thromboembolic events was similar in AF patients with bioprosthesis compared to those with ‘non valvular’ AF (hazard ratio [HR] 1.10 95 % confidence interval [CI] 0.83–1.45, p=0.52, adjusted HR 0.93, 95 %CI 0.68–1.25, p=0.61). Factors independently associated with increased risk of stroke/TE events were older age (HR 1.25, 95 %CI 1.16–1.34 per 10-year increase, p> 0.0001) and higher CHA2DS2-VASc score (HR 1.35, 95 %CI 1.24–1.46, p> 0.0001) whilst female gender (HR 0.75, 95 %CI 0.62–0.90, p=0.002), use of vitamin K antagonist (HR 0.83, 95 %CI 0.71–0.98, p=0.03) were independently associated with a lower risk of stroke/TE. Neither the presence of bioprosthesis nor the location of bioprosthesis was independent predictor for TE events. In conclusion, AF patients with bioprosthesis had a non-significantly higher risk of stroke/TE events compared to patients with non-valvular AF. Second, the CHA2DS2-VASc score was independently associated with an increased risk of TE events, and was a valuable determinant of TE risk both in AF patients with non-valvular AF as well as those with bioprosthesis, whether treated or not treated with OAC.

Note: The review process for this paper was fully handled by Christian Weber, Editor in Chief.

How to define valvular atrial fibrillation?

Atrial fibrillation (AF) confers a substantial risk of stroke. Recent trials comparing vitamin K antagonists (VKAs) with non-vitamin K antagonist oral anticoagulants (NOACs) in AF were performed among patients with so-called "non-valvular" AF. The distinction between "valvular" and "non-valvular" AF remains a matter of debate. Currently, "valvular AF" refers to patients with mitral stenosis or artificial heart valves (and valve repair in North American guidelines only), and should be treated with VKAs. Valvular heart diseases, such as mitral regurgitation, aortic stenosis (AS) and aortic insufficiency, do not result in conditions of low flow in the left atrium, and do not apparently increase the risk of thromboembolism brought by AF. Post-hoc analyses suggest that these conditions probably do not make the thromboembolic risk less responsive to NOACs compared with most forms of "non-valvular" AF. The pathogenesis of thrombosis is probably different for blood coming into contact with a mechanical prosthetic valve compared with what occurs in most other forms of AF. This may explain the results of the only trial performed with a NOAC in patients with a mechanical prosthetic valve (only a few of whom had AF), where warfarin was more effective and safer than dabigatran. By contrast, AF in the presence of a bioprosthetic heart valve or after valve repair appears to have a risk of thromboembolism that is not markedly different from other forms of "non-valvular" AF. Obviously, we should no longer consider the classification of AF as "valvular" (or not) for the purpose of defining the aetiology of the arrhythmia, but for the determination of a different risk of thromboembolic events and the need for a specific antithrombotic strategy. As long as there is no better new term or widely accepted definition, "valvular AF" refers to patients with mitral stenosis or artificial heart valves. Patients with "non-valvular AF" may have other types of valvular heart disease. One should emphasize that "non-valvular AF" does not exclude patients with some types of valvular heart disease from therapy with NOACs.

Antithrombotic strategy in the three first months following bioprosthetic heart valve implantation

Heart valve prosthesis unquestionably improve quality of life and survival of patients with severe valvular heart disease, but the need for antithrombotic therapy to prevent thromboembolic complications is a major challenge to clinicians and their patients. Of the articles analyzed, most were retrospective series of cases or historical cohorts obtained from the database. The few published randomized trials showed no statistical power to assess the primary outcome of death or thromboembolic event. In this article, we decided to perform a systematic literature review, in an attempt to answer the following question: what is the best antithrombotic strategy in the first three months after bioprosthetic heart valve implantation (mitral and aortic)? After two reviewers applying the extraction criteria, we found 1968 references, selecting 31 references (excluding papers truncated, which combined bioprosthesis with mechanical prosthesis, or without follow-up). Based on this literature review, there was a low level of evidence for any antithrombotic therapeutic strategy evaluated. It´s therefore interesting to use aspirin 75 to 100 mg / day as antithrombotic strategy after bioprosthesis replacement in the aortic position, regardless of etiology, for patients without other risk factors such as atrial fibrillation or previous thromboembolic event. In the mitral position, the risk of embolism, although low, is more relevant than in the aortic position, according to published series and retrospective cohorts comprised mostly of elderly non-rheumatic patients.

Aortic valve replacement in an elderly patient with factor XI deficiency

Factor XI (FXI) deficiency is rare and associated with bleeding after surgical procedures. We report a case of an 80-year-old woman with severe aortic valve stenosis. FXI deficiency was diagnosed due to prolonged activated partial thromboplastin time. Aortic valve replacement was performed using a porcine bioprosthetic valve. Intra-operation bleeding was controlled by the transfusion of a fresh frozen plasma. The postoperative course was uneventful.

Antithrombotic therapy in patients with heart valve prostheses

Heart valve prostheses carry a risk for thrombosis and require an antithrombotic strategy to prevent stroke, systemic embolism, and prosthetic valve thrombosis. Contemporary randomized trials to guide the clinician on the optimal anticoagulant treatment are scarce, and the validity of the historical data for current recommendations can be questioned in view of the changes in valve prostheses, the patient population, and antithrombotic therapies. This limited evidence from clinical trials translates into divergent recommendations from the different scientific societies on the optimal intensity of oral anticoagulation and on the indication for antiplatelet therapy. The availability of new antithrombotic agents and the unclear thrombotic risk of the currently used prostheses underscore the need to redefine antithrombotic treatment in patients with heart valve prostheses.

Guideline on antiplatelet and anticoagulation management in cardiac surgery

This document presents a professional view of evidence-based recommendations around the issues of antiplatelet and anticoagulation management in cardiac surgery. It was prepared by the Audit and Guidelines Committee of the European Association for Cardio-Thoracic Surgery (EACTS). We review the following topics: evidence for aspirin, clopidogrel and warfarin cessation prior to cardiac surgery; perioperative interventions to reduce bleeding including the use of aprotinin and tranexamic acid; the use of thromboelastography to guide blood product usage; protamine reversal of heparin; the use of factor VIIa to control severe bleeding; anticoagulation after mechanical, tissue valve replacement and mitral valve repair; the use of antiplatelets and clopidogrel after cardiac surgery to improve graft patency and reduce thromboembolic complications and thromboprophylaxis in the postoperative period. This guideline is subject to continuous informal review, and when new evidence becomes available. The formal review date will be at 5 years from publication (September 2013).