An audit of the antithrombotic therapy for the management of valve repair or replacement

1. An audit of the antithrombotic therapy for the management of valve repair or replacement Gellatly RM1,2, Maydelmin D1,Connell C1, Marasco S3, Zimmet A3, White V4 (1) Pharmacy Department, Alfred Health (2) Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (3) Department of Cardiothoracic Surgery, Alfred Hospital, (4) Department of Cardiology, Alfred Hospital Background Results cont. Table 4 summarises the ESC guidelines used to assess concordance. Of the 78 patients reviewed, only 31 patients (40%) could have the guideline applied to them. For the primary outcome, of those 31 patients, 10 patients (32%) received therapies concordant to guideline recommendations. In those patients where the ESC guidelines could be applied, bleeding and thrombotic events were recorded (Table 5). Eleven bleeding events were recorded, with 5 bleeds occurring in patients with therapy discordant to guidelines. Three thrombotic events were documented, including 2 ischaemic strokes. Antithrombotic therapy is an important consideration after valve replacement or repair. It can reduce the risk of thromboembolism, however, at an increased risk of bleeding.1 In February 2012, the American College of Cardiology (ACCP) up-dated evidence-based recommendations for antithrombotic therapy in valvular heart disease.1 Additionally, the European Society of Cardiology (ESC) published guidelines on the management of valvular heart disease in 2012.2 Currently, at the Alfred Hospital, antithrombotic management post valve replacement can vary, and therefore a review of the management strategies as compared to current evidence-based guidelines was completed. Table 4. ESC Guideline Recommendations Aim To evaluate compliance with ACCP guidelines for antithrombotic therapy in patients post-aortic and/or mitral valve replacement/repair. Secondary outcomes are to compare antithrombotic management strategies to those outlined in the ESC 2012 guidelines; and determine the incidence of thromboembolic and bleeding events in patients’ post-valve replacement/repair. Methods This was a retrospective, single centre, chart review of patients who underwent aortic and/or mitral valve repair or replacement between 1st March to 31st August 2012. Relevant exclusion criteria were those with contraindications to antithrombotic therapy; incomplete scanned medical records; those undergoing percutaneous valve replacement. The benchmark for concordance to the ACCP guidelines was set at 90% for the primary outcome and was achieved by evaluating medication prescribed and INR target, when applicable. Bleeding events were defined according to the Graafsma study.3 Bleeding leading to medical or surgical intervention at the operative site was also reported. Stroke was defined as haemorrhagic or ischaemic stroked confirmed by CT or MRI. Other thrombotic events were defined as valvular thrombosis, atrial or ventricular thrombosis confirmed by echocardiography or on re-operation. Discussion This study aimed to evaluate compliance with ACCP antithrombotic guidelines for patients post-aortic and/or mitral valve replacement/repair. Although the primary outcome of 90% concordance was not met, compliance with guidelines at 73% suggested overall compliance was relatively high. Despite this, the guidelines could only be applied to the minority of patients undergoing valvular heart surgery. This was largely due to patients undergoing other concurrent thoracic surgeries, including additional valve surgeries or CABG. This identifies a gap in the current literature with respect to how to adequately manage this patient group. The bleeding and thrombotic rates reported in this study are higher than that reported in the literature.4,5 This may reflect the use of other antithrombotic therapies used in the peri-operative period which were not evaluated in detail, as well as the significant blood loss that can occur during surgery. Several limitations exist in this study. Assumptions were made for assessing concordance to guidelines, as often the correct therapy was used but no duration of therapy was stated. This is increasingly important for patients who undergo valve surgeries which require short term anticoagulation, with step-down to aspirin therapy. Patient reported pre-operative use of antiplatelet agents without a clear indication. This therapy was often continued post-operatively without any rationale stated. The quality of evidence used to compile the ACCP and ESC antithrombotic guidelines is of low quality. This has resulted in varying interpretations of the evidence and therefore more challenging to provide concrete recommendations in this patient group. Lastly, this study had a short duration of patient follow up, and therefore only captures early bleeding and thrombotic events. Longer follow up would better quantify the risks and benefits of these therapies. Results Between 1st March to the 31st of August, 78 patients were reviewed. Baseline characteristics are highlighted in Table1. The population was pre-dominantly male and the average age of patients was 68 year of age. Most patients received bioprostheic valve replacements, with 47% of patients receiving concurrent surgeries, including additional valve replacements/repairs or concurrent coronary artery bypass grafting (CABG). Table 2 summarises the ACCP guidelines used to assess concordance. Of the 78 patients reviewed, only 33 patients (42%) could have the guideline applied to them. For the primary outcome, of those 33 patients, 24 patients (73%) received therapies concordant to guideline recommendations. Bleeding and thrombotic events were recorded in guideline eligible patients (Table 3). Of the six major bleeding events, 3 patients experienced cardiac tamponade requiring surgical intervention and 3 patients required transfusions. One major bleed occurred when therapy was discordant to guidelines. Two patients experienced a thrombotic event, with one event when therapy was discordant to guidelines. Table 2. ACCP Guideline Recommendations Conclusion The majority of eligible patients received antithrombotic therapy concordant to the ACCP guidelines, however opportunities for improvement exist. Concordance with ESC guidelines occurred less frequently. Most patients included in this study were too complex for the guidelines to be relevant, suggesting a need for more robust guidance in this population. References Whitlock RP, et al.Antithrombotic and Thrombolytic Therapy for Valvular Disease.Chest 2012;141(2) (Suppl):e576S-e600S. Vahanian A, et al. Guidelines on the management of valvular heart disease. Eur Heart Journ 2012;33: 2451-96. Graafsma YP,et al. Bleeding classification in clinical trials: observer variability and clinical relevance. Thromb Haemost 1997;78:1189-92. Dong MF, et al. Anticoagulation therapy with combined low dose aspirin and warfarin following mechanical heart valve replacement. Thrombosis Research 2011;128(5):e91-4. Brennan JM, et al. Patterns of anticoagulation following bioprosthetic valve implantation: observations from ANSWER. J Heart Valve Dis 2012;21(1):78-87.