Cardiothoracic Surgery; Critical Care Medicine; Cardiology
Background: Although bridging anticoagulation may be necessary for those patients at highest risk for thromboembolic (TE) complications, for most patients, bridging can result in excessive bleeding, greater need for transfusions, longer hospital stays, while providing no clear prevention or decrease in thromboembolic events1. Unfortunately, in current clinical practice, providers continue to favor interruption of oral anticoagulation (OAC) and the subsequent use of bridging anticoagulation. The literature reviewed, in conjunction with current clinical studies and hospital protocols favors non-bridging anticoagulation to promote reduction in adverse bleeding events along with decreasing other morbidity and mortality factors. The development of the Miller Model is based off of literature review and current clinical practice guidelines and aims act as a guide to help clinicians assess if a non-bridging protocol would be appropriate for their patient.
Methods: Digital databases including Embase, NCBI, The Annals of Thoracic Surgery, American College of Cardiology, and Cochrane database were searched and reviewed for relevant articles. The search strategy was guided by the terms: valve replacement, anticoagulation, bleeding and complications, HAS-BLED, BleedMAP, CHADVASC and Wells Score. Filtered data used included, adults, randomized clinical trials (RCT), and literature published within the last 10 years.
Results: Over 2000 titles were reviewed and twenty-eight articles were integrated after analysis and inclusion criteria reviewed. Of the literature reviewed, many were retrospective analysis studies, literature reviews and current common practice algorithms. All studies reported that employing a non-bridging protocol with warfarin postoperatively yielded a significant reduction in bleeding complications2. Additionally, a decrease in hospital length of stay and patient care cost when not bridging with heparin was appreciated3. There was a significant amount of medication errors noted with the use of unfractionated heparin (UFH) from multiple sources, potentially increasing the risk for adverse bleeding events4. Current algorithms used to analyze patient risk factors for bleeding and thromboembolic events were cross examined to determine associations. These relations, in conjunction with literature review, were used to develop the Miller Model. The Miller Model aims to serve as a risk stratifying algorithm to help guide the practice of choosing to bridge or not to bridge anticoagulation for mechanical valves patients.
Conclusions: Although the overall reduction in mortality is unclear, utilizing non-bridging anticoagulation can improve clinical outcomes by significantly reducing hemorrhagic complications, decreasing hospital length of say, minimizing clinical costs and medication errors. Introducing literature and the Miller Model into clinical practice we aim to guide periprocedural management of anticoagulation for mechanical heart valves, decrease adverse bleeding risks and lead better clinical outcomes for both patients and providers. Future study implementing the Miller Model into retrospective and prospective research is needed to fully assess clinical effectiveness of the model.
Miller AL. To Bridge or Not to Bridge: The Miller Model To Determine Anticoagulation Therapy for Mechanical Valves. Lynchburg Journal of Medical Science. 2020; 2(1).
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