J Clin Outcomes Manage
Perioperative anticoagulation for patients with mechanical heart valves: a model comparing unfractionated and low-molecular-weight heparin
Garcia DA, Libby EN, Rich JS
Abstract Objective: To assess the cost-effectiveness of perioperative anticoagulation with intravenous unfractionated heparin (UFH) in patients with mechanical heart valves. Design: Decision analysis using a Markov model. Setting and participants: A hypothetical cohort of men and women aged 55 years with a St. Jude mitral valve and a history of atrial fibrillation receiving perioperative antithrombotic agents. Inputs: Rate of major thromboembolic events (stroke, valve thrombosis, peripheral embolus) in patients with a mechanical mitral valve who are anticoagulated with warfarin or heparin (2.3 events per 100 patient-years) or with low-molecular-weight heparin (LMWH) (3.4 events per 100 patient-years); risk of death or permanent sequelae following a thromboembolic event; and costs from the third-party payer perspective of the thromboprophylaxis strategies and the long-term costs associated with thromboembolic complications. Measurements: Incremental cost-effectiveness ratios and potential thromboembolic events averted. Results: Assuming a relative risk increase of 50% in valve-related thromboembolic events in patients treated with LMWH, the incremental cost-effectiveness ratio for intravenous UFH is more than $3,000,000 per quality-adjusted life-year. Relative to the protection provided by LMWH, an additional 4167 patients would have to be hospitalized for intravenous UFH to prevent 1 thromboembolic event. Conclusion: Bridging all patients with mechanical heart valves with intravenous UFH is prohibitively expensive. Consensus panels charged with establishing guidelines for the management of this increasingly common clinical problem must weigh patient safety and medicolegal concerns along with the potential economic impact of their recommendations.
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