Prosthetic Heart Valve Replacement and a Case Study Article Analysis

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Background
Prosthetic heart valve replacement is performed in several hundred thousand patients per year worldwide and is recommended for many patients with severe valvular heart disease. Bioprosthetic heart valves and mechanical heart valves are the two major valve types. Mechanical valves are more durable than bioprosthetic valves but require lifelong anticoagulant therapy with vitamin K antagonists (warfarin) due to persistent risk of thrombosis and stroke. Warfarin has a narrow therapeutic window and requires frequent monitoring such as international normalized ratio (INR) and restrictions on food, drugs and alcohol. Due to limitations of warfarin many patients prefer bioprosthetic valve replacement rather than a mechanical valve, despite the risk of premature valve failure and repeated valve replacement surgery with bioprosthesis.1 Warfarin works by inhibiting coagulation factors II, VII, IX and X, as well as proteins C and S and hence reduces synthesis of active clotting factors.4
Dabigatran is a direct reversible thrombin inhibitor that has been approved for treatment of nonvalvular atrial fibrillation (AF) based on results of the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) study, but its use for other indications remains untested. It works by inhibiting both free and clot-bound thrombin, which enables the conversion of fibrinogen into fibrin. Dabigatran is eliminated primarily by the kidneys and it’s dosed orally.5

Literature search
A literature search was conducted using EMBASE database (1980 to 2014 Week 06) and MEDLINE database (1946 to February Week 2 2014) accessed through Ovid. The databases were accessed on February 8, 2014. Keywords included dabigatran etexilate, warfarin, thrombosis, and...

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...e of warfarin over dabigatran as the preferred anticoagulant for the prevention of thromboembolic and bleeding complications in patients with mechanical heart valves. o Warfarin starting dose 2 to 5 mg orally/IV once a day.3,4 o Dose adjustment should be based on the results of INR.3,4 o Usual maintenance dose 2 to 10 mg orally/IV once a day.3,4
• Monitoring parameters o Daily monitoring for INR following initial dose until INR stabilized to the therapeutic range, then every 4 weeks based on clinical need.3,4 o Target INR of 2.5 (range 2 to 3 for aortic mechanical valve).3,4 o Target INR of 3 (range 2.5 to 3.5 for mitral mechanical valve)3,4

Thank you for this consult. I will continue to follow up with you on this patient. If you have any questions, please do not hesitate to contact me via email.
Augustine Owusu PharmD candidate
Email: Augustine.owusu@my.mcphs.edu

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