Evaluation of Warfarin Initiation at 3mg versus 5mg for Anticoagulation of Mechanical Mitral Valve Replacement Patients

Abstract

It has been estimated that 300,000 prosthetic heart valve replacements are performed each year worldwide (Sun et al., 2009). Mechanical heart valves are more durable than bio-prostheses but more thrombogenic. Hence, postoperative warfarin anticoagulation is recommended for all patients receiving mechanical aortic or mitral heart valve replacement (Whitlock et al., 2012),. Mechanical heart valves necessitate lifetime anticoagulation, with an international normalized ratio (INR) target range of 2.0 to 3.0 for aortic valves, and 2.5 to 3.5 for mitral valves. Warfarin starting doses between 5 and 10 mg per day given on the first 1 or 2 days of warfarin treatment were consistently accepted in earlier medical practice and were recommended by the American College of Chest Physicians (ACCP) to be applied for individuals who need long-term anticoagulation with consequent dose adjustment based on the INR findings (Ansell et al., 2008). The exaggerated sensitivity of warfarin after heart valve surgery is well recognized (Rose et al., 1998, Ageno and Turpie, 1999, Rahman et al., 2006). Many factors contribute to this postoperative sensitivity including; patient’s age, gender, body weight, concomitant medications like amiodarone and cefazoline, baseline INR, and serum albumin level (Mohammadi and Kargar, 2018). Owing to lack of evidence in this field, currently available guidelines offer no clear recommendation concerning warfarin initiation after heart valve surgery (Ageno et al., 2012, Vahanian et al., 2012b, Nishimura et al., 2014a, Baumgartner et al., 2018, Otto et al., 2021).