Factors associated with sub-optimal control of anticoagulation in patients with prosthetic heart valves taking oral anticoagulants in a sub-Saharan African setting

BACKGROUND: Replacement of diseased valves reduces the morbidity and mortality rate associated with native valvular disease but comes at the expense of risking complications related to the implanted prosthetic device. Establishing the desired anticoagulation level in a sub-Saharan African setting may be a challenge. OBJECTIVES: This study was conducted to determine the challenges of maintaining a desired level of anticoagulation and factors associated with sub-optimal anticoagulation in patients with prosthetic heart valves on chronic anticoagulation. METHODS: We reviewed 73 patients who had undergone prosthetic valve replacement for chronic rheumatic valvular heart disease and were taking warfarin. The follow up ranged from one to 13 years. We studied international normalised ratio (INR) profiles of the patients for the six months preceding the study and defined optimal control as an INR of 2.5-3.5. We aimed to determine if there were factors associated with sub-optimal control of INR. RESULTS: Forty-two patients (57.5%) were female. Mean age of the participants was 21.5 ± 3.1 years (range 14-25 years). Warfarin was the anticoagulant in 55 (75.3%) of the patients and 18 (24.7%) were on combined warfarin and aspirin anticoagulation. Thirty-five (47.9%) patients had optimal control of their INR. Educational level of primary school or less, distance from follow-up medical facility of more than 300 km, quarterly or less-frequent check-up visit, and public health institution as a source of free warfarin supply were found to be significantly associated with sub-optimal control of INR. CONCLUSIONS: Educational level, distance from follow-up facility, number of follow-up visits and source of warfarin supply were found to be significantly associated with sub-optimal control of INR.