Incidence and risk factors for thromboembolism and major bleeding in patients with mechanical heart valves: a tertiary hospital-based study in Botswana.

Introduction: Mechanical heart valve (MHV) prostheses increase the risk of thromboembolic complications. While warfarin anticoagulation reduces this risk, its use increases the risk of bleeding. We sought to estimate the rate of thromboembolic and bleeding complications among patients with MHVs at a tertiary hospital in Botswana. Factors associated with bleeding and thromboembolic complications are also described. Methods: This retrospective cohort study involved a cohort of patients with MHV at Princess Marina Hospital who were operated on before September 2017. The study documented bleeding and thromboembolic events since the valve replacement, patients' demographic information, co-existing medical conditions, drug history and details of valve replacement. Using the recent international normalised ratio (INR) results, each patient's time in therapeutic range (TTR) was calculated to assess the level of anticoagulation control. Results: The study enrolled 142 patients with a mean (SD) age of 42 (12) years and a median (IQR) duration since valve replacement of four years (1.8-10.0). The median (IQR) TTR was 29.8% (14.1-51.0) and only 14.8% of the patients had an optimal anticoagulation control. The rates of major bleeding and thromboembolic complications were 1.5 per 100 person-years and 2.80 per 100 person-years, respectively. A longer duration of warfarin use was associated with an increased risk of both bleeding (p = 0.008) and thromboembolic complications (p = 0.01). Conclusion: Bleeding and thromboembolic complications were common in MHV prosthesis patients in this study. Long duration of anticoagulation, albeit sub-optimal control, was a risk factor for bleeding and thromboembolic complications in these patients. Therefore, long-term efforts are necessary to address these complications and possibly improve the quality of life of these patients.