Abstract
Background: Available evidence suggest that the optimum prothrombin time-international normalised ratio (PT-INR) intensities recommended for anticoagulation of patients with mechanical heart valve prosthesis may not apply to all race groups. Optimal PT-INR target ranges and effectiveness of warfarin oral anticoagulation were determined among black South African patients fitted with St Jude bileaflet mechanical heart valve prosthesis (SJBMHVP) at Dr George Mukhari Academic Hospital (DGMAH). Methods: A convenience sample of 95 medical records of patients fitted with SJBMHVP from 1994 until 2013 was reviewed. Optimum PT-INR target ranges were estimated using two different methods: the classical two PT-INR target level method and the alternative, PT-INR specific incident rate method. The quality of warfarin anticoagulation was assessed using the fraction in therapeutic range method.Results: Optimum PT-INR target ranges for all participants fitted with SJBMHVP in the aortic position was estimated to be 2.0–3.5 and 2.6–3.5, respectively, by the classical and alternative methods. That of the patients with mitral valve replacement was estimated to be in the range 2.6–3.5 by the classical method and that of patients with double heart valve replacement was estimated to be 3.5 by both methods. The quality of warfarin anticoagulation of participants with SJBMHVP replacement was found to be inadequate as indicated by percentage time in treatment range (TTR) of 49.7% for all study participants compared with the ideal TTR of 70% and above.Conclusion: Optimum Caucasian-based PT-INR intensities recommended for oral anticoagulation of patients fitted with mechanical heart valve prosthesis are applicable to black patients fitted with SJBMHVP at DGMAH.
Highlights
In clinical practice, warfarin oral anticoagulation of patients with mechanical valve replacement is monitored through frequent laboratory measurement of prothrombin time and calculation of the prothrombin time-international normalized ratio (PTINR).[1,2] The prothrombin time-international normalised ratio (PT-INR) values are compared with the recommended optimum INR target ranges available in most treatment guidelines[2,3,4] to allow for the timeous adjustment of warfarin dosage
To the best knowledge of the authors of this article, no study has ever been conducted to determine or estimate the optimum PT-INR target ranges for warfarin oral anticoagulation of mechanical heart valve prosthesis in a public health setting that caters for mostly black African people, such as Dr George Mukhari Academic Hospital (DGMAH)
The objectives of the study were to determine the three-year (January 2012– January 2015) incident rates of both thromboembolic and haemorrhagic events, to estimate the PT-INR target ranges for warfarin oral anticoagulation and to determine effectiveness of warfarin oral anticoagulation among black South African patients fitted with St Jude bileaflet mechanical heart valve prosthesis (SJBMHVP) at DGMAH
Summary
Warfarin oral anticoagulation of patients with mechanical valve replacement is monitored through frequent laboratory measurement of prothrombin time and calculation of the prothrombin time-international normalized ratio (PTINR).[1,2] The PT-INR values are compared with the recommended optimum INR target ranges available in most treatment guidelines[2,3,4] to allow for the timeous adjustment of warfarin dosage. To the best knowledge of the authors of this article, no study has ever been conducted to determine or estimate the optimum PT-INR target ranges for warfarin oral anticoagulation of mechanical heart valve prosthesis in a public health setting that caters for mostly black African people, such as Dr George Mukhari Academic Hospital (DGMAH). The objectives of the study were to determine the three-year (January 2012– January 2015) incident rates of both thromboembolic and haemorrhagic events, to estimate the PT-INR target ranges for warfarin oral anticoagulation and to determine effectiveness of warfarin oral anticoagulation among black South African patients fitted with SJBMHVP at DGMAH. Optimal PT-INR target ranges and effectiveness of warfarin oral anticoagulation were determined among black South African patients fitted with St Jude bileaflet mechanical heart valve prosthesis (SJBMHVP) at Dr George Mukhari Academic Hospital (DGMAH).
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