Thromboembolic and bleeding colviplications, risk factors involved and anticoagulant adequacy among patients with mechanical heart valves as seen at Muhimbili National Hospital

Abstract

Background: Thromboembolic and bleeding complications are the main causes of morbidity and mortality in patients with mechanical heart valves. The magnitude and risk factors for these complications in Tanzania has not been established. Methods: A retrospective cohort study was conducted among patients with mechanical heart valves operated from 1990 to 2003 attending the Muhimbili National Hospital. Information on occurrence and risk factors for thromboembolic and bleeding complications was obtained from medical records and interviews. Anticoagulation adequacy was assessed basing on the proportion of Prothrombin ratio measurements within the therapeutic ranges during the study follow-up. Findings: Among the 232 study patients, 59 (25.4%) suffered a total of 83 thromboembolic episodes. The linearized incidence of minor (grade I and II) episodes was 5.5% person-years and 3.5 % person-years for major (grade IlI) episodes. In a »: multivariate Cox regression analysis, residing very far a~ml)ar es Salaam and mitral valve replacement were found to be predictors of thromboembolism. In a univariate logistic regression analysis, increased left ventricular diameters, mean aortic valves pressure gradient and reduced ejection fraction were significantly associated with thromboembolism. The study also indicates that 87 (37.5%) patients suffered a total of 132 bleeding events. The linearized incidence rate of minor bleedings was 11.4% person-years while that of major bleeding was 2.9 % person-years. In the multivariate Cox regression of potential

risk factors, those patients who attended both cardiac and anticoagulation clinic had less