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
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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
