The On-X heart valve: mid-term results in a poorly anticoagulated population

The study aim was to evaluate the clinical performance of the On-X heart valve in a socioeconomically disadvantaged population. Most patients were from an indigenous, poorly educated and geographically dispersed segment of the population where anticoagulation therapy was generally erratic.

Between 1999 and 2004, a total of 530 valves (242 mitral valves, 104 aortic valves, 92 double valves) was implanted in 438 patients (average age 33 years; range: 3-78 years). The most common reason for surgery was rheumatic valve disease (57%), followed by degenerative valve disease (11%) and infective endocarditis (9%). Follow up was 95% complete for a total of 746 patient-years (pt-yr). Among the patient population, 40% were either not anticoagulated or were unsatisfactorily anticoagulated.

Hospital mortality was 2.3%, and none of the hospital deaths was valve-related. Mean (+/- SE) actuarial survival (including hospital deaths) at four years was: AVR 73.8 +/- 8.1%, MVR 83.4 +/- 5.7% and DVR 60.9 +/- 10.3%. Linearized rates (for AVR, MVR and DVR, respectively) for late complications (%/ pt-yr) were: bleeding events 0.6, 1.0, and 2.3; thrombosis 0.0, 0.2, and 0.0; endocarditis 0.6, 1.0, and 2.3; paravalvular leak 0.6, 0.2, and 0.0; systemic embolism 1.1, 1.5, and 3.5. Most systemic emboli were related to infective endocarditis. Among patients there were seven uncomplicated, full-term pregnancies.

Bearing in mind the erratic anticoagulation coverage and high incidence of infective endocarditis, the results of this study may be regarded as encouraging. The low incidence of valve thrombosis (one case) was noteworthy. These data also suggest that the On-X valve may be implanted with relative safety in women wishing to have children.