Bone mineral density in patients given oral vitamin K antagonists.

Background: Divergent results have been obtained in studies of bone mineral density in patients under oral vitamin K antagonists.

Objective: To gather prospective data on bone mineral density and bone metabolism in 70 aortic valve replacement patients.

Study Design: 49 patients who had been under oral vitamin K antagonists for at least one year after implantation of a mechanical aortic valve were compared with 21 recipients of a tissue aortic valve that did not require anticoagulant therapy. The following investigations were done in all patients: (1) dual-energy X-ray absorptiometry measurement of bone mineral density at the lumbar spine and femoral neck; (2) roentgenograms of the spine and pelvis; (3) serum assays of calcium, phosphate, creatinine, alkaline phosphatase, osteocalcin, 25-OH-vitamin D3, and parathyroid hormone.

Results: The two groups were comparable regarding age and sex ratio. No differences were found in lumbar or femoral neck bone mineral density even after adjustment for age and sex. A trend toward an increase in bone mineral density at both sites with increasing duration of vitamin K antagonist therapy was demonstrated. The only bone turnover marker difference between the two groups was a significantly lower serum osteocalcin level in the group under vitamin K antagonist therapy (P < 0.0001).

Conclusions: Long-term vitamin K antagonist therapy does not affect bone mineral density at the lumbar spine or femoral neck and also fails to modify bone turnover markers, with the exception of osteocalcin.