Bone mineral density in patients given oral vitamin K antagonists

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

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

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.

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).

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.