A DYNAMIC INVITRO METHOD FOR STUDYING BIOPROSTHETIC HEART-VALVE CALCIFICATION

The most predictable cause of failure of a biological prosthetic heart valve is calcification. The deposition process appears to be related both to the biomaterial composition and to the presence of dynamic stresses in the leaflets. A dynamic in vitro test has been developed to investigate the calcification process. The test apparatus consists of a modified Rowan Ash fatigue tester with the test fluid maintained at 37-degrees-C. Six valves can be tested simultaneously under similar physical conditions, but with individual incubation media. The valves tested were glutaraldehyde-fixed bovine pericardial valves (the Glasgow Heart Valve). These have been tested in a range of different simple salt solutions containing approximately physiological concentrations of calcium and phosphate. Calcification has been analysed by assay of the incubation media for depletion of calcium and phosphate and direct measurement of uptake of calcium by the valves. There is a wide variability among pericardial valves treated similarly. This may be related to the variability in calcification rate seen in patients with valve implants.