A novel in vitro assessment of tissue valve calcification by a continuous flow type method

A dynamic flow type testing to study calcification was self-designed to inv estigate calcification in bioprosthetic heart valves. The apparatus consist s of a container into which leaflets from a porcine aortic valve are placed , a chamber that contains calcium solution, and a peristaltic pump that pro vides a continuous supply of the solution toward the container. Efficacy of the apparatus was compared with the conventional batch type calcification testing at 37 degrees C through measuring the amount of calcium and phospha te deposited by inductively coupled plasma (ICP) and scanning electron micr oscope (SEM). After 14 days, calcium levels detected from the calcified dep osit on leaflets were 470.4 +/- 37.0 mu g/cm(3) in the flow type testing wh ereas in the batch type testing levels were 81.0 +/- 6.7 mu g/cm(3). Though the calcium level on the leaflet increased as the exposure time to calcium solution increased in both testings, the rate and the tendency of calcific ation could be assessed very rapidly by flow type testing in comparison wit h batch type testing. [Ca]/[P] molar ratio decreased over time, and after 1 4 days, the ratio was close to 1.83 +/- 0.18 in the flow type testing. The ratio could not be determined in the batch type testing because the deposit was too small to assess. The descending rate of [Ca]/[P] molar ratio demon strates that deposited calcium-complex at the earliest stage may interact w ith inorganic phosphate ions to create a calcified deposit mineral precurso r. This in vitro dynamic flow type calcification testing was a favorable to ol for rapid investigation of calcification.