In Vitro Calcification of Bioprosthetic Heart Valves: Investigation of Test Fluids

  • N. Kiesendahl
  • C. Schmitz
  • A. Von Berg
  • M. Menne
  • T. Schmitz-Rode
  • J. Arens
  • U. SteinseiferEmail author


Calcification is a major reason for the failure of bioprosthetic heart valves. Therefore, several attempts towards an accelerated in vitro model were undertaken in order to provide a cost- and time-saving method for the analysis of calcification processes. Due to the problem of superficial or spontaneous precipitation, which occurred in the fluids applied, we focused our study on the development of a near-physiological calcification fluid. The desired fluid should not precipitate spontaneously and should neither promote nor inhibit calcification. Eleven different fluid compositions were tested without contact to potentially calcifying materials. Crucial factors regarding the fluid properties were the ionic product, the ionic strength, and the degree of supersaturation concerning dicalciumphosphate-dihydrate, octacalciumphosphate, and hydroxyapatite. The fluids were kept in polyethylene bottles and exposed to a slight vibration within a durability tester at 37 °C. The precipitation propensity was monitored optically and colorimetrically. A structural analysis of the deposits was carried out by x-ray powder diffraction and IR-spectroscopy, which showed the development of the crystal phases that are relevant in vivo. Only two of the fluids did not precipitate. Resulting from the computations of the effective fluid contents, the saturation degree concerning dicalciumphosphate-dihydrate seems to be the key factor for spontaneous precipitation.


Fluid study Spontaneous precipitation Ionic strength Ionic products Supersaturation 



Arbitrary unit


Total calcium


Calcium gluconate




Activity coefficient of z-valent ionic species


Fourier transform infrared spectroscopy




Ionic strength


Thermodynamic ionic product




Thermodynamic solubility constant


Octacalcium phosphate




Total phosphate




Degree of supersaturation


Simulated body fluid




x-Ray powder diffraction



We thank the Institute of Laboratory Animal Science, Uniklinik RWTH Aachen for the chemical analysis of the fluid compositions, and Irmgard Kalf (Institute of Inorganic Chemistry, RWTH Aachen University) for the FTIR measurements.


Parts of this study were funded by INTERREG Program V-A Euregio Maas-Rhine of the European Union (Grant No. 2016/98602) and by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—403041552.

Supplementary material

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Supplementary material 1 (PDF 70 kb)


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Copyright information

© Biomedical Engineering Society 2019

Authors and Affiliations

  1. 1.Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute AachenRWTH Aachen UniversityAachenGermany
  2. 2.Institute of Applied Medical Engineering, Helmholtz Institute AachenRWTH Aachen UniversityAachenGermany
  3. 3.Monash Institute of Medical Engineering and Department of Mechanical and Aerospace EngineeringMonash UniversityMelbourneAustralia
  4. 4.Institute of CrystallographyRWTH Aachen UniversityAachenGermany

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