Impact of hypertension on bioprosthetic heart valve calcification – a short-term in vitro study

Introduction: Calcification is the major reason for failure of bioprosthetic heart valves. It is hypothesized that hypertension is a main culprit. The objective of this study was to determine the impact of supra-physiologic pressures on the calcification of bioprosthetic heart valves using an in vitro system capable of inducing real-time physiologic and hypertensive pressures. Methods: Two xenografts of Cambridge BioMedical and four SJM Epic TM Supra Valves were exposed to a pressure of 180/100mmHg in calcification medium at a frequency of 1.33Hz and another two and four valves, respectively, were exposed to a pressure of 120/80mmHg. The heart valves were examined haemodynamically (calculation of effective orifice area) every week and after six weeks by X-ray computed tomography. Von Kossa and Alizarin Red staining were performed as well as calcium and phosphate extraction for quantification by o-cresolphthalein and ammonium molybdate complexation method. Results: Xenografts of Cambridge BioMedical showed higher calcification when exposed to higher pressure. In SJM Epic TM Supra Valves no evidence of pressure dependent significant calcium accumulation could be detected. In conclusion, this in vitro study revealed that high pressure simulating hypertension has impact on the degree of calcification of bioprosthetic heart valves. However state-of-the-art anticalcification treated bioprosthetic valves are of high quality do not calcify in a six-week set-up. Further in vitro experiments analyzing long-term effects are mandatory.