Mechanical behavior of bovine pericardium treated with hyaluronic acid derivative for bioprosthetic aortic valves.

We studied the mechanical behavior of bovine pericardium (BP) after anticalcification treatment using hyaluronic acid (HA) derivative. To simulate the physiological environment and stimulate the calcification process, the BP samples were immersed into simulated body fluid solution. We conducted scanning electron microscopy with energy dispersive X-ray spectrometry, and uniaxial mechanical tests of HA-treated and non-treated samples. Although our microstructural analyses indicated that the HA treatment actually prevents the formation of calcium phosphate deposits, the mechanical tests show significant increase of stiffness of the HA-treated samples. Using data from our mechanical tests as input parameters, we performed finite element (FE) computer simulations to estimate how this increase in the BP stiffness affects the stress distribution in the bioprosthetic leaflet. Although the maximum stress observed during the closing phase of the membrane in vivo is below the experimental yield stress in all cases we analyzed, our FE results indicate that increase of BP stiffness due to HA anticalcification treatment results in higher risk of disruption and failure of the leaflets in bioprosthetic heart valves. Since our FE results indicate that the commissure and the fixed edge are the regions that withstand the highest mechanical stresses during the closing phase, new designs of the valve might be efficient to enhance the endurance of the prosthesis. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2273-2280, 2019.

Culture-negative endocarditis caused by Bartonella henselae.

A 4-year-old girl presented with clinical evidence of infective endocarditis involving her aortic valve, but blood cultures were sterile. Serologic studies and analysis of resected valve by immunohistochemistry and polymerase chain reaction established the diagnosis of Bartonella henselae endocarditis. Clinicians should be aware that B. henselae can cause apparent culture-negative endocarditis in children.