Age dependent differences in collagen alignment of glutaraldehyde fixed bovine pericardium.

Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4-7 days old) is advantageously thinner and is considered as an alternative to that from adult animals. Here, the structures of adult and neonatal bovine pericardium tissues fixed with glutaraldehyde are characterized by synchrotron-based small angle X-ray scattering (SAXS) and compared with the mechanical properties of these materials. Significant differences are observed between adult and neonatal tissue. The glutaraldehyde fixed neonatal tissue has a higher modulus of elasticity (83.7 MPa) than adult pericardium (33.5 MPa) and a higher normalised ultimate tensile strength (32.9 MPa) than adult pericardium (19.1 MPa). Measured edge on to the tissue, the collagen in neonatal pericardium is significantly more aligned (orientation index (OI) 0.78) than that in adult pericardium (OI 0.62). There is no difference in the fibril diameter between neonatal and adult pericardium. It is shown that high alignment in the plane of the tissue provides the mechanism for the increased strength of the neonatal material. The superior strength of neonatal compared with adult tissue supports the use of neonatal bovine pericardium in heterografts.

Trilogy pericardial valve: hemodynamic performance and calcification in adolescent sheep.

BACKGROUND: We assessed the hemodynamic performance and calcification potential of a new design of bovine pericardial valve, the Trilogy valve (Arbor Surgical Technologies Inc, Irvine, CA). We compared this new valve with the Perimount valve (Edwards Lifesciences, Irvine, CA) in a randomized prospective study in adolescent sheep. METHODS: Nine Trilogy valves (size 21) and six Perimount valves (size 23 or 25) were implanted in the mitral position in adolescent sheep and studied during five months. Hemodynamic measurements were performed at one week, three months, and five months using transthoracic echocardiography. Valve calcification was assessed by X-ray and calcium content was measured by atomic absorption spectrometry after five months implantation in sheep. Tissues were also evaluated histologically (Von Kossa staining). RESULTS: The nine Trilogy valves had lower peak velocity, peak gradient, and mean gradient compared with the six Perimount valves. These 21-mm Trilogy valves had similar deceleration time and effective orifice area compared with the 23- and 25-mm Perimount valves. Calcification of the Trilogy valves was significantly lower than Perimount valves (p < 0.01), particularly in the commissural (p < 0.01) and free margin regions (p < 0.03). In all parameters assessed, the Trilogy valves exhibited less variation valve-to-valve compared with Perimount valves. CONCLUSIONS: These findings demonstrate that a valve designed to reduce stress in the tissue, improve leaflet kinematics, with advanced antimineralization treatment, can exhibit superior calcification resistance in the mitral position of adolescent sheep. The trilobal geometry and independent leaflet suspension design, combined with an advanced tissue treatment, appears to be a promising breakthrough in the effort to develop a more durable and hemodynamically efficient bioprosthetic valve.

In-vitro verification of the electron beam tomography method for measurement of heart valve calcification.

BACKGROUND AND AIM OF THE STUDY: Electron beam tomography (EBT) has been used previously to study aortic root wall and leaflet calcification. However, the sensitivity of this method must be validated by comparing EBT findings with calcification in the cusps as determined using other techniques. An in-vitro study was designed to examine the correlation between EBT scores of calcification, visual observations, traditional X-radiography, dual-energy X-ray analysis (DEXA) and atomic absorption spectroscopy (AAS). METHODS: Seven commercial and experimental pericardial valves were implanted in the mitral position in juvenile sheep for up to 20 weeks. Valves were examined thoroughly upon explantation and traditional x-radiographs were taken using standard techniques and ranked in increasing order of calcification. A calcification score in Hounsfield Units (HU) and a calcified volume score in mm3 were calculated for each valve by EBT. Calcium content was then calculated by means of DEXA and AAS. RESULTS: Calcification scores ranged from 1.03 to 538.93 HU, and calcified volume scores from 6.18 to 1804.6 mm3. Correlation analysis showed a good agreement between the physical observations, in-vitro traditional X-radiography and both the calcification score and calcified volume score. EBT measurements were highly correlated with the DEXA examinations (r = 0.98, p = 0.0001 versus calcification score; and r = 0.97, p = 0.0003 versus calcified volume score) and AAS analyses (r = 0.98, p = 0.0001 versus calcification score; and r = 0.99, p = 0.0000 versus calcified volume score). CONCLUSION: These preliminary results indicate a good correlation between the physical observations of calcification, X-radiographic observations, DEXA, AAS analyses and EBT measures of calcification.