Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.
Epic bioprostheses have non-linear stress-strain behavior similar to native valve tissue, but they are significantly stiffer and hence less elastic compared to native porcine and human aortic valves. These differences in mechanical properties may cause variations in stress distribution within leaflets of the bioprosthetic valves and accelerate their deterioration.
BackgroundCarriers of plasminogen activator inhibitor -1 (PAI-1) -675 genotype 5G/5G may be associated with lower preoperative PAI-1 plasma levels and higher blood loss after heart surgery using cardiopulmonary bypass (CPB). We speculate if polymorphisms of PAI-1 -844 A/G and angiotensin converting enzyme (ACE) intron 16 I/D also might promote fibrinolysis and increase postoperative bleeding.MethodsWe assessed PAI-1 -844 A/G, and ACE intron 16 I/D polymorphisms by polymerase chain reaction technique and direct sequencing of genomic DNA from 83 open heart surgery patients that we have presented earlier. As primary outcome, accumulated chest tube drainage (CTD) at 4 and 24 h were analyzed for association with genetic polymorphisms. As secondary outcome, differences in plasma levels of PAI-1, t-PA/PAI-1 complex and D-dimer were determined for each polymorphism. SPSS® was used for statistical evaluation.ResultsThe lowest preoperative PAI-1 plasma levels were associated with PAI-1 -844 genotype G/G, and higher CTD, as compared with genotype A/A at 4 and 24 h after surgery. Correspondingly, 4 h after the surgery CTD was higher in carriers of ACE intron 16 genotype I/I, as compared with genotype D/D. PAI-1 plasma levels and t-PA/PAI-1 complex reached nadir in carriers of ACE intron 16 genotype I/I, in whom we also noticed the highest D-dimer levels immediately after surgery. Notably, carriers of PAI-1 -844 genotype G/G displayed higher D-dimer levels at 24 h after surgery as compared with those of genotype A/G.ConclusionsIncreased postoperative blood loss secondary to enhanced fibrinolysis was associated with carriers of PAI-1 -844 G/G and ACE Intron 16 I/I, suggesting that these genotypes might predict increased postoperative blood loss after cardiac surgery using CPB.Electronic supplementary materialThe online version of this article (doi:10.1186/s12871-015-0101-1) contains supplementary material, which is available to authorized users.
Abstract-Porous electrospun nanofiber materials are very promising as matrixes for heart valve tissue engineering. The perfect material for this purpose has to be both mechanically strong and deformable at the same time.Materials from gelatin, polyurethane (PUR), polylactic acid (PLA) and polycaprolactone (PCL) made in several density variants were analyzed using uniaxial tensile tests and compared to mechanical properties of porcine aortic valve (AV) leaflets in radial and circumferential directions.In circumferential direction modulus of elasticity (E) of AV is 9.7±1.3MPa and -1.0±0.2MPa in radial. Ultimate strain and stress is 44.8±5.9% and 2.3±0.6MPa in circumferential and 95.6±31.4% and 0.5±0.2MPa in radial direction for AV. Closest of the materials to native AV in circumferential direction was PUR with area density 6.2 g/m 2 showing E of 3.9±0.5 MPa, ultimate stress and strain -5.3±1.68MPa and 141.8±43.9% respectively. Closest to radial direction was gelatin with area density 5.7 g/m 2 showing E of 0.64±0.14 MPa, ultimate stress and strain -0.38±0.05MPa and 82.53±10.20% respectively.Native AV leaflets have a non-linear and anisotropic response to stress in uniaxial tensile tests. To model their mechanical properties we suggest using a combined material made of gelatin and PUR with their fibbers predominantly orientated in perpendicular directions.
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