Shear wave imaging was evaluated for the in vivo assessment of myocardial biomechanical properties on ten open chest sheep. The use of dedicated ultrasonic sequences implemented on a very high frame rate ultrasonic scanner ( > 5000 frames per second) enables the estimation of the quantitative shear modulus of myocardium several times during one cardiac cycle. A 128 element probe remotely generates a shear wave thanks to the radiation force induced by a focused ultrasonic burst. The resulting shear wave propagation is tracked using the same probe by cross-correlating successive ultrasonic images acquired at a very high frame rate. The shear wave speed estimated at each location in the ultrasonic image gives access to the local myocardial stiffness (shear modulus μ). The technique was found to be reproducible (standard deviation ) and able to estimate both systolic and diastolic stiffness on each sheep (respectively μ(dias) ≈ 2 kPa and μ(syst) ≈ 30 kPa). Moreover, the ability of the proposed method to polarize the shear wave generation and propagation along a chosen axis permits the study the local elastic anisotropy of myocardial muscle. As expected, myocardial elastic anisotropy is found to vary with muscle depth. The real time capabilities and potential of Shear Wave Imaging using ultrafast scanners for cardiac applications is finally illustrated by studying the dynamics of this fractional anisotropy during the cardiac cycle.

BackgroundRefusal of heterogenic blood products can be for religious reasons as in Jehovah's Witnesses or otherwise or as requested by an increasing number of patients. Furthermore blood reserves are under continuous demand with increasing costs. Therefore, transfusion avoidance strategies are desirable. We describe a historic comparison and current results of blood saving protocols in Jehovah's Witnesses patients.MethodsData on 250 Jehovah's Witness patients operated upon between 1991 and 2003 (group A) were reviewed and compared with a second population of 250 patients treated from 2003 to 2012 (group B).ResultsIn group A, mean age was 51 years of age compared to 68 years in group B. An iterative procedure was performed in 13% of patients in group B. Thirty days mortality was 3% in group A and 1% in group B despite greater operative risk factors, with more redo, and lower ejection fraction in group B. Several factors contributed to the low morbidity-mortality in group B, namely: preoperative erythropoietin to attain a minimal hemoglobin value of 14 g/dl, warm blood cardioplegia, the implementation of the Cornell University protocol and fast track extubation.ConclusionsCardiac surgery without transfusion in high-risk patients such as Jehovah Witnesses can be carried out with results equivalent to those of low risk patients. Recent advances in surgical techniques and blood conservation protocols are main contributing factors.

The implantation of a biomaterial for tissue engineering requires the presence of a suitable scaffold on which the tissue repair and regeneration will take place. Polymers have been frequently used for that purpose because they show similar properties to that of the natural extracellular matrix. Scaffold properties and biocompatibility are modulated by the composition of the polymers used. In this work four polysaccharide-based hydrogels (PSH) made of dextran and pullulan were synthesized. Their in vitro properties were determined and then tested in vivo in a rat model. As pullulan concentration increased in dextran hydrogels, the glass transition temperature and the maximum modulus decreased. In vitro degradation studies for 30 days demonstrated no significant degradation of PSH except for 100% pullulan hydrogel. In vivo tissue response evaluated 30 days after PSH subcutaneous implantation in rats indicated that all PSH were surrounded by a fibrous capsule. Adding pullulan to dextran induced an increased inflammatory reaction compared to PSH-D(100% dextran) or PSH-D(75)P(25)(75% dextran). This in vitro and in vivo data can be used in the design of hydrogels appropriate for tissue engineering applications.