Analysis Of Valve Motion Research Articles

Analysis of valve motion after the reimplantation type of valve-sparing procedure (David I) with a new aortic root conduit

Background. The reimplantation type of valve-sparing procedure does not allow proper reconstruction of the sinuses of Valsalva. We assessed the valve motion after a reimplantation type (David I) of valve-sparing procedure using a new Dacron conduit that incorporates sinuses of Valsalva. Methods. Nine consecutive patients undergoing an aortic valve-sparing procedure using the new conduit were studied using two-dimensional transesophageal echocardiography shortly (2 ± 1 months) after operation to determine root distensibility, expressed as percent change in radius and as pressure strain of the elastic modulus. Next, monodimensional view was used to assess valve motion in its various phases (rapid valve opening velocity, slow closing leaflet displacement, rapid valve closing velocity, maximal leaflet displacement, and leaflet displacement before valve closure). Seven healthy individuals served as control subjects. Results. Root distensibility was reduced at the level of the annulus and sinotubular junction but was similar to control subjects at the level of the sinuses (percent change in radius, 4.1% ± 0.8% versus 4.5% ± 1.2%; pressure strain of the elastic modulus, 1,286 ± 674 g/cm 2 versus 1,195 ± 628 g/cm 2). Rapid valve opening (69 ± 34.4 cm/s versus 51 ± 11.9 cm/s) and closing (47.6 ± 16 cm/s versus 36.4 ± 9 cm/s) velocity as well as slow closing leaflet displacement (24% ± 4.7% versus 22.1% ± 7.9%), maximal leaflet displacement (20.1 ± 4 mm versus 22.7 ± 1.9 mm), and leaflet displacement before valve closure (15.2 ± 3 mm versus 17.6 ± 0.8 mm) were similar to control subjects. Conclusions. The new aortic root conduit used in a reimplantation type of valve-sparing procedure allows the anatomic reconstruction of the aortic root with leaflet motion similar to that of normal subjects.

Analysis of Valve Motion in Overhead Valve Linkages : 1st Report, Measurement of Valve Motion and Discussion of Single Mass System

Analysis of valve motion would reduce a great deal of experimental work preceding the final decision of valve gear design. A lot of attempts for such analysis have not been quite successful with their poor experimental data to be compared with the calculated results, which in due course mada authors take great care for such measurements at the beginning of the study. In this report authors introduced their methods of measurements for such use and discussed a single mass system (serial system composed of cam-equivalent push rod-equivalent valve mass-valve spring) for the description of valve motion. New definition of single mass system has enabled authors to give elegant explanation of various dynamic behaviors which characterize actual systems. This new equivalent system was applied to the calculation of valve motions, which were closely compared with the experimental results mentioned above.