Design Parameter And Tissue Mechanics Of Fixed Anchor In The Heart Apex

Mitral and tricuspid regurgitation is a common heart valve disease,and is treated by open heart surgery mainly.Although open heart surgery has good curative effect,it has the problem of great trauma and apply only to low-risk patients.For high-risk patients who have undergone open-heart surgery or who are older,minimally invasive treatment can only be used with small trauma.Minimally invasive treatments for mitral and tricuspid regurgitation include: annuloplasty,papillary muscle and tendon repair,transcatheter valve replacement and valve plug,etc.Whatever therapy methods,it needs to be fixed inside the heart.The fixation inside the heart is always hard.The anchoring mechanism has been widely used in the minimally invasive treatment of heart disease.Hook-type anchor and screw-type anchor are the most common anchoring mechanisms.The main contents and conclusions of this paper ware as follows:1)A six-teeth Nitinol anchor was designed for the fixation inside the heart.Finite element was applied to calculate the process of the 13 anchor models compressing into a sheath by ABAQUS,and the influence of each characteristic parameter on the performance of the anchor was analyzed.An anchor was made for experimental verification of the calculation results.The results showed that:(1)The maximum strain decreased with the decrease in tooth width,thickness and the increased radius of curvature.(2)the pulling force depends primarily on the tooth width,thickness and radius of curvature.(3)Axial penetration depth depends on the tip length,and radial penetration depth is determined by the radius of curvature.2)Taking the apex fixation as an example,four kinds of anchors with different specification were made and tested in vitro.The optimal release position of the apex anchor was verified by analyzing the anatomical structure of the apex.Verify the best release position of the anchor and find out the appropriate size.The results showed that:(1)Left and upper left parts of the right heart apex were the best release parts of the anchor.(2)The curvature radius,the tip length and the tip angle were the determinants of whether punctured the epicardium after anchors were released.(3)the pulling force effectively increased with the decreased in tip angle and radius of curvature.T3 and T4 anchors could provide sufficient apex fixing force without tearing the heart.(4)Results of finite element analysis in Chapter 2 can provide guidance for the design of apex anchor.3)Taking the apex fixation as an example,the design parameters of screw anchor were studied.Three design parameters were defined: line diameter,screw pitch,cylinder number and external diameter.Three stainless steel screw anchors with different specifications were manufactured,and static screw anchor release experiments were carried out respectively.The results showed that:(1)the pericardial gasket sutured on the root of screw anchor can effectively limit the position.(2)the rotary depth of screw anchor should be within 2.2 mm in order to meet the apex release requirements.(3)no.3 screw anchor could provide less fixation force,which cannot meet the requirements of plug device and other products.