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Timestamp: 2019-07-20 22:43:31
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Device and method for restructuring heart chamber geometry - The University of Cincinnati
United States Patent 6221103
09/165887
A61F2/00; A61F2/02; A61M1/10; A61M1/12; (IPC1-7): A61F2/00
600/16-18, 600/37, 623/3.1, 623/3.11, 623/3.12, 623/3.16, 623/3.17
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6050936 Heart wall tension reduction apparatus 2000-04-18 Schwiech, Jr. et al.
6045497 Heart wall tension reduction apparatus and method 2000-04-04 Schwiech, Jr. et al.
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Melvin, D. B.; Melvin, A.J.; Trossman, C.A.; and Glos, D.L., "Reduction of Ventricular Wall Tensile Stress by Geometric Remodeling Device," A
This is a continuation in part application of United States patent application Ser. No. 08/581,914, filed Jan. 2, 1996, entitled "Activation Device for the Natural Heart and Method of Doing the Same," now U.S. Pat. No. 5,957,977.
An alternative procedure is to transplant a heart from another human or animal into a patient. The transplant procedure requires removing an existing organ (i.e., the natural heart) for substitution with another organ (i.e., another natural heart) from another human, or potentially, from an animal. Before replacing an existing organ with another, the substitute organ must be "matched" to the recipient, which can be, at best, difficult and time consuming to accomplish. Furthermore, even if the transplanted organ matches the recipient, a risk exists that the recipient's body will reject the transplanted organ and attack it as a foreign object. Moreover, the number of potential donor hearts is far less than the number of patients in need of a transplant. Although use of animal hearts would lessen the problem with fewer donors than recipients, there is an enhanced concern with rejection of the animal heart.
FIG. 8 is a cross sectional view of a connector of the present invention taken along line 8--8 in FIG. 7;
Turning now to FIG. 3, the chambers of the heart 10, including the left ventricle chamber 12, is generally shaped as a hollow truncated ellipsoid having, at any circular cross-section perpendicular to its long axis, a center point "C1 " and a radius "R1 " extending from center point C1 to the endocardial surface 38. The cardiac tissue 32 of the heart 10 has athickness "w," which is generally the distance between the epicardial surface 34 and the endocardial surface 38.
The assembly 60 of the present invention exemplified in FIGS. 4 to 7 preferably is configured and positioned relative to the natural heart 10 to displace at least two portions of the cardiac tissue 32 inwardly (see, e.g., FIG. 4) from the unrestricted position, as exemplified in FIG. 3. By displacing portions of the cardiac tissue 32 inwardly, the shape of the chamber (e.g., the left ventricle chamber 12) of the heart 10 is generally restructured or reconfigured from a generally hollow truncated ellipsoid (see, e.g., FIG. 3) to a chamber generally shaped as having at least two continuous communicating portions of truncated ellipsoids (see, e.g., FIG. 4). In generally reconfiguring or restructuring the heart 10 as such, each of the truncated ellipsoids has an adjusted radius "R2," which is preferably shorter than radius "R1."
The collar 62 may include two or more bands (e.g., 76) configured for positioning around the heart 10. Preferably, bands 76 are circumferentially flat and may be oriented with the surface 78 being positioned generally tangent to the epicardial surface 34 of the heart 10, and having the smaller dimension, as compared with surface 80. Surface 80 is generally oriented perpendicular to the epicardial surface 34. Band 76 should be sized so as to provide for low deformation in the direction perpendicular to the epicardial surface 34 of the heart 10, but only require a low strain energy for tortial deformation as the heart 10 beats. Band 76 can have a thickness "th" across surface 78 and a width "w" across surface 80, that each varies depending on the selected material and its particular deformation characteristics. When metallic material is used with the present invention, the band 76 can have a thickness "th" across surface 78 of about 0.2 mm, and can have a width, "w" across surface 80 from about 5 mm to about 12 mm, and more preferably, about 7 mm. It should be noted that the particular dimensions of each assembly 60, and of its components (e.g. collar 62 and its various portions, bands 76, etc.) will depend, as will be discussed later, according to particular anatomy, the desired application, and upon the particular size and configuration of the individual natural heart 10.
To assist the epicardial surface 34 in separating from each of the collars 62, 162, or 262 adjacent or at the lateral portions 85 of inner surface 84 without creating substantial negative pressure, a pad 56 can be positioned and/or interposed between the epicardial surface 34 and the inner surface 84 of one or more of the connectors 82. Pad 56 can be, as exemplified in FIGS. 9A and 9B, a fluid-filled or gel-filled pad or cushion, which generally will occupy space laterally beyond the collar 62 and the lateral portions 85 of inner surface 84 while the heart 10 is in a relaxed state. However, as the heart 10 contracts and the wall shortens (see, e.g., FIG. 9B), generally circumferentially (reducing cavity radius), the epicardial surface 34 will "peel away" from the collar 62 and the lateral portions 85 of inner surface 84 and thus, fluid or gel in the pads 56 can fill this space so that the inner surface 84 and epicardial surface 34 remain in contact and effect focal restraint whereby the chamber 12 is restructured, as detailed above.
In accordance with the teachings of the present invention, the assembly 60 should be so configured and positioned adjacent the heart 10 whereby the wall tension is reduced in accordance with LaPlace's theory of a chamber, which is as follows: (Tension of wall)=(K*(chamber pressure)*(radius of chamber))/(wall thickness)
As an illustrative example of one embodiment in accordance with the teachings of the present invention, calculations will be performed based on the following model as exemplified in FIGS. 3 and 5. It is assumed that the long axis of the left ventricle 12 of the heart 10 is 100 mm, that the equatorial or short axis of the chamber 12 is 70 mm, that the equatorial wall thickness "w" of the chamber is about 10 mm and the basal diameter of the heart 10 is 60 mm. An arbitrary slice or plane of the left ventricle 12 will be analyzed to illustrate local dimensional computations for the present invention.
Furthermore, this model will assume that the inner radius "R1 " (of the slice or plane) of the unrestricted heart 10 (see, e.g., FIG. 3) is about 28.982 mm and that the heart 10 has an outer radius of about 38.406 mm. As is known to those skilled in the industry, the width "w" and radius "R1 " can be directly obtained from high-resolution imaging, such as an echocardiogram, or preferably, by computation based on an assumed geometric model. The ratio of the restraint contract pressure of the left ventricle 12 of the device 60 to the cavity pressure can vary from 1 to about 2. This example will further assume that the allowed ratio of the restraint contact pressure of the left ventricle 12 of device 60 to the cavity pressure is to be limited to a maximum of about 1.5, which is represented by symbol K in the mathematical formulas below. Also, it is desired to achieve an altered radius "R2 " of the left ventricle 12 to 80% of its original radius R1, and as such: R2 =0.8*R1 R2 =0.8*28.982 mm R2 =23.186 mm
In order to calculate the radius of curvature "g" of the inner surface 64 of member 62 in the transverse plane, the following formula can be used: g=(w+R2)÷(k-1) g=(9.424 mm+23.186 mm)÷(1.5-1) g=(32.61 mm)÷0.5 g=65.22 mm.
Now that the value of radius of curvature of the inner surface 84 "g" has been calculated, the angle "θ" between the line g1 (joining the center of curvature of the member 62 with one margin, in this plane, of the contact area between inner surface 84 and the epicardial surface 34) and line g2 joining the same center of curvature with the center of the inner surface 84 in the same plane) can be calculated using the following formula: θ=(π/2)*[R2 -R1 ]÷(R2 +w+g) θ=(π/2)*[28.982 mm-23.186 mm]÷(28.982 mm+9.424 mm+65.22 mm) θ=(π/2)*[5.796 mm]÷(103.636 mm)
Using the formula below, the distance inwardly that the heart 10 should be displaced can be calculated so that the desired restructuring can be achieved. If "e" is the distance that the center of either member 62 is to be separated from the absolute center of a remodeled ventricle in this plane, then: e =[(g+w+R2)*cosθ]-g e =[(65.22 mm+9.424 mm+23.186 mm)*cos 5.332 degrees]-65.22 mm e =32.21 mm.
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