Method of laser cutting pericardial tissue for use with an implantable medical device

Abstract

A method of cutting material for use in an implantable medical device employs a plotted laser cutting system. The laser cutting system is computer controlled and includes a laser combined with a motion system. The laser precisely cuts segments out of source material according to a predetermined pattern as designated by the computer. The segments are used in constructing implantable medical devices. The cutting energy of the laser is selected so that the cut edges of the segments are melted to discourage delamination or fraying, but communication of thermal energy into the segment beyond the edge is minimized to avoid damaging the segment adjacent the edge.

Description

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 09/772,526, now U.S. Pat. No. 6,682,559, entitled PROSTHETIC HEART VALVE; which was filed on Jan. 29, 2001

For the above embodiment, the laser energy per pulse is about:
(7.5 joules/second)/((1 inch/second)×(1000 pulses/inch))=0.0075 joules/pulse.

Other materials, such as bovine or other kinds of pericardium tissues and laminar materials can also be advantageously laser cut with a CO₂ laser as discussed above. In another preferred embodiment wherein such materials, including equine pericardium, are laser cut, about 0.005-0.5 joules of laser energy are supplied per pulse, with a laser spot size of about 0.002 to 0.005 inches in diameter, a cutting speed of about 1 inch/second, and a pulse rate of about 1000 PPI. More preferably, about 0.005-0.02 joules of laser energy are supplied per pulse. For the Universal Laser Systems M-series laser discussed above, the following sample settings enable laser cutting within the above-discussed parameters: a 1.5 Lens, 20% power setting, 3.4% speed, 1000 PPI and 1000 dots per inch.

It is to be understood that if parameters such as the pulse rate and cutting speed are adjusted, corresponding adjustments to other parameters can be made so that the energy imparted to the material substantially stays within the desired parameters. In this manner, a generally uniform weld can be formed along a cut edge without discoloring the edge or imparting excessive heat to other portions of the segment.

It is also to be understood that other types of lasers, such as an erbium laser that generates a laser beam having a wavelength of about 2.7-3.0 μm, can suitably be used to cut segments. Such alternative lasers can be operated at settings so that the cut edges are welded as discussed above.

Alternative techniques may be employed for laser cutting of segments for use in prosthetics, such as disclosed in U.S. Patent Application Publication No. U.S. 2002/0091441, which was published on Jul. 11, 2002. The entire disclosure of this publication is hereby incorporated herein by reference.

Various types of tissue and man-made materials can be cut with a laser by using generally the same principles as discussed above. For example, other types of laminar tissue can be cut so that the cut edges are welded and have a generally uniform consistency with little or no discoloration. Similarly, for man-made materials such as woven or knitted polymers, the cut edges preferably are melted so that fraying of the woven filaments or yarns is minimized or avoided, but discoloration is also avoided.

With reference next to FIG. 9, an embodiment of a laser cutting apparatus for cutting curved or tubular materials is illustrated. This embodiment is substantially similar to the embodiment presented in FIG. 6 except that the support surface 80 comprises a rotary axis 104 configured to accept a tubular source material 106. In addition to vertical movement about a Z-axis, the rotary axis 104 is adapted to rotate in order to help position the tubular source material 106 in an advantageous cutting position relative to the focused laser beam 88.

Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.

Claims

1. A method of creating an implantable medical prosthesis, comprising:

providing a sheet of pericardium, wherein the pericardium has at least two tissue layers;

cutting a segment of tissue out of the sheet of pericardium with a laser beam;

said cutting comprising operating a laser at a power and pulse rate such that said beam welds the layers of the pericardium together along a laser cut edge;

wherein the laser is operated in a pulsed manner, supplying between about 0.005-0.5 joules of laser energy per pulse, with a laser spot size of about 0.002-0.005 inches in diameter, thereby producing a laser cut edge without significantly burning the pericardium adjacent the cut edge.

2. The method of claim 1, wherein the pericardium tissue comprises equine pericardium.

3. The method of claim 1, wherein the laser beam power and pulse rate are selected so that there is substantially no discoloration of the pericardium along the cut edge.

4. The method of claim 1, wherein the prosthesis comprises a heart valve, said cutting comprising cutting a plurality of segments of tissue out of the sheet of pericardium with the laser beam and attaching the cut segments to one another to form the valve.

5. The method of claim 1, comprising moving the laser beam at a cutting speed of about 1 inch per second and a pulse rate of about 1000 pulses per inch.

6. The method of claim 5, wherein the laser beam supplies between about 0.005-0.02 joules of laser energy per pulse.

7. The method of claim 1, wherein the laser beam operates at a wavelength of about 10.6 microns.

8. The method of claim 1, wherein the laser beam operates at a wavelength of about 2.7-3.0 microns.

9. The method of claim 1, wherein the laser energy is about 0.0075 joules per pulse and a laser spot diameter of about 0.003 inches.