Eccentric rotational atherectomy device

ES 2 249 805 T3

DESCRIPTION

Eccentric rotational atherectomy device.

Technical field

The invention relates to devices for removing tissue from body conduits, such as removing atherosclerotic plaque from arteries, using a rotational atherectomy device.

Background of the invention

A variety of techniques and instruments have been developed for use in the removal or repair of tissue in arteries and similar body conduits. A common goal of such techniques and instruments is the removal of atherosclerotic plaques in the arteries of a patient. Atherosclerosis is characterized by the accumulation of fatty deposits (atheromas) in the intimal layer (under the endothelium) of a patient's blood vessels. Very often over time, what is initially deposited as a relatively soft, cholesterol-rich atheromatous material hardens into a calcified atherosclerotic plaque. Such atheromas limit blood flow and are therefore often referred to as stenotic lesions or stenosis, the blocking material being referred to as stenotic material. If left untreated, such strictures can lead to angina, hypertension, myocardial infarction, stroke, and the like.

Rotational atherectomy procedures have become a common technique to remove such stenotic material. Such procedures are most often used to initiate the opening of calcified lesions in the coronary arteries. Most often, the rotational atherectomy procedure is not used alone, but is followed by a balloon angioplasty procedure which, in turn, is most often followed by placement of a stent (endoprosthesis) to help maintain the patency of the open artery. For noncalcified lesions, balloon angioplasty is most often used alone to open the artery, and stents are often placed to maintain patency of the open artery. However, studies have shown that a significant percentage of patients who have undergone balloon angioplasty and who had a stent placed in an artery experience stent restenosis, that is, stent blockage that most often develops over a period of time. time as a result of overgrowth of scar tissue within the stent. In such situations, an atherectomy procedure is the preferred procedure to remove excessive scar tissue from the stent (balloon angioplasty within the stent is not very effective), thus re-establishing the patency of the artery.

Various classes of rotational atherectomy devices have been developed to attempt to remove stenotic material. In one type of device, such as that shown in U.S. Patent No. 4,990,134 (Auth), a bore covered with abrasive cutting material such as diamond particles is driven to the distal end of a flexible drive shaft. . The drill is rotated at high speeds (typically, for example, in the range of about 150,000 - 190,000 rpm) as it is advanced along the stenosis. However, when the drill is removing stenotic tissue, it blocks blood flow. Once the bore has been advanced through the stenosis, the artery will have opened to a diameter equal to or only slightly greater than the maximum external diameter of the bore. Often times, drills of more than one size must be used to open an artery to the desired diameter.

U.S. Patent No. 5,314,438 (Shturman) shows another atherectomy device having a drive shaft, one section of the drive shaft having an enlarged diameter, at least a segment of this enlarged diameter section being covered with a abrasive material to define an abrasive segment of the drive shaft. When rotated at high speeds, the abrasive segment can remove stenotic tissue from an artery. Although this atherectomy device has certain advantages over the Auth device due to its flexibility, it can also open only one artery to a diameter approximately equal to the diameter of the enlarged diameter section of the motor shaft.

Summary of the invention

The invention provides a rotational atherectomy device having a flexible, elongated, rotating drive shaft with an enlarged diameter eccentric section as specified in claim 1. At least part of the enlarged diameter eccentric section has a removal surface of tissue (typically an abrasive surface) to define a tissue removal segment of the motor shaft. When positioned within an artery against stenotic tissue and rotated at high enough speeds (eg, in the range of about 20,000 rpm to about 200,000 rpm) the eccentric nature of the enlarged diameter section of the motor shaft renders such a section rotate in such a way as to open the stenotic lesion to a diameter substantially larger than the outer diameter of the enlarged diameter section. The enlarged diameter eccentric section of the motor shaft has a center of mass radially spaced from the axis of rotation of the motor shaft, facilitating the ability of the device to open the stenotic lesion to a diameter substantially greater than the external diameter of the diameter section. extended. This is normally accomplished by moving the geometric center of the enlarged diameter eccentric section of the drive shaft from the axis of rotation of the drive shaft. Such a separation of the geometric center from the axis of rotation of the motor shaft can also be carried out in rotational atherectomy devices having an eccentric tissue removal section with a diameter that

ES 2 249 805 T3 is not enlarged, or by attaching an eccentric abrasive drill to a drive shaft. The rotational atherectomy device of the invention can open stenotic lesions to a diameter large enough that balloon angioplasty is not required to complete the procedure. The device is particularly useful for cleaning partially blocked stents.

Brief description of the drawings

Figure 1 is a perspective view of a rotational atherectomy device of the invention;

Figure 2 is a separated perspective view of an enlarged diameter eccentric section of the drive shaft of a rotational atherectomy device of the invention;

Figure 3 is a sectional longitudinal sectional view of an enlarged diameter eccentric section of the rotational atherectomy device of the invention;

Figures 3A-3E are cross-sectional views of Figure 3, taken along lines 3A-3A through 3E-3E thereof;

Figure 4 is a sectional longitudinal sectional view similar to Figure 3 illustrating the geometry of one embodiment of an enlarged diameter eccentric section of the atherectomy device of the invention;

Figure 5 is a cut away longitudinal sectional view of the drive shaft of an atherectomy device of the invention;

Figure 6 is a longitudinal sectional view of an enlarged diameter eccentric section of the atherectomy device of the invention, shown just prior to use to remove stenotic tissue from an artery;

Figure 7 is a longitudinal sectional view similar to Figure 6, showing the enlarged diameter eccentric section moving distally to remove stenotic tissue from an artery;

Figure 7A is a cross-sectional view of Figure 7, taken along lines 7A-7A thereof;

Figure 8 is a longitudinal sectional view similar to Figures 6-7, showing the enlarged diameter eccentric section after it has been moved distally through a stenosis;

Figure 9 is a longitudinal sectional view similar to Figures 6-8, showing a later phase of removal of stenotic tissue from an artery, with the enlarged diameter eccentric section moving proximally through a stenosis;

Figure 9A is a cross-sectional view of Figure 9, taken along lines 9A-9A thereof;

Figure 10 is a longitudinal sectional view similar to Figures 6-9, showing the enlarged diameter eccentric section after it has been moved proximally through a stenosis;

Figure 11 is a longitudinal sectional view similar to Figures 6-10, showing the enlarged diameter eccentric section moving again distally through a stenosis;

Figure 11A is a cross-sectional view of Figure 11, taken along lines 11A-11A;

Figure 12 is a longitudinal sectional view similar to Figures 6-11, showing the enlarged diameter eccentric section after it has been moved distally through a stenosis;

Figure 13 is a longitudinal sectional view similar to Figures 6-12, showing yet another later phase of removal of stenotic tissue from an artery, with the enlarged diameter eccentric section moving proximally through a stenosis;

Figure 13A is a cross-sectional view of Figure 13, taken along lines 13A-13A thereof;

Figure 14 is a longitudinal sectional view similar to Figures 6-13, showing the enlarged diameter eccentric section in a resting position (not rotated) after a stenosis has been substantially opened by the device;

Figure 14A is a cross-sectional view of Figure 14, taken along lines 14A-14A thereof;

Figure 15 is a cross-sectional view similar to Figure 14, illustrating three different positions of the rapidly rotating enlarged diameter eccentric section of an eccentric rotational atherectomy device of the invention;

ES 2 249 805 T3 Figure 16 is a schematic diagram illustrating in an exaggerated manner the spiral path taken by the eccentric enlarged diameter section when removing stenotic tissue from an artery;

Figure 17 is a graph illustrating the maximum centrifugal force with which a tissue removal surface of an enlarged diameter eccentric section, having a maximum diameter of approximately 1.75mm, can press against a surface of a stenosis at various speeds of rotation;

Figure 18 is a graph of experimental data illustrating the degree to which the enlarged diameter eccentric section, having a maximum diameter of approximately 1.57mm, opens a 1.6mm conduit to a progressively larger diameter when tapped. gives the eccentric atherectomy device more time to function;

Figure 19 is a sectional longitudinal sectional view similar to Figure 3 illustrating the flexibility of the eccentric enlarged diameter section of the atherectomy device of the invention;

Figure 20 is a cut away longitudinal sectional view of a mandrel used in the manufacture of an eccentric rotational atherectomy device of the invention;

Figure 21 is a perspective view of a jaw used in the manufacture of an eccentric rotational atherectomy device of the invention;

Figure 22 is a longitudinal sectional view of the jaw of Figure 21;

Figure 23 is an enlarged-scale view showing in longitudinal section details of a part of Figure 22;

Figure 24 is an enlarged, partially broken-away cross-sectional view of Figure 22, taken along lines 24-24 thereof;

Figure 25 is a longitudinal sectional view of an alternative embodiment of the invention employing a slightly differently enlarged diameter eccentric section;

Figures 25A-25C are cross-sectional views of Figure 25, taken along lines 25A-25A through 25C-25C thereof;

Figure 26 is a cut away side view of a mandrel that can be used to fabricate the eccentric rotational atherectomy device of Figure 25;

Figures 26A-26K are cross-sectional views of Figure 26, taken along lines 26A-26A through 26K-26K thereof;

Figure 27 is a longitudinal sectional view of Figure 26K, taken along lines 27-27 thereof;

Figures 28-30 are schematic diagrams of steps in the machining process of the enlarged diameter eccentric component of the mandrel of Figure 26;

Figure 31 is a longitudinal sectional view of another alternative embodiment of the invention employing another eccentric section of differently enlarged diameter;

Figures 31A-31C are cross-sectional views of Figure 31, taken along lines 31A-31A through 31C-31C thereof;

Figure 32 is a cut away side view of a mandrel that can be used to fabricate the eccentric rotational atherectomy device of Figure 31;

Figures 32A-32K are cross-sectional views of Figure 32, taken along lines 32A-32A through 32K-32K thereof;

Figure 33 is a longitudinal sectional view of Figure 32K, taken along lines 33-33 thereof;

Figure 34 is a longitudinal sectional view of another alternative embodiment of the invention employing a slightly differently enlarged diameter eccentric section;

Figures 34A-34A are cross-sectional views of Figure 34, taken along lines 34A-34A through 34E-34E thereof;

Figure 35 is a perspective view of an enlarged diameter section of an alternative embodiment of the invention;

Figure 36 is a longitudinal sectional view of a very low profile embodiment that is not of the invention that

ES 2 249 805 T3 employs a tissue removal section which is eccentric, but whose yarn turns are generally the same diameter as the yarn turns of the rest of the motor shaft;

Figures 36A-36C are cross-sectional views of Figure 36, taken along lines 36A-36A through 36C-36C thereof;

Figure 37 shows a longitudinal sectional view of the eccentric atherectomy device of Figure 36 with its tissue removal segment just prior to being advanced distally along a stenosis;

Figure 38 is a longitudinal sectional view similar to Figure 37, showing the tissue removal segment that is moving distally to remove stenotic tissue from an artery;

Figure 38A is a cross-sectional view of Figure 38, taken along lines 38A-38A thereof;

Figure 39 is a longitudinal sectional view similar to Figures 37-38, showing the tissue removal segment once it has moved distally through a stenosis;

Figure 40 is a longitudinal sectional view similar to Figures 37-39, showing a later phase of removal of stenotic tissue from an artery, with the tissue removal segment moving proximally through a stenosis;

Figure 40A is a cross-sectional view of Figure 40, taken along lines 40A-40A thereof;

Figure 41 is a longitudinal sectional view of another very low profile embodiment that is not of the invention; and Figure 42 is a longitudinal sectional view of another embodiment of the invention employing an eccentric abrasive drill attached to a drive shaft.

Detailed description of the invention

Figure 1 illustrates a typical rotational atherectomy device of the invention. The device includes a handle portion 10, an elongated, flexible drive shaft 20 having an enlarged diameter eccentric section 28, and an elongated catheter 13 extending distally from the handle portion 10. The drive shaft 20 and its elongated diameter eccentric section 28 are constructed from helically wound wire. Catheter 13 has a lumen in which most of the length of motor shaft 20 is disposed, except for its enlarged diameter section 28 and a short section distal to enlarged diameter section 28. The motor shaft 20 also contains an internal lumen, which allows the motor shaft to be advanced and rotated on a guide wire 15. A liquid supply path may be provided to introduce a cooling and lubricating solution (usually saline or other biocompatible liquid) into the catheter 13.

Handle 10 desirably contains a turbine (or similar rotational drive mechanism) to rotate drive shaft 20 at high speeds. The handle 10 can be normally connected to a power source, such as compressed air supplied through a tube 16. A pair of fiber optic cables 25 may also be provided to monitor the rotational speed of the turbine and motor shaft 20 (details regarding such handles and associated instrumentation are well known in the industry and are described, for example, in the U.S. Patent No. 5,314,407, issued to Auth). Handle 10 also desirably a control knob 11 for advancing and retracting the turbine and drive shaft 20 relative to catheter 13 and handle body.

Figures 2-5 illustrate details of enlarged diameter eccentric section 28 of one embodiment of the invention. The motor shaft 20 is comprised of one or more helically wound wires 18 defining a guide wire lumen and a hollow cavity 25 within the enlarged diameter section 28. Except for guidewire 15 passing through hollow cavity 25, hollow cavity 25 is substantially empty. The eccentric enlarged diameter section 28 includes proximal 30, 36 intermediate, and 40 distal portions. The turns 31 of the wire of the proximal portion 30 of the eccentric enlarged diameter section 28 preferably have diameters that progressively increase distally at a generally constant rate, thus generally giving rise to the shape of a cone. The turns 41 of the wire of the distal portion 40 preferably have diameters that progressively decrease distally at a generally constant rate, thus generally giving rise to the shape of a cone. The turns 36 of the wire of the intermediate portion 35 are provided with gradually changing diameters to provide a generally convex outer surface that is shaped to provide a smooth transition between the proximal and distal tapered portions of the enlarged diameter section 28 of the shaft 20 motor.

At least part of the enlarged diameter eccentric section 28 (preferably the middle part 35) includes an outer surface that can remove tissue. Preferably, the tissue removal surface comprises a coating of an abrasive material 24 to define a tissue removal segment of the motor shaft 20. The abrasive material can be any suitable material, such as diamond powder, fused silica, titanium nitride, tungsten carbide, aluminum oxide, boron carbide, or other ceramic materials. Preferably, the abrasive material is comprised of diamond chips (or diamond dust particles) bonded directly to the turns of the motor shaft 20 by a suitable bonding material 26 (such bonding can be achieved using

ES 2 249 805 T3 well known techniques, such as conventional fusion or electrodeposition technologies (see, for example, US Patent No. 4,018,576). Alternatively, the outer tissue removal surface may simply be a section of the yarn turns that has been roughened to provide a suitable abrasive surface. In still another variation, the outer surface can be etched or cut (eg, laser) to provide small but sharp cutting surfaces. Other similar techniques can also be used to provide a suitable tissue removal surface.

Figures 3-4 illustrate the particular geometry of one embodiment of an enlarged diameter eccentric section 28 of the invention. The elongated motor shaft 20 has an axis 21 of rotation (see FIG. 4) which is coaxial to the guide wire 15 (see FIGS. 3-3E), the guide wire 15 being disposed within the lumen 19 of the motor shaft 20. The proximal portion 30 of the enlarged diameter eccentric section 28 has an outer surface that is defined substantially by the lateral surface of a truncated cone, the cone having an axis 32 that intersects the axis 21 of rotation of the motor shaft 20 at a relatively relatively high angle. small relative to horizontal. Similarly, the distal portion 40 of the eccentric enlarged diameter section 28 has an outer surface that is defined substantially by the lateral surface of a truncated cone, the cone having an axis 42 which intersects the axis 21 of rotation of the motor shaft 20 at a relatively small angle relative to the horizontal The conical axis 32 of the proximal part 30 and the conical axis 42 of the distal part 40 intersect each other and are coplanar to the axis 21 of longitudinal rotation of the motor shaft.

The opposite sides of the cones should generally be at an angle α of between about 10 ° and about 30 ° to each other; preferably the angle α is between about 20 ° and about 24 °, and most preferably the angle α is about 22 °. Furthermore, the tapered axis 32 of the proximal portion 30 and the tapered axis 42 of the distal portion 40 typically intersect the axis 21 of rotation of the drive shaft 20 at an angle β of between about 2 ° and about 8 °. Preferably, the angle β is between about 3 ° and about 6 °. Although in the preferred embodiment shown in the drawings, the angles α of the distal and proximal portions of the enlarged diameter section 28 are generally equal, they need not be equal. The same is true for angles β.

Since the tapered shafts 32 and 42 intersect the axis 21 of rotation of the motor shaft 20 at an angle β, the eccentric section 28 of enlarged diameter has a center of mass that is radially spaced from the axis 21 of longitudinal rotation of the motor shaft 20. As will be described in greater detail below, the displacement of the center of mass with respect to the axis 21 of rotation of the motor shaft endows the enlarged diameter section 28 with an eccentricity that allows it to open an artery to a diameter substantially greater than that of nominal diameter of expanded diameter 28 section.

Figures 3A-3C depict the positions of the centers of mass 29 of three cross sectional units (shown as the cross sectional faces) of the eccentric enlarged diameter section 28. The entire enlarged diameter eccentric section 28 can be divided into many such fine cutting units, each cutting unit having its own center of mass. Figure 3B is taken in a position where the enlarged diameter eccentric section 28 has a maximum transverse diameter (which, in this case, is the maximum diameter of the intermediate portion 35 of the enlarged diameter eccentric section 28), and Figures 3A and 3C are taken, respectively, at the distal and proximal portions 40 of the eccentric enlarged diameter section 28. In each of these transverse cutting units, the center 29 of mass is separated from the axis of rotation of the motor shaft, the axis of rotation of the motor shaft 20 coinciding with the center of the guide wire 15. The center 29 of mass of each cross-sectional unit also generally coincides with the geometric center of such cross-sectional unit. Figure 3B shows the cutting unit having the largest transverse diameter. In this cutting unit, both the center of mass 29 and the geometric center are located farthest (ie, as far apart) from the axis of rotation of the motor shaft. Naturally, the center of mass of the entire enlarged diameter section is a combination of the individual centers of mass of multiple cutting units in the enlarged diameter section, and thus the overall center of mass will be closer to the axis of rotation. of the motor shaft than the center of mass of the cutting unit shown in Figure 3B. Figures 3D-3E illustrate the fact that both the centers 29 of mass and the geometric centers of these cutting units of the motor shaft 20 that are taken both proximally and distally of the eccentric section 28 of enlarged diameter, coincide with the center of the guide wire 15 and, therefore, with the axis of rotation of the motor shaft 20. Thus, such parts of the drive shaft located proximally and distally of the enlarged diameter section 28 are not eccentric (balanced) with respect to the axis of rotation of the drive shaft.

Considering the eccentricity of the enlarged diameter section 28 of the drive shaft, the enlarged diameter section 28 can be geometrically divided into two generally symmetrical lobes, such lobes being on opposite sides of a plane P₁ drawn through the longitudinal axis of rotation and / or the center of mass of the eccentric enlarged diameter section (see Figures 3A - 3C, showing the centers of mass 29 of the individual cutting units) or the point at which the outer surface of the eccentric enlarged diameter section that is farthest from the axis of rotation. A second plane P₂, perpendicular to the first plane P₁ and containing the axis of rotation, divides the enlarged diameter eccentric section 28 into lobes 38 major and 39 minor (located respectively above and below plane P2 in Figures 3A-3C). The larger lobe 38 has a greater mass than the mass of the smaller lobe 39, mainly due to the fact that the larger lobe 38 includes a larger portion of the outer surface area than the smaller lobe 39. Thus, the center of mass of the entire enlarged diameter eccentric section 28 lies within the larger lobe 38. The maximum distance from the axis of rotation of the motor shaft to the outer surface of the larger lobe 38 is greater than the maximum distance from the axis of rotation of the drive shaft to the outer surface of the smaller lobe 39.

ES 2 249 805 T3

It should be understood that, as used herein, the word "eccentric" is intended to refer to either a difference in location between the geometric center of the enlarged diameter section 28 and the axis of rotation of the drive shaft, or a difference in location between the center of mass of the enlarged diameter section 28 and the axis of rotation of the drive shaft. Any such difference, at appropriate rotational speeds, will allow the enlarged diameter eccentric section 28 to open a stenosis to a diameter substantially greater than the nominal diameter of the enlarged diameter eccentric section. Also, for an enlarged diameter eccentric section having a shape that is not a regular geometric shape, the concept of "geometric center" can be approximated by locating the midpoint of the longest chord that is drawn through the axis of rotation. of the drive shaft and connecting two points on a perimeter of a cross section taken at a position where the perimeter of the eccentric enlarged diameter section has its maximum length.

Referring to Figure 5, the elongated drive shaft 20 has proximal and distal sections, located proximally and distally of the enlarged diameter eccentric section 28 of the drive shaft. Except, of course, for the enlarged diameter section 28, the bore 19 of the drive shaft 20 has a generally constant diameter along substantially its entire length. To reduce vibrations that may occur during rotation of the drive shaft 20 and its enlarged diameter eccentric section 28 around the guidewire 15, portions of the drive shaft 20 immediately proximal and distal to the enlarged diameter section 28 are provided with reduced internal diameters. slightly, the reduced diameter portions of the drive shaft thus functioning as bearings to facilitate sufficiently smooth rotation of the drive shaft 20 around the guide wire 15. In Figure 5, the entire distal section 60 of the drive shaft 20 and the proximal section portion 62 are provided with such reduced internal diameters. If desired, the reduced diameter portion can be limited only to the distal segment of the drive shaft 20. It is also possible to limit the reduced diameter portion only to the proximal segment of the drive shaft 20, but it is less desirable. In addition, if desired, more than one such reduced diameter segment could be provided on either side of the enlarged diameter section 28.

A portion of the drive shaft 20 proximal to the enlarged diameter eccentric section 28 may be coated with a thin, flexible, low friction wrap or coating 22. In a preferred embodiment, sheath or liner 22 is long enough so that its proximal end remains disposed within catheter 13, even though drive shaft 20, with its enlarged diameter section 28, has been fully advanced distally with relative to catheter 13. Applicants have successfully used heat shrinkable polyester tubing to make such wrap 22 (available, for example, from Advanced Polymers, Inc. of Salem, New Hampshire). The wrapper or coating 22 can be made from other suitable materials, including, for example, polytetrafluoroethylene compounds.

Figures 6-14A illustrate a series of stages in which the eccentric rotational atherectomy device of the invention is used to open a stenotic lesion to a diameter substantially greater than the nominal diameter of the enlarged diameter eccentric section 28 of the motor shaft 20. .

In Figure 6, the enlarged diameter eccentric section 28 has been advanced over guidewire 15 to a position just proximal to a stenosis in an artery "A", the diameter of the stenosis (defined by plate "P" being ) slightly less than the nominal maximum diameter of the enlarged diameter eccentric section 28 of the motor shaft 20. In Figure 7, the enlarged diameter eccentric section 28 is being advanced along the stenosis, removing a first thin layer of plate "P". As can be seen in Figure 6, guidewire 15 is centered relative to the stenosis, while enlarged diameter section 28 is in its eccentric "at rest" configuration relative to guidewire 15. As described above, in the eccentric "at rest" configuration, both the geometric center and the center of mass of the enlarged diameter section 28 are separated from the center of the guidewire 15 and therefore from the axis of rotation of the shaft. 15 engine. Figures 7 and 7A illustrate that further advancement of the enlarged diameter eccentric section 28 into the stenosis causes the section 28 to deform by the stenosis to a configuration in which the enlarged diameter section 28 becomes substantially symmetrical with respect to the stenosis. thread 15 guide. Thus, in Figures 7-7A, the enlarged diameter section 28 has temporarily changed its shape to a configuration in which its center of mass and its geometric center have moved near the center of the guidewire 15, thereby causing the enlarged diameter section is temporarily balanced substantially (not eccentrically) with respect to guidewire 15 and the axis of rotation of the motor shaft. This change in the configuration of the enlarged diameter section 28 is made possible because the adjacent turns of the wire in the proximal and distal portions 30 of the enlarged diameter section 28 are not clamped together, thus allowing these parts to interlock. flex to the configuration depicted in Figures 7-7A.

In Figure 8, the enlarged diameter eccentric section 28 has completely traversed the stenosis, removing a first layer of the "P" plate of the stenosis. Upon distal exit from the stenosis, the enlarged diameter eccentric section 28 has returned to its eccentric "at rest" configuration.

In Figures 9-9A, the eccentric enlarged diameter section 28 is being withdrawn proximally through the stenosis. During this passage through the stenosis, the internal diameter of plate "P" is greater than the nominal diameter of the enlarged diameter eccentric section 28. However, the enlarged diameter eccentric section 28 of the invention may continue the tissue removal process due to a force pressing the intermediate portion 35 of the enlarged diameter eccentric section 28 laterally against the plate "P". The actual total force F, which presses the rotating enlarged diameter eccentric section 28 against the plate "P", is the sum of two forces, F_c, and F_s (i.e. F_t = F_c + F_s), in which F_t is the total force, F_c is the centrifugal force resulting from the center

ES 2 249 805 T3 of masses of the eccentric section 28 of enlarged diameter that has been displaced from the axis of rotation, and F_s is the lateral elastic force that results from deformation of the proximal and distal portions of the eccentric section 28 of enlarged diameter by the stenosis. The more the eccentric section 28 of diameter enlarged by the plate "P" is deformed into a "symmetric" or "balanced" configuration, the larger F becomes_s. The further the center of mass is from the axis of rotation and the faster the drive shaft and the enlarged diameter eccentric section 28 are rotated, the larger F becomes_c.

In Figure 10, the enlarged diameter eccentric section 28 has again completely traversed the stenosis, removing a second layer of the plate "P" of the stenosis. As it emerges proximally from the stenosis, the enlarged diameter eccentric section 28 is depicted in its eccentric "at rest" configuration.

When the drive shaft 20 is advanced and retracted to successively move the enlarged diameter section 28 along the stenosis, the rotating enlarged diameter eccentric section 28 will continue to remove plaque "P" from the artery "A", opening stenosis to a diameter substantially greater than the nominal diameter of the enlarged diameter section 28. Figures 11-14A show the successive stages of such tissue removal.

In Figure 11, the diameter of the stenosis has been sufficiently increased so that the stenosis no longer deforms the eccentric enlarged diameter section 28, thereby reducing the lateral elastic force Fs to essentially zero and causing the total force pressing the tissue removal surface against plate "P" is essentially equal to the centrifugal force Fc.

In the configuration depicted in Figures 13-13A, the enlarged diameter eccentric section 28 is again in a deformed shape, but this time the deformation is caused by centrifugal force Fc rather than by the wall of the stenosis. In this situation, the lateral spring force Fs is actually negative, since the lateral spring force is directed opposite the centrifugal force Fc. The lateral spring force thus tends to reduce the overall force pressing the tissue removal surface against the "P" plate. When the inner wall of the enlarged diameter eccentric section 28 comes into contact with the guidewire 15, as shown in Figure 13, the operator can detect additional friction between the inner wall and the guidewire 15, signaling the fact that the device has opened the stenosis to a diameter that is approximately the maximum diameter to which the stenosis can be easily opened by the eccentric rotational atherectomy device of the invention.

Figures 14-14A depict the device in a "at rest" position after the stenosis has substantially opened. These figures illustrate the ability of the device to open a stenosis to a diameter well above the nominal diameter of the device.

The degree to which a stenosis can be opened in an artery, to a diameter greater than the nominal diameter of the enlarged diameter eccentric section, depends on several parameters, including the shape of the enlarged diameter eccentric section, the mass of the section eccentric with enlarged diameter, the distribution of that mass and, therefore, the location of the center of mass of this section with respect to the axis of rotation of the motor shaft, and the speed of rotation. Rotational speed is a significant factor in determining the centrifugal force with which the tissue removal surface of the enlarged diameter section is pressed against the stenotic tissue, thus allowing the operator to control the rate of tissue removal. Controlling the speed of rotation also allows, to some extent, to control the maximum diameter to which the device will open a stenosis. Applicants have also found that the ability to reliably control the force with which the tissue removal surface is pressed against stenotic tissue not only allows the operator to better control the rate of tissue removal, but also provides better control of the size of particles being removed.

These advantages over the devices described above in the patents cited in the background section are the result of a different operation of the invention than those devices of the prior art. That is, in Patents 4,990,134 issued to Auth and 5,314,438 issued to Shturman, tissue is removed by a single distal passage of the atherectomy device through the stenosis (although this passage may consist of repeated distal tours of the device), the abrasive surface being mainly on the "front" part of such devices. The pressure of the abrasive surface on the plate in these prior art devices is completely dependent on the distal force applied by the operator. In contrast, Figures 15-16 illustrate the generally spiral path taken by the lateral abrasion device of the invention. The degree of inclination of the spiral path in Figures 15-16 is exaggerated for illustrative purposes; in reality, each spiral path of the enlarged diameter eccentric section 28 removes only a very thin layer of tissue, and the enlarged diameter eccentric section performs many, many such spiral steps as the device is repeatedly moved back and forth along stricture to fully open the stricture. Figure 15 schematically shows three different rotational positions of the enlarged diameter eccentric section 28 of a rotational atherectomy device of the invention. In each position, the abrasive surface of the enlarged diameter eccentric section 28 comes into contact with the plate "P" to be removed (the three positions are identified by three different points of contact with the plate "P", being designated those points in the drawing as points B1, B2 and B3). Note that at each point it is generally the same part of the abrasive surface of the eccentric enlarged diameter section 28 that comes into contact with the tissue (the part of the abrasive surface that is radially most distant from the axis of rotation of the motor shaft). .

ES 2 249 805 T3

While not wishing to be limited to any particular theory of operation, Applicants believe that displacement of the center of mass with respect to the axis of rotation produces an "orbital" motion of the enlarged diameter section of the drive shaft, the diameter of the drive shaft being controllable. "Orbit" by varying the speed of rotation of the motor shaft. It has not been determined whether the "orbital" motion is as geometrically regular as shown in Figures 15-16 or not, but applicants have empirically demonstrated that by varying the rotational speed of the drive shaft, the centrifugal force pressing the shaft can be controlled. tissue removal surface of the eccentric enlarged diameter section against the surface of the stenosis. Centrifugal force can be determined according to the formula

F_c = m Δχ (π n / 30)² in which F_c is the centrifugal force, m is the mass of the eccentric section with enlarged diameter, Ax is the distance between the center of mass of the eccentric section with enlarged diameter and the axis of rotation of the motor shaft, and n is the speed of rotation in revolutions per minute (rpm). The graph shown in Figure 17 illustrates the calculations of the maximum centrifugal force Fc with which a tissue removal surface of an enlarged diameter eccentric section, having a maximum diameter of approximately 1.75 mm, can be pressed against a surface. of a stenosis at rotational speeds of up to approximately 200,000 rpm. Controlling this force Fc provides control over how quickly the tissue is removed, control over the maximum diameter to which the device will open a stenosis, and improved control over the particle size of the tissue being removed.

Using the rotational atherectomy device of the invention, the operator repeatedly moves the enlarged diameter eccentric section 28 distally and proximally through the stenosis. By changing the speed of rotation of the device, you can control the force with which the tissue removal surface is pressed against the stenotic tissue, thus being able to better control the rate of plaque removal as well as the particle size of the plaque. tissue removed. Since the stenosis is opening to a diameter greater than the nominal diameter of the enlarged diameter section, the cooling solution and blood can constantly flow around the enlarged diameter section. Such a constant flow of blood and cooling solution constantly expels the removed tissue particles, thus providing a more uniform release of the removed particles than with the Auth and Shturman devices cited above.

Figure 18 represents the experimental data of an enlarged diameter eccentric section having a nominal diameter of 1.57 mm that is used to open a conduit in calcite (a rock that is predominantly composed of CaCO₃) at a rotational speed of approximately 180,000 rpm. The experiment was started on test rocks having 10 mm long conduits with 1.6 mm diameters. The dots and squares represent two data sets from two independent tests, and show that the enlarged diameter eccentric section, which has a nominal diameter of 1.57mm, could open the conduit to a diameter of approximately 2.3mm. The data illustrates the time dependence of the procedure, that is, an operator can control the diameter to which the stenosis will open by controlling the length of time that the eccentric enlarged diameter section is rotated within the stenosis. The data also illustrates the ability of the device to open a stenosis to a diameter substantially greater than the nominal diameter of the enlarged diameter eccentric section.

Figure 19 illustrates the flexibility of the enlarged diameter eccentric section 28 of the invention. In the embodiment shown in this drawing, adjacent yarn turns of the intermediate portion 35 of the eccentric enlarged diameter section of the drive shaft are held together by the bonding material 26 that holds abrasive particles 24 to the yarn turns 36. The adjacent yarn turns of the proximal and distal portions 30 of the enlarged diameter eccentric section of the drive shaft are not clamped together, thus allowing such portions of the drive shaft to flex, as shown in the drawing. Such flexibility facilitates advancement of the device through relatively winding conduits. If desired, adjacent yarn turns of even the middle portion 35 of the enlarged diameter eccentric section 28 of the drive shaft may not be clamped together, thus providing even greater flexibility.

Helically wound multi-wire drive shafts that can be used in the invention can be made by winding suitable wires around a mandrel. Figure 20 depicts a mandrel 50 that may be used to fabricate the enlarged diameter eccentric section 28 of the atherectomy device depicted in Figures 2-5. The mandrel 50 includes a mandrel shaft 52 having a generally constant diameter along its entire length. An enlarged diameter eccentric chuck component 54 may be machined from a suitable material, such as brass (for example, the round brass rod sold by Vincent Metals of Minneapolis, Minnesota as "low lead" brass rod. which is made up of 62.0% copper, 36.2% zinc and 1.8% lead, or the “high speed, no cut” brass rod which is made up of 61.5% copper, 35.5% zinc and 3.0% lead). The enlarged diameter eccentric component 54 is disposed on the mandrel shaft 52 at the desired location and is then held in place with a suitable material, such as solder 56. Preferably, the composition of the solder is 61% of tin and 39% lead. The flux used to weld the enlarged diameter eccentric component 54 to the mandrel shaft 52 is preferably 75% ZnCl₂ and 25% NH₄Cl, these compounds dissolving in distilled water at maximum concentration (that is, producing a saturated solution). The weld joint can be further machined or sanded to achieve a smooth transition between the enlarged diameter eccentric component 54 and the mandrel shaft 52.

ES 2 249 805 T3

After the mandrel 50 is thus constructed, suitable threads may be wound around the mandrel 50, including both the mandrel shaft 52 and the enlarged diameter eccentric component 54. Before the tension on the wires has been released, a clamp 72 (shown in Figures 21-24) is clamped onto the drive shaft at the appropriate location. The jaw includes a jaw structure 72 with a slot 73, two sets of clamping blocks 74 and 75, and a pair of set screws 78. Clamping of the jaw onto the drive shaft is accomplished by first passing the drive shaft through the slot 73 in the jaw frame 72, then by positioning the clamping blocks 74 and 75 around the drive shaft 20 and moving them toward the jaw structure 72, and finally tightening the set screws 78 to firmly tighten the drive shaft with the enlarged diameter eccentric section 28 between the clamping blocks 74 and 75. Once the set screws 78 have been tightened, the winding tension on the wires of the motor shaft can be released. Those parts of the drive shaft wires not captured by the jaw will unwind to a diameter slightly larger than that of the mandrel, but the jaw will prevent such unwinding of the entire portion of the drive shaft located between the two sets of clamping blocks 74 and 75 . Clamping blocks 74 and 75 are preferably made from a relatively ductile metal such as nickel.

Figure 22 illustrates in longitudinal section section how the motor shaft 20 is tightened by the clamping blocks 74 and 75. In Figures 22 and 23, the parts of the drive shaft not captured by the jaw are shown as having been unwound to a diameter greater than the diameter of the portion captured by the jaw. However, Figure 23 significantly exaggerates the degree of unwinding; normally the outer diameter of the drive shaft, as a result of unwinding, will only increase by about 2-10%.

Once the jaw has been attached to the drive shaft and the parts not captured by the jaw have been allowed to unwind to a slightly larger diameter, then the distal length of the drive shaft, along with the jaw, are heat treated to facilitate the threads of the motor shaft the desired "residual deformation". Only the distal length of the motor shaft, including the motor shaft section that is distal to the enlarged diameter section 28, the enlarged diameter section 28 itself, and approximately 80 mm of the length of the motor shaft proximal to the eccentric diameter section 28 expanded need to be placed in the heat treatment furnace.

Preferably, the heat treatment is in the range of about 500 ° C to about 560 ° C for about 30-60 minutes, to provide the yarns with the desired set-up. The particular temperature selected will depend on the maximum diameter of the enlarged diameter eccentric section. Applicants have successfully used stainless steel with a diameter of about 0.006 inches for drive shafts having enlarged diameter eccentric sections with diameters up to about 2.2 mm. Applicants have successfully used Type 304 stainless steel available from Fort Wayne Metals Research Products Corp. (Fort Wayne, Indiana) under the name "Hyten." Preferably, the yarn has a tensile strength of about 445 ± 10 ksi.

After the heat treatment is complete and both the drive shaft 20 and the jaw have cooled, the drive shaft is removed from the jaw. Then, the mandrel 50 is removed from the drive shaft. Applicants have found that the mandrel 50 can be removed by constructing the components of the mandrel 50 from materials other than the drive shaft thread, so that the components of the mandrel can be dissolved in appropriate solutions that do not adversely affect the materials of the drive shaft itself. . For example, the mandrel shaft 52 can be made from high carbon steel, the enlarged diameter eccentric portion 54 from brass (as described above), and the helically wound wire from stainless steel wire. "Hyten" mentioned above. The entire drive shaft, along with the mandrel 50, is immersed in a 15% solution of hot nitric acid (typically about 80-100 ° C) for about 8-10 hours until the mandrel shaft 52 is completely dissolved. Applicants have found that the process of dissolving the mandrel shaft 52 is usually complete when gas bubbles no longer rise to the surface of the nitric acid. As with the heat treatment process described above, preferably the drive shaft is kept generally straight when immersed in the hot nitric acid. Alternatively, the drive shaft can be wound, but preferably the diameter of the coil should not be less than about seven or eight inches in that case, because the heat from this process can also affect the shape of the drive shaft.

Once the mandrel shaft 52 has dissolved, the distal portion of the drive shaft, along with the enlarged diameter portion 54 of the mandrel (which has not yet dissolved), preferably including at least a short section of the proximal drive shaft The enlarged diameter section is immersed in a hot 35% nitric acid solution (typically about 80-100 ° C) for 8-10 hours to dissolve the enlarged diameter portion 54 of the mandrel and the weld 56.

Immediately after removing the drive shaft from its second nitric acid dip, the drive shaft is washed for several minutes under running water. The motor shaft is then placed in boiling distilled water for 15-20 minutes and then immersed in 96% alcohol and air dried or wiped with a clean cloth.

Following these procedures, the entire drive shaft can be heat treated a second time at temperatures ranging from 200 to 300 ° C to relieve tension in the yarn turns of the drive shaft. The drive shaft is then finished by electropolishing.

ES 2 249 805 T3

If desired, the eccentricity of the enlarged diameter section can be increased by placing the enlarged diameter section in a mold having the desired shape and then heat treating the enlarged diameter section to give it the new, more eccentric shape. Alternatively, the enlarged diameter section can be initially constructed by winding the wire around a mandrel having an enlarged diameter symmetric (i.e. non-eccentric) component, placing the resulting enlarged diameter symmetric section in an eccentric mold and heat treating the diameter section enlarged to give it the desired eccentric shape.

The above procedures can be used to fabricate eccentric atherectomy devices for various desired diameters. Since, as described above, the eccentricity of the enlarged diameter section depends on several parameters, the applicants have found that the following design parameters can be considered with regard to the distance between the axis of rotation of the motor shaft and the geometric center of a face of a cross section, taken at a position of maximum cross diameter of the eccentric enlarged diameter section: For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.0mm and about 1.5mm, desirably the geometric center should move away from the axis of rotation of the drive shaft by a distance of at least about 0.02mm and preferably a distance of at least about 0.35mm; For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.5mm and about 1.75mm, desirably the geometric center should be separated from the axis of rotation of the motor shaft by a distance of at least 0.05mm, preferably a distance of at least about 0.07mm, and most preferably a distance of at least about 0.09mm; For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.75mm and about 2.0mm, desirably the geometric center should move away from the axis of rotation of the drive shaft by a distance of at least about 0.1mm, preferably a distance of at least about 0.15mm and most preferably a distance of at least about 0.2mm; and for a device having an enlarged diameter eccentric section with a maximum transverse diameter greater than 2.0mm, desirably the geometric center should move away from the axis of rotation of the motor shaft a distance of at least about 0.15mm, preferably a distance of at least about 0.25 mm and most preferably a distance of at least about 0.3 mm.

Design parameters can also be based on the location of the center of mass. For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.0 mm and about 1.5 mm, desirably the center of mass should be away from the axis of rotation of the drive shaft by a distance of at less about 0.013mm and preferably a distance of at least about 0.02mm; For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.5mm and about 1.75mm, desirably the center of mass should be offset from the axis of rotation of the drive shaft by a distance of at minus 0.03mm and preferably a distance of at least about 0.05mm; For a device having an enlarged diameter eccentric section with a maximum transverse diameter of between about 1.75mm and about 2.0mm, desirably the center of mass should move away from the axis of rotation of the motor shaft by a distance of at minus about 0.06mm and preferably a distance of at least about 0.1mm; and for a device having an enlarged diameter eccentric section with a maximum transverse diameter greater than 2.0mm, desirably the center of mass should move away from the axis of rotation of the drive shaft by a distance of at least about 0.1mm. and preferably a distance of at least about 0.16mm.

Preferably, the design parameters are selected so that the enlarged diameter section is eccentric enough so that, when rotated on a stationary guidewire (held tight enough so that any substantial movement of the guidewire is prevented) at a speed of rotation not more than 60 rpm, at least a portion of its tissue removal surface rotates through a path (whether or not such a perfectly regular or circular path) that has a diameter greater than the maximum nominal diameter of the enlarged diameter eccentric section (for example, for an enlarged diameter section having a maximum diameter of between about 1.5mm and about 1.75mm, at least a portion of the tissue removal section must rotate through a path having a diameter at least 10% greater than the maximum nominal diameter of the enlarged diameter eccentric section, preferably at least about 15% greater than the maximum nominal diameter of the enlarged diameter eccentric section and most preferably at least about 20% greater than the maximum nominal diameter of the enlarged diameter eccentric section; For an enlarged diameter section that has a maximum diameter of between about 1.75mm and about 2.0mm, at least a portion of the tissue removal section must rotate through a path that has a diameter of at least one 20% larger than the maximum nominal diameter of the enlarged diameter eccentric section, preferably at least about 25% greater than the maximum nominal diameter of the enlarged diameter eccentric section and most preferably at least about 30% greater than the maximum nominal diameter of the enlarged diameter eccentric section; and for an enlarged diameter section that has a maximum diameter of at least about 2.0mm, at least a portion of the tissue removal section must rotate through a path that has a diameter at least 30% greater than the maximum nominal diameter of the enlarged diameter eccentric section and preferably at least about 40% greater than the maximum nominal diameter of the enlarged diameter eccentric section).

Preferably, the design parameters are selected so that the enlarged diameter section is eccentric enough that, when rotating on a stationary guidewire at a speed between about 20,000 rpm and about 200,000 rpm, at least a portion of its surface will broken tissue removal

ES 2 249 805 T3 through a path (whether or not such a perfectly regular or circular path) is substantially greater than the maximum nominal diameter of the enlarged diameter eccentric section. Desirably, such path is at least about 30% greater than the maximum nominal diameter of the enlarged diameter eccentric section, preferably the path is at least about 50% greater than the maximum nominal diameter of the enlarged diameter eccentric section. , and most preferably the path is at least about 70% greater than the maximum nominal diameter of the enlarged diameter eccentric section.

Figures 25-25C depict a modified embodiment of an enlarged diameter eccentric section 128 of the invention. (Reference numerals in Figures 25-30 are in the 100 series, but otherwise generally correspond to those used in Figures 1-24). The general shape, and in particular, the longitudinal section profile of the enlarged diameter eccentric section 128, are substantially similar to the general shape and longitudinal section profile of the enlarged diameter biconical eccentric section 28 of Figures 3-4. . The proximal and 140 distal portions 130 of the enlarged diameter eccentric section 128 are substantially equal in length and mirror images of each other, being generally symmetrical with respect to a plane passing through the intermediate portion 135 of the eccentric section 128 of enlarged diameter and is generally perpendicular to the axis of rotation of the motor shaft. The difference between the enlarged diameter eccentric section 128 and the enlarged diameter eccentric section 28 can be seen by comparing the cross-sectional profiles of the proximal and distal portions 130 of the enlarged diameter eccentric section 128 (shown in Figures 25A and 25C ) with cross-sectional profiles of corresponding parts of enlarged diameter eccentric section 28 (shown in Figures 3A and 3C).

The three-dimensional shape of the enlarged diameter eccentric section 128 can be more easily understood with reference to Figures 26-27, which illustrate a mandrel 150 that can be used in the manufacture of the drive shaft 120 and the enlarged diameter eccentric section 128. Chuck 150 includes a round chuck shaft 152 and an enlarged diameter eccentric component 154. The enlarged diameter eccentric component 154 is secured to the mandrel shaft 152 with a suitable material, such as weld 156. All materials used in the manufacture of the mandrel components 150 may be the same materials used to manufacture the corresponding components of the mandrel. mandrel described above and shown in figure 20.

Figures 28-30 illustrate a preferred method of machining an enlarged diameter eccentric component 154 of mandrel 150. These figures are also helpful in understanding the three-dimensional shape of the enlarged diameter eccentric component 154 and the corresponding three-dimensional shape of the section. 128 enlarged diameter eccentric shaft 120 motor.

As with the proximal and distal portions of the enlarged diameter eccentric section 128, the corresponding proximal and distal portions of the extended diameter eccentric component 154 of the mandrel are not equal in length but are essentially mirror images of each other. Each part has an outer surface comprised of at least two areas, a first of the two areas being substantially defined by a lateral surface of a first truncated cone 157 and a second of the two areas being substantially defined by a lateral surface of a second cone 158 truncated. The junction of the conical surfaces of the first and second cones is shown as a line 159 in Figure 26. Section views 25A-25K also illustrate the surfaces of these cones. Both of the first cones 157 of the proximal and distal portions of the enlarged diameter eccentric component 154 have a common axis 170 (shown in Figures 27-30), which coincides with the axis of rotation of the motor shaft 120. Both second cones 158 of the proximal and distal portions of the enlarged diameter eccentric component 154 also have a common axis 180 (shown in Figures 27 and 29-30) that is parallel to and spaced from the common axis 170 of the first cones 157 and , therefore, of the axis of rotation of the motor shaft 120. The center bases of the second cones 158 of both the proximal and distal portions of the enlarged diameter eccentric component 154 have diameters that are generally equal to each other. These diameters are also equal to the diameter of the cylinder that substantially defines the outer surface 155 of the intermediate portion of the enlarged diameter eccentric component 154. The axis of this cylinder coincides with the common axis 180 of the second cones 158, thus placing the axis of the cylinder parallel to and separated from the axis of rotation of the motor shaft 120. The shape of the cylinder can be modified, if desired, so that the corresponding intermediate portion of the eccentric enlarged diameter section has a surface that is shaped to provide a smooth transition between the surfaces of the proximal and distal portions of the cylinder. eccentric section of enlarged diameter.

As mentioned above, Figures 28-30 illustrate a preferred method of machining the enlarged diameter eccentric component 154 of the mandrel. Preferably, the enlarged diameter eccentric component 154 is machined from approximately 8mm brass brace rod using a twin spindle computer numerically controlled (CNC) lathe center. It is important that the rotation of both spindles be synchronized to ensure that both proximal and distal portions of the mandrel enlarged diameter eccentric component 154 represent mirror images of each other. The “220 CNC” lathe center sold by Schaublin (Switzerland) and the “CNC 230” lathe center sold by Ebosa (Switzerland) are both suitable for this purpose. The brass brace rod 190 is first rotated about an axis 170 and a cutting element 195 is moved along a path, the result of which is to give the brace 190 the combination of shapes 157 conical and 155 cylindrical. shown in figure 28. Brace 190 is automatically reassembled on the CNC lathe center so that it can be rotated about a second axis 180, parallel but spaced from the first axis 170, as shown in Figures 29-30 (eccentric component 154 enlarged diameter mandrel is shown rotated 180 degrees in Figure 30 from the position shown in Figure 29). The cutting element 195 moves

ES 2 249 805 T3 then along a second path, the result of which is to add the second conical profile 158, resulting in the shape shown in Figures 26-27. Preferably, the angle γ formed between the lateral surface of the first cone 157 and the axis 170 of the first cone 157 is greater than the angle φ formed between the lateral surface of the second cone 158 and the axis 180 of the second cone 158. The result of this reproducible machining process is an enlarged diameter eccentric component 154 that can be used to fabricate the enlarged diameter eccentric section 128 of the atherectomy device depicted in Figures 25-25C.

Figures 31-33 depict another variation of the inventive enlarged diameter eccentric section 228 and an enlarged diameter eccentric component 254 of a mandrel 250 for fabricating the drive shaft of the invention. (Reference numerals in Figures 31-33 are in the 200 series, but otherwise generally correspond to those used in Figures 1-24 and Figures 25-30).

Both the longitudinal and cross sectional profiles of the enlarged diameter eccentric section 228 are slightly different from the corresponding profiles of the enlarged diameter eccentric sections 28 and 128 described above. The relatively small differences between the three-dimensional shape of the enlarged diameter eccentric section 228 and the three-dimensional shapes of the enlarged diameter eccentric sections 28 and 128 can be better understood by referring to Figures 31-31C, which show the diameter eccentric section 228. enlarged and referring to Figures 32-33, which show chuck 250 for manufacturing the drive shaft. As can be seen from Figures 31-33, the proximal and 240 distal portions 230 of the enlarged diameter eccentric section 228 each have an outer surface that is comprised of at least two areas, a first of which is defined. the two areas being defined substantially by a lateral surface of a cone and a second of the two areas being defined substantially by a lateral surface of a cylinder. Figures 32-33 show that the cones 257 of both the proximal and distal portions of the enlarged diameter eccentric component 254 of the mandrel 250 have a common axis 221 that coincides with the axis of rotation of the motor shaft. The intermediate portion 235 of the enlarged diameter eccentric section 228 has an outer surface that is defined substantially by a lateral surface of a cylinder, which has an axis that is parallel to and spaced from the axis of rotation of the drive shaft. The same cylinder that defines the outer surface of the intermediate portion 235 of the enlarged diameter eccentric section 228 also defines cylindrical areas of the outer surfaces of both the proximal and distal 230 portions 230 of the enlarged diameter eccentric section 228. The junction of the cylindrical surface with the proximal and distal conical surfaces is shown as lines 259 in Figure 32. Again, the geometric shape of cones 257 and cylinder 258, as well as the fact that axis 280 of cylinder 258 is parallel to and spaced from common axes 270 of cones 257, can be better understood with reference to the figures 32-33, showing mandrel 250 and its various cross sections.

As with the proximal and distal portions of the mandrel enlarged diameter eccentric component 254, the corresponding proximal and distal portions of the motor shaft enlarged diameter eccentric section 228 are not equal in length but are also essentially mirror images of each other.

Figures 34-34E depict yet another variation of the enlarged diameter eccentric section of the invention. (Reference numerals in Figures 34-34E are in the 300 series, but again and otherwise generally correspond to those used in Figures 1-33). As can be seen (particularly in the cross-sectional sections shown in Figures 34A-34C), the larger lobe 338 of the enlarged diameter eccentric section 328 extends laterally significantly further from the axis of rotation of the motor shaft than larger lobes of the enlarged diameter eccentric sections 28, 128 and 228 described above, thus providing a substantially elongated shape to the cross-sectional sections shown in Figures 34A-34C. The center of mass 329 of each cross-sectional unit (and the center of mass of the entire enlarged diameter section 328) is further spaced from the axis of rotation of the drive shaft than are eccentric enlarged diameter sections 28, 128, and 228. Obviously, the further the center of mass is separated from the axis of rotation, the more eccentric is the rotational atherectomy device of the invention. For an enlarged diameter eccentric section 328 having an elongated shape, the eccentricity can be quantified by referring to a chord of maximum length (i.e., the longest chord, coinciding with plane P1 in Figure 34B), drawn through of the axis of rotation of the motor shaft, the chord connecting two points on a perimeter of a cross-sectional section taken at a position where the perimeter of the enlarged diameter section 328 has its maximum length. The midpoint of this chord of maximum length is spaced from the axis of rotation of the drive shaft and, in Figure 34B, substantially coincides with the center 329 of mass of the cross-cutting unit. For an enlarged diameter eccentric section 328 having a maximum chord length between about 1.5mm and about 1.75mm, the midpoint of the chord is desirably spaced from the axis of rotation of the drive shaft by a distance of at least about 0.07mm, preferably a distance of at least about 0.1mm and most preferably a distance of at least about 0.13mm; For an enlarged diameter eccentric section 328 having a maximum chord length of between about 1.75mm and about 2.0mm, the midpoint of the chord is desirably spaced from the axis of rotation of the motor shaft by a distance of at least about 0.15mm, preferably a distance of at least about 0.2mm and most preferably a distance of at least about 0.25mm; and for an enlarged diameter eccentric section 328 having a maximum chord length of at least 2.0mm, the midpoint of the chord is desirably spaced from the axis of rotation of the motor shaft by a distance of at least about 0, 3mm, preferably a distance of at least about 0.35mm and most preferably a distance of at least about 0.4mm.

ES 2 249 805 T3

In the embodiments shown in Figures 1-34, the abrasive surface of the eccentric enlarged diameter section is disposed around both the major and minor lobes and, in all of these embodiments, the abrasive surface of the major lobe is preferably longer longitudinally than the abrasive surface of the minor lobe. In the embodiment shown in Figure 35, the abrasive surface of the enlarged diameter eccentric section 28 of the drive shaft 20 is disposed substantially only over the major lobe, defining a tissue removal segment that does not extend the entire distance around eccentric section 28 of enlarged diameter. Such asymmetric location of the abrasive surface around the enlarged diameter section is possible because normally only a portion of the abrasive surface of the larger lobe performs almost all of the tissue removal.

Although most of the drawings illustrate the abrasive surface defining a tissue removal segment of the drive shaft to be contained in the middle of the enlarged diameter section of the drive shaft, the abrasive surface can also be extended, if used. desired, in the proximal and distal portions of the enlarged diameter section.

The invention has been described with reference to a rotational atherectomy device consisting of a helically wound motor shaft with an enlarged diameter eccentric section. However, the eccentric tissue removal device concept could be applied to other types or forms of rotational atherectomy devices, as shown in Figures 36-41, with respect to a rotational atherectomy device comprising a motor shaft 420. helically winding of generally constant diameter (i.e. without an enlarged diameter section) having an abrasive surface formed by electrodeposition of abrasive particles 424 on the motor shaft 420. (Reference numerals used in Figures 36-41 are in the 400 series, but again and otherwise generally correspond to those used in Figures 1-35). As shown in the figure in Figure 36, the tissue removal section 428 of the motor shaft 420 can be made eccentric simply by forming a short length of the motor shaft with an axis that is parallel but slightly offset from the axis. (and hence the axis of rotation) of the remainder of the motor shaft 420. Shaping the drive shaft can be accomplished by winding a straight drive shaft, placing it in a mold or die with the appropriate shape, and heating it for an appropriate period of time at a suitable temperature to give the drive shaft the new shape. Typically, displacement of the axis of the tissue removal section will cause the center of mass of the tissue removal section 428 to be offset relative to the axis of rotation of the drive shaft 420. Electrodeposition of abrasive particles 424 on only one side of the tissue removal section 428 (or removal of abrasive material from one side of the tissue removal section 428), as shown in Figure 36, will further increase the performance. eccentricity of the atherectomy device of the invention. Thus, in such a device, a face of a cross-sectional section (such as FIG. 36B) of the tissue removal section 428 has a geometric center that is axially spaced from the axis of rotation of the drive shaft 420. Such a device has an extremely low profile, and can still open a stricture to a diameter greater than the nominal diameter of the device. Figures 37-40A illustrate the multiple forward and backward movements of the eccentric tissue removal section 428 in rotation along a stenosis, thus demonstrating that the use of the device shown in Figures 36-36C is substantially the same. than the device having an enlarged diameter eccentric section 28 (shown in use in Figures 6-14A).

Alternatively, the tissue removal section 428 of the motor shaft 420 having an abrasive surface can be made eccentric by adding mass to one side (such as by abrasive coating material 424 only on one side of the tissue removal section 428) and / or removing mass from only one side (such as reducing helically wound wire 418 on one side), both techniques being illustrated in Figure 41. Reduction of the helically wound yarn on one side of the tissue removal section 428 can be accomplished, for example, by electropolishing or grinding.

In yet another application of the invention, FIG. 42 illustrates a rotational atherectomy device employing an eccentric tissue removal drill 528 attached to a flexible drive shaft 520, which is rotated on a guidewire 515. The eccentric tissue removal drill 528 has a coating of abrasive particles 524 attached to a portion of its outer surface by a suitable bonding material 526. As with the other embodiments described above, the eccentricity of the bore 528 can be achieved by positioning the center of mass offset from the axis of rotation, positioning the geometric center offset from the axis of rotation, or a combination of these techniques. Preferably, the center of mass of the eccentric tissue removal bore 528 is radially spaced from the drive shaft by a distance of about 0.02 mm, and preferably the geometric center of the eccentric tissue removal bore 528 is axially spaced from the axis of rotation a distance of at least about 0.035mm.

Although a preferred embodiment of the present invention has been described, it should be understood that various changes, adaptations and modifications can be made without departing from the scope of the appended claims.