ANGIOPLASTY DILATING GUIDE WIRE

Abstract: A dilating guide wire (12) for use in percutaneous transluminal angioplasty has a very small outside diameter which permits it to be used advantageously with a percutaneous transluminal coronary angioplasty (PTCA) catheter for treatment of very tight stenoses in the coronary arteries that cannot be treated by conventional PTCA catheters alone. The dilating guide wire (12) is small enough to pass through the lumen of the PTCA catheter and extend beyond the distal tip thereof for predilating the stenosis to open it sufficiently for subsequent crossing and dilation by the PTCA catheter. The small dimensions of the vent path (16) in the core (14) result in self-sealing of the vent (16) with respect to inflation fluid. A control handle (65) is provided for selectively imparting an axial force to the balloon (20) of the dilating guide wire (12) to cause axial stretching thereof, thereby reducing its profile and facilitating withdrawal of the balloon (20).

Description: ANGIOPLASTY DILATING GUIDE WIRE Field of the Invention This invention pertains to the field of angioplasty, and particularly to the field of per¬ cutaneous transluminal angioplasty. Background of the Invention Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating certain types of vascular diseases. In par¬ ticular, angioplasty is widely used for opening of ste¬ noses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system. Treatment and opening of the stenosis is effected by maneuvering a catheter having an inflatable balloon area near its tip through the vascular system to position the inflatable balloon at the site of the ste¬ nosis. The balloon is then inflated to cause stretching of the artery and pressing of the lesion into the artery wall to reestablish acceptable blood flow to the artery. Guide wires are often used for establishing the path to the stenosis so that the dilating catheter can subsequently be positioned. In percutaneous transluminal coronary angioplasty (PTCA), a steerable guide wire and PTCA catheter may be introduced into the vascular system at a site remote from the stenosis through a guiding catheter and delivered to either the left or right coro¬ nary ostia (entrance to the left and right coronary artery) by that guiding catheter. The guide wire is then maneuvered into the branch of the coronary artery for which treatment is intended. After the guide wire has been advanced past the lesion to be treated, the PTCA catheter is then positioned with its hollow central lumen at the distal tip over the end of the guide wire which is outside the body. With the guide wire held in place, the dilating catheter is then advanced over the guide wire to bring the inflatable balloon portion to the lesion. Thereafter, fluid pressure is applied through external apparatus connected to the catheter to inflate the balloon. Various problems may be encountered in the above-described angioplasty procedure. One problem which occurs in the case of very tight stenoses with small openings is the inability to advance the dilating catheter across the stenosis after the guide wire has been successfully positioned. Since the tip of the dilating catheter has a significantly greater diameter than the guide wire, there is a practical limit to treatment of such small, tight stenoses using translu¬ minal catheters. Efforts to reduce the diameter of the transluminal catheter are limited by the size of the guide wire. Since a clearance is required to allow the guide wire to pass with relatively minimal frictional resistance, one lumen of the transluminal design must have a diameter of at least .002 inch greater than the guide wire to be functional. Guide wires are available in sizes ranging from .012 inch to .018 inch in diameter. Reduced diameter guide wires have less axial strength, which may make them subject to buckling as they are being advanced, and reduced torsional stiff¬ ness, which makes them more difficult to steer and control during insertion. In addition, very small diameter guide wires might under some circumstances create a risk of injury to the blood vessels because the applied axial force is concentrated over a small tip area, which could create a risk of puncturing the artery and creating false lumens. The standard PTCA catheter, which is passed over the guide wire, is limited in size by the need to allow adequate diametral clearance bet- ween the guide wire and the inner diameter of the PTCA through channel. Another device used in coronary angioplasty is a catheter in which a balloon is installed on a wire with a spring tip. This type of catheter offers slightly lower profiles than a transluminal design, but unlike the transluminal design cannot be used in con¬ junction with a conventional guide wire. Like a stan¬ dard guide wire, the tip of these catheters are shaped in order to try to navigate the path from the right or left ostia to and past the vessel to be treated. The primary difficulty associated with this type of device is the inability to duplicate the performances of con¬ ventional guide wires, particularly the torsional and axial stiffness, as well as the tip flexibility and smoothness of wire transition from the core to the tip safety wire (which secures the spring tip). The second drawback of this type of device is the fact that when catheter balloon size changes are required because of the extreme difficulty of accurately estimating the artery and occlusion sizes, the entire coronary arterial path must be renegotiated with the next catheter since no guide wire is in place reserving an easily renego¬ tiated path. Once the path has been established, it is highly desirable that the path be maintained, yet the use of single lumen systems requires loss and reestablishment of the the path. Because of these and other problems as outlined above, there is still a need in the field of angioplasty for effective treatment of very tight steno¬ ses with very small openings which cannot be crossed by present angioplasty catheters. Of course, it is highly desirable to be able to treat the small stenosis through percutaneous coronary angioplasty techniques, since the alternative is surgical bypass grafting techniques. -4- Summary of the Invention The present invention provides a dilating guide wire that overcomes the problems encountered in the catheters described above. The dilating guide wire of the present invention is adapted for use in conjunction with a conventional guide wire and dilating catheter for dilatation of very tight stenoses which can then be subsequently treated with the conventional angioplasty catheter, use of the present invention does not require loss and reestablishment of the path to the stenosis site. This is accomplished by passing the dilating guide wire through the conventional catheter while it is held in place with its tip immediately proximal the site of the stenosis. The dilating guide wire of the present inven¬ tion is configured with an extremely low profile, i.e., a very small diameter, so that it can successfully be advanced and withdrawn through the central lumen of a coaxial conventional angioplasty catheter. Special means are provided for axially extending the balloon segment of the dilation guide wire to flatten the balloon to reduce its profile. This is especially important in allowing the tip to be drawn back into the tip of the conventional dilating catheter at the end of the dilata¬ tion, and avoids bunching-up of the dilating balloon which might otherwise occur and prevent withdrawal. According to another feature of the invention, special means are provided in the form of a hollow core for removal of air from the dilating balloon during pre¬ paration with radiopa ue liquid and which self-seals during pressurization with the liquid during balloon inflation. According to another feature of the invention, axial stretching of the tip provides a deflection thereof which can be used for steering during posi¬ tioning of the dilating tip. According to another feature of the invention, the central hollow core of the catheter is provided in a stepped configuration with the distal tip section which is extended into the coronary arteries from the PTCA having a smaller outer diameter and cross-sectional area than the main body of the core which is contained within the PTCA. This feature provides an extremely flexible member which is relatively non-traumatic to the coronary artery. This feature also contributes to the next features of this invention. According to another feature of this inven¬ tion, the inner diameter of the catheter inflation lumen is stepped to provide optimum hydraulic clearance which is intended for the purpose of providing an acceptable deflation time (time required to remove the entire volume of radiopaque fluid from the balloon after dila¬ tation has been completed, thus restoring blood flow through the dilated channel) after the application of an 80% or greater vacuum. The stepped features of both the central core and the catheter tubings combined provide both the hydraulics and the profile requirement needed to provide a central balloon profile of approximately .020 inches. According to another feature of the invention, the inner diameter of the core provides an origination point and structural support for the spring tip safety system. Brief Description of the Drawing In the drawings, FIGURE 1 is a view of a dilating guide wire according to the present invention including its control manifold assembly, portions thereof broken away for pur¬ poses of this illustration; FIGURE 2 is a schematic cross-sectional repre¬ sentation, at an enlarged scale, of a portion of the dilating guide wire of Figure 1 illustrating certain features thereof; FIGURE 3 is a partially cut-away view at an enlarged scale of the tip portion of the dilating guide wire of Figure 1; FIGURES 3A and 3B are sections taken as indi¬ cated along the tip portion of Figure 3; " FIGURE 4 is a fragmentary view in perspective of a portion of the control manifold assembly of Figure 1; FIGURE 5 is a sectional view taken along the center axis of the apparatus of Figure 3 with the control knob removed; FIGURE 6 is a view of a dilating guide wire according to the present invention extending through a PTCA catheter with which it is advantageously used, including control manifolds for both the dilating guide wire and the PTCA; FIGURE 7 is a schematic representation of the use of the dilating guide wire according to the pre¬ sent invention in conjunction with a PTCA catheter for the treatment of a stenotic lesion in an artery; FIGURES 8A and 8B are schematic represen¬ tations in sectional view of the dilating guide wire inserted in the through lumen of the PTCA catheter; FIGURE 9 is a schematic representation at an enlarged scale of the tip area of a PTCA catheter with the dilating guide wire inserted in the through lumen thereof; FIGURE 10 is a schematic representation at an enlarged scale of the tip area of a PTCA catheter illustrating attempted withdrawal of the dilating guide wire without the use of the axial stretch feature of the invention; FIGURE 11 is a view similar to Figure 10 but with the use of the axial stretch feature of the inven¬ tion; and FIGURE 12 is a view of the tip portion of the dilating guide wire illustrating the controlled deflec¬ tion thereof through the use of the axial stretch feature of the invention. Detailed Description of the Preferred Embodiment The construction of the preferred embodiment of the dilating guide wire is shown in Figures 1-5. Reference number 10 generally designates the control manifold assembly, while reference number 12 generally designates the dilating guide wire portion. Dilating guide wire portion 12 includes an inner, hollow core 14. Core 14 is made of stainless steel and extends the full length of the dilating guide wire and also substan¬ tially through the control manifold assembly 10. Core 14 is made of a suitable wall thickness and diameter for transmitting axial and torsional forces as the dilating guide wire is being advanced, while still maintaining an overall narrow diameter so that the dilating guide wire can fit through the guide wire-receiving lumen of a con¬ ventional angioplasty catheter. In the preferred embo¬ diment the core has an outer diameter d- of .012 inch, which tapers or necks downwardly near the distal end to a diameter d of .0075 inch throughout the region where the balloon is. Beyond the balloon, core 14 tapers again as indicated at reference number 15 to a final narrow configuration. The tapered portion 15 can be formed by a compressional step that essentially closes off the interior hollow passage of core 14 at the tip. In the preferred embodiment, tapered portion 15 is tapered from a circular section, as indicated in Figure 3A f to a rectangular section as indicated at Figure 3B. Although circular, square or rectangular sections can be used, the rectangular section is used in the preferred embodiment because it has the advantage of greatest flexibility for bending due to the short dimen¬ sion of the rectangular section, while still maintaining sufficient cross-sectional area to preserve ultimate yield strength. The greater flexibility of the rec¬ tangular section facilitates bending of the tip by the cardiologist prior to insertion for navigation purposes, and permits the tip to orient itself to various shapes within the artery. Balloon 20 is positioned around core 14 near the distal end of the apparatus. Balloon 20 is formed from polyolefin. The distal end 21 of the balloon 20 is bonded to core 14. The proximal end 22 extends up to outer catheter tubing 30, and is secured thereto. In the preferred embodiment, the outside diameter of the dilating guide wire at the location of distal end 21 is .014 inch. The diameter in the balloon area when the balloon 20 is collapsed is .018 to .020 inch. A hole 16 is provided in the core 14 approxi¬ mately adjacent the distal end of the balloon to provide an air return path as is explained in greater detail below. Outer catheter tubing 30 is made of polyethy¬ lene as is generally known in the art and is of somewhat greater outer diameter and stiffness than the balloon. Proxi al end 22 of the balloon may fit inside the inner lumen of outer catheter tubing 30 for a short distance where it is bonded thereto. The proximal end of outer catheter tubing 30 extends up to and is joined to the control manifold assembly 10. Referring again to Figure 3, the tip area includes a radiopaque flexible coiled spring 25 which is positioned around tapered tip 15 of the hollow core. The diameter of the coiled spring tip area is .012 to .014 inch. Coil spring 25 is brazed to core 14 at the point indicated by reference number 26 where it abuts the distal end 21 of the balloon. A smoothy radiused safety button 27 is brazed to the distal end of coil spring 25 and hollow core 14. Gold brazing is the pre¬ ferred form of brazing because it does not anneal the steel around the brazed area. The control manifold assembly includes a main housing 50 which has an interior pressure manifold or chamber 51 formed therein. Hollow core 14 extends from the dilating catheter portion 12 all the way through housing 50 and its included pressure chamber 51. A branch of housing 50 forms the inflation port 52 which communicates internally with pressure chamber 51. Inflation port 52 may have a suitable threaded fitting as shown, and is used for connection to the apparatus for applying radiopaque fluid, which is generally known in the art, for causing controlled inflation of balloon 20. Housing 50 has a distal end 53 which receives the dilating guide wire portion 12 and which forms the end of pressure chamber 51. A short piece of relatively stiff tubing 54 is molded into distal end 53 and extends a short distance outwardly therefrom. Tubing 54 is of sufficient diameter to allow hollow core 14 to extend therethrough with sufficient clearance to provide an annular lumen for inflation of the balloon. The outer catheter tubing 30 fits over tubing 54 and is bonded thereto. A strain relief 55, for example in the form of a piece of heat-shrink tubing, fits over outer catheter tubing 30 and tube 54 to help ensure mechanical security of the assembly. The annular lumen within the dilating guide wire between outer catheter tubing 30 and hollow core 14 communicates through tube 54 to pressure chamber 51. At the other end of housing 50 there is formed a threaded bore 56 which receives a threaded tip of a control handle housing 60. Positioned in a recess of thread bore 56 is a pressure seal 61 in the form of an O-ring. This allows hollow core 14 to pass through from housing 50 into control handle housing 60, while sealing pressure chamber 51 and preventing passage of pressurize'd fluid past seal 61. A control knob 65 is attached to a shaft 66 which extends into a central bore in control handle housing 60, as also seen in Figure 4. Shaft 66 has a central bore 67 which receives hollow core 14. The proximal end of hollow core 14 is indi¬ cated by reference number 14a and is positioned within shaft 66 near the opening of central bore 67 at the end of the control knob 65. In this manner the interior core air passage of hollow core 14 is vented to the external atmosphe.re. As seen in Figure 4, shaft 66 has a tab 70 projecting therefrom. This tab works in conjunction with grooves formed in the inner wall of central bore 62 of housing 60 to limit and define the permissible motion of shaft 66. As seen in Figures 4 and 5, the groove includes a longitudinally extending portion indicated by reference number 75. At the forward end of groove por- tion 75 it connects with a hook-shaped groove portion 78. At an intermediate position groove 75 connects with another hook-shaped groove portion 77. Knob 65 may move longitudinally of the apparatus as indicated by direc¬ tion arrow 80 in Figure 1, through a limited range of motion determined by the length of groove 75. Since the end of hollow core 14 is firmly secured in shaft 66 as by potting or the like, the above-described motion of control knob 65 causes corresponding axial movement of hollow core 14. Specifically, axial movement of knob 65 as indicated by direction arrow 80 causes axial movement of the core with respect to the outer catheter tubing 30 and causes axial stretching or relaxing of balloon 20. The system is designed so that when knob 65 is in the aft position, the balloon 20 is in the normal or unstressed condition. When knob 65 is pushed forward to bring tab 70 toward groove 78, this causes axial pushing of core 14 and stretching of balloon 20. Handle 65 can be rotated slightly to position tab 70 in the end of hook groove 78, which serves as a lock to hold the apparatus in the stretched position. The apparatus can similarly be locked with tab 70 in hook groove 77 to hold the appara¬ tus in an intermediate position. Axial stretching causes a reduction in profile or diameter of the balloon portion 20, as it is stretched out and thus positions itself more closely about core 14. This is explained in greater detail below with reference to Figures 10 and 11. When the tip area is not constrained inside a PTCA catheter, axial stretching can cause the tip portion including coil spring 25 to take a deflection toward one side, due to the nature of the axial force applied to core 14 and resisted by outer catheter tubing 30. This is indicated in Figure 12, where the side wall of balloon 20 opposite the deflection is pulled relatively smoothly along core 14. The other side of the balloon in the direction of the deflection is also stretched out somewhat to reduce the amount of slack, but is not pulled as tightly as the other side. Use of the present invention is illustrated with reference to Figure 7, in which reference number 90 generally designates a portion of a patent's vascular system, specifically an artery and several branches thereof. Since the preferred embodiment of the inven¬ tion is for use in treating the coronary arteries, the dilating guide wire is used in conjunction with a PTCA which is sized to cooperate with it. For that reason, the larger dilating catheter will be referred to herein as a PTCA catheter, but it will be understood that the dilating guide wire of the present invention may be used in conjunction with a dilating catheter for treatment of other arteries besides coronary arteries. The artery system includes a stenotic lesion 91 which is to be opened by angioplasty techniques. The first step is introducing a conventional guide wire in the custo¬ mary manner and steering it into the appropriate branch of artery 90 to cross the lesion. (This step is not shown in Figure 6.) Next, a PTCA catheter is advanced over the conventional guidewire. If all goes well, it is advanced across the lesion so that its balloon can be inflated to open the stenosis. However, if the stenosis is very tight, the situation is encountered where the guide wire is successfully advanced across the lesion, but the PTCA catheter cannot cross the lesion because of its too-large diameter. When this situation is encountered, the pre¬ sent invention can be advantageously employed in con- junction with a PTCA catheter of the type which has a central lumen, or through lumen, through which the dilating guide wire can pass. This means that the central lumen of the angioplasty catheter in the tip area thereof must accomodate the .020-inch maximum outer diameter of the dilating guide wire, which is in the balloon area with the balloon collapsed, and also the slightly larger diameter of outer catheter tubing, which is not in the balloon or tip area, but which starts a distance therefrom and extends back to the manifold assembly. This is not a significant limitation on the PTCA catheter since many of them are designed to work with conventional guide wires of .012 to .018 inch. Therefore any of a number of conventional-type angioplasty catheters or PTCA catheters can be used, or a catheter especially designed to work with the dilating guide wire can be used, so long as it will receive the dilating guide wire. In Figure 6, the dilating guide wire is inserted in the through lumen of the PTCA catheter. The PTCA catheter includes a balloon 100, a shaft portion 101, and a manifold assembly 105, which may be of con¬ ventional design. The through lumen of the catheter is accessible through fitting 106, and the dilating guide wire, distal tip first, has been threaded and extended through the through lumen so that the tip area including balloon 20 of the dilating guide wire extends beyond the balloon 100 of the PTCA catheter. In the preferred embodiment, the dilating guide wire balloon can extend up to 5.5 inches beyond the PTCA catheter balloon. This condition is indicated also in Figure 9. The PTCA catheter includes an inner tubular member 110 which extends from the proximal to the distal end of the catheter. At reference number 111 in Figure 9, approxi- mately midway within balloon 100, tubular member 110 steps to a smaller diameter, and at this reduced diameter extends out to the distal tip as indicated by reference number 110a. This reduction in diameter helps reduce the profile of the tip portion of the catheter and increases its flexibility. Tubular member 110 has a central lumen 115 which is the through lumen of the catheter. A radiopaque marker ring 117 is attached around member 110 at the approximate midpoint of balloon 100. The proximal end of the member forming balloon 100 connects to an outer tubular member (not shown) which extends up to the manifold assembly 105. An annular inflation lumen 119 is formed between this outer tubular member and inner tubular member 110. Figure 9 shows the dilating guide wire inserted as far as it will go into the PTCA catheter. The step in outer diameter which occurs between the proximal end of the balloon material 22 and the distal end of outer catheter tubing 30 is accomodated by the step in inside diameter of tubular member 110 at 111. The balloon 20 of the dilating guide wire is not shown in Figure 9, but would be off the drawing to the right thereof, approximately 5.5 inches beyond balloon 100 of the PTCA catheter. Referring again to the situation where the PTCA catheter has been advanced over the guide wire but cannot be advanced across the lesion, the PTCA catheter is held in place, and the guide wire is withdrawn and removed from the patient. The dilating guide wire according to this invention is then introduced through the central lumen of the PTCA catheter to replace the guide wire. When the tip of the dilating guide wire emerges from the tip of the PTCA catheter it is advanced further until it crosses the lesion, which is the poεi- tion indicated in Figure 6. Balloon 20 of the dilating guide wire can then be inflated to partially compress lesion ' 91 and partially open the flow. The balloon and tip profile and the spring tip and core flexibility are very important in the ability to advance and cross the lesion. It is also important that the spring tip and inflated balloon are radiopaque so that the procedure can be monitored by fluoroscopy. After the balloon 20 has partly opened the flow in the artery, balloon 20 is then deflated and the dilating guide wire is advanced further down the coronary artery. The PTCA catheter is then advanced along the dilating guide wire to the lesion, which can now be successfully crossed since it has been partially dilated. The PTCA catheter can then be used in the usual manner to complete the angioplasty procedure and open the stenosis. If necessary, the con¬ ventional guide wire can be reinserted after removal of the dilating guide wire to aid in advancing the conven¬ tional catheter. The present invention provides several useful features to aid in maneuvering the dilating guide wire to advance it across a lesion in an artery. First and foremost is the small effective diameter of the dilating guide wire, which permits it to be advanced through an angioplasty catheter in which has previously been maneuvered along a conventional guide wire to a short distance from the stenosis, typically one-half inch to one inch. Since the lesion may be around a turn in an artery or may be offset from the center of an artery, some maneuvering may still be needed. One possibility is pre-bending of the tip area as previously mentioned to give it a deflection which can then be steered by a rotation of the catheter. Another possibility is using the axial extension feature as previously discussed with reference to Figure 12, which also will deflect the tip area. A bent or deflected tip, viewed under fluoroscopy, can be steered to cross the lesion. The steering is advantageously accomplished by rotating the entire angioplasty catheter-dilating guide wire assembly, which can be done by manipulating the control manifold assembly 105 for the PTCA catheter. There is sufficient contact between the outer surface of tubing 30 of the dilating guide wire and the inside of the through lumen of the angioplasty catheter so as to transmit torque from the latter to the former. In the preferred embodiment, the outer diameter of outer catheter tubing 30 is .026 inch, and the inner diameter of tubular member 110 of the PTCA catheter is .030 inch. This provides sufficient clearance to allow easy inser¬ tion and withdrawal of the dilating guide wire. However, once it is in place, there will be a waving, random distribution of surface contact zones between the catheters, as suggested in Figure 8A, as the two undergo a series of bends in various directions. This is also indicated in Figure 8B, which shows the catheters con¬ tacting along one edge, in response to a bend. Typically, blood and/or contrast media occupy the space between the dilating guide wire and the inside wall of the through lumen of the PTCA catheter. These contact zones provide sufficient torque transmission that when the control manifold assembly 105 on the PTCA catheter is rotated, the PTCA catheter and the dilating guide wire rotate together as a unit. This takes advantage of the inherently greater torque transmission capability of the PTCA catheter, which it has by virtue of its thicker walls and larger diameter, and utilizes it for steering control of the relatively smaller and less stiff dilating guide wire. Also, the blood cells in and adja- cent the zones of contact between the catheters tend to provide a high viscosity which aids in torque transmission. The net effect is that the cardiologist, viewing the procedure with the aid of fluoroscopy, has a very high degree of control over deflection of the dilating guide wire tip and steering of it to navigate the final inch or so to the lesion. The two can be advanced together as well as rotated. Because of the small dimensions of the dilating guide wire and the demanding performance requirements it must meet, special fluid transport features and characteristics are provided. It is impor¬ tant that means are provided to completely purge the dilating guide wire shaft and balloon of air. This refers to the process of replacing all the air that occupied the volume of the catheter and balloon with a radiopaque contrast medium. This has been a problem with other types of catheters, and if some air remains in the balloon area it can change the radiopaque appearance of the inflated balloon, which causes dif¬ ficulties for the cardiologist. The catheter must also be able to contain the pressure of the inflation applied • to open the stenoses. Finally, deflation time for the balloon is very important, since the coronary artery is totally occluded during inflation of the balloon and the patient is in stress during that period. After the dilation is deemed complete by the cardiologist, it is very important that the balloon deflate rapidly, pre¬ ferably in less than 20 seconds, so that blood flow is restored. The small dimensions of the balloon and core wire which are required in order to pass through the tip of a PTCA catheter can create difficulties in attaining rapid deflation rate. However, through consideration of the fluid transport parameters through the entire dilating guide wire catheter, an optimum design can be achieved which meets the low profile, strength and fluid transport requirements. Figure 2 illustrates the important dimensions which determine the flow characteristics through the catheter. The predicted physical behavior of the flow rates can be attained using the following mathematical relation: Q « i? 2 where ZIP = differential pressure driving the fluid Q = fluid flow rate Z = fluid-surface resistive factors, and Z - S A L M - ~ fluid kinematic viscosity L = length of fluid path B = surface friction constant R = inner radius of outer annulus channel and r= outer radius of contained member of annulus As can be seen from the above equation, the relationship which includes a series of annuli which is the applica¬ tion in the fluid path of the dilating guide wire is a complex balance needed to provide the required profile that is needed to be contained within the inner lumenal path of the PTCA catheter while also providing a suf¬ ficient hydraulic channel for the balloon volume to deflate in the required 20-second maximum time frame. In the preferred embodiment, the length , of Figure 2 is 56 inches; L- is 1.5 inches; and L is 5.5 inches. Diameter D = D = .020 inch; diameter d = .012 inch; D. = .013 inch; and, d = d = .0075 inch. The purging of air from the catheter and balloon so that it can be completely filled with radiopaque contrast medium is taken care of by creating return path through the center of core 14 through which the air escapes when fluid is introduced. This path uses the central opening of hollow stainless steel drawn core 14 and aperture 16 provided therein near the distal end of the balloon. Aperture 16 is from .001 to .003 inch in diameter and communicates between the outer fluid flow channel between the balloon and tubing 22 and core 14, and the hollow central lumen of core 14. During inflation air is forced through aperture 16 and out the core as the radiopaque fluid is introduced. After the balloon has been filled and the air removed, some of the radiopaque fluid will enter aperture 16 and proceed back up the central lumen of core 14 toward the proximal end thereof. The advance of this fluid is controlled by two factors. First, the fluid column is forced through the hole 16 by pressure applied to the fluid, and fluid flow is resisted to an extent by the small diameter of the hole. Second, once the fluid has entered the central lumen of core 16, capillary action which is governed by the surface tension between the fluid and the central lumen surface characteristics and ' diameter will allow the fluid into the core along a cer¬ tain length until a state of equilibrium is reached. At this point, more pressure would be required to begin movement of the fluid in the column than the catheter can be subject to, and therefore the fluid advances no further. This applies to both the application of posi¬ tive pressure and vacuum. For this reason, the catheter is not only ventable through aperture 16 and the hollow core, but is also self-sealing. No additional seal or valve is required to prevent fluid and pressure from bleeding off through this vent passage. The flow characteristics of the radiopaque fluid in the core are dependent on optimization of the capillary action and static breakaway pressure shears. It will be appreciated that due to the small diameter of spring 25 and the low profile of balloon 20 in its deflated state, the dilating guide wire can be advanced through a tight stenosis essentially anywhere that can be crossed by a conventional guide wire. The balloon 20 when slack tends to streamline itself and lie back along core 14 as the device is being advanced, thus providing a low profile. This low profile can be enhanced even further by pushing knob 65 forward, as discussed above, to axially stretch balloon 20 and thus further reduce its profile. The axial stretching of the balloon is very important in withdrawing the balloon of the dilating guide wire into the PTCA catheter to remove it. After the inflation of balloon 20 has been completed, pressure is removed and the balloon deflated. At this point, if one were to attempt to withdraw the dilating guide wire back into the conventional catheter without the axial stretch feature of this invention, the undesirable effect illustrated in Figure 10 would take place. The proximal end of the balloon 20 would withdraw into the PTCA catheter as the deflated balloon 20 would tend to streamline along hollow core 14. However, the excessive slack of the balloon, now larger due to its having been stretched in the dilating process, would tend to bunch up or accordion toward the distal end as indicated at reference number 20a, and this bunching would prevent the dilating guide wire from being fully withdrawn into and through the central lumen 115 of the PTCA catheter. To solve this problem, the axial stretch feature of the present invention is used to stretch the balloon, thus drawing it thinner and lowering its profile to permit complete withdrawal through lumen 115 as illustrated in Figure 11. In Figure 11, the control knob 65 has been pushed forward and rotated to lock tab 70 in hook-shaped groove 78. This pushes the core 14 toward the distal end and stretches the balloon. This might be needed to reinsert the guide wire to advance further along the artery, and without the axial stretch feature to permit withdrawal of the dilating guide wire, it would be necessary to remove the PTCA catheter also, which would result in loss of the path. The present invention thus provides an extre¬ mely low profile dilating guide wire for predilation of tight stenoses which cannot be crossed by a conventional PTCA or other angioplasty catheter. The low profile permits the device to be inserted through the PTCA in place of a guide wire, without loss of the path to the stenosis. The dilating guide wire together with a PTCA or other angioplasty catheter sized to receive it form a system which can be easily steered and manipulated for predilation and subsequent dilation of the stenosis more effectively than previously feasible with other catheter types.

Claims: WHAT IS CLAIMED IS: 1. A predilatation catheter for use in angioplasty with a percutaneous transluminal coronary angioplasty (PTCA) catheter of the type having a through lumen and a distal region small enough for insertion in a coronary artery, comprising: an elongate flexible hollow tubular member; an elongate core member stiffer than said tubular member and having a diameter less than the inside diameter of said tubular member, said core member positioned inside said tubular member to define an annu¬ lar inflation passage therebetween; means forming an inflatable balloon member adjacent the distal end of said tubular member and in fluid communication with said inflation passage with the distal end of said core member extending through the interior of said balloon; means for sealing the distal end of said balloon to the distal end of said core member; said tubular member and balloon member having an outside diameter small enough to fit within the through lumen of the PTCA catheter to permit advancing the inflatable balloon member through and beyond the distal end of the PTCA catheter; control means attached to the proximal end of said tubular member and having means for fluid com¬ munication with said annular passage for inflation and deflation of said balloon; and said control means having selectively operable means connected for applying axial force to said core member relative to said tubular member, to transmit the axial force to the distal end of said balloon to effect axial stretching and reduction of pro- file thereof, whereby to facilitate withdrawing the balloon back into the distal end of the through lumen of the PTCA catheter. 2. A catheter for use in angioplasty, comprising: an elongate flexible hollow tubular member; an elongate core member stiffer than said tubular member and having a diameter less than the inside diameter of said tubular member, said core member positioned inside said tubular member to define an annu¬ lar inflation passage therebetween; means forming an inflatable balloon member adjacent the distal end of said tubular member and in communication with said inflation passage for receiving inflation fluid and pressure therefrom, the distal end of said core member extending through the interior of said balloon; means for sealing the distal end of said balloon to the distal end of said core member; control means attached to the proximal end of said tubular member and having means for fluid com¬ munication with said annular passage for applying infla¬ tion fluid and pressure thereto to control the inflation and deflation of said balloon; and said core member having a fluid vent passage from its proximal end to a vent opening in the portion thereof within said balloon to provide a vent path for removing air from said balloon as it is inflated with pressurized inflation fluid, the cross-sectional dimen¬ sions of said vent passage being small enough to provide self sealing of the vent passage with respect to infla¬ tion fluid entering the passage as the balloon is being inflated due to capillary action and surface tension of the fluid within the passage, whereby the inflation fluid will move along the passage only until an equilibrium is reached between the inflation pressure and the decay of pressure along the vent passage, thus effectively sealing the vent passage. 3. A catheter according to claim 2 wherein said control means includes means attached to said core member for selectively applying axial force thereto relative to holding said tubular member to effect axial, stretching and reduction of profile of said balloon. 4. A catheter according to claim 2 wherein the outside diameter of the distal end of a catheter with, the balloon deflated is about .02 inch or less. 5. A catheter for use in angioplasty, comprising: an elongate flexible tubular member; an elongate hollow metallic core, said core having a diameter less than the inside diameter of said tubular member, and positioned generally coaxially therein and having a distal end extending beyond the distal end of said tubular member; an inflatable balloon member having one end attached adjacent the distal end of said tubular member and having its other end attached adjacent the distal end of said core with the balloon member extending around the core and in fluid communication with said annular passage; a vent hole formed in said core in the portion thereof within said balloon to provide fluid com¬ munication between the balloon and the interior of the hollow core; control means attached to the proximal end of said tubular member and said core and having means for introducing inflation fluid in said annular passage to inflate said balloon; means for venting the proximal end of said hollow core to permit removal of air displaced from said balloon through said vent hole and said hollow core as the balloon is filled with inflation fluid; and the inside dimensions of said hollow core being small enough to provide self sealing due to capillary action and surface tension with respect to inflation fluid entering therein through said vent hole as the balloon is being inflated, whereby the inflation fluid will move along the hollow core from the balloon toward the proximal end only to a point at which an equilibrium is reached between the inflation pressure and the decrease of pressure along the hollow core due to capillary action and surface tension, thus effec¬ tively forming a fluid seal. 6. A catheter according to claim 5 further including a flexible spring safety tip attached to said core at the distal end thereof. 7. A catheter according to claim 5 wherein said control means includes means for attachment to said core for selectively applying axial compression force thereto relative to said tubular member, to selectively axially stretch said balloon to reduce its profile. 8. A catheter according to claim 7 wherein said means for applying axial force includes means for locking said core with respect to said tubular member with said balloon in the stretched condition. 9. Apparatus according to claim 5 wherein said core extends beyond the point of attachment of the distal end of said balloon and tapers to a smaller diameter non-hollow region and further including a flexible safety spring disposed about and attached to the tip of said core. 10. A catheter according to claim 9 wherein said tip portion of said core tapers to a thin rectangular sectioned ribbon, to provide greater flexibility. 11. A catheter according to claim 5 wherein the outside diameter of the distal end of a catheter with the balloon deflated is about .02 inch or less. 12. Angioplasty apparatus for use in opening of very tight stenoses in the coronary arteries, compr sing: a PTCA catheter including an elongate tubular body adapted for introduction into a patient's vascular system, and having a through lumen -28- and an inflatable balloon adjacent a distal end thereof, the distal end of the PTCA catheter being small enough with the balloon uninflated to fit in a coronary artery, and including a control handle at the proximal end thereof for controlling motion of the catheter in the vascular system and inflation of the balloon in an angioplasty procedure; a dilating guide wire adapted for fitting in the through lumen of said PTCA catheter, including an elongate, relatively stiff core, an elongate, relatively flexible hollow tubular member disposed generally coaxially around and along said core, an inflatable balloon at the distal end of the tubular member with its distal end sealed to the distal end of said core, a vent passage extending through said core and communicating with said balloon through a small opening in said core.,- said vent passage extending substantially to the proxi¬ mal end but not the distal end of the core, and a control handle attached to the proximal end of said dilating guide wire to control motion thereof and infla¬ tion of said balloon with inflation fluid through an annular passage between said tubular member and said core; and said dilating guide wire having an outside diameter small enough to permit introduction into the through lumen of said PTCA catheter through an access in the control handle thereof, and movement through said lumen to extend the balloon of said dilating guide wire beyond the balloon and distal tip of said PTCA catheter, whereby said dilating guide wire may be used to predi- late a stenosis to open it sufficiently for subsequent crossing and dilation by said PTCA catheter without requiring the loss of and reestablishment of the path across the stenosis to change catheters. 13. Apparatus according to claim 12 wherein said dilating guide wire fits within said PTCA catheter with sufficient contact for torque transmission so that the distal end of said dilating guide wire extending beyond said PTCA catheter can be rotated for steering by manual rotation of the system consisting of said PTCA catheter and said dilating guide wire. 14. Apparatus according to claim 12 wherein said dilating guide wire includes control means associated with said control handle and operatively connected for selectively imparting axial force to said core relative to the hollow tubular member to stretch the balloon of the dilating guide wire to permit withdrawing it back into the through lumen of the PTCA catheter, to permit removal of the dilating guide wire without removal of the PTCA catheter from the patient's vascular system. 15. Apparatus according to claim 12 wherein said vent passage has small enough internal dimensions to cause self sealing of inflation fluid entering therein as said balloon is inflated due to capillary action and surface tension of the inflation fluid in the vent passage. 16. Apparatus according to claim 1 wherein the outside diameter of the distal end of the predilatation catheter with its balloon deflated is about .02 inch or less. 17. Angioplasty apparatus for use in opening of tight stenoses in the coronary arteries, comprising: a PTCA catheter including an elongate tubular body adapted for introduction into a patient's vascular system, and having an inflatable balloon adjacent a distal end thereof, a through lumen, and a control means at the proximal end thereof for controlling motion of the PTCA catheter and inflation of the balloon for dila¬ tion, the distal end of the PTCA catheter when said balloon in uninflated being small enough to fit in a coronary artery; a dilating guide wire adapted for fitting in the through lumen of said PTCA catheter, and including an elongate core, an elongate hollow tubular member disposed generally coaxially around and along said core to define an inflation passage therebetween, an infla¬ table balloon adjacent the distal end of the tubular member in communication with said inflation passage, and means for sealing the distal end of said balloon so that said balloon can be inflated with inflation fluid applied thereto through said inflation passage, a vent passage in said core extending from the balloon area substantially to the proximal end of the core and com¬ municating with said balloon through a small opening in the core to provide a path for venting displaced air as the balloon is inflated, and control means attached to the proximal end of said dilating guide wire for controlling motion thereof and inflation of said balloon with inflation fluid through said inflation passage; and said dilating guide wire having an outside diameter small enough, with its balloon uninflated, to permit the dilating guide wire to be placed in the through lumen of the PTCA catheter, and movement therein to extend the balloon area of said dilating guide wire beyond the distal end of said PTCA catheter, and the balloon of the dilating guide wire when inflated having a diameter greater than the uninflated diameter of the balloon of the PTCA catheter, so that the dilating guide wire may be used to predilate a stenosis to open it sut- ficiently for subsequent crossing and dilation by said PTCA catheter without requiring the loss of and reestab- lishment of the path across the stenosis to change catheters. 18. Apparatus according to claim 17 wherein said dilating guide wire fits within said PTCA catheter with sufficient contact for torque transmission so that the distal end of said dilating guide wire extending beyond said PTCA catheter can be steered by manual rota¬ tion and advancing of the system consisting of said PTCA catheter and said dilating guide wire. 19. Apparatus according to claim 17 wherein said control means of said dilating guide wire includes means operatively connected for selectively imparting axial force to said core relative to said tubular member to stretch the balloon of the dilating guide wire to permit withdrawing it back into the through lumen of the PTCA catheter. 20. Apparatus according to claim 17 wherein said vent passage within said core has small enough internal dimensions to cause self-sealing of inflation fluid entering therein as said balloon is inflated, due to capillary action and surface tension of the inflation fluid within the vent passage. 21. Apparatus according to claim 17 wherein the outside diameter of the distal end of the dilating guide wire with its balloon deflated is about .02 inch or less. 22. A method of dilation of stenoses in coronary arteries, comprising the steps of: placing a PTCA catheter having a predilatation catheter within its through lumen in the patient's vascular system adjacent lesion to be treated; advancing the distal end of the predilatation catheter to cross the lesion to be treated with the distal end of the PTCA catheter remaining on the pro-xi- mal side of the lesion; inflating the balloon of the predilatation catheter to at least partially open the stenosis, then deflating the balloon; advancing the PTCA catheter to cross the par¬ tially opened stenosis; and inflating the PTCA catheter balloon to further open the stenosis. 23. A method according to claim 22 wherein the first-mentioned step includes advancing the PTCA catheter over a guide wire to position its distal end adjacent the lesion, removing the guide wire, and replacing it with the predilatation catheter. 24. A method according to claim 22 wherein said step of advancing said predilatation catheter includes steering and advancing the PTCA catheter and predilata¬ tion catheter together as a system, with the distal end of the predilatation catheter extending beyond the distal end of the PTCA catheter. 25. A method according to claim 22 wherein said step of advancing the PTCA catheter comprises advancing the predilatation catheter to a point more distal in the artery after partially opening the stenosis, then advancing the PTCA catheter along the predilatation catheter to cross the partially opened stenosis. 26. A method according to claim 25 including treatment of a second lesion more distal in the coronary artery than the first lesion treated, comprising advancing the predilatation catheter to the more distal lesion and inflating and deflating its balloon to at least partially open the stenosis, then advancing the PTCA catheter and inflating and deflating its balloon to further dilate said further stenosis. 27. A method according to claim 22 further including the step of withdrawing the predilatation catheter into the through lumen of the PTCA catheter after predilating the stenosis, by axially stretching the balloon of the predilatation catheter to reduce its profile. 28. A method according to claim 27 further including replacing the predilatation catheter with a guide wire to preserve the path across the lesion for possible further treatment of the artery. 29. A method of dilation of stenoses in coronary arteries which are too narrow to be crossed and treated by conventional PTCA catheters which are advanced along a guide wire, comprising the steps of: introducing a PTCA catheter into the patient's vascular system along a guide wire and advancing the distal end thereof to the lesion to be treated; removing the guide wire while leaving the PTCA catheter in place and replacing it with a predila¬ tation catheter having an outside diameter small enough to pass through the through lumen of the PTCA catheter; advancing the distal end of the predilatation catheter beyond the distal end ot the PTCA catheter to cross the lesion to be treated; inflating the balloon of the predilatation catheter to at least partially open the stenosis, then deflating the balloon; advancing the predilatation catheter to move its balloon to a region of the coronary artery more distal than the lesion just treated; advancing the PTCA catheter along the predila¬ tation catheter to cross the partially opened stenosis; and inflating the PTCA catheter balloon to further dilate stenosis. 30. A method according to claim 29 including treatment of a second lesion more distal in the coronary artery than the first lesion treated, comprising advancing the predilatation catheter to the more distal lesion and inflating and deflating its balloon to at least partially open the stenosis, then advancing the PTCA catheter and inflating and deflating its balloon to further dilate said further lesion. 31. A method of dilation of stenoses in coronary, arteries which are too narrow to be crossed and treated: . by conventional PTCA catheters which are advanced along- a guide wire, comprising the steps of: introducing a PTCA catheter into the patient's vascular system along a guide wire and advancing the distal end thereof to the lesion to be treated; removing the guide wire while leaving the PTCA catheter in place and replacing it with a predila¬ tation catheter having an outside diameter small enough to pass through the through lumen of the PTCA catheter; advancing the distal end of the predilatation catheter beyond the distal end of the PTCA catheter to cross the lesion to be treated; inflating the balloon of the predilatation catheter to at least partially open the stenosis, then deflating the balloon; partially withdrawing the predilatation catheter while leaving the PTCA catheter in place in the patient's coronary artery; advancing the PTCA catheter across the par¬ tially opened lesion; and inflating the PTCA catheter balloon to further dilate the stenosis. 32. (NEW) A method according to claim 31 wherein said step of withdrawing the predilatation catheter includes applying an axial stretching force to its balloon after deflation thereof to reduce the balloon profile to faci¬ litate reentry thereof into the distal tip of the through lumen of the PTCA catheter. 33. A method according to claim 33 wherein said step of advancing the PTCA catheter includes introducing and advancing a guide wire through the through lumen of the PTCA catheter, then advancing the PTCA catheter along said guide wire to cross said partially opened lesion.

Inventors: EUTENEUER CHARLES L, WILLARD LLOYD K, EUTENEUER, CHARLES, L., WILLARD, LLOYD, K.
Applicants: SCIMED LIFE SYSTEMS INC, SCIMED LIFE SYSTEMS, INC.
Application year: 1987
Main classification: A61M29
IPC codes: A61M29, G01M3