IMPROVED INTRA-AORTIC BALLOON CATHETER

Abstract: An improved intra-arotic balloon catheter (21) of the present invention with a kink-resistant outer tube (22, 42) formed a helically wound metal coil (60) overlaid with a plastic covering (61) which maintains the patency of the air passageway, and a central tube (24, 44) forming a secondary lumen (45), formed of a strong resilient, flexible, kink-resistant material, such as a super elastic metal alloy.

Description: IMPROVED INTRA-AORTIC BALLOON CATHETER Background of the Invention Intra-aortic balloon catheters are used in patients with left heart failure to augment the pumping action of the heart. Intra-aortic balloon therapy increases coronary perfusion, decreases the workload of the left ventricle, and allows healing of the injured myocardium. The catheters have an inflatable and deflatable balloon at the distal appropriatly 3 meter long. The catheter is typically inserted into the femoral artery, and moved up the descending thoracic aorta until the distal tip of the balloon is positioned just below or distal to the left subclavian artery. An air passageway for inflating and deflating the balloon extends through the catheter and is connected at its proximal end to an external pump. The patient's ECG may be used to produce balloon inflation in synchronous counter pulsation to the patient's heart beat. Intra-aortic balloon catheters may also have a secondary passageway or lumen which may be used to measure aortic pressure, which may also be used to regulate balloon inflation however, ECG regulation is preferred. In a dual lumen construction, the central, secondary lumen may accommodate a guide wire to facilitate placement of the catheter or may be used with infuse fluids. Timing for the counter pulsation is established from the patient's ECG or measurement of the pressure in the descending thoracic aorta. Ideally, the balloon should be inflating just as the aortic valve closes and deflating just prior to the onset of systole. When properly coordinated, the inflation of the balloon raises the patient's diastolic pressure thereby indirectly increasing the oxygen supply to the myocardium. Balloon deflation just prior to the onset of systole lowers the patient's diastolic pressure, thereby indirectly reducing myocardial oxygen consumption. Typical dual lumen intra-aortic balloon catheters have an outer, flexible, plastic tube and a central tube there through formed of plastic tubing stainless steel tubing, or wire coil embedded in plastic tubing. Polyurethane is used to form the balloon. Problems associated with current intra-aortic balloon catheter constructions are kinking of the outer tube or central tube, and restriction of a blood flow to the legs caused by the position and size of the catheter in the artery. It is an object of the present invention to provide an improved intra-aortic balloon catheter with a kink-free outer tube leading to reduced kinking of the air passage lumen. It is another object of the present invention to provide an improved intva-aortic balloon catheter with a flexible kink-resistant central tube formed of a resilient, flexible kink-resistant metal alloy tube.. It is another object of the present invention to provide an improved intra-aortic balloon catheter with an air passage lumen of increased cross section for greater air flow. It is another object of the present invention to provide an improved intra-aortic balloon catheter of reduced outer diameter to decrease its resistance to blood flow in the descending aorta. Summary of the Invention The improved intra-aortic balloon catheter of the present invention has a kink-resistant outer tube formed of a helically wound metal coil overlaid with a plastic covering which maintains the patency of the air passageway. In addition, the central tube, forming the secondary lumen may be formed of a resilient, flexible, kink resistant material, such as a super elastic metal alloy. Brief Description of the Drawings FIG. 1 is a plane view of a prior art intra-aortic balloon catheter. FIG. IA is a transverse cross sectional view of the prior art catheter of FIG. 1 taken along lines 1A-1A. FIG. 2 is a plane view of an improved intra-aortic balloon catheter of the present invention with a kink resistant inner tube. FIG. 2A is a transverse cross-section of the catheter of FIG. 2, taken along lines 2A-2A. FIG. 3 is a plane view of an improved intra-aortic catheter of the present invention. FIG. 3A is a transverse cross sectional of the catheter of FIG. 2 taken along lines 3B-3B. FIG. 3B is a longitudinal cross section of a catheter of FIG. 2 taken along lines 3A-3A. r . , ιnr , 0 . n PCT/US95/10955 97/07849 FIG. 3C is a longitudinal cross-section of an alternative embodiment of the catheter construction of FIG. 3 and 3A. Description of the Invention The general structure of an intra-aortic balloon catheter is best described in relation to FIGS. 1 and IA which illustrate a dual-lumen prior art intra-aortic balloon catheter. The catheter, shown generally at 1, is constructed of a clear plastic outer tube 2 forming an air passageway lumen 3; and another clear plastic central tube, 4, disposed within outer tube 2 and creating a secondary passageway or lumen 5 as may best be seen in FIG. IA. The central tube 4 has also been formed of stainless steel tubing, or of a metal coil embedded in a plastic tube. A balloon is disposed at the distal end of the catheter, shown generally at 6. The distal end 7 of the central tube 4 extends beyond the distal end 10 of outer tube 2, and the distal end of the balloon. 7A is attached to a tip formed on the distal end 7 of central tube . The proximal end of the balloon, 8B is attached to the distal end 10 of the outer tube. The balloon is formed of polyurethane, an antithrombogenic flexible material, and has folds, 11, formed as a result of wrapping the balloon about the central tube to ease insertion of the catheter. Radio-opaque bands 20 at the distal end of the catheter aid in positioning the balloon in the descending aorta. At the proximal end of the catheter, shown generally at 12, a hub 13 is formed on the proximal end of 14 fourth tube 2. The secondary passageway or lumen, 5, extends through the hub, and a connector 16 is provided at the proximal end 15 (or exit) of the secondary passageway or lumen 5. The proximal end 18 of the air passageway lumen 3 exits through a side arm 17 of the hub, on which is provided a connector 19. Inflation and deflation of the balloon is accomplished through the air passageway lumen. The secondary passageway or lumen can accommodate a guide wire for placement or repositioning of the catheter. When the guide wire is not disposed in the secondary lumen, the central lumen may be used for measuring blood pressure in the descending aorta. This pressure measurement may be used to coordinate the inflation and deflation of the balloon with the pumping of the heart, however, use of the patient's ECG is preferred. Additionally, the secondary lumen may be used to infuse liquids into the descending aorta. An improved intra-aortic balloon catheter of the present invention is illustrated in FIGS. 2 and 2A. The improved catheter shown generally at 21 comprises an outer tube 22 of e.g. polyurethane and a central tube 24 of kink- resistant metal alloy.. A balloon 28 is disposed at the distal end 26 of the catheter and a hub 33 disposed at the proximal end 32 of the catheter. Use of the kink-resistant metal alloy such as nitinol, manufactured and sold by Raychem Corp., permits the central tube 24 to be constructed with a much smaller diameter than conventional central tubes made of plastic material. Thus, the cross-sectional area of the air passageway lumen 25 may be increased and/or the outer diameter of the outer tube 22 may be decreased, improving blood flow to the legs. In use, intra-aortic balloon catheters are generally inserted through an introducer sheath into the femoral artery and threaded up through the descending aorta until the balloon tip is disposed just distal to the left subclavian artery. Insertion of the catheter through the sheath, and the process of placement of the catheter, can lead to kinking of either or both the contrab and outer tubes of the catheter. Kinking of the catheter is often not apparent until the catheter has been fully placed. Indeed kinking of the central lumen may not become apparent until the wire guide has been removed. Inability to infuse through the secondary lumen or to measure blood pressure through the secondary lumen requires that the catheter be removed from the body and another inserted. Hence it is highly desirable that the lumens remain kink free. Through nitinol is the preferred material for tube 24, the tube may alternatively be formed of a similar non-kinking material. When formed of nitinol, the central tube 24 may have a wall thickness of 2.0 to 2.5 mils. This is in contrast to the wall thickness of 10 mils of the current intra-aortic balloon catheters where the central tube 2 is made of plastic. The reduction in wall thickness of 7.5 to 8 mils can be used to effectively increased the cross-sectional of the air passageway lumen and/or to decrease the outer diameter of the outer tube 22. Specifically, reduction in the central tube wall thickness to 2 to 2.5 mils can lead to a reduction in catheter size or outer diameter or outer tube from 8-1/2 French, to 7 to 7-1/2 French, permitting the use of a reduced size introduces sheath. Reduction in outer diameter of outer tube 22 and the ability to use a smaller sheath reduces the blockage of blood flow to the legs making the catheter safer to use for longer periods of time. The balloon 28 is attached at its proximal end 28B by conventional means such as a solvent based adhesive, to the distal end 30 of the tube 22, and at its distal end 28A to the distal end 29 of tube 24. Preferably, a tip 28 is formed at the distal end 29 of tube 22 to facilitate fastening of the distal end of the balloon. Folds 31 may be formed in the balloon to wrap the balloon about the central tube for insertion through a sheath or directly through the skin. At the proximal end 32 of the catheter the hub 33 is attached to the proximal end 34 of outer tube 22. The proximal end 35 of the secondary lumen extends through the hub and a connector 36 may optionally be provided for connecting the proximal end of the secondary lumen to tubing connecting the lumen with a pressure transducer, or source of injectate. The proximal end 35 of the secondary lumen extends generally straight back through the hub to make that lumen available as a guide wire lumen in placement of the catheter. The proximal end 38 of the air passageway lumen may extend through a sidearm 37 of the hub as shown, such that the proximal end of the air passageway lumen exits at a point displaced from the exit of the central lumen. A connector 39 is provided for the proximal end of the air passageway lumen to connect it with a source for pumped gas, preferably helium. When the central tube 24 is formed of a metal alloy it is identifiable under X-ray or fluoroscope, and radio-opaque bands may not be needed at the distal end of the catheter for locating the balloon within the body of the patient. Another improved intra-aortic balloon catheter of the present invention is illustrated in FIGS. 3 to 3C. The improved catheter shown generally at 41 comprises kink resistant outer tube 42 formed of a metal coil within a plastic covering. Description of the remaining elements 43- 59 may be had by reference to the description of corresponding elements 23-39 of FIG. 2. Insertion of the catheter through the sheath, and the process of placement of the catheter, can lead to kinking of the outer tube of the catheter. Inability to inflate and deflate the balloon through the annular lumen, requires that the entire catheter be removed from the body and another inserted. Hence it is highly desirable that the air passageway lumen remain kink free. Use of an outer tube with metal coil only, or of a central metal or metal alloy tube alone, might require addition means to identify the ends of the balloon by X-ray or fluoroscopy. However, use of an outer tube 42, and inner tube 24 require no additional radio-opaque bands at the distal end of the catheter for locating the balloon within the body of the patient. The construction of outer tube 42 may best be seen in FIGS. 3A through 3C. The tube 42 may be formed of an central helical metal coil 60 which lies within a plastic covering 61. This non-buckling kink-free construction, used to form a catheter insertion sheath, is described in U.S.P. 5,180,376 and co-pending application Serial No. 07/965,961. The metal coil is typically fabricated from a flat stainless steel wire or an equivalent springy metal. The thickness of the metal is typically between 1 and 5 mils and the width of the wire is typically between 5 to 50 times the wire thickness. The flat wire is typically be wound on a mandrel in a manner similar to the way that spring wire guides are made at the present time. The plastic covering 61 is typically be made from polyethylene, polyurethane, PVC or a similar plastic material. One method of forming the covering 61 so that it fits tightly around the helical coil 60, would be by sliding the coil 60 through a tube of plastic and then heat shrinking the plastic onto the helical coil 60. Another method would be to dip coat the coil 60 into a liquid plastic material that hardens onto the coil. In the alternative construction shown in FIG. 3C, the helical coil may be constructed of two separate metal coils, one inside the other, wound in opposite directions to improve the strength of the tube. As shown in FIG. 3C, the outer tube 42 comprises an central metal coil 62 and an outer helical metal coil 42 which lie within the plastic covering 61. Various other modifications, adaptations, and alter- native designs are of course possible in light of the above teachings. Therefore, it should be understood at this time that within the scope of the appended claims, the invention may be practiced otherwise then as specifically described herein.

Claims: WHAT IS CLAIMED IS: 1. In a balloon catheter including an outer tube with proximal and distal ends, and a central tube having proximal and distal ends and being disposed within said outer tube and extending beyond said distal end of said outer tube, and a balloon with a proximal end attached to said distal end of said outer tube and a distal endattached to said distal end of said central tube, the improvement comprising said central tube being formed of a resilient, kink-resistant material. 2. The balloon catheter of Claim 1 wherein said resilient, kink-resistant material of said central tube is a super elastic metal alloy. 3. The balloon catheter of Claim 1 wherein said resilient, kink-resistant material of said central tube is Nitinol. 4. The balloon catheter of Claim 1 characterized in that at least a proximal portion of said outer tube comprises a kink-resistant construction of a flat wire metal coil consisting of a multiplicity of turns having some separation between adjacent turns of said metal coil, the interior surface of said coil forming an air passageway lumen of the catheter, a plastic covering fitted onto and in contact with the exterior surface of said coil, said plastic covering extending into the space between adjacent turns of said metal coil. 5. The balloon catheter of Claim 4 wherein said flat wire coil is stainless steel. 6. The balloon catheter of Claim 4 wherein said flat wire of said metal coil has a thickness between 2.5 and 3.5 mils and a width-to-thickness ratio of between 3 and 20. 7. The balloon catheter of Claim 4 wherein said flat wire of said metal coil has a thickness between 1.5 and 2.49 mils and a width-to-thickness ratio of between 5 and 50. 8. The balloon catheter of Claim 4 wherein said flat wire of said metal coil has a thickness between 0.75 and 1.49 mils and a width-to-thickness ratio of between 12 and 80. 9. The balloon catheter of Claim 4 wherein said metal coil has a space between adjacent turns that is less than the width of a single turn of said metal coil. 10. The balloon catheter of Claim 4 wherein the interior surface of said metal coil is coated with plastic. 11. The balloon catheter of Claim 4 wherein said flat wire of said metal coil comprises an inner helical metal coil covered by an outer helical metal coil which is covered by said plastic covering.

Inventors: LEWIS JEFFREY P, POSTELL SUSAN J, LEWIS, JEFFREY, P., POSTELL, SUSAN, J.
Applicants: ARROW INT INVESTMENT, ARROW INTERNATIONAL INVESTMENT CORP.
Application year: 1995
Main classification: A61M29
IPC codes: A61M25