INCREASING RADIUS CURVE CATHETER

Abstract: A guide catheter for insertion into the cardiovascular system having a straight portion and an improved distal end portion for more precise and easier positioning in a left coronary artery. The improved distal portion includes a secondary curved portion, followed distally by a primary curved portion, terminating with a distal tip portion. The primary and secondary curved portions are constructed such that the primary and secondary curved portions have an approximately equal curvature radii when the distal tip portion is positioned in the ostium of the left coronary artery, thereby forming a constant radius curve.

Description: INCREASING RADIUS CURVE CATHETER Background of the Invention This invention relates generally to catheters adapted to be inserted into the cardiovascular system and, more particularly, to an improved guide catheter having a distal end portion for more precise and easier positioning in the left coronary artery. Catheters are often advanced in the performance of medical procedures such as angioplasty to widen the lumen of a coronary artery which has become at least partially blocked by a stenotic lesion causing an abnormal narrowing of the artery due to injury or disease. In these techniques, an angioplasty catheter is usually introduced into the aorta and then the coronary artery through a previously placed guide catheter. Tc place the guide catheter in the coronary artery, the proximal end of the guide catheter is manipulated until its distal end is steered into the ostiu of the coronary artery branching off from the aorta. Other therapeutic catheters such as atherecto y catheters may also be advanced through the guide catheter. A commonly used guide catheter used in treatment of the left coronary artery iβ often referred to as a "Judkins" catheter which has a specially shaped distal end portion for facilitating insertion into the left coronary artery. The Judkins catheter, from proximal to distal end, comprises a long firεt straight portion, a 180 degree curved portion, a shorter second straight portion parallel to the first straight portion, a bend, and a distal tip portion perpendicular to the second straight portion. The Judkins catheter forms relatively large angles when inserted into the cardiovascular system. An improvement on the Judkins catheter includes a straight portion followed distally by a curved portion, followed distally by a second straight portion, followed distally by a second curved portion, followed distally by a tip. This straight portion lies against the ascending aorta wall opposite the ostium of the left coronary artery, providing support for the catheter. This improved design allows for better coaxial alignment in the lumen of the selected artery. An angioplasty or other therapeutic catheter advanced through a guide catheter having numerous transitions between the straight and curved portions, or curves of varying radii encounter some resistance to advancement at each of the transitions. More specifically, when a therapeutic catheter encounters a transition point or bend in a guide catheter, this results in a force by the guide catheter tending to make the intravascular catheter assume the path of the guide catheter. There is an opposite force by the intravascular catheter tending to make the guide catheter assume the path of the intravascular catheter. In the region of the ascending aorta, a therapeutic catheter advanced through the transitions in the guide catheter will tend to straighten out the guide catheter curve and dislodge the guide catheter tip portion from the ostium of the left coronary artery. If the tip is dislodged from the ostium, time consuming replacement of the tip of the guide catheter into the ostium may be required. Summary of the Invention The present invention pertains to a guide catheter having a substantially constant radius curve when the distal tip of the catheter is positioned in the ostium of the left coronary artery. The constant radius curve has no significant bends or transition points while in this position. This improved shape reduces the resistance by the guide catheter against the advance of the therapeutic catheter, where the opposing force by the advancing therapeutic catheter acts to straighten out the guide catheter and pull it from its desired position. This easier advance of the intravascular catheter means there is less force tending to dislodge the distal tip of the guide catheter from the ostium of the left coronary artery. In a preferred embodiment, the guide catheter in accordance with the present invention is for a catheter having a proximal end, a straight portion extending distally, and a curved portion. The curved portion has a secondary curved region, a primary curved region, and a distal end, where the primary and secondary curves have unequal radii ex vivo but form a single continuous curve when the distal end is inserted in the ostium. Consequently, less force is required to advance a therapeutic catheter through the guide catheter than through a guide catheter with transitions in curve radii. The guide catheter can be made from materials such as polymers, which exhibit sufficient softness and flexibility to be steerable to the coronary artery, yet rigid enough to permit the transmission of twisting forces along its length by manipulation of its proximal end. Such materials and methods of fabrication are well known in the art. Brief Description of the Drawinσs The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred, but nonetheless embodiments, in accordance with the present invention when taken into conjunction with the accompanying drawings wherein: Fig. 1 is a cross sectional view of a cardiovascular system with a prior art catheter positioned with the catheter distal tip positioned in the ostium of the left coronary artery; Fig. 2 is a side view of an embodiment of the instant invention catheter, ex vivo; and Fig. 3 is a cross sectional view of a cardiovascular system with an embodiment of the instant invention catheter positioned with the catheter distal tip positioned in the ostium of the left coronary artery. Description of the Prior Art Referring to Fig. 1 of the drawings, the reference numeral 40 refers, in general, to a prior art guide catheter. Catheter 40 is in the form of an elongated tubular member having a straight portion 42, and a distal end portion consisting of a secondary curved portion 44, a transition 48, a primary curved portion 46, and a distal tip 50. Secondary curved portion 42 and primary curved portion 46 have in vivo radii of curvature such that the secondary radius of curvature is larger than the primary radius of curvature resulting in a pronounced transition 48 which presents increased resistance to devices advancing through the guide catheter curved shape. Description of the Preferred Embodiment A guide catheter in accordance with the present invention is shown in general by reference numeral 22 in Figs. 2 and 3. Guide catheter 22 of the present invention is configured to overcome the aforementioned deficiency of resistance to advancement of intravascular catheters and the resultant tendency to dislodge a guide catheter distal tip. Fig. 2 shows the ex vivo structure of the catheter. Guide catheter 22 has a proximal end 24 and a distal tip 34. Extending from proximal end 24 is a straight portion 26, where straight portion 26 is sufficiently long to reach from the arterial point of insertion to the aortic arch 112. In one embodiment of the present invention, where guide catheter 22 is inserted into the femoral artery near the groin, the length of straight portion 26 is approximately 36 inches. Extending distally from straight portion 26 is, in turn, a curved portion 28, which begins with a secondary curve portion 30 followed by a primary curve portion 32. Secondary curve portion 30 has a radius of curvature, Sr, and primary curve portion 32 has a radius of curvature, Pr. In one embodiment of the invention, secondary curve portion 30 has a radius of curvature of 0.6 inches, describing an angle of 155 degrees, and primary curve portion 32 has a radius of curvature of 0.9 inches, describing an angle of 60 degrees. Some embodiments of the invention have Pr and Sr such that the ex vivo Pr/Sr ratio are in the range of 1.3 to 2.0. It can be appreciated that these elements of the present invention may have different dimensions. Distal tip portion 34 follows primary curve portion 32. In one embodiment of the invention, distal tip portion 34 extends tangentially from primary curve portion 32. In another embodiment of this invention, there is a bend (not shown) between primary curve portion 32 and distal tip portion 34. Fig. 3 illustrates the placement of the present invention in vivo. Catheter 22 is normally inserted through aorta 102 by inserting catheter 22 in the femoral artery near the groin. Catheter 22 lies in the aortic arch 112, with distal tip portion 34 coaxially within the ostium 110 of the left coronary artery 114. Straight portion 26 which was straight ex vivo, is curved somewhat in vivo and extends over the aortic arch 112. Secondary curve portion 30 radius of curvature in vivo is larger than the radius of curvature ex vivo. This increased in vivo secondary curve portion 30 radius now closely matches the radius of the primary curve portion 32. The substantially equal radius of primary curve portion 32 and secondary curve portion 30 form essentially a single curve with a substantially constant radius. The aforementioned constant radius curve lies in the aorta 102, preferably lying against the inner wall of the ascending aorta 106 oppqsite the ostium 110 of the left coronary artery 114. As a result of this constant radius curve, an intravascular catheter advancing through catheter curved portion 28 encounters insubstantial transition points, rather than encountering resistance at such points which would tend to dislodge a distal tip portion from the ostium of the left coronary artery. It is understood that several variations may be made in the foregoing without departing from the scope of the invention. For example, the specific lengths and angles of the present invention can be varied within the scope of the invention. Moreover, it is understood that, instead of the identical radii of curvature and angles shown and described in the above examples, the catheters of the present invention can vary. For example, for patients with different sizes and geometries, the radii and angles may vary to achieve the in vivo constant curve guide catheter of Fig. 3.

Claims: What is claimed is: 1. A catheter for insertion through the aorta to reach the ostium of the left coronary artery, said catheter comprising:' an elongated tubular member including; a proximal end, a straight portion extending distally from said proximal end, and a curved portion extending distally from said straight portion; said curved portion including; a secondary curve portion extending distally from said straight portion, said secondary curve portion having a radius of curvature, Sr, and a primary curve portion extending distally from said secondary curve portion, said primary curve portion having a radius of curvature, Pr; and wherein when the distal end of said catheter is positioned in the ostium of the left coronary artery said Pr is approximately equal to said Sr. 2. The catheter of claim 1 wherein when said catheter is in the ex vivo state, said Pr is greater than said Sr. 3. The catheter of claim 1 wherein when said catheter is in the ex vivo state, said Pr is different than said Sr. 4. The catheter of claim 1 wherein when said catheter is in the ex vivo state, said Pr is greater than or equal to said Sr. 5. The catheter of claim 4 wherein said primary curve and secondary curve have the ratio Pr/Sr; and the ex vivo Pr/Sr ratio is in the range 1.3 to 1.8. 6. The catheter of claim 4 wherein said primary curve and secondary curve have the ratio Pr/Sr; and the in vivo ratio is close to 1.0.

Inventors: BERG TODD A, BERG, TODD, A.
Applicants: SCIMED LIFE SYSTEMS INC, SCIMED LIFE SYSTEMS, INC.
Application year: 1997
Main classification: A61M25
IPC codes: A61M25