Variable shaped catheter system and method for catheterization.

0001This invention relates to improved angiographic and cardiovascular catheter assembly.

0002For many years it has been the common practice in angiographic and cardiovascular procedures to use various angiographic catheters having different distal tip shapes in order to perform various angiographic studies. For example, when performing coronary angiography, it is common to perform studies of the left coronary artery, the right coronary artery, and the left ventrical by injecting X-ray opaque contrast liquid into each of the right and left coronary arteries and also into the left ventrical. Each injection is done with a separate catheter having a specially formed distal tip adapted to facilitate entry into the ostium of the right or left coronary artery. Typically, a catheter having a pigtail shape is used for left ventricular studies. In order to perform these studies it has been the typical practice to exchange catheters for each study. That is time consuming and subjects the patient to the trauma of multiple catheter insertion and removal. Additionally, the use of multiple catheters increases the risk of a blood clot and, in general, presents greater risk for complications.

0003The desirability of reducing the time involved in performing such angiographic studies as well as minimizing trauma to the patient by making a catheter having a tip shape adjustable while in the patient has been suggested in the prior art. US Patent 4.033.331 (Guss) discloses a specially formed catheter having two lumens, including a main lumen through which the radiopaque contrast liquid may be injected into the blood vessel and another lumen which receives a relatively stiff elongated contour wire. The distal end of the catheter has a predetermined curved shape which can be progressively straightened by advancing the contour wire distally through its lumen. The system discussed in the Guss patent has several disadvantages, the principal one being that it cannot be used with a conventional angiographic catheter. The practice of the technique disclosed in the Guss patent requires the use of the special two lumen catheter construction. Additionally, that catheter construction necessarily has reduced flow area in the main lumen because of the necessity of providing the cross-sectional area for the contour wire lumen. In that regard, it is important to maintain a large flow area as possible in an angiographic catheter so that the radiopaque contrast liquid can be injected at a relatively high flow rate. With the two lumen catheter construction this desirable feature of such catheters is compromised.

0004The present invention overcomes the problems of the prior art by providing a variable shaped catheter assembly suitable for use in angiographic procedures of the type comprising a flexible elongated catheter having a proximal end and a distal end, and a distal portion formed to a predetermined curved shape and a sheath. The catheter assembly is however characterised by the features that the sheath is flexible and has an internal diameter which receives the catheter and enables longitudinal movement of the catheter therein, the sheath being shorter than the catheter by an amount at least as great as the length of the curved distal portion of the catheter, the sheath having a degree of flexibility with respect to the catheter such that when the sheath is advanced over the curved portion of the catheter, the distal portion of the catheter and the sheath together assumes a less curved configuration whereby the shape of the curve at the distal end of the catheter can be controlled by adjusting the longitudinal position of the sheath with respect to the catheter.

0005Preferably, the lumen in the catheter extends from its proximal to its distal end and is open at its distal end, and has a fitting on the proximal end of the catheter in communication with the proximal end of the lumen for connection to a fluid instrumentality.

0006Suitably, the catheter has a Judkins left curve formed in the distal portion and the sheath is approximately 5 to 30 centimeters shorter than the catheter.

0007In a preferred embodiment, the internal diameter of the sheath is greater than the outer diameter of the catheter thereby to define an annular space extending along the length of the assembly, the distal tip of the sheath being tapered to merge smoothly with and to contact the outer diameter of the catheter, at least one side hole being formed at the distal portion of the sheath and a fitting at the proximal end of the sheath in communication with the annular flow space for connection to a fluid instrumentality. Preferably, the catheter extends through the fitting and the fitting has a gasket adapted to contact and seal the periphery of the catheter and the seal is adjustable thereby to vary the degree with which the gasket seals against the catheter.

0008Preferably, the sheath is dimensioned so that it contacts the outer surface of the catheter in close sliding contact therewith and the sheath is formed from a low friction polymeric material.

0009In one preferred embodiment, the catheter is approximately 125 centimeters long and sheath is approximately 115 centimeters long.

0010The distal tip of the catheter is preferably tapered to merge smoothly with and contact the outer diameter of a guidewire when a guidewire is received in the lumen, the distal tip of the sheath being tapered to merge smoothly with and contact the outer diameter of the catheter whereby the assembly of the catheter and sheath may be inserted percutaneously into a blood vessel over the guidewire inserted into the blood vessel, said tapered portions forming self-dilating means.

0011It will be seen from the foregoing that the preferred angiographic catheter assembly of the invention includes a flexible angiographic catheter of conventional construction having a full size lumen and a pre-shaped curve at its distal end. The catheter extends through a sheath that is several centimeters shorter than the catheter, by an amount at least as great as the length of the curved distal segment of the catheter, the shape of the curve at the distal end of the catheter being variable by advancing the sheath over the catheter. The sheath has sufficient stiffness so that it tends to straighten the catheter curve as it advances over it, thereby progressively changing the shape of the curve. The catheter assembly enables a method of angiography by which different procedures can be performed on the patient without requiring catheter exchanges for each procedure.

0012The sheath of the preferred catheter assembly of the invention also may be used to deliver fluids or make pressure measurements at the distal tip of the sheath. To this end the proximal end of the sheath may be provided with a fitting having a side leg for liquid infusion. The inner diameter of the sheath may be somewhat larger than the outer diameter of the catheter to define an annular flow space along the length of the assembly. It is desirable that the distal tip of the sheath fit closely to the outer diameter of the catheter, the tip of the sheath being tapered for this purpose. In order to provide for fluid communication at the distal end of the sheath, the sheath may be provided with several side holes at its distal end. In addition, the sheath may be used as an introducer should it be desired to remove the catheter and replace it with another catheter.

0013It will be appreciated from the foregoing that the catheter assembly of the invention can be used in a method in which the relative position of the sheath on the catheter is selected to place the distal end of the catheter in a particular curved configuration suited for the angiographic procedure to be performed. After the dye injection and procedure have been completed, the longitudinal position of the sheath with respect to the catheter may be adjusted either to increase or decrease the curvature at the distal end or to permit the catheter to assume its more curved relaxed configuration, depending on which procedure is next to be performed. The change in configuration is effected quickly and simply with no additional trauma to the patient and without increasing the risk of complications that may result from a succession of catheter exchanges.

0014An advantage of the invention is that it provides an improved catheter assembly for performing multiple cardiovascular and angiographic procedures which minimizes or reduces catheter exchanges due to the fact that the curvature at the distal end of a cardiovascular or angiographic catheter may be adjusted quickly and simply while within the patient. Furthermore, the assembly can use a conventional angiographic catheter having a full size flow lumen, the degree of curvature at the distal region of the catheter being controlled by a sheath that is slidably received over the catheter and which can be advanced or withdrawn over the catheter.

0015If required, means can be provided for injecting radiopaque contrast liquid and for making pressure measurements at the distal end of the sheath. Furthermore, the sheath may also serve as a catheter introducer should it be desired to make a catheter exchange.

0016A preferred catheter assembly of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: <ul id="ul0001" list-style="none"><li>Figure 1 is a fragmented illustration of the catheter system in accordance with the invention.</li><li>FIG. 2 is an illustration of the system with the sheath advanced distally over the primary curve in a Judkins left coronary catheter;</li><li>FIG. 3 is an illustration similar to Fig. 2 but with the sheath advanced over the secondary curve of the angiographic catheter;</li><li>FIG. 4 is an enlarged illustration of the distal end of the sheath and catheter; and</li><li>FIG. 5 is a sectional illustration as seen along the line 5-5 of FIG. 4.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENT

0017The system illustrated includes an angiographic catheter 10 having a proximal end 12 and a distal end 14. The proximal end is provided with a fitting 16 which can be connected to a syringe for injecting radiopaque contrast liquid through the catheter 10 and into the patient. The distal end 14 of the catheter 10 is formed to define a predetermined curvature and, in the illustrative embodiment, the curvature is that conventionally known as the left Judkins curve, adapted for use in left coronary artery angiography. The left Judkins shape may be considered as having a primary curve 18 and a secondary curve 20. A lumen 22 extends fully through the angiographic catheter 10, from the fitting 16 to the distal outlet tip 24. The lumen 22 is full diameter, that is, it is uncompromised by the presence of any other elements in the catheter. The construction of the catheter 10 may be conventional as will be appreciated by those skilled in the art. For example, the catheter may be formed from extruded plastic material and may have woven or braided elements embedded in the catheter wall. By way of example the catheter may be approximately 125 centimeters in length although the length may be varied depending on the specific type of angiographic or cardiovascular procedure that is to be employed. If desired, the distal tip of the angiographic catheter 10 also may be provided with side holes 26 to increase outlet capacity. Typically, the tip of the catheter 10 will be tapered as indicated at 23 so that it may fit closely about a guidewire extending through the lumen 22 for smooth percutaneous entry, as will be appreciated by those familiar with the art.

0018The system of the present invention also includes an outer sheath indicated generally by the reference character 28 through which the catheter 10 extends. The sheath is circular in cross-section, as is the catheter 10, and may be formed from an appropriate extruded tube, such as FEP or PTFE fluorinated polymer. The sheath 28 is several centimeters shorter than the catheter 10, by an amount at least equal to the length of the curved distal portion 14 of the catheter 10. In the illustrative embodiment, the sheath is between 5 and 30 centimeters, preferably approximately 10 centimeters shorter than the catheter. Typically, the sheath length will be between 30 to 150 cm, depending on the length of the catheter. The proximal end of the sheath may be provided with a hemostasis fitting 30 that receives the catheter 10 and includes an internal proximal gasket 32 (FIG. 2) that engages the outer surface of the catheter 10 to form a seal against the catheter 10. The fitting 30 may be provided with an adjustable gasket such as a Tuohy-Borst adapter (illustrated in phantom at 33 in FIG. 3) by which the constricting force of the gasket about the catheter may be varied thereby to vary the degree with which the gasket seals against the catheter. The fitting 30 also may be provided with a side leg 34 through which liquids may be injected, pressure measurements may be made and sampling performed. The side leg on the sheath fitting also may be used to aspirate if there is to be a catheter exchange, in order to withdraw embolisms, or to inject heparin.

0019The sheath is formed so that when it is advanced over the curved distal portion 14 of the catheter 10, the stiffness of the sheath will cause the curve in the angiographic catheter 10 to become somewhat straighter. To this end, the sheath should be formed from a material and should have a wall thickness and stiffness sufficient to cause the catheter to assume the particular desired shape. Figure 2 shows a sheath in an extended position in which it has been advanced over the primary curve 18 of the Judkins left catheter. In this configuration, the catheter is suited somewhat for a right coronary arteriography procedure. Figure 3 illustrates the configuration of the system with the sheath advanced over both the primary and the secondary curves 18,20 respectively. In this configuration, the assembly is best suited for an arteriography of coronary artery by-pass or for left ventriculography in the angiographic procedure. By way of example the catheter 10 may be between about 1.32mm-2.97mm (0.052" to about 0.117") (4F to 9F) in outer diameter and may be formed from polyurethane material with a braided tubular element embedded therein. The sheath preferably is formed from a tube of Teflon fluorinated polymer also in a 4F to 9F size with an inside diameter to match and receive the catheter. The sheath also preferably is radiopaque, as by incorporating barium sulfate or some other suitable radiopaque material into the polymer.

0020Figures 4 and 5 illustrates a tip construction for the sheath in which the sheath is adapted to provide fluid communication between its proximal and distal ends while receiving the catheter. In this embodiment the inner diameter of the sheath is somewhat larger than the outer diameter of the catheter to define an annular flow area 36 that communicates with the side leg 34. In the illustrated embodiment the tip of the sheath is tapered as indicated at 38 and fits closely against the outer surface of the catheter 10 to facilitate percutaneous introduction of the entire systems as a unit into the patient's blood vessel. One or more side holes 40 may be formed adjacent the tip of the sheath to provide for fluid communication with the annular area 36. The foregoing arrangement enables infusate to be delivered, pressure recordings to be made as well as sampling and purging. It may be noted that the distal portion of the sheath may have a straight configuration when relaxed or itself may be provided with a pre-formed curve.

0021The foregoing system also enables pressure differentials to be measured across a patient's aortic valve. By locating the system so that the distal tip of the catheter is located distally of the aortic valve and with the side holes 40 at the distal end of the sheath 28 located proximally of the aortic valve, pressure measurements can be made on both sides of the valve thereby providing an indication of the pressure differential.

0022From the foregoing it will be appreciated that the system may be percutaneiously introduced and used by advancing into the patients blood vessels in a conventional manner as is well known to those skilled in the art. The sheath may be positioned along the catheter to present the desired curved configuration for the first study to be performed. After that study is performed the relative position of sheath and catheter may be adjusted to change the configuration of the catheter distal curve without requiring catheter exchanges. Dye injections and pressure measurements also may be made through the side leg 34 of the sheath if desired. Should it be desired to perform catheter exchanges that is facilitated by the sheath which may be permitted to remain in the patient's blood vessel thereby to serve as a catheter introducer. The system utilizes a full bore conventional angiographic catheter and thus permits full flow of radiopaque contrast liquid into the patient's blood vessels.