NO901227L - ANGIOPLASTIC CATS. - Google Patents

Description

The invention relates to the field of surgery, and more particularly to instruments for carrying out surgical processes involving blood flow. The technique has generally been described as precut transluminal angioplasty surgery.

Coronary artery disease is generally considered a serious health problem in the United States and most of the Western world. When medical treatments fail or are insufficient to control angina pectoris, bypass grafting is generally used. In 1964, a transluminal coaxial catheter dilation method for dilation of atheromatous lesions in peripheral arteries was introduced by Dotter and Judkins. This technique requires sequential dilation of stenotic lesions and uses progressively larger dilation catheters. Furthermore, in 1971, a "Fogarty balloon catheter" was used to perform transluminal arterioplastic surgery. Furthermore, Gruntzig previously used techniques with a single double lumen catheter with a non-expandable balloon segment at the tip that was positioned in the lumen of the stenotic segment of a peripheral artery. The elastic balloon segment was then inflated, resulting in compression of the atheromatous lesion in a manner directly opposite the device thereby widening the lumen. The balloon was kept inflated for 10 to 15 seconds at 7 atmospheres of internal pressure and then deflated. As a result, there was a significant reduction in the complications due to endothelial damage, such as that due to the previously known coaxial translumen dilation technique and thus a marked improvement in the opening of the veins through the use of the Gruntzig catheter was achieved.

In previous embodiments, the amount of pressure that could be applied through a balloon-type expander was limited, and thus insufficient for expansion of particular stenotic lesions. This deficiency existed as a result of the use of polyvinyl chloride balloons with structural limitations that limited the internal pressure to about seven atmospheres.

Other catheter designs result in a total stoppage of blood flow on the other side of the treatment site. Studies of living dogs with normal coronary arteries have shown that coronary transluminal angioplasty surgery can result in brief, self-limiting ventricular tachycardia. When the balloon is inflated, the blood pressure on the other side drops to zero. Due to the lack of blood flow and pressure on the other side of the treatment site during the period such catheters are used, this period must be relatively short to prevent complications due to lack of blood supply. This limitation in inflation time tends to reduce the success rate of coronary translumenal angioplasty surgery.

The transluminal coronary angioplasty technique involves a catheter system introduced via the femoral artery under local anaesthesia. A preformed guided catheter is positioned in the coronary artery and through this catheter a second dilation catheter is advanced into the branch of the coronary artery. The dilation catheter has an elliptically shaped expandable balloon portion near the tip that can be inflated and deflated. After passing the stenotic lesion in the coronary artery, the expandable portion was inflated with fluid that compressed the atherosclerotic material in a direction generally across the wall of the vessel and thus widened the lumen of the vessel. Peripheral arterial lesions treated by this technique have shown that the atheroma can be compressed, leaving a smooth luminal surface. Studies have shown that the opening rate two years after the expansion of iliac and femoropopliteal atherosclerotic lesions was greater than 70%.

Although the lead catheter is used instead of angioplasty (dilation) catheters, the angioplasty catheter can be placed in stenotic lesions using only cable routing, if the lesion is close to the point of penetration in the body. The word "guide" is used in this application both for cable guides and guided catheters separately or used in tandem. Typically, a guide of a suitable size is passed through the stenotic lesion and the balloon catheter is threaded onto this and guided to the area of stenosis. Once the area of stenosis is reached, the balloon in the catheter is inflated to a high pressure depending on the size of the balloon and the type of stenosis, and the pressure is maintained for a certain time. During this procedure, distal and proximal pressures are measured to evaluate the physiological conditions of the organ. More specifically, the pressure difference is measured after deflation of the balloon and used as an indication of the degree of inflated expansion achieved.

Previous embodiments have used a rigid catheter tip

on the angioplasty catheter, which often resulted in pulling the guidewire out of the stenotic lesion as the catheter was advanced towards the lesion. In addition to this, when using an angioplasty catheter, it was often necessary to measure the pressure on the other side of the catheter. Previous embodiments have used a guide that closely fits the internal cross-section of the distal lumen of the catheter, thereby making it difficult to obtain adequate pressure measurements due to large pressure drops as a result of the use of small tolerances. Pressure measurements were made as dynamic measurements, the accuracy and frequency response of which were highly and significantly affected by the pressure drop within the catheter measurement lumen. This often required the guide to be withdrawn and replaced to obtain accurate pressure measurements.

Applications of angioplasty catheters often made it necessary to administer medicine or oxygenated blood, remotely

to the stenosis to provide adequate physiological function of the organ in question. Prior embodiments did not allow for such separate lumens to carry sufficient medication to prevent irregular contractions of the arterial wall as a result of delivery of the angioplasty catheter. To the extent that such meds were necessary to relax the arterial wall, the lumen through which the guide wire passed was used for the auxiliary function of an injection port for meds. However, the use of the same lumen for pressure measurement as well as the infusion of medicine or other fluids made it difficult to maintain continuous and accurate pressure measurement.

Anginoplasty catheters that were previously used had relatively large catheter body diameters, which tended to occlude the artery in question, which resulted in reduced blood flow to the lesion or the organ it supplied. Such a catheter is shown in US patent 4,323,071 (fig. 4). Other catheters, although using a tapered body, employ a rigid tip which, if the arterial path was particularly tortuous, tends to pull the guidewire away from the stenosis. Such a catheter is shown in US patent 4,413,989 (fig. 8).

Flexible tips attached to the distal end of an angiographic catheter have been used to inject radiopague contrast or drugs into femoral arteries as part of diagonistic or therapeutic procedures. Such deformable tips were intended to prevent punctures of the wall of the aorta, and have been designed with a larger cross-sectional profile than the catheter body to which they are connected. Some designs have also had means for inflation of the deformable tip to increase the contact area between the tip and the body part to reduce the pressure per area unit added to the part. Such an embodiment is described in US patent 4,531,943.

In previous designs, it was often difficult to estimate the location of the tip of the catheter. Previous embodiments employed the use of gold bands near the distal end of the catheter thereby marking the portion of the catheter that was visible to an X-ray machine. However, since it was risky to connect such rings with the very distal end of the catheter, the distal end of the catheter was not visible under X-rays and often the physiologist performing the procedure had to guess its location. This disadvantage of previous catheters has been addressed in the catheter of the present invention by using a radiopaque tip.

Known angioplasty catheters have expansion balloons connected to the catheter body by gluing or heat sealing. Typically, these balloons are made of polyvinyl chloride or non-irradiated polyethylene. Polyvinyl chloride balloons are normally dissolvably or adhesively bonded to the catheter bodies of the same material and the polyethylene balloons are glued or heat-shrunk to the catheter bodies of the same material, or a mixture of polyethylene and polypropylene, to achieve the catheter body's rigidity. Most such catheters have relatively stiff tips at their distal ends, which often allows the misplaced guide to be pulled out of the lesion area during catheter advancement in tortuous arteries as well as intimal damage. Known catheters also have relatively rigid bodies to carry balloons near the distal end of the catheter. The stiffness of the catheter body continues in the area of the balloon to the distal end of the catheter.

Known catheters contain air holes in the balloon lumen, so that air can be removed directly out of the balloon cavity and out of the catheter during delivery of the balloon. These added lumens, either in the form of small metal tubes or as a multi-lumen catheter tube, take up valuable cross-sectional area of the catheter tube that could otherwise be used for other purposes, such as pressure measurement.

Known catheter designs have placed an inner and outer tube in which the outer tube contains the balloon as an integral part thereof or a separate balloon which is tied to the outer tube. The cavity between the inner and outer tube is used for inflation of the balloon.

Known angioplasty catheters have been sold in a sterilized state to doctors and hospitals with the balloon in a deflated state and with gas introduced. Before the use of such catheters, doctors or technicians must inject contrast fluid into the balloon to remove the gas inside. This procedure involves sequential inflation and evacuation of the balloon using a plug connected to the proximal end of the catheter. Such catheters were sold to doctors and hospitals with the balloon in a wing-folded state. Wing folding involves substantially flattening the balloon along the catheter body and folding the balloon over to the catheter body in two segments similar to wings on an airplane fuselage. Previously, the catheter was wing-folded at the factory before shipment. However, to remove the introduced gases, doctors and technicians had to unfold the wings and fill the balloon with contrast fluid while the gases were evacuated from there. As a result, the advantage of the balloons maintaining their wing-folded position after sale was lost. The doctor or technician had to refill the balloon with contrast fluid, and again attempt to manipulate the balloon with his or her fingers to reactivate the wing-folded position that reduced the profile of the catheter.

The catheter of the present invention has tackled this problem of pre-filling the catheter with contrast fluid, and places a sleeve over the balloon after it has been wingfolded. Accordingly, the advantage of wing folding is retained and the doctor only removes the sleeve and the sterile catheter is ready for insertion with the balloon in a low profile position.

It is an object of the present invention to provide a soft atreumatic catheter tip with radio-paque filling such as e.g. bismuth oxychloride or bismuth subcarbonate is introduced.

It is an object of the invention to provide a relatively soft catheter tip to minimize the tendency of catheters to bring a lead out of stenosis when the catheter is advanced in a tortuous path, and also to minimize intimal damage.

It is another object of the present invention to provide a catheter tip which can be inserted melted, heat-bonded or glued firmly to a relatively rigid catheter body in the vicinity. It is a further object of the present invention to use such materials as nylon, polyvinyl chloride, polyurethane, or different stiffnesses which are easily bondable according to the previously mentioned methods.

It is a further object of the present invention to provide an inner tube which is relatively large in inner diameter and which is bent down in the area of the balloon and several cm near the balloon to provide a large cavity for pressure measurement. The catheter provides an improved frequency response without sacrificing the overall outer diameter and has a relatively small diameter in the area of the balloon and thus maintains a catheter design with a low profile.

It is a further object of the present invention in one of the various embodiments to provide an air lumen for venting gases out of the balloon so that the lumen extends within the wall of the outer tube and thus avoids sacrificing some of the catheter's cross-sectional area for other lumens by to allow such other lumens to have maximum cross-sectional area within a low profile catheter.

It is a further object of the present invention to provide in one embodiment an opening in the balloon cavity at its extreme distal end and thus enable the removal of gases during filling with contrast liquid.

The object of the invention is solved with an angioplasty catheter with an elongated body with at least one lumen extending through it. A tip constructed of materials softer than the extended body is coupled to the distal end of the body. The tip portion has at least one lumen passing therethrough that is aligned with the lumen of the elongated body. A guide is adapted to pass through the adapted lumens. A balloon is coupled to the distal segment of the elongated body over its outer periphery, thereby creating a balloon cavity therebetween. At least one further lumen is provided in the elongated body in flow communication with the balloon cavity for selective inflation and deflation thereof with a contrast fluid.

In what follows, the invention will be described in more detail with reference to the attached drawings, where

fig. 1 is a cross-section of an embodiment of a catheter in accordance with the present invention with a coaxial embodiment and with a tip with an outer shoulder,

fig. 2 is a cross-section of the coaxial embodiment as shown in fig. 1 with an alternative balloon assembly,

fig. 3 is a cross-section of a coaxial embodiment of FIG. 1 showing an alternative assembly of the proximal end of the balloon,

fig. 4 is a cross-sectional view of an alternative assembly of the distal end of the balloon;

fig. 5 is a cross-section of an embodiment with the tip comprising a spring,

fig. 6 is a cross-section of an alternative embodiment of a catheter in accordance with the present invention,

fig. 7 is a cross-section taken along line 7-7 in fig. 6,

fig. 8 is a cross-section of an alternative embodiment of a catheter in accordance with the invention,

fig. 9 is a cross-section taken along line 9-9 in fig. 8,

fig. 10 is a cross section through the balloon showing the sleeve,

fig. 11 is a view of a catheter showing the sleeve over the balloon,

fig. 12 is a schematic representation of an angioplasty catheter showing the pressure measurement technique used using externally mounted transducers;

fig. 13 is a schematic representation of an angioplasty catheter illustrating the placement of the pressure sensing transducers on the catheter,

fig. 14 is a cross-sectional view of the distal end of an embodiment of an angioplasty catheter illustrating a two-stage balloon;

fig. 15 is a detailed cross-section of an area shown in a broken circle in FIG. 14, and

fig. 16 is a representation of an angioplasty catheter as shown in FIG. 1 and which illustrates several unique dimensional conditions in this.

The catheter C of the present invention has several designs described here and illustrated in the figures. Fig. 1 shows a coaxial embodiment for a catheter with an inner body I, an outer body B. Cavity A is defined between the inner body I and the outer body B. A tip T is connected to the inner body I. A balloon D is connected to the outer body B at one end and near the distal end of 10 of the inner body I.

As shown in fig. 1, the inner body I has at least one internal, through-cavity 12. The tip T has an axial lumen 14 which is adapted to the lumen 12 when the tip T is connected to the distal end 10 of the inner body I. As shown in fig. 1 and 2, the inner body I extends past the outer body B. As previously mentioned, one of the purposes of catheter C in accordance with the present invention is to obtain a low profile, without at the same time affecting the sensitivity of the dynamic pressure measurement within the relevant artery. At this end, the lumen 12 has a relatively large cross-sectional area as shown by arrow 16 for substantially the entire length of the catheter. However, to avoid obstruction of blood flow into the stenotic region where the angioplasty procedure is to take place, it is desirable to have the distal end 18 of the catheter assembly C as small as possible to avoid interruption of blood flow. Accordingly, the inner body I is provided with threaded segment 20 which acts as a neck for the cross-sectional area of the lumen 12 for the section as shown by arrow 16 to a smaller cross-sectional area shown at 22.

As shown in fig. 1, the balloon D, which is preferably constructed of polyethylene or polyester, has an elongated shape defining a cavity-shaped cavity 24 between the outer surface 26 of the inner body I and the inner surface 28 of the balloon D. The cavity 24 is in flow communication with the cavity A The cavity 24 is cut off at its distal end 30 (Fig. 2) by one of several alternative methods.

In the first alternative, the balloon D has a remote neck 32 which is attached, sealed or otherwise connected by known methods to the outer surface 26 of the inner body I. The tip T has an inner mounting shoulder 34 (Fig. 2) which comprises cavity surface plate 36 and radial surface 38 in the vicinity thereof. The tip T is blunt against the far surface 40 of the inner body I, which can be seen in fig. 2. The tip T is secured to the inner body I by methods known in the art on at least two adjacent surfaces 36 and 38. The tip T can further be secured to catheter C by connecting the distal neck 32 of balloon D to radial surface 42 of balloon D With the arrangement described above, the distal end 18 (see Fig.1) of the catheter C maintains a low profile as the outer surface 44 of the balloon D at the distal neck 32 is kept substantially flush with the outer surface 46 of the tip T.

Alternatively, as shown in fig. 1, the tip T can have the same internal shoulder design 32 as illustrated in fig. 2. In the alternative embodiment shown in fig. 1, the tip T has an externally mounted shoulder 48 having a circular surface 50 and a radial surface 52 in the vicinity. The distal neck 32 of balloon D is secured to the circular surface 50 and radial surface 52 to the tip T. The coupling method illustrated in fig. 1 provides additional security in mounting the tip T in that, in addition to contact between the inner body I and the circular surface 36 and the radial surface 38 of the internal mounting shoulder 34, additional mounting points exist due to the bend between the remote neck 32 and the external mounting shoulder 48. It should be understood that the remote neck 32 can be secured to the external mounting shoulder 48 by various means known in the art. Furthermore, shoulder 34 can be secured to inner body I by known means. The assembly method is illustrated in fig. 1 results in outer surface 44 of balloon D's proximal neck 32 being flush with outer surface 46 of tip T. However, due to the application of external shoulder, the profile of catheter C is as illustrated in fig. 1 somewhat larger than the profile illustrated in fig. 2.

Fig. 4 illustrates yet another alternative embodiment for securing the tip T to the distal end 40 of the inner body I. The tip T is preferably fused to the distal end 40 and has an outer periphery similar to that of the outer surface 26 of the inner body I Accordingly, outer surface 46 of tip T is aligned with outer surface 26 of inner body I. The distal neck 32 of balloon D connects the fusible link 76 between tip T and inner body I. A threaded transfer 78 is provided. between outer surface 44 of the balloon D and outer surface 46 of the tip

T to avoid damage to the arterial wall during insertion and removal of the catheter C. The inner surface 26 of the balloon D is preferably connected to both the outer surface 26 of the inner body I and the outer surface 46 of the tip T by known methods. Alternatively, inner surface 26 may be coupled only to outer surface 46 although it may also be in contact surface 26. As a result, the adjacent neck 32 secures tip T to inner body I, circular with tip T also coupled to inner body I along the conforming radial surfaces constituting the link 76. The arrangement shown in fig. 4 also presents a low profile for catheter C while also having the advantage of a flexible tip to counteract the tendency of an otherwise rigid catheter to give the guide to the wrong place from the stenosis where it has to be passed through a special dented arterial path to reach the stenosis.

Experience has shown that by removing the neck 32 of balloon D, 0.004 inch thick can be constructed. The proximal end 54 (Fig. 2) of the tip T can also be manufactured to the same thickness, resulting in a smooth transition between the balloon D and the tip T with minimal increase in the profile of the catheter.

To further reduce the profile of the catheter and thereby provide blood flow to the lesion as the distal end of the catheter is moved toward the stenosis, the proximal neck 56 of the balloon D is secured to the inner surface 58 of the outer body B near the distal end 60 of the outer body B. A polished smooth edge 62 is used near the outer surface 44 of balloon D near the distal end 60 of outer body member I. Use of the smooth edge 62 which is somewhat tapered eliminates sharp edges which could irritate or tear through the arterial wall when inserting or removing catheter C. As can be easily seen by studying fig. 1 and 2 when the balloon D is deflated, the maximum profile of the distal end 18 of the catheter C is represented by the diameter of the tip T (surface 46) as measured in a plane perpendicular to the longitudinal axis of the catheter C.

The flexibility of the catheter C can be adjusted in several ways. One way to influence the relative stiffness of the distal end 18 of catheter C extending from the distal end 60 of the outer body B to the end of the tip T is to vary the length of the proximal neck 56 of balloon D. This neck 56 can e.g. varies in the range 1 to 60 mm. Along the same lines, the overall length of the tip T can be adjusted to affect the bendability of the catheter C. Another way to affect the overall stiffness of the distal end 18 of the catheter C is to prepare the shape of the inner body I and the tip T to vary for the hardness. Typically, the tip T ah can have a hardness in the range 50 to 90A, measured by the Shore method, and can be made of a material such as e.g. nylon. The inner body I can be made of a stiffer grade than nylon such as e.g. 140 on the Rockwell scale. The relative hardness of the tip T and the inner body I can be adjusted in conjunction with adjusting the length of the proximal neck as well as the total length of the tip T to achieve the desired stiffness of the catheter C for a particular application. Typically, the tip lengths can be in the range of 1 to 30 mm, although an interval of 1 to 10 mm is preferred. Similarly, the proximal neck 56 can be placed in different lengths in the same range from 1 to 6 cm.

As an alternative way of changing the relative stiffness of the distal end 18 and catheter C, FIG. 5 the tip T or the embodiment illustrated in fig. 3 with an inserted coil spring 80 mounted against the most distant end 74 of the tip T. As shown in fig. 4, the spring 80 goes around the lume;- 14 extending through the tip T. The length and suspension effect of the spring 80 can be adjusted depending on the desired stiffness. However, the overall profile of the tip must be kept as low as possible. It should be noted that when the spring 80 is inserted into the tip T, an infusion lumen 70 as shown in fig. 6 generally not used.

As can be seen in fig. 1 and 2, cavity A has a substantially constant cross-section in the vicinity and remote from the cone segment 20 of inner body member I. This is achieved by a cone 64 on an outer body member B near the distal end 60. Cone 64 is adapted to the cone segment 20 to the inner body I. As suitable contrast fluid (not shown) is inserted into the cavity A at the near end of catheter C (not shown) to fill up the cavity 24 from this by inflation of the balloon and exerts radial forces against the stenosis.

The low profile of catheter C in the present invention as shown in fig. 1 and 2 are essential to allow continuous blood flow while catheter C is inserted into an artery such as e.g. a coronary artery. The low profile of the catheter of the present invention represents an improvement over other known designs in that the low profile allows continuous blood flow as catheter C is inserted into the artery and at the same time catheter C of the present invention allows sensitive pressure measurements during the angioplasty procedure.

As the measurement of pressure is a dynamic type of measurement, it is essential not to increase the flow resistance in the lumens 12 and 14. A substantially smooth wall in the lumens 12 and 14 can reduce such flow resistance. As shown in Figures 1 and 2, a guide must be passed through the lumens 12 and 14. The neck down to the lumen 12 to the cross-section shown by arrow 22 acts to increase the flow resistance, and thus tends to make pressure measurement more difficult. However, this portion of the lumen is of relatively short length and is necessary to achieve the low profile of the distal end 18 of catheter C. Transfers 20 and 64 allow the cross-sectional area of the lumen 12 to be increased in size measured in a proximal direction as quickly as possible. As a result, the total flow resistance of the lumens 12 and 14 is kept to a minimum, which in turn increases the sensitivity for accurate pressure measurements. At the same time, the cross-sectional area of cavity A is kept constant up to the nearest neck 56 of balloon D mounted to the inner surface 58 of the outer top member B. By keeping the cross-sectional area of cavity A as large as possible, the resistance felt by a doctor or technician at inflation of the balloon D kept to a minimum.

Fig. 3 represents an alternative assembly of the proximal end of the balloon to the distal end 60 of outer body B. As shown in Fig. 3, the inner surface 28 of the balloon is fitted to the outer surface 66 of the outer body B in the vicinity of the distal end 60. An air cavity 68 is provided within the wall of the outer body B. As can be seen in fig. 3 by placing an aeration lumen 68 in the wall of the outer body B, the cross-sectional area of the lumen 12 or cavity A is kept unaffected. The presence of a ventilation lumen 68 extending longitudinally in cavity 24 from the proximal end of catheter C (not shown) provides purging of the introduced gases within the balloon for insertion of catheter C into the body. In order to use catheter C, the introduced gases are removed from cavity 24 as well as cavity A by injection of contrast liquid. The contrast fluid (not shown) is injected with an acid into cavity A. The contrast fluid flows into cavity 24 which is in flow communication with cavity A. By holding the distal end 18 of catheter C in a vertical position when the tip T points towards the ground, and at further withdrawal of the plug of the syringe which injects contrast liquid, air or other introduced gases within the cavity 24 due to of the vacuum that results when the plug (not shown) is pulled from the cavity 24 through the cavity A and out of the catheter C. The ventilation lumen 68 in the embodiment in fig. 3 also includes purification of introduced gases. Experience has shown that with a suitable amount of care the introduced gases can be effectively removed from the cavity 24 without the use of

the ventilation lumen 68. However, the pressure from the lumen 68 will streamline the procedure.

Although inner body I and tip T have been shown with respective common lumens 12 and 14, alternative constructions may fall within the scope of the invention. For example, inner body I and tip T can have two adapted lumens. The first lumen cooperates with a guide wire and/or a guide catheter C in the zone remote from the stenosis. The proximal lumen which is substantially parallel to the first lumen can be used to infuse oxygenated blood and other fluids distal to the balloon. The infusion lumen 70 preferably extends radially from the tip T near the distal end of the tip T as shown in FIG. 6. Lumen 70 can also exit at an acute angle to the longitudinal axis of the tip

T.

As can be seen from fig. 3, the tip T may further be made with a reduced taper 72 to further reduce the cross-sectional area of the tip distal end 74. To aid in the performance of the angioplasty procedure, the tip T may be made of radio-paque material to allow close monitoring of its axial position in the arterial system of the body.

An alternative embodiment of catheter C in the present invention is shown in fig. 6 to 9. In this embodiment, catheter C comprises an elongated body E with a proximal segment 82 and a distal segment 84 with a cone transfer 86 therebetween. The elongated body E has at least one lumen extending through from the proximal segment 82 through the distal segment 84. As shown in Figures 6 and 7, in one embodiment of catheter C, the elongated body E has three lumens 88, 90 and 92 extending longitudinally through . Lumen 88 is adapted to tip lumen 14 (Fig. 6). A guide passes through the adapted lumens 88 and 14. The lumen 90 is adapted with the infusion lumen 70 at the tip T for injection of medicine or oxygenated blood required in angioplasty procedures. As shown in fig. 6, lumen 70 preferably exits sharply radially from tip T near its distal end 74. Lumen 92 is a balloon inflation lumen extending longitudinally through elongated body E and into balloon cavity 94 near its distal end 96. The proximal neck 56 of the balloon D is secured along the inner surface 28 of the balloon to the outer surface 98 of the elongate body E spaced from the cone transfer 86. The distal neck 32 of the balloon D may be secured to the elongate body or tip T in the manner shown in fig. 6 or as previously described with respect to fig. 2 or 4. In order to achieve the lowest possible profile on catheter C for the embodiment using the extended body E, it is preferred to use the assembly method illustrated in fig. 2 or 4 to secure the distal neck 32 of the balloon D to the distal end 18 of catheter C. The foregoing discussion regarding variation in material hardness and tip and balloon lengths with respect to the embodiment illustrated in FIG. 1 to 3 is also applicable in the alternative embodiment of the elongated body E. Similarly, the characteristic of the tip T can be varied to include a reduced taper 72 as shown in fig. 3 or the addition of a coiled wire 80 inserted near the distal end 74 of the tip T. The tip T in the embodiment comprising the elongated body E may also be made of a radio-paque material to facilitate tracking of the advancement of the catheter C within the artery is talking about.

The tip T can be produced from an elastomeric polymer material such as special types of nylon copolymer or the like.

Inflation and deflation means F effect balloon inflation through lumen 92 which is in fluid communication with balloon cavity 94 near its distal end 96. When using the catheter of the embodiment comprising extended body E, the balloon cavity is filled with contrast fluid before the catheter is advanced into the body of the patient. To enable the removal of introduced air within the balloon cavity 94, the doctor or technician will place the distal end 18 of the catheter C evenly with a vertical position of the tip T pointing upwards. A syringe (not shown) is connected to the near end of the lumen 92 whereby pressure on the syringe plunger pushes contrast liquid upwards through the lumen 92 whereby the contrast liquid falls downwards within the balloon cavity 94 towards its near end 100. At the same time the introduced gas, usually air, will precoil through the lumen 92 to allow contrast fluid to enter balloon cavity 94. To enable removal of the entrained gas within balloon cavity 94, the plunger of the contrast fluid injection needle will be retracted thereby creating a vacuum near the distal end 96 of balloon cavity 94 thereby pulling return the gas that is inside. Alternatively, to further enable filling of the balloon cavity 94 with contrast liquid, fig. 9 the cross-section of the elongated body E showing the lumen 88 as well as the balloon inflation lumen 102 and the balloon ventilation lumen 92. When using a combination of the inflation lumen 102 and the ventilation lumen 92, it is desirable to have the inflation lumen 102 in the balloon cavity 94 near its proximal end 100 and the ventilation lumen 92 enters the balloon cavity 94 near its distal end 96. When a technician or physician adjusts the catheter C in a vertical position with the tip T pointing upward, contrast fluid may enter the balloon cavity 94 through the lumen 102 near the proximal end and gradually replacing the introduced gas through lumen 92 for removal from catheter C. As soon as contrast fluid enters from the near end (not shown) of lumen 92, the doctor or technician can know that the entire balloon cavity 94 is full of contrast fluid. It should be noted that the embodiment shown in fig. 8 can be used with lumen 90 for the introduction of medicine as well as lumen 88, and balloon inflation and wait in lation lumens 102 and 92.

In the past, manufacturers of angina plastic catheters made it so that the balloon was wingfolded as shown in fig. 10. Wing folding is a technique where digital manipulation or a machine is used to grip the balloon D above and below the extended body E and in effect fold the balloon into a pair of wing-like segments above and below the extended body E. These two wing segments are folded over the extended body E as shown in fig. 10. However, when a doctor or technician fills the balloon cavity 94 in the operating room before the angioplasty procedure, for a proper filling of the balloon cavity 94 with contrast fluid, the wing folding must be redone and thus the advantage of keeping the balloon D in the wing folded position is lost. In order to take advantage of the tendency for the balloon D to be held in a wing-folded position in order to maintain the lowest possible profile for introducing catheter C, the device in accordance with the present invention comprises a sleeve 104 which is adapted to be fitted over balloon D as shown in fig. . 10. In the device according to the present invention, the balloon cavity 94 is filled with contrast liquid at the factory and the wing folded carefully by suitable machines. Sleeve 104 is fitted over the wing-folded balloon which has already been filled with contrast liquid. The wing folding will remove some liquid from the cavity 94. As shown in fig. 11, the sleeve 104 is threaded over the entire balloon D and holds the balloon D in a wing-folded position. To prevent removal of contrast fluid, the assembly of catheter C is equipped with a valve 106. The entire assembly is then sterilized so that it is ready for introduction into the body when unpacked. To use the device of the present invention with sleeve 104, the doctor simply removes the sleeve 104. With the balloon cavity 94 already full of contrast fluid, holding the sleeve 104 over the wing-shaped balloon D during shipping will act to keep the balloon D in a wing-folded position even after sleeve 104 is removed. When the catheter is properly inserted by known means, contrast fluid can additionally be introduced to inflate balloon B through the balloon inflation lumen 92 (Fig. 8). It should be noted that the same advantages are available in the embodiment with catheter C comprising an inner body I and outer body V except that the balloon is expanded by adding more contrast fluid through annulus A after removal of sleeve 104 and insertion of catheter C into the body. To deflate the balloon, the valve 106 is opened thereby relieving the pressure within the balloon cavity 94 and deflating the balloon.

Catheter C of the present invention offers advantages over known catheters. By using a soft tip, there is a reduced tendency for a rigid catheter to pull the guiding catheter and/or guidewire out of a stenosis when the angioplasty catheter C is passed through a tortuous arterial channel. The low profile of the distal end 18 of catheter C allows further blood flow to the stenotic area in contrast to previous designs of larger profile catheters. Mounting the tip T, where the tip T is secured to the catheter body on several surfaces, further improves safety and operational aspects of the catheter, in that the risk of losing the tip T is greatly reduced. Catheter C of the present invention provides a low-profile distal end 18 with a larger profile near the end so that the dynamic measurement of the pressure distal to the stenosis is independent of the guide catheter or guide wire through the measurement lumen of catheter C. The embodiment of the present invention provides the advantage of a low profile remove end 18 with a larger profile nearby, thus somewhat eliminating the need to remove the guidewire to provide the correct dynamic pressure measurement response required during the angioplasty procedure. The use of an additional lumen aids blood and drug delivery, providing remote pressure measurements while maintaining a low catheter profile 1. In the embodiment comprising inner body I and outer body B, mounting the proximal neck 56 of balloon D to an inner surface helps of the outer body element B further by reducing the profile of the catheter when the balloon D is deflated. Prefilling the balloon cavity 94 (Fig. 8) or cavity 24 (Fig. 2) with contrast fluid, as well as wing folding and insertion of the sleeve 104 allows the doctor to insert the catheter in a state where the balloon D maintains its low profile shape due to the wing folding.

Catheter C of the present invention has a soft tip T extending from the distal end point 74 (Fig. 3) to a point near the distal neck 32 of the balloon D. The soft tip T is lateral to the distal end 10 of the inner body 1 (fig. 3). The soft tip T reduces the tendency of a rigid catheter to pull the guide catheter out of the coronary artery opening and/or pull the guide wire out of stenosis with the angioplasty catheter C passed through a tortuous arterial passage. At the same time, the distal end 10 of the inner body I is relatively stiffer than the tip T, which provides the necessary stiffness for precise positioning of the balloon D within the stenosis. In addition, the relative stiffness of the distal end 10 below the balloon D will resist sealing of the lumen 12 due to hydrostatic pressure applied from an inflated balloon D. The resistance to lumen compression is achieved e.g. in the case of catheter designs as shown in fig. 1 or.

One of the problems associated with prior art catheters is the need to maintain accurate dynamic pressure measurements of arterial pressure upstream and downstream of the balloon D during inflation and after deflation of the balloon. The system previously used is illustrated in fig. 12. As can be seen in fig. 12 is a schematic representation of the angioplasty catheter C. A termination fitting 200 comprises a coupling 202 and a transducer 204 which converts upstream pressure at a position indicated by arrow 206 into an electrical signal indicating the pressure on receiver 208. Furthermore, another termination fitting allows 210 fluid communication with the pressure in the artery 212 remote to the balloon D. The arrow 214 represents a point where the arterial pressure is measured downstream of the balloon D through a fluid connection through the termination fitting 210. The transducer 216 converts the pressure measured at a point indicated by arrow 214.

Previously, many problems arose in connection with the use of the pressure measurement system illustrated in fig. 12. To enable the use of catheter C, guide lines 218 and 220 were often quite long. Guide lines 218 and 220 were often made of soft, elastic material, which tends to affect the dynamic pressure readings at the point indicated by arrows 214 and 216. In addition, during angiopolastic procedure, blood or contrast medium must be injected into connectors 202 and/or 222 which requires temporary disconnections of the pipes.

Previously, prior to catheter insertion, the long guide lines 218 and 220 had to be flushed with fluid to remove all air from these lines. In addition, when blood or contrast fluid was to be injected through connections 202 or 222, such injections took place through connections in lines 218 and 220. As the connections were temporarily removed by injection of blood or contrast medium, the possibility of air in lines 218 and 220 was a potential problem. Therefore, the doctor had to take his time and ensure that the air was eliminated from lines 218 and 220 before connecting lines 218 and 220 back to the catheter.

The length of guides 218 and 220 along with the elastic wall of such lines also affected the sensitivity of dynamic pressure measurements at recorder 208.

Fig. 13 shows an improvement of the known pressure measurement system shown in fig. 12. As can be seen from fig.

13, guide catheter 224 is equipped with a pressure transducer 226 mounted to the hub or associated "Y" connector and has a sensor exposed to arterial pressure upstream of balloon D at a point illustrated by arrow 206. Transducer 226 may also be mounted to the body of the catheter. C without removing himself from the idea of the invention. The angioplasty catheter C has, in the construction illustrated in Figures 1 or 8, for example, a transducer 228 mounted to the hub or "Y" connection of the PCTA catheter or, alternatively, embedded in the wall a sensing element exposed to arterial pressure downstream of the balloon D at a point indicated by arrow 214. Suitable wires pass through connectors 200 and 210. Wires 230 and 232 are then connected to recorder 208 to provide a visible reading of the pressure between two points, upstream and downstream of the inflated balloon D.

The inaccuracy in the pressure measured in the system illustrated in fig. 12 and that described above is eliminated with a more sensitive system, which more accurately follows the pressure near the far end of the balloon D during inflation. In addition, with the system as illustrated in fig. 13, couplings such as 222 and/or 202 can be mounted close to the end fitting 210 and 200 so that medication or blood can be introduced with minimal risk of introducing air into the catheter.

Another aspect of the present invention is for the introduction of blood remote from the inflated balloon to reduce ischemic reactions downstream of the balloon. With perfused blood, preferably from the patient's renal vein during balloon inflation, ischemic manifestations during extended coronary artery expansions of the balloon D will be effectively prevented. Hemoperfusion allows a more adequate and more permanent coronary artery dilation during angioplasty surgery. A suitable device for withdrawing blood is connected to the renal vein (not shown) and through the blood pump directed in connection 222 as represented by arrow 234. Renal blood is preferred because its high oxygen content. In the case of perfusion of renal blood, the balloon inflation time is allowed to be extended to 5 min. or more. Without remote hemoperfusion, the patient may experience chest pain and electrocardiographic signs of increasing significant ischemia with a period of 60 seconds of balloon inflation. Previously, only low flow rates were achieved through the coronary artery dilation catheter. And since most PCTA procedures had to be performed without myocardial protection for 60 seconds of balloon inflation, efforts to provide remote preperfusion were rejected. In 1984 in an article in the Journal of the American College of Cardiology, Meier and Gruentzig, in an article entitled "Percutaneous Arterial Perfusion of Acutely Occluded Coronary Arteries in Dogs", described an experimental canine model in which a roller pump was used in long time like 150 minutes to allow flow up to 100 ml per min. The incidence of hemolysis and thrombosis was considered to be unacceptable. Other experiments involving selective injections of hexogenic fluids for distant coronary perfusion during PCTA. Fluorocarbon emulsions were somewhat successful in reducing ischemic manifestations during balloon inflation, but were associated with a high rate of ventricular fibrillation.

Experiments have shown that with existing catheters

available on the US market, manufactured at USCI, inflated to 10 atmospheres, pressures of 50 - 75 psi, was sufficient to achieve blood flows of 40 - 60 ml per min. However, inflation of the balloon at certain times caused collapse of the flowing lumen of the catheter. However, other commercially available catheters such as those made by ACS Company require pressures as high as 250-270 psi to achieve the same flow rates. Infusion of 40-60 ml/min. of blood allows adequate suppression of ischemic manifestation with residual reduction of coronary artery occlusion.

Relatively long term-subselective coronary hemoperfusions can be used with patients with acute or chronic myocardial infarction whether PTCA is used or not. Such long-term applications require catheters with as low as possible resistance to blood flow along automatic pumping equipment to provide safe current for extended periods. The resulting improvement in regional coronary blood flow will be immediate and dramatic. Chest pain would be reduced or eliminated, ST-T segment changes would be reduced or normalized. The patient's hemodynamic status and rhythm would also stabilize. The application of long-term hemoperfusion would give patients hope to undergo angioplasty or even surgery under partially elective conditions. The use of oxygenated renal blood allows the use of lower flow rates to prevent ischemia with a low risk and not a complicated method of blood withdrawal, compared to the use of arterial blood from the femoral artery. Thus, lower pressure on the pump can be used with a suitably designed catheter. Damage to the blood under high operating pressure is reduced. Contamination or other complications that may arise from the use of foreign blood as a source of perfused blood are greatly reduced, if not eliminated.

In order to provide remote hemoperfusion with blood with a hemocrit level of around 30-50%, it is desirable to reduce the resistance to blood flow through the lumen 12 (see fig.l). To achieve this, it is desirable to maintain the following conditions:

L = Length shown by arrow 224 in inches

L2= Length shown by arrow 248 in inches

D^= Lumen inside diameter given by arrow 242

T>2 = Lumen inside diameter given by arrow 246

K has an interval from around 2-4 for blood with a 30-50% hemocrit level.

It has also been found that a specific dimensional relationship between the diameter of the lumen 12, at the position of arrows 16 and 22, as well as the length of the distal end of the catheter (measured from the cone segments 20 and 64 to the distal tip 74) and the length of the catheter in the vicinity of transfers 20 and 64, provides optimal conditions for providing remote perfusion at reduced resistance to flow.

The variables just described are identified in fig. 16. Inner diameter D^ of lumen 12 is indicated by arrow 242. Length L1 is represented by arrow 244. Diameter D2

of lumen 12 is represented by arrow 246. The length L2 of the distal segment of lumen 12 is represented by arrow 248.

For human whole blood with a hemocrit level of 30-50%, the dimensional ratio that gives the lowest pressure drop for the catheter is shown in fig. 8 or 16:

The number 5.2 x 10~10 is a constant for the blood

described above and includes a factor for adjusting the units on both sides of the equality sign. Different values for this constant are used for other fluids. Q is the flow rate in cubic inches per my.

Another improvement over the angioplasty catheter previously known is illustrated here in fig. 14. The PTCA catheter of known construction or of the type illustrated in fig. 1 or fig. 8, can be performed with multistage balloon D illustrated in fig. 14. The balloon can be shaped in two steps as illustrated in fig. 14 or more steps as desired. The advantage of using a multistage balloon is that the same catheter can be used to shape or dilate the coronary artery during angioplasty surgery without the necessity of removing a catheter and inserting another with a larger balloon capable of further dilation than the previous catheter . Thus, during operation as shown in fig. 14, the first dilation of the plaque is done by placing the smaller steps 236 of the balloon D in the stenosis and dilating the plaque. The balloon D is then deflated and advanced into the stenosis so that the distal stage 238 can be inserted into the stenosis. The balloon is reinflated for further dilatation of the coronary plaque. The ratio between the steps can be varied depending on the application in question. The balloon can be equipped with two stages or more as desired depending on the application.

The dotted circle with reference number 15 in fig. 14 is shown in cross section in fig. 15. Fig. 13 shows a coating of the entire catheter, especially the balloon, comprising a combination silicone type 4159 from the Dow Corning Company and heparin layer 240 as illustrated in fig. 15. The silicone improves lubrication and heparin prevents the formation of blood clots. Heparin is placed interwoven within the silicon matrix, and then adhered to the catheter C wall including the balloon D. Previous applications involved heparin coated catheters in combination with a polymer that did not provide lubrication. The combination of silicone and heparin provides both benefits at the same time. The catheter is plasma-treated to achieve a suitable bond of the silicone/heparin layer of the catheter material, which e.g. may be polyethylene.

The foregoing presentation and description of the invention is illustrated by means of examples, and various changes in size, shape and material as well as details of the illustrated embodiment can be made without departing from the spirit of the invention.

Claims (17)

1. Catheter for expansion of stenotic lesions in the vascular system and other body cavities, insertable via a guide, characterized by comprising: a tubular outer body; a tubular inner body disposed substantially within the outer body and thereby defining a cavity therebetween; an inner body having a distal end extending beyond the distal end of the outer member; the internal body defines at least one continuous lumen; an elongated tip segment coupled to the distal end of the inner body, the tip defining at least one through lumen, the lumen of the inner body being in fluid communication with the lumen of the tip, thereby allowing the catheter to be advanced over a guide extending through the lumen of the inner body and the tip; the inner body is harder than the tip; the outer body is blunt near its distal end; the inner body comprises a blunt segment, positioned near the tapered segment of the outer body, thus reducing the catheter profile at the distal end of the inner body while allowing a larger lumen cross-section in the inner body near the tapered segment ; a balloon with a proximal neck connected to the outer body near the distal end of the outer body; the balloon has a distal neck coupled near the outer surface to the distal end of the inner body; the balloon defines a cavity extending from and in flow communication with the cavity and terminating in near the tip. 2. Catheters in accordance with claim 1, characterized by that the proximal end of the tip has an adjacent internally mounted shoulder which surrounds the penetrating lumen; the shoulder is fitted to the distal end of the inner body; the distal neck of the balloon is coupled directly to the outer surface of the distal end of the inner body in the vicinity of the proximal end of the tip, whereby the outer surface of the distal neck of the balloon is aligned substantially longitudinally with the outer surface of the tip in proximity to the nearest end. 3. Catheters in accordance with claim 1, characterized by that the proximal end of the tip has an adjacent internally mounted shoulder which surrounds the penetrating lumen; the shoulder is fitted to the distal end of the inner body; and the tip further includes: an externally mounted shoulder near the proximal end; and the distal neck of the balloon is coupled to the external shoulder, whereby the outer surface of the distal neck of the balloon is substantially aligned with the outer surface of the tip near the proximal end of the tip. 4. Catheters in accordance with claim 3, characterized in that the inner shoulder includes: a circular surface; and a radial surface near one end of the circular surface; the circular and radial surface of the shoulder is connected to the distal end of the internal body. 5. Catheters in accordance with claim 1 characterized in that the tip is mounted to the distal extremity of the inner body and thereby defines an intermediate joint; the tip has an outer surface substantially longitudinally aligned with the outer surface of the distal end of the inner body; and the distal neck of the balloon is mounted over the conforming outer surfaces. 6. Catheters in accordance with claim 5, characterized by further comprising a blunt transfer segment extending from the distal end of the outer surface of the distal neck of the balloon to the outer fold of the tip. 7. Catheters in accordance with claim 2, characterized by that the proximal neck of the balloon is connected to the inner surface of the outer body. 8. Catheters in accordance with claim 5, characterized by that the proximal neck of the balloon is connected to the inner surface of the outer body, the outer bodies further comprise at least one aeration lumen located within the wall of the outer body and extending longitudinally therethrough substantially throughout its length, the aeration lumen being in flow communication with the circular cavity. 9. Catheters in accordance with claim 1, characterized by that the inner body and the tip are further formed with a continuous infusion lumen, which extends substantially parallel to the lumen receiving the guide. 10. Catheter in accordance with claim 1, characterized in that the tip further comprises at least a cone between its proximal and distal ends; the tip has a total length in the range of 1-30 mm; the tip is formed from a soft elastomeric polymeric material. 11. Catered in accordance with requirement 1, characterized by that the tip further comprises a spring located in the tip near the distal end, the spring having a Longitudinal axis aligned with the longitudinal axis of the tip, the spring embraces the cavity that receives the guide. 12. Catheter in accordance with claim 1, characterized by that the balloon is shaped with a plurality of steps or different outer diameters when the balloon is inflated; whereby the same catheter can be used for widening a stenosis in progressively increasing dimensional steps. 13. The catheter in accordance with claim 1, characterized in that it further includes: a first pressure sensing element mounted to the catheter, the first element is positioned to sense pressure in the vascular system or the patient's body cavity remote from the balloon during inflation, and transmit a first electrical signal accordingly; a second pressure sensing element mounted to the catheter, the second element is arranged to sense pressure in the vascular system or the patient's body cavity in the vicinity of the balloon during inflation and transmit a second electrical signal accordingly; signal conduction means mounted to the inner and outer bodies of the catheter coupled to the first and second pressure sensing elements for transmitting the first and second electrical signals to the proximal end of the catheter located outside the patient's body. 14. Catheter in accordance with claim 1, is characterized by the fact that it further includes: in coupling means mounted in flow communication with the j lumen of the inner body of the catheter at a first end and arranged to be coupled to a blood supply source in the j patient's vascular system at a second end, to selectively . s allow perfusion of the patient's own blood during inflation of the balloon. 15. The catheter in accordance with claim 14, characterized in that it further includes: pumping means fitted to the coupling means to overcome the flow resistance within the coupling means and the lumen. 16. Catheter in accordance with claim 1 characterized by: the length (L-^) of the catheter proximal to the cone divided by the inside diameter (D-^) of the lumen proximal to the cone to the fourth power is less than or equal to 2-4 times the quotient of the length (L^) of the catheter distal to the cone divided by the inside diameter (D2 ) of the lumen distant from the cone to the fourth power. 17. Catheter in accordance with claim 1, characterized in that the balloon is positioned proximate the tip, the distal neck of the balloon is mounted proximate the junction between the elongated tip segment and the distal end of the distal segment of the body; and means within the body for selectively inflating and deflating the balloon through the cavity.