Low profile catheter for angioplasty and occlusion

A low profile device for simultaneous angioplasty and occlusion includes an angioplasty balloon and an occlusion element which adjoin a common catheter. The occlusion element may be either self-expanding (in which case it is deployed with a sheath that surrounds the catheter) or non-self-expanding (in which case it is deployed with a pull wire that passes through the catheter). The angioplasty balloon is inflated with fluid that either passes through the catheter or a separate tube (or lumen) that adjoins the catheter.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates generally to catheters that treat a stenosis
 site while simultaneously providing occlusion, and more generally to low
 profile catheters.
 2. Description of the Related Art
 Coronary heart disease is an extremely common disorder and is the leading
 cause of death in the U.S. Damage to, or malfunction of, the heart may be
 caused by narrowing or blockage of the coronary arteries (atherosclerosis)
 that supply blood to the heart. Myocardial infarction (i.e., dying or dead
 heart muscle) can result from atherosclerosis, especially from an
 occlusive or near occlusive thrombus that overlies or is adjacent to
 atherosclerotic plaque. Thrombi and emboli often result in myocardial
 infarction, and these clots can block the coronary arteries, or can
 migrate further downstream, causing additional complications. Should a
 blockage form at a critical place in the circulatory system, serious and
 permanent injury, or even death, can occur. To prevent this, some form of
 medical intervention is usually performed when significant blockage is
 detected.
 Various intervention techniques have been developed to reduce or remove
 blockage in a blood vessel, allowing increased blood flow through the
 vessel. One technique for treating stenosis or occlusion of a blood vessel
 is balloon angioplasty. Generally, a percutaneous or arterial sheath is
 introduced through a puncture or incision in the patient's skin to provide
 percutaneous access to blood vessels. This is followed by insertion of a
 balloon catheter through the arterial sheath and its advancement through
 the blood vessels to the target site, where the occluded blood vessel is
 then dilated. The catheters are commonly guided through blood vessels by
 thin wires called guidewires, which may be either solid or hollow.
 Angioplasty balloon catheters can be roughly divided into three categories:
 over-the-wire (OTW) systems, single-operator-exchange (SOE) or monorail
 systems, and fixed-wire systems (also called "balloon-on-a-wire"). In an
 OTW system, a solid guidewire is used to guide a balloon catheter, which
 is tracked coaxially over the guidewire and can be moved relative to it.
 SOE balloon catheters are modified OTW catheters, i.e., only the distal
 portion of a SOE balloon catheter tracks coaxially over the guidewire. In
 a fixed-wire system, tubing is in fluid communication with a balloon
 mounted at its distal end to supply inflation fluid to the balloon. The
 tubing typically has a soft tip at its distal end to guide the placement
 in the vessel.
 It can be difficult, however, to treat plaque deposits and thrombi in the
 coronary arteries, since the coronary arteries are small, making it
 difficult to access them with commonly used catheters. Vessels as small as
 3 mm in diameter are commonly found in the coronary arteries, and even the
 diameter of certain saphenous vein bypass graft vessels can be as small as
 3 or 4 mm.
 The application of balloon angioplasty to certain blood vessels has been
 limited by the risk of forming emboli during the procedure. For example,
 when angioplasty is applied to lesions in the carotid artery, there is the
 possibility of dislodging plaque from the lesion, which can enter the
 various arterial vessels of the brain and cause permanent brain damage.
 Another angioplasty-related complication stems from the wide range of sizes
 of the emboli resulting from the procedure. Although definitive studies
 are not available, it is believed that emboli may have diameters anywhere
 from tens to a few hundred micrometers. More specifically, emboli which
 are considered dangerous to the patient may have diameters as large as 200
 to 300 micrometers or even greater. Thus, an effective emboli containment
 and/or removal system must be able to accommodate relatively large embolic
 particles while still fitting within relatively small vessels.
 These difficulties are not limited to, say, the carotid arteries. Indeed,
 balloon dilatation of saphenous vein grafts is more likely to produce
 symptomatic embolization than dilatation of the coronary arteries, not
 only because of the difference in the plaque, but also because vein grafts
 and their atheromatous plaques are generally larger than the coronary
 arteries to which they are anastomosed. Therefore, balloon angioplasty of
 vein grafts is performed with the realization that involvement by friable
 atherosclerosis is likely. Because of these complications and high
 recurrence rates, angioplasty and atherectomy are generally
 contraindicated for old, diffusely diseased saphenous vein grafts, thereby
 limiting the options available for minimally invasive treatment. However,
 some diffusely diseased or occluded saphenous vein grafts may be
 associated with acute ischemic syndromes, necessitating some form of
 intervention.
 Yet another difficulty with angioplasty is the limited time available to
 perform the emboli removal procedure. That is, in order to contain the
 emboli produced as a result of intravascular therapy, the vessel is
 generally occluded, meaning that no blood perfuses through the vessel to
 the end organ. Thus, depending upon the end organ, the complete
 angioplasty procedure, including time for therapeutic treatment as well as
 exchanges of angioplastic balloons, stents, and the like, must generally
 be completed within just a few minutes.
 Accordingly, there is a need for a low profile angioplasty device that
 provides containment of emboli and other particulates.
 SUMMARY OF THE INVENTION
 The present invention satisfies the need for a low profile device that
 reduces the risk from emboli by simultaneously providing occlusion,
 preferably at the distal end of the device.
 In one embodiment of the present invention, there is provided a low profile
 device by incorporating an occlusion device and an angioplasty device onto
 a common catheter. This substantially reduces the cross section of the
 device, making the treatment of narrow vessels possible, while guarding
 against complications that can arise from emboli and other particulates.
 In another embodiment, an angioplasty apparatus includes a catheter and a
 therapy balloon that adjoins the catheter, in which the balloon is
 inflatable to permit a stenosis site in a vessel to be enlarged. The
 apparatus further includes a mechanically deployed occlusion element, in
 which the occlusion element adjoins the catheter and is preferably located
 distal to the balloon. The occlusion element is expandable to permit the
 vessel to be at least partially occluded.
 In one preferred embodiment, the angioplasty apparatus further comprises a
 sheath for deploying the occlusion element, in which the sheath surrounds
 the catheter. The balloon may be in fluid communication with the interior
 of the catheter, permitting the balloon to be inflated and deflated, or
 alternatively, the catheter may comprise two lumens, in which one of the
 lumens is in fluid communication with the balloon.
 In another preferred embodiment, the angioplasty apparatus further includes
 a pull wire for deploying the occlusion element, in which the catheter
 surrounds the pull wire. The apparatus may further include a hole (an
 opening, passageway, etc.) in the catheter so that the catheter and the
 balloon are in fluid communication, and also include a sealing member that
 adjoins the pull wire, in which the sealing member makes an internal seal
 as the occlusion element is deployed to isolate the distal end of the
 catheter from the balloon. The apparatus may further include a second hole
 in the catheter as well as a hole in the pull wire, so that fluid can be
 aspirated from outside of the catheter and directed through the second
 hole in the catheter and then through the hole in the pull wire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The embodiments disclosed herein comprise a low profile catheter to which
 both an angioplasty balloon and a mechanically deployed (i.e., not
 deployed by inflating) occlusion element are attached. If the occlusion
 element is self-expanding, it is deployed by retracting a sheath, whereas
 a nonself-expanding occlusion element can be deployed by retracting a pull
 wire.
 1. Low profile catheters with self-expanding occlusion elements
 One preferred embodiment of the present invention is shown in FIG. 1A, in
 which a stenosis site 100 of a vessel 102 is to be treated. A therapy
 catheter 110 has a self-expanding, mechanically deployed occlusion element
 114 near its distal end and an angioplasty balloon 118 which is positioned
 at the stenosis site 100 during treatment. Alternatively, the occlusion
 element in the embodiments disclosed herein may be located proximal to the
 angioplasty balloon. The therapy catheters disclosed herein preferably
 have an inside diameter (ID.) of 0.017", a wall thickness of 0.003", and
 may be constructed from polyethylene, polyimid, or Pebax, which may be
 braided for enhanced flexibility. An integral guidewire tip 122 (e.g.,
 platinum or gold) at the distal end of the therapy catheter 110 aids in
 positioning the catheter 110 in the vessel 102. Prior to treatment, a
 catheter sheath 126 surrounds the angioplasty balloon 118 and the
 occlusion element 114, with the occlusion element being deployed by
 retracting the catheter sheath. Those expansion members disclosed herein
 which are deployed with a catheter sheath are self-expanding. When
 deployed, the occlusion element 114 prevents emboli and other particulates
 formed during the angioplasty procedure from moving downstream. Following
 treatment, the catheter sheath 126 is removed from the vessel.
 FIG. 1B shows the corresponding cross sectional view of the embodiment of
 FIG. 1A. The mechanically deployed occlusion element 114 preferably
 includes an expansion member 130 surrounded by a membrane 134 that
 contacts the wall of the vessel 102 when the expansion member expands. The
 expansion members discussed herein may be made from such materials as
 stainless steel 304 or 400, Elgiloy, titanium, superelastic or heat
 activated Nitinol, an iron base shape memory alloy, and a polymer (such as
 polyethylene or polypropylene). From the structural standpoint, the
 expansion members may include braids, coils, ribs, ribbon-like structures,
 slotted tubes, and filter-like meshes, as discussed in Assignee's
 co-pending U.S. application Ser. No. 09/026,106, filed Feb. 19, 1998
 (Atty. Docket No. PERCUS.001CP2), entitled OCCLUSION OF A VESSEL, now
 abandoned, the entirety of which is hereby incorporated herein by
 reference. The occlusion element 114 may be secured to the therapy
 catheter 110 with adhesives, for example. The membrane 134 facilitates the
 making of a seal with the vessel 102, and may be either impervious to the
 flow of blood or perforated to allow the passage of blood cells (nominally
 6-10 microns in diameter) while still blocking larger particulates such as
 emboli.
 As indicated in FIG. 1B, the angioplasty balloon 118 may be secured to the
 therapy catheter 110 with adhesives 140. For X-ray positioning of the
 balloon 118, one or more radiopaque, metallic rings 144 are preferably
 secured to the therapy catheter 110. In the embodiment of FIGS. 1A and 1B,
 the balloon 118 is inflated (generally up to 2 to 20 atmospheres) by
 passing fluid 148 (such as a saline solution or contrast medium such as
 renographin) into the therapy catheter 110, through one or more holes 152
 in the therapy catheter, and into the balloon 118. Following the
 treatment, the fluid 148 is aspirated from the balloon 118, so that the
 balloon returns to its placid state. Although aspiration out of the
 balloon 118 preferably occurs through the catheter 110, separate
 aspiration lumens may be used in the embodiments disclosed herein,
 although these may increase the profile of the device. Once the balloon
 118 has been deflated, the volume around the balloon is preferably
 aspirated to remove any emboli or other particulates that form during the
 angioplasty procedure. This is preferably done by withdrawing blood
 between the catheter sheath 126 and the therapy catheter 110 in the
 direction indicated by arrow 156, although a separate lumen (not shown) in
 the therapy catheter 110 may be used for this purpose. The balloons
 disclosed herein are preferably made of PET, polyethylene, Nylon, or
 composite materials, and may have a thickness of between 0.002 and 0.005".
 Another embodiment is illustrated in FIG. 2A, which is substantially
 similar to its counterpart of FIGS. 1A and 1B. In this and the other
 figures, like parts are indicated with like numerals, and a primed numeral
 generally differs only slightly from its unprimed counterpart. In the
 embodiment of FIG. 2A, a guidewire 158 extends through a therapy catheter
 110'. Further, a microlumen 160 forms part of the therapy catheter 110'
 and extends along its length. The microlumen 160 is in fluid communication
 with a balloon 118' (transporting fluid 148 for inflation and deflation of
 the balloon), and preferably adjoins the balloon through an inflation port
 164. As an alternative to using the microlumen 160, a separate inflation
 tube may be joined to the therapy catheter 110', as discussed below in
 connection with FIGS. 3A and 3B. Also, the radiopaque rings in these
 embodiments may alternatively be located inside the therapy catheters.
 The relationship between the microlumen 160 and the therapy catheter 110'
 is illustrated in greater detail in the radial cross sectional views of
 FIGS. 2B and 2C. To reduce the profile of the therapy catheter 110', the
 microlumen 160 is preferably as small as possible in accordance with its
 function, i.e., the microlumen 160 is preferably no larger than required
 to rapidly deflate and inflate the balloon 118'. For compliant expansion
 balloons, microlumen diameters (FIG. 2B) of about 0.008 inches may be
 satisfactory. Furthermore, in the embodiment illustrated in FIGS. 2A, 2B
 and 2C, the outer diameter of that part of the therapy catheter 110'
 residing within the patient is preferably reduced by providing the
 microlumen 160 with an oval cross-sectional configuration, as seen in FIG.
 2C. However, the microlumen 160 may have other cross-sectional
 configurations that reduce the profile of the device, e.g., the microlumen
 may have a triangular, rectangular, or other non-oval cross sectional
 profile. A variety of manufacturing methods may be used in forming the
 microlumen 160, such as those described in Applicant's co-pending U.S.
 application Ser. No. 08/858,900, filed on May 19, 1997 (Atty. Docket No.
 PERCUS.009CP1) entitled CATHETER FOR EMBOLI CONTAINMENT, the entirety of
 which is hereby incorporated herein by reference.
 Another embodiment that includes a self-expanding element is illustrated in
 FIGS. 3A and 3B. A therapy catheter 110" includes an outer tube 180 for
 transporting inflation fluid 148, rather than the microlumen 160 of FIGS.
 2A, 2B, and 2C. The outer tube 180 is separated from an inner tube 184 of
 the catheter 110" by an annular region 190 through which the inflation
 fluid 148 flows. The annular region 190 is in fluid communication with an
 angioplasty balloon 118", so that the balloon can be inflated and
 deflated. The fluid 148 preferably enters the patient through an access
 port 194 (not shown in the figures of the previously discussed
 embodiments) of a Touhy-Borst fitting 198. Adhesive 202 can be used to
 secure the fitting 198 to both the outer tube 180 and the inner tube 184.
 As in the embodiments shown in FIGS. 1A, 1B, 2A, 2B, and 2C, the occlusion
 element 114 of FIG. 3A is deployed with the catheter sheath 126. In the
 embodiment of FIGS. 3A and 3B, blood is preferably aspirated following
 deflation of the balloon 118" through the region between the outer tube
 180 and the catheter sheath 126, in the direction indicated by arrow 156.
 In this and the other embodiments, the therapy catheter may include a
 separate lumen for aspirating emboli and other particulates, although this
 may increase the profile of the device.
 2. Low profile catheters with nonself-expanding occlusion elements
 FIG. 4A illustrates a device comprising a therapy catheter 290 to which. an
 angioplasty balloon 300 and an occlusion element 310 are attached, in
 which the occlusion element is deployed by retracting a pull wire 320. The
 distal end of the catheter 290 preferably includes a guidewire tip 324 to
 aid in the placement of the device within the patient. The occlusion
 element preferably includes a membrane 328 that surrounds an expansion
 member 332 (shown in FIG. 4A in cutaway). The expansion member 332 is
 similar to its self-expanding counterpart 130, except that it is not
 deployed with a sheath but rather with the pull wire 320, which indirectly
 engages a first ring member 336 attached to the expansion member 332. On
 the proximal end of the expansion member 332 is a second ring member 340
 which is firmly secured to the catheter 290. The second ring member 340
 prevents the expansion member 332 from advancing proximally beyond the
 second ring member, thereby forcing the expansion member 332 to expand
 radially so that it contacts the walls of the patient's vessel. The
 membrane 328 is constructed and functions similarly to its counterparts in
 the self-expanding embodiments to make an occlusive seal with the
 patient's vessel, preventing emboli from travelling downstream.
 The internal workings of the device are more clearly evident in the
 longitudinal cross sectional view of FIG. 4B. Specifically, the pull wire
 320 (which in this embodiment is preferably hollow) is attached at its
 distal end to a plug 344 that moves in the direction indicated by arrow
 348 when the pull wire is retracted. The plug 344 engages a sliding disk
 member 352 that moves within the catheter 290 but preferably has
 0.001-0.002" clearance with the catheter 290. The disk member 352
 preferably has oppositely facing notches 354 that adjoin the first ring
 member 336, as illustrated in FIG. 4C. The notches 354 slide within an
 opening 358 (see FIG. 4A) within the catheter 290. As the first ring
 member 336 is moved proximally, the expansion member 332 expands radially
 to occlude the vessel 360, as illustrated in FIG. 4D.
 When the pull wire 320 is retracted, a sealing member 364 which adjoins the
 pull wire mates with a seat 368 to block off the distal end of the
 catheter 290. This permits the balloon 300 to be inflated (FIG. 4D) by
 forcing fluid 372 through the catheter 290 and into the balloon,
 preferably through an inflation port 376. To prevent the plug 344 and the
 first ring member 336 from being retracted too far, which would either
 damage the expansion member 332 or let it expand too much and potentially
 damage the patient's vessel 360, a safety ring 398 is preferably used. As
 illustrated in FIG. 4D, safety ring 398 is firmly secured to the inner
 surface of the catheter 290 and blocks the first ring member 336 from
 advancing proximally to it.
 After treating the stenosis site 378 and deflating the balloon 300 (e.g.,
 by aspirating the fluid 372 through the inflation port 376 and the
 catheter 290), the volume 380 around the balloon may be aspirated through
 the pull wire 320 via aspiration ports 384 and 388 in the catheter 290 and
 the pull wire 320, respectively. Blood along with any entrapped emboli are
 evacuated in the direction indicated by the arrows 392.
 The volume 380 may also be aspirated by moving the pull wire 320 distally
 to create a space between the sealing member 364 and the seat 368, and
 then aspirating through the aspiration port 384, past the seat 368 and out
 of the catheter 290. In this case, there is preferably sufficient friction
 between the ring member 336 and the edges of the opening 358 to keep the
 occlusion element 310 deployed while volume 380 is being aspirated. The
 occlusion element 310 may be returned to its undeployed position by moving
 the pull wire 320 distally so that a ring member 400 (which is attached to
 the pull wire) engages the disk member 352. Also, instead of aspirating
 the volume 380 through the catheter 290, a separate sheath that surrounds
 catheter 290 may be used for aspiration, analogous to the embodiment shown
 in FIG. 2A.
 Another pull wire embodiment is illustrated in FIG. 5, which is similar to
 the embodiment of FIGS. 4A-4D. In this embodiment, however, aspiration of
 the angioplasty balloon 300' is accomplished by passing fluid 372 through
 a separate tube 420 that is attached to the catheter 290'. The tube 420 is
 secured to the catheter 290' but acts functionally like the microlumen 160
 of FIG. 2A. In this embodiment, there is no need for the sealing member
 364 or the seat 368 of FIGS. 4B and 4C, since the angioplasty balloon 300'
 is not inflated through the catheter 290'. Further, aspiration of emboli
 can be accomplished through the catheter 290', and there is no need for an
 aspiration port in the pull wire 320 (such as the aspiration port 388 of
 FIGS. 4B and 4D).
 The pull wires of FIGS. 4A-D and 5 may be retracted using the techniques
 illustrated in FIGS. 6 and 7. In FIG. 6, the catheter 290 is secured to a
 handle 430 to which a knob 434 is attached. The knob 434 is secured to the
 pull wire 320 and slides over a series of locking ridges 438 which keep
 the knob from advancing or receding when the knob is not engaged. Thus,
 the knob 434 and locking ridges 438 function much like an electrician's
 razor blade retraction device. The handle 430 preferably further includes
 a transition region 446 for relieving strain in the handle.
 If inflation fluid 372 is to be injected into the catheter 290 (as in FIGS.
 4B and 4D) for inflation of an angioplasty element, then the inflation
 fluid may be injected through an inflation fitting 440 and then through an
 inflation port 442 in the catheter 290. The inflation fitting 440 is
 preferably secured to the handle 430 with epoxy 452.
 An internal sealing element 450 as well as a sealing plug 454 within the
 pull wire 320 at its proximal end prevent the fluid 372 from escaping from
 the catheter 290. For a pull wire 320 of diameter 0.007-0.008", for
 example, the sealing element 450 may have a bore diameter of 0.005". In
 this way, the pull wire 320 is restricted or compressed as it passes
 through the sealing element 450, so that the fluid 372 is contained.
 An alternative to the pull wire take-up apparatus of FIG. 6 is shown in
 FIG. 7, in which the knob 434 has been replaced by a rotating take-up reel
 460 that includes a spindle 464. In this embodiment, the pull wire 320
 wraps around the take-up reel 460. The diameter of the spindle 464 is
 preferably selected by considering the elasticity and outside diameter of
 the pull wire 320. For example, if the pull wire 320 has an outside
 diameter of 0.005" and is constructed from stainless steel (which has an
 elasticity of 0.4%), then the diameter of the spindle 464 is preferably at
 least 0.005"/0.004=1.25".
 It should be understood that the scope of the present invention is not
 limited by the illustrations or the foregoing description thereof, but
 rather by the appended claims, and certain variations and modifications of
 this invention will suggest themselves to one of ordinary skill in the
 art.