CA1232331A - Flexible tip cardiac pacing catheter - Google Patents

Abstract

FLEXIBLE TIP CARDIAC PACING CATHETER

ABSTRACT OF THE DISCLOSURE

A flexible tip catheter for electrically stimu-lating the heart comprising an elongated body having an elongated passage therein and an enlongated conductor par-tially in the passage. The elongated conductor has a dis-tal end portion outside of the passage which is flexible and resilient along its length. The distal end portion includes a flexible resilient electrode exposed at the outer periphery of the catheter so that current can be passed along the conductor to the electrode to electrically stimulate the heart. The flexi-bility of the distal end portion and of the electrode greatly reduces the risk of penetration of the heart wall.

Description

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BACK~ROUND OF THE I NVE~T I ON
This application is a divi~ion o~ application no. ~38,50~, filed October 6, 1983.
~ pacing ca~heter and a pulse genecato~ are u~ed to electrically stimulate or pace the heart. To accomplish thi6, the catheter i~ inserted through a v~in into the heart. Typically, the catheter is inserted into the right ventricle. The catheter may be either unipola~, i.e., have one electrode, or bipolar, i.e., have two electrodes. In either event, the di6tal electrode 1~l of the catheter must be brought into ~ontact with the heart wall in order that pul~es of electrical energy can be transmitted from the pulse generator through the catheter to the heart. Pacing of the heart in ~hi~ fashion is often temporaLy and may be Lequired, for exam~le, in surgery following a myocardial infarction.
One problem with pacing ca~heters ls thae the insertion of the catheter throught the heart and into engagement with the heart wall creates a risk o~ ~enetrat~on of the heart wall by the catheter. The rizk of penetea~ion canno~ be avoided by making the catheter uniformly flimsy because the catheter must have enough stiffness to be inserted into tha heart. In addition, the catheter must have ~ome re~ilience so that it can maintain the electrode~ in substantially COntinUoUB con~act with the heart r~

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l wall in the presence of factors such as the beating of the heart and patient mo~ement, which tend to interrupt engagement 3 between the electrodes and the heart wall.
4 I t is ~nown to provide a ~lexible tail on a heart stimulation cathe~er and to space the electrodes proximally 6 from the tail as shown ~n Harm~anz U.S~ Patent 3,664,347.
7 In this construction, the ~ail mus~ be in an artery of the 8 lungs and neither of the electrode3 is a~ or near the distal 9 end of the catheter, One way to insert a cardiac pacing ca~heter is to advance it through the lumen of a guiding cathe-12 ter. To accomplish this, the guiding catheter mus~
i3 first be lnserted through a vein and the rlght heart 14 to the pulmonary artery, and this requires ~hat ~e g~iding catheter be formed into a curve, which ~s 16 essentially a 180-degree curve in th~ right heart ventricle.
l~ The guiding catheter has a port within or adjacent the 18 curve through which the pacing catheter can axtend.
19 One problem with this composite guiding catheter-pacing catheter system is that the guiding catheter 21 tends to form a sharp reverse bend or kink immediately 22 distally of the port, and this is undesirable in that 23 the kink can close of~ the lumens in the catheter.

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3 This invention overcomes the pacing catheter 4 insextion problem described above by prov~ding a cathe-5 ter with a f lexible, resilient distal ea~d portion and a 6 f lexible electrode . The distal end portion of he 7 catheter has insufficient column strength to perfor~
8 ate the heaxt wall when the distal end portion is axi-9 ally pushed against the heart wallO When the distal end 10 portion contacts the heart wallO it bend~ or deflect s ~ and guides the distal end along the heart wall rather 12 than through it, Also, in this ~ent~over condition, a 13 larger surface area of the dis al end portion engages 14 the heart wall thereby decreas~ ng unit loading and mak-15 ing heart wall per~oratiorl much less likely ~o occur.
16 With this in~ention~ the resilient, ~lexible 17 characteristic of the distal end portion extends all the 18 way ~o the distal end of the catheter. This is true even 19 if an electroda of the catheter is at the dlstal snd.
The catheter o~ thi invention can advantage-21 ously include an elongated body having an elongated pas 22 sage therein and an elongated conductor partially in the 26 _3 ;33~

1 passage, The elongated conduc~or ha~ a distal end por-

2 tion outside of the passage which is flexible and resil-

3 ient along its length, The distal end portion terminates

4 substantially at a distal end of the catheter. The flexi-ble, resilient distal end portion includes a flexible 6 electrode exposed at the outer periphery of the catheter 7 so that current can be passed along the conductor to the ~ electrode to electrically stimulate the heart. The dis-9 tal end portion is preferably more flexible ~losely ad-jacent the distal end of the catheter than at a location 1~ spaced proximately from the distal end of the catheter.
12 More specifically, the conductor may include a first sec-13 tion lyin~ partially withln the body, a dist~l section 14 and a transition ~ection joining the first section to the distal section with each o~ such sections being more 16 flexible than the section located immediately proximally 1~ of such sec ion~
18In a preferred implementation, the conductor 19 includes an elongated wire with a distal section and a transition section of the conductor being wound into a 21 coil with the coils of the transition section being 2~ -4-~.q ~3~33~

1 spaced greater axially than the spacing between the coils 2 of the distal section. Thi~ provides the transition sec-3 tion wi~h greater rigidity and less flexibility than the 4 distal section. Alternatively, or in addition thereto, to enhance flexibility of the wire at distal locations, 6 the cross-sectional axea o~ the wi~e can be progressively 7 reduced as the wire extends distally. The first section 8 of the wire may be uncoiled.
9 The transition section i5, therefore, a stiff-ness transition zone between the relatively stiff first 1~ section and the relatively flexible distal section. This 12 transition zone prevents high stxess points between the 13 relatively stif~ and relatively flex~ble sections. With-14 out this transition section, permanent deformation i5 more likely to occur and its fatigue strength reduced.
16 The featur~s of this invention are applicable to 17 a unipolar or bipolax catheter. I~ one preferred form of 18 bipolar catheter, the body includes a conduct$ve wire 19 having a plurallty o~ coils with a region of the coils being exposed to define a second electrode. Preferably 21 this wire is rectangular ln cross section to increase the 2~ stiffness of the body and reduce its electrical resistance.
23 If desir d, the inter~or of the coils can be 24 filled with an elastomeric material to aid in control-ling the flexibility o~ the d~stal end portion of the 2'7 28 - S' 2g :~2~2~3~

l catheter. Also, the elastomeric material ~an extend be-2 yond the distal tip of the coils to provide a soft dis-3 tal end to the catheter. Filling o the interior o the 4 coils also prevents the ingrowth of ti~sue ~nto the coils.
Finally, in a bipolar catheter, the elastomer can provide 6 insulation between the two conductors, and by axially 7 spacing coils of the spring forming the second electrode, 8 the elastomer can be provided between the spaced coils 9 to tend to lock the structure tog~ther.
The concepts o~ this invention are no~ limited l~ to the use of a conductor wound in~o coils. For example, 12 the conductor may lnclude a body o~ conductlve elasto-13 mexic material at the di tal end o~ the catheter. The 14 elastom~.ric material is ~oft, fl~x~ble and r~sillent so that it can at least partially def~ne a flexible, re-16 silient distal electrode which performs much like the 17 distal electrode formed by the flexible, re~ilient coil 18 spring as described above.
l9 The ilexible tip catheter of khis invention can be inserted without any guiding implement through a 21 vein into the heart. Alternatively, the catheter can be 22 advanced through the lumen of an indwelling right heart 23 monitoring catheter and exit at a side port in either the 24 ventricle or atrium to perform it~ functions.

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1 This invention also provides a guiding cathe-2 ter which read~ly forms into a gentle bend or curve in 3 heart and does not ~ink when used with ~ pacing cathe-4 ter. One reason that a composite catheter system tends to ~in~ is that the catheter system proximally of the 6 port out of which ~he pacing catheter emerges is rela-7 tively stiff, and the guiding catheter dls~ally of the 8 port is relatively flexible. This abrup change in stiff-9 ness at the poxt tends to cause kinking of the guiding catheter.
lX ~ith this invention, a stiffening element, such 12 as an elongated polymeric or metallic wire, is permanently 13 fixed, as by bonding, within the guid~ng catheter. The 14 stiffening element begins proximally of the port and extends to a location distally of th~ port 50 that 16 the region through the port and distally thereof`is 17 stiffened. The degree of stiffening ~s such as to 18 permit the guidlng catheter ~o form into the de~ired 19 gentle curve without ~inklng. Preferably, the stiff-ening element terminates no farther distally than the 2~ right ventrical and no farther proximally than the su-22 perior vena cava. ~ihen the catheter system is used 23 for pacing the right ventrical, the stiffening element 26 ~7-~9 33:~

1 preferably terminates at its opposite ends in the right atrium and the right ventricle.
3 The guiding catheter and ~he pacing cathe~er 4 of thls invention can be used separately or in combi-nation. Also, the guiding catheter can be used with 6 other pacing cathetexs, and the pacing catheter of 7 this invention can ~e used with other gulding cathetersO
8 The invention, together with additional fea-9 tures and advan~ages thereof, may best be understood by reference to the following description taken in connec-11 tion with the accompanying illustrative drawing.

.__ _ _ _ Fig. 1 is a sid~ ~levational view partially in 16 sPction of a bipolar catheter constructed in accordance with 1~ the teachings of th~s invention coupled to a pulse generator.
1~ Figs. 2a and 2b are fragmentary sid~ elevational 19 views showing two dlfferent forms o~ wire which can b~ us-ed for the conductor.

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l Figs. 3a, 3b and 3c are side elevational views of three forms o bipolar rlexible tip cathe-3 ters of ~his invention, respectively. T~e elasto-4 meric material within the coils i5 not shown in Figs.
3a and 3b.
6 Fig. 4 is a front elevational view of a unipolar 7 catheter cons~ructed in accordance wi~h the teachings of 8 this invention-9 Fig. 5 is a sectional view ~hrough a human heart showing one way in which the catheter of this in-l~ vention can be used.

13 DESCRIPTION OF THE P~EF9R~ED ~DODIM~N~S
-~ig. l shows a bipolar catheter ll electrically 16 coupled to a pulse ~enerator 130 Generally, the cathetPr ll 17 comprises a body 15 and an elongated inner conductor 17.
18 The body 15 include~. a backshell l9 having an 19 interior chamber 21, a tube 23 received wlthin one end of the backshell l9, an out r conductor 25 and a flexible 21 outer cover 27 o~ a suitable material, such as polytetra-22 fluoroethylene. The conductors 17 and 25 are suitably 23 coupled within the chamber 21 to leads 29 leading to the ~3~33:~

1 pulse generator 13, The chamber 21 may contain a suit-2 able potting compound (not shown3 ~f desir~d.
3 Xn the embodiment illustrated, the outer con 4 ductor 25 is in the form of a flat wire, i.e., a wire of nearly rec~angular cro~s section, wound into a series of 6 contiguous coil~ 31 which extend from the chamber 21 to a 7 location distally o~ the cover 27 and axially spaced coils 8 33 located distally o~ the contiguous coils 310 The cover 9 27 terminates proximally of the distal end of th~ con-ductor 25, and the exposed portion o~ this conductor forms 1~ an electrode 35.
12 The inner conductor 17 is also in the form of 13 an elongated wire having a f ~ r~t section 37 ~xtending 14 from the chamher 21 axially throu~h the body 15, a trans-i~ion section 39 and a distal sect~o~ 41 with the portion 16 of the inner co~ductor 17 which i5 outside o~ said body 17 being the distal end portion o~ the inner conductor. As 18 best shown in Fig. 3a, th~ first ~ection 37 is straight 19 and is covexed by insulation 43. The transition section 39 comprises a plurality of coils 45 which is spaced 21 apart axially, with the axial .~pacing between adjacent 22 coils progressively reducing as the txansi~ion sec~ion 23 extends distally. This progressive reduction in spacing 2~ ~10 ;33~

1 is preferred but not essential. The distal section 41 2 comprises a plurality o~ contiguous coils 47 and terminates 3 at a distal end 48 of the catheter 11. The~e coils could 4 be tightly or loosely wound to further control flexibility.
The inner conductor 17 may ~e formed, for exam-6 ple, of a wire 49 (Fig. 2a) or of a wire 51 (Fig. 2b).
7 The wire 49 has a cylindrical section 53 o~ rela~ively large diameter which can be used to form the first sec-9 tion 37 and cylindrical sections 55 and 57 which can be used to form the transition section 39 and the distal 11 section 41, respe~tively. Each of the sections 55 and 12 57 is of lesser diameter than the cylindric~l section 13 immsdiately proximally thereo~.
14 The wire 51 also has a cyl~ndrical section 53 fro~ which the flrst section 37 can be formed. However, 16 in lieu oP the cylindrical section 55, the wire 53 has a 17 conical section 59 whlch is o~ progressively reducing 18 diameteL as it extends dlstally and from which the transi~
19 tion section 39 can he constructed. The wire 53 a~so has a cylindrical section 57 from which the distal section 21 41 can be constructed. The wires 49 and 51 can be con-22 s~ructed of var~ OU5 suitable material~, such as stainless 23 steel. The wires 49 and 51 can be formed of multiple .~3,~33~

l sectio~s which are suitably joined togethex as by solder-ing or welding bu~, preerably, each of hese wlres is 3 integral. In this latter ~vent, the wixe Sl can 4 be tapered by electropolishing or centerless grinding.
Wi~h the construc~ion described above, the first 6 section 37 is less flexible than the transition section 39 7 and the transition section 39 is le~s flexible than the 8 distal section 41. Also, the first seckion 37 is rein-9 forced by the body 15. Moreover, the flexibility of the transition section 39 increases as the transition sec-l~ tion ex~ends distally. The relative stiffne s of the 12 first section 37 is obtained ~y leaving the first section l~ 37 uncoiled and cons ructing it of larger diameter wire.
14 The~transition section 39 is more flex~ble than the first lS section 37 becaus~ it ls co~led and cons ructed of small~
16 er diameter wixe. The flexibility of the transit$on 17 section 39 increa es because ~he axial spacing be-18 tween the coils 45 decreases a~ the transition section l9 extends distally and because the conical sections 55 and 57 of the wires 49 and 51 are o pro~ressively de-21 creasing diameter~ The distal section 41 is more flexible 22 than the transitlon section 39 because the ooils 47 are 23 contiguous and because wire of minimum diameter is used 24 to construct it. If the wire 49 i5 used to construct ;~ ~3~3~

l the inner conduc~or 17, then the progre~sive decraase 2 in diameter of the conical ~c~ion 55 tend~ to produce 3 progressively greater flexibility in the distal section 4 41 as the distal section extends distally. The distal section 41 is flexible and resilient all the way to the 6 distal end 48.
7 In the embodiment of Figs~ 1-3, a non-conduc-8 tive elastomer 61 ~ills the central space within the 9 coils 47, 45 and 33. The ela.~tomer 61 helps insulate the conductors 17 and 25 from each other. In the embodiment il-l~ lustrated, the elastomer 61 term~nates, along with the 12 distal section 41, at the distal end 48. In this embodi-13 men~, the presence of the elastomer 61 does not alter the 14 above-described relative stif~nes~ relationship~ of the sections 37, 39 and 41. Th~ elastomer 61 16 fills the spaces between the coil~ 45 and the coils 1~ 33, and in addition, encases the co~ls 45 of the transi-18 tion section 39 so that only the coils 47 are exposed to 19 define an electrode 620 In this embodiment, the distal sec-tion 41 forms the electrode 62. If the elastomer 61 is elimi-Z1 nated, then it is preferred to encase the coils 45 of the 22 transition sectîon 39 in a suitable insulation jacket.
23 Fig. 5 shows how the catheter can be used by 24 inserting it through the lumen of a guiding catheter 63.

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1 Except for a stiffenin~ element 64, the guiding cathet~r 2 63 may be of conventional construct~on and may be a 3 Swan-Ganz thermodilution ca~heter which is available 4 from American Edwards Laboratories of Irvine, California.
The guiding catheter 63, which may have multiple lumens extending longi~udinally through a.catheter body, may be 7 inserted into the heart through a vein using convention-8 al techniques, and following such insertion, a balloon 65 9 adjacent the distal end of the guiding catheter is lodged in the pulmonary artery 67. As shown in Fig. 5, the 1~ catheter 63 extends through the superior vena cava 12 66 and is formed into a curve 68 o~ about 180 de-13 grees as it extends through the xight atr~um 69 and 14 the right ventricle 71. The guidlng catheter 63 has a port 72 leading ~rom one of lts lumens into the right 16 ventricle 71 1~ In the embodiment illustrated, the stiffen-18 ing element 64 is in the form of ~n elongated, flexible, 19 resilient wire of metal or plastic bonded into the guid-ing catheter 63 outside of the lumen with which the port 21 72 communicates. In the preferred cons~ruction illus-22 trated, the stiffening element 64 extends from a loca-23 tion in the right atrium 69 proximally of the port 72 2~ continuously to a location in the right ventricle 71 located distally of the port 72. Thus, regions of the ~f~3~3~L

1 guiding catheter on the oppo~ite sides of the port 72 2 are stiffen d, and such stlffenin~ i~ controlled to 3 cause the catheter 63 to form the relatively gentle 4 curve 68 in the right heart without kinking as the catheter extends through the right heart to the pul-6 monary artery 67.
7 With the guiding catheter 63 positioned in the right heart as shown in Fig. 5, the catheter 11 9 can be inserted through a lumen of the guiding cathe--ter 63 and out the port 72. A~ the catheter 11 lI continues its advancing movement, the electrode 62 12 contacts a wall 73 of the right ventrlcle and ~ends over 13 or deflects alo~g the wall due to the resillence of the 14 distal section 41 all the way to the dlstal end 48. This .
causes the electrode 62 and the transition ~ection 39 to 16 resiliently flex and causes the electrode to lie agains~
1~ the wall 73 without penetrating the wall. A circuit 18 can then be complet~d from the electrode 62 through the 19 heart waLl 73 and body fluids in the heart to the elec-trode 35. The flexibility of the ~atheter 11, and in 21 particular, of the conductors 17 and 25 at, and distally 22 of the distal electrode 35, maintains the d~stal elec-23 trode 62 in continuous engagement with the wall 73, Of 24 course, the catheter 11 can be inserted directly throuqh :~3~3:~

1 an artery or vein into the heart without using the guid-2 ing catheter 63. Th. catheter 11 1~ ~lexible throughout 3 its length. However, the re~ilience and ~lexibility of 4 the catheter are carefully controlled primarily at the sections 39 and 41 to provide insufficient column 6 strength to penetrate the heart wall 73 and sufficient re-7 silience to maintain contact between the distal electrode 8 62 and with the heart wall.
9 Fig. 3b shows a catheter lla which is iden ical in all respects not shown or described herein to the 1~ catheter 11. ~ortions of the catheter lla corresponding 12 to portions of the catheter 11 are d~signated by corre-13 sponding reference numerals followed by the letter "a."
14 The only dif~erence betwee~ the catheters 11 and lla is that the inner conductor 17a o~ the catheter 16 lla is provided in two parts, i.e., a straight segmen~
1~ 75 and a coiled segment 77 appropr~ately joined to 18 gether as by solder or weldin~, ~or this purpose, the 19 distal end of the straight segme~t 75 is i~serted with in a few of the proxima1 coils of the coiled segment 77.
21 The straight segment 75 defines the first ~ection 37a 22 and the coiled segment 77 defines the transition sec-23 tion 39a and the distal section 41a, i.e., the elec-24 trode 62a.

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1 Fig. 3c shows a catheter llb which is iden-2 tical to the catheter 11 in all respects not shown or 3 described herein. Portions of the catheter llb corre-4 sponding to por~ions o~ the ca~heter 11 are designated by corresponding reference numerals followed by the 6 ~etter "b."
7 In the catheter llb, the inner conductor 17b 8 comprises a segment 79 and a body 81 oE 50f~ flexible 9 resilient, conductiv~ elastomerlc material attached to the distal end of the segment 7g. The segment 79 may 1~ be a wire or cable. The distal portion of ~he segment 12 79 projects beyond the lnsulation 43b and terminates 13 in a headO83 of enlar~ed cross-sectional area.
14 The segment 7g betwe~n the body 81 and the electrode 35b is encased ln a jac~t 85 of soft, ~lexi-16 ble, resilient plastic material~ which is a ~onconduc~or.
1~ This portion of the segment 79 and the jacket 85 Eorm a 18 transition section 39b of a 5tiffness interm~diate the 19 stiffness of the body 81 and the region of the catheter llb proximally oE such portion of the segment 79. The 21 segment 79 projects only a short d$stance into the body 22 81, and hence, th body 81 is the most flexible part 23 of the inner conductor 17b. The jacket 85 may extend 24 into the coils defining the electrode 35b.

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1 The body 81 of elastomeric material may be, 2 for example, molded around the d~stal tip o the seg-3 ment 79 so that the head 83 i~ embedded within the 4 body 81. This ~ightly retains ~he bod~ 31 of elasto-meric material against the distal end of the jacket 6 85. If desired, the body 81 may be adhered or bonded 7 to the jac~et 85. The ~ody 81 forms the distal elec-trode 62b. The catheters lla and llb may be used in 9 the same ~annex described above for the catheter 11.
Fig. 4 shows a unipolar catheter llc which is lI identical in all respects not shown or de~cribed herei~
12 to the bipolar catheter 11. ~he only difference between 13 the catheters 11 and llc i5 that the ou~er conductor 25 14 is replaced with a flexible tube 87 o~ a suitable bis~
compatible plastic ma~er~al, Portions of the catheter 16 llc corresponding to portions of the catheter ll are des-17 ignated by corre~pond~ng reference numerals followed by 18 the letter "c." As shown schematically in Fig. 4, with 19 the unipolar catheter llc, the circuit is completed through the heart wall 73 to ground, and to accomplish 21 this, the patient is appropriately grounded.

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1 Although exemplary embodiments of the invention 2 have been shown and described, many changes, modifications 3 and substitution~ may be made by one having ordinary skill 4 in the art without necessarily departing from the spirit and scope of this invention.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A guiding catheter adapted to be passed through the right side of the heart into the pulmonary artery, said guiding catheter comprising:
an elongated catheter body having proximal and distal ends, at least one lumen extending longitudinally in the body and a port extending from the lumen to the exterior of the catheter body, said port being in the right ventricle when the catheter extends through the right ventricle into the pulmonary artery:
an elongated stiffening element permanently fixed within the catheter body and extending from a first location on the proximal side of said port to a second location on the distal side of said port, said stiffening element being curved, flexible and sufficiently stiff to cause the catheter to form a gentle curve without forming a kink when the catheter extends through the right ventricle to the pulmonary artery: and said lumen being adapted to have an inner catheter passed through the lumen and the port into the right ventricle.

2. A guiding catheter as defined in claim 1 wherein said stiffening element extends no farther proximally than the superior vena cava when the guiding catheter extends through the right heart to the pulmonary artery and no farther distally than the right ventricle when the guiding catheter extends through the right heart to the pulmonary artery.

3. A guiding catheter as defined in claim 1 wherein said elongated stiffening element terminates in the right atrium and the right ventricle when the catheter extends through the right heart to the pulmonary artery.

4. A guiding catheter as defined in claim 1 wherein said stiffening element extends farther distally of said port than proximally of said port.

5. A guiding catheter as defined in claim 1 wherein the center of said port is generally on the outside of said curve.

6. A guiding catheter as defined in claim 1 including a balloon on said catheter body distally of the port and said first location being distally of said proximal end and said second location being proximally of said balloon.

7. A guiding catheter as defined in claim 1 wherein said catheter body has a injectate port located proximally of said first location.

8. A guiding catheter as defined in claim 1 wherein said locations are spaced substantially from said ends of the catheter body.

9. A catheter system for pacing the heart comprising:
a guiding catheter having proximal and distal ends, at least one lumen extending longitudinally in the guiding catheter and a port extending from the lumen to the exterior of the guiding catheter, said guiding catheter being adapted to be passed through the right ventricle and into the pulmonary artery with the port being exposed in the right ventricle;

an elongated stiffening element permanently fixed within the catheter and extending from a location on the proximal side of said port of a location on the distal side of said port, said stiffening element being flexible and sufficiently stiff and cause the guiding catheter to be gently curved without forming a kink when the guiding catheter extends through the right ventricle to the pulmonary artery:
a cardiac pacing catheter including at least one electrode: and said pacing catheter extending through said lumen and passing through said port.

10. A catheter system and defined in claim 9 wherein said stiffening element extends no farther proximally than the right atrium when the guiding catheter extends through the right heart into the pulmonary artery and no farther distally than the right ventricle when the guiding catheter extends through the right heart into the pulmonary artery.