Assemblies for creating compound curves in distal catheter regions

Compound steering assemblies, usable in both diagnostic and therapeutic applications, enable a physician to swiftly and accurately steer the distal section of the catheter in multiple planes or complex curves to position and maintain ablation and/or mapping electrodes in intimate contact with an interior body surface.

FIELD OF THE INVENTION 
This invention relates to catheters that can by steered by external 
controls. More particularly the invention relates to such catheters that 
can assume complex three dimensional curves. In addition, the invention 
relates to the use of such complex curves to ablate arrhythmia substrates 
in body tissue. 
BACKGROUND OF THE INVENTION 
Cardiac mapping is used to locate aberrant electrical pathways and currents 
emanating within the heart. Such aberrant pathways cause irregular 
contractions of the heart muscle resulting in life-threatening patterns or 
disrhythmias. 
Ablation of cardiac tissue to create long curvilinear lesions within the 
heart is also desired for treatment of various disorders such as atrial 
fibrillation. Various steering mechanisms for catheters carrying such 
electrodes have heretofore been developed and used. 
To access various endocardial sites, physicians have used a number of 
different catheters and techniques, each of which provides a different 
characteristic. The use of catheters having limited steering 
characteristics increases the risk inherent in any catheterization 
procedure and limits the accessibility of many potential ablation sites. 
Site access using standard distal tip steerable catheters is less of a 
problem because those catheters position a single electrode into contact 
with the endocardium and a specific electrode orientation is not required. 
Problems of endocardial site access are accentuated when trying to 
simultaneously position multiple electrodes into intimate tissue contact. 
In this scenario, standard steerable catheter configurations orient 
multiple electrodes in planes emanating about the axis of the introduction 
vessel. 
A need has thus existed for catheters which, in the nonlinear environment 
found within the heart as well as other body cavities, are capable of 
being steered to place ablation elements at a number of locations while 
creating intimate tissue contact throughout the length of all active 
ablation elements. 
Particularly, a need has existed for a catheter which could effectively and 
accurately form curves in more than one plane for better access or tissue 
contact. Previous attempts to provide such devices are represented by U.S. 
Pat. No. 5,383,852 wherein there was suggested the use of steering wire 
extending from a central lumen of a catheter radially outward to the 
periphery of a distal end component. Another suggestion in represented by 
U.S. Pat. No. 5,358,479 wherein a single pull cable is attached to the 
distal end of a shim which has two flat sections that are twisted relative 
to each other. This arrangement, however limits the device to bending, 
first, of the more distal portion of the shim followed by subsequent 
bending of the more proximal section, thus limiting the procedures using 
the device. 
SUMMARY OF THE INVENTION 
The present inventions provides a catheter, usable in both diagnostic and 
therapeutic applications, that enables a physician to swiftly and 
accurately steer the distal section of the catheter containing the 
ablation and/or mapping element(s) in multiple planes or complex curves 
within the body of a patient. The catheters that embody the invention 
allows physicians to better steer a catheter to access various endocardial 
sites. In its broadest aspect, the invention provides catheters which 
enable a physician to position ablation and/or mapping electrodes inserted 
within a living body by manipulation of external controls into intimate 
contact with an interior body surface that curves in more than one plane. 
One aspect of the invention provides a catheter having more than one 
steering mechanism for bending the distal section by external manipulation 
into more than one curvilinear direction. Movement of the individual 
controls results in bending of the distal section at more than one 
location and in more than one direction. Thus the ease of accessing and 
measuring electrical activity in all portions of the heart is increased. 
In accordance with another embodiment, the catheter steering assembly may 
include a proximal section containing a preformed portion in conjunction 
with a distal steering mechanism which enables steering in a different 
plane that is non-parallel to the bending plane of the preformed proximal 
section, and/or improving tissue contact by moving the focal point of the 
steering mechanism to increase the angle of steering capable of applying 
force against the endocardial surface. This configuration may be 
accomplished by preforming the proximal section of the catheter into the 
desired curve or manipulating a preformed wire or other support structure 
which, when freed from the constraints of a sheath such as the catheter 
main body, causes the proximal section to assume the preformed shape. 
In accordance with a further embodiment of the invention, a loop catheter 
has a preformed proximal end and a moveable wire attached to the distal 
end of the spline housing the ablation element(s). The preformed proximal 
end enables the loop to access varying planes relative to the catheter 
axis. 
Further, objects and advantages of the invention will become apparent from 
the following detailed description and accompanying drawings.

The invention may be embodied in several forms without departing from its 
spirit or essential characteristics. The scope of the invention is defined 
in the appended claims, rather than in the specific description preceding 
them. All embodiments that fall within the meaning and range of 
equivalency of the claims are therefore intended to be embraced by the 
claims. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
This Specification discloses electrode-carrying structures that can be bent 
in compound and complex manners for greater maneuverability within the 
body and enhanced contact with tissue. The illustrated and preferred 
embodiments discuss these structures, systems, and techniques in the 
context of catheter-based cardiac ablation. That is because these 
structures, systems, and techniques are well suited for use in the field 
of cardiac ablation. 
Still, it should be appreciated that the invention is applicable for use in 
other tissue ablation applications. For example, the various aspects of 
the invention have application in procedures for ablating tissue in the 
prostrate, brain, gall bladder, uterus, and other regions of the body, 
using systems that are not necessarily catheter-based. 
FIG. 1 shows a catheter 10, which embodies features of the invention. The 
catheter 10 includes a handle 12 and a flexible catheter body 14. The 
distal region 16 of the catheter body 14 carries at least one electrode 
18. In the illustrated and preferred embodiment, the distal region 16 
carries an array of multiple electrodes 18. 
The electrodes 18 can serve to monitor electrical events in heart tissue, 
or transmit electrical energy to ablate heart tissue, or both. Signal 
wires (not shown)are electrically coupled to the electrodes 18 in 
conventional fashion. The signal wires extend through the catheter body 14 
into the handle 12. The signal wires electrically connect to an exterior 
plug 22, which can be connected to signal processing equipment or a source 
of electrical ablation energy, or both. 
The catheter 10 shown in FIG. 1 includes a steering mechanism 20. The 
mechanism 20 includes two control knobs 24 and 26 on the handle 12, which 
can be individually manipulated by the physician. 
As will be described in greater detail later, the steering mechanism 20 is 
coupled to a compound steering assembly 28, which is carried within the 
distal region 16 of the catheter body 14. Operation of the control knobs 
24 and 26 bend the steering assembly 28 to flex the distal region 16 (as 
FIG. 1 generally shows) in ways that aid in orienting the ablation element 
18 in intimate contact with tissue. 
FIG. 3 shows one embodiment of a compound steering assembly, designated by 
reference numeral 28(1), that embodies features of the invention. The 
compound steering assembly 28(1) includes a spring element formed as a 
single piece in two bendable sections 30 and 32. The bendable section 30 
is distal to the bendable section 32. 
In the illustrated embodiment, the bendable sections 30 and 32 are arranged 
essentially orthogonally relative to each other, being offset by about 
90.degree.. Different offset angles between 0.degree. and 180.degree. may 
be used. 
The proximal end of the proximal bendable section 32 is secured within a 
guide tube 34. In the illustrated embodiment, the guide tube 34 takes the 
form of a coiled stainless steel spring. The guide tube 34 extends from 
the steering assembly 28(1) rearward within the catheter body 14 to the 
handle 12. The guide tube 34 serves to stiffen the catheter body 14 and to 
help impart twisting motion from the handle to the steering assembly 
28(1). 
As FIG. 3 shows, a distal steering wire 36 is attached by soldering or 
adhesive to one surface of the distal bendable section 30. The steering 
wire 36 extends from the bendable section 30 through a guide tube 38 
secured by soldering or adhesive to a surface 40 of the proximal bendable 
section 32. From there, the steering wire 36 extends through the guide 
tube 34 into the handle 12. The steering wire 36 is coupled to the control 
knob 24 within the handle 12, as will be described in greater detail 
later. 
A proximal steering wire 42 is attached by soldering or adhesive to the 
surface 44 of the proximal bendable section 32 opposite to the surface 40. 
From there, the steering wire 42 extends through the guide tube 34 into 
the handle 12. The steering wire 42 is coupled to the control knob 26 
within the handle 12, as will be described in greater detail. 
Flexible heat shrink tubing 56 (shown in FIG. 1 and in phantom lines in 
FIG. 3) encloses the compound steering assembly 28(1). 
As FIG. 2 shows, the control knobs 24 and 26 are individually coupled by 
shafts, respectively 45 and 46, to rotatable cam wheels, respectively 48 
and 50, within the handle 12. Rotation of the respective knob 24 and 26 
serves to rotate its respective cam wheel 48 and 50. The steering wire 36 
is attached to the cam wheel 48, and the steering wire 42 is attached to 
the cam wheel 50. 
Further details of the structure of the cam wheels 48 and 50 and their 
attachment to the steering wires 36 and 42 are not essential to the 
invention and can be found in U.S. Pat. No. 5,254,088, which is 
incorporated herein by reference. 
Rotation of the cam wheel 48 (by manipulation of the knob 24) pulls upon 
the distal steering wire 36. This, in turn, pulls upon the distal bendable 
section 30, flexing the bendable section 30 in the direction of the wire 
36 (shown by arrow 52 in FIG. 3). The guide tube 38 facilitates movement 
of the steering wire 36 and the transmission of the pulling force from the 
cam wheel 48 to the bendable section 30. In the absence of the pulling 
force upon the wire 36, the bendable section 30 resiliently returns to its 
normal unbent condition (shown in FIG. 3). 
Likewise, rotation of the cam wheel 50(by manipulation of the knob 26) 
pulls upon the steering wire 42. This, in turn, pulls upon the proximal 
bendable section 32, flexing the bendable section 32 in the direction of 
the wire 42 (as arrow 54 shows in FIG. 3). In the absence of the pulling 
force upon the wire 42, the bendable section 32 resiliently returns to its 
normal unbent condition (as FIG. 3 shows). 
In the illustrated and preferred embodiment, the guide tube 38 comprises a 
stainless steel coil. As a steel coil, the guide tube 38 provides bending 
resistance and bias for the assembly 28(1) to return to the unbent 
orientation after deflection. 
The compound steering assembly 28(1) makes possible the formation of 
complex curves in the distal region 16. Pulling on the distal wire 36 
bends the distal region 16 in the direction 52. Pulling on the proximal 
steering wire 42 further bends the distal region 16 in a different 
direction 55. 
FIG. 3 shows a single steering wire 36 and 42 attached to each bendable 
section 30 and 32 to provide unidirectional bending of each section 30 and 
32. Of course, either or both bendable sections 30 and 32 may include an 
opposing pair of steering wires (not shown) to provide bidirectional 
bending action. If bidirectional bending of the distal section 30 is 
desired, a guide tube 38 is preferably provided for each steering wire 
attached to the section 30. In this arrangement, the guide tubes should 
preferably comprise a material at least as flexible as the proximal 
section 32 itself, so as to not impede the desired bending action. 
FIG. 4 shows an alternative embodiment of a compound steering assembly, 
designated 28(2). The compound steering assembly 28(2) includes a spring 
element formed as a single piece in two bendable sections 58 and 60. The 
bendable section 58 is distal to the bendable section 60. 
Like the embodiment shown in FIG. 3, the proximal end of the bendable 
section 60 is secured within a guide tube 34. Unlike the embodiment shown 
in FIG. 3, the bendable sections 58 and 60 are not offset from each other, 
but extend in the same plane. 
A pair of steering wires 62 and 64 are attached to opposite surfaces of the 
distal bendable section 58. The steering wires 62 and 64 extend rearward 
through the guide tube 34 within the catheter body 14 for attachment to 
opposite sides of a rotatable cam wheel (not shown) within the handle 12. 
U.S. Pat. No. 5,254,088 shows the details of this construction, which is 
incorporated herein by reference. Rotation of the cam wheel in one 
direction pulls on the steering wire 62 to bend the distal section 58 in 
one direction (shown by arrow 66A in FIG. 4). Rotation of the cam wheel in 
the opposite direction pulls on the steering wire 64 to bend the distal 
section 58 in the opposite direction (shown by arrow 66B in FIG. 6). 
Bi-directional steering of the distal section 58 is thereby achieved. 
The compound steering assembly 28(2) shown in FIG. 4 further includes a 
preformed wire 68 secured by soldering or adhesive to the proximal 
bendable section 60. The preformed wire 68 is biased to normally curve. 
The preformed wire 68 may be made from stainless steel 17/7, nickel 
titanium, or other memory elastic material. It may be configured as a wire 
or as a tube with circular, elliptical, or other cross-sectional geometry. 
The wire 68 normally imparts its curve to the attached bendable section 60, 
thereby normally bending the section 60 in the direction of the curve. The 
direction of the normal bend can vary, according to the functional 
characteristics desired. The wire 68 can impart to the section a bend in 
the same plane as the distal bendable section 58 (as shown by arrow 66C in 
FIG. 4), or in a different plane. 
In this arrangement, the steering assembly 28(2) further includes a main 
body sheath 70. The sheath 70 slides along the exterior of the catheter 
body 14 between a forward position overlying the junction between the wire 
68 and proximal bendable section 60 and an aft position away from the 
proximal bendable section 68. In its forward position, the sheath 70 
retains the proximal bendable section 60 in a straightened configuration 
against the normal bias of the wire 68, as FIG. 4 shows. The sheath 70 may 
include spirally or helically wound fibers to provide enhanced tensile 
strength to the sheath 70. Upon movement of the sheath 70 to its aft 
position, the proximal bendable section 60 yields to the wire 68 and 
assumes its normally biased bent position. The slidable sheath 70 is 
attached to a suitable control mechanism on the handle 12. 
As FIG. 5A shows, during introduction of the proximal catheter region 16 
into the body, the sheath 70 is retained in its forward position. This 
retains the proximal bendable section 60 in a substantially straight 
orientation (as FIG. 4 also shows). After introduction of the distal 
catheter region 16 into a desired heart chamber, the sheath 70 is 
withdrawn (as shown in a stepwise fashion by FIGS. 5B and SC). The wire 68 
urges the proximal bendable section 60 to assume a curvature in the 
direction indicated by arrow 66C. 
The embodiment of FIGS. 4 and 5A/B/C provides compound curves. The amount 
of curvature of the preshaped wire 68 is selected in accordance with the 
projected shape of the body chamber into which the catheter is introduced. 
Further bending of the distal section 58 is accomplished by pulling on the 
steering wires 62 and 64. 
It should be appreciated that, instead of a stationary preshaped wire 68 
and movable sheath 70, the steering assembly 28(2) can include a precurved 
stylet 72 (see FIGS. 6A to 6C) moveable along the proximal bendable 
section 60 within a stationary sheath 74. A mechanism (not shown) mounted 
in the handle affects movement of the stylet 72 under the control of the 
physician. The stationary sheath 74 extends about the catheter body 14 up 
to distal region 16. 
When located within the region of the sheath 74 (as FIG. 6A shows), the 
stylet 72 is retained by the sheath 74 in a straight condition. When the 
preshaped stylet 72 is advanced beyond the sheath 74 (as FIGS. 6B and 6C 
show, the stylet 72 imparts its normal curve to the proximal section 60, 
causing it to assume a curvature determined by the stylet 72. 
FIGS. 7 to 9 show another alternative embodiment for a compound steering 
assembly, designated 28(3), embodying features of the invention. The 
compound steering assembly 28(3) includes a composite spring 76 formed 
from two individual spring sections 78 and 80 (see FIG. 7). The spring 
sections 78 and 80 include mating central notches 82 and 84, which nest 
one within the other to assemble the spring sections 78 and 80 together. 
Soldering or brazing secures the assembled sections 78 and 80 to complete 
the composite spring 76. 
The resulting composite spring 76, like the spring shown in FIG. 3, 
comprises a bendable distal section 30 (spring section 78) and a bendable 
proximal section 32 (spring section 80). The bendable proximal section 32 
is secured to a guide coil in the catheter body in the same manner shown 
in FIG. 3. 
As FIG. 8 and 9 further show, the compound steering assembly 28(3) 
preferably includes two steering wires 86 and 88 attached by soldering or 
adhesive to opposite surfaces of the distal bendable section 30. The 
steering wires 86 and 88 each extend from the distal bendable section 30 
through a guide tube 90 secured by soldering or adhesive to one surface 92 
of the proximal bendable section 32. From there, the steering wires 86 and 
88 extend through the main guide tube 34 within the catheter body 14 into 
the handle 12 for attachment to a control mechanism in the handle, as 
already described. 
As FIGS. 8 and 9 also show, the compound steering assembly 28(3) preferably 
includes one steering wire 94 attached by soldering or adhesive to the 
proximal bendable section 32 on the surface opposite to the surface to 
which the guide tubes 90 are attached. The steering wire 94 likewise 
passes through guide tube 34 within the catheter body 14 for attachment to 
a second control mechanism in the handle, as already described. 
As also previously described, the guide tubes 90 preferable take the form 
of metal coils. As coils, the guide tubes 90 provide increased spring bias 
to aid the return of the proximal bendable section 32 to the straightened 
position in the absence of pulling force on the steering wire. 
The compound steering assembly 28(3) shown in FIGS. 8 and 9 permits flexing 
the distal bendable section 30 in opposite directions normal to the 
surface of spring section 78. The compound steering assembly 28(3) also 
permits independent flexing of the proximal bendable section 32 in a 
single direction normal to the surface of spring section 80 to which the 
steering wire 94 is attached. 
While the illustrated and preferred embodiment of the proximal bendable 
section 32 shown in FIGS. 8 and 9 does not permit bidirectional bending, 
it should be appreciated that two oppositely attached steering wires may 
be attached to the proximal section 32 to allow bidirectional steering. In 
this arrangement, the guide tubes 90 should be made of materials no less 
flexible than the proximal section itself. 
FIGS. 10A and 10B show another alternate embodiment of a compounding 
steering assembly, designated 28(4). The compound steering assembly 28(4) 
includes two separate steering assemblies 96 and 98 radially offset from 
each other within the catheter body 14 (see FIG. 10B). Each steering 
assembly 96 and 98 includes a bendable spring, respectively 100 and 102, 
carried by relatively small diameter spring coils, respectively 104 and 
106. The bendable spring 100 extends distally to the bendable spring 102. 
A pair of steering wires 108 and 110 are attached to the opposite sides of 
the distal steering spring 100 to enable bending in a first plane (shown 
by arrows 112 in FIG.10A). A second pair of steering wires 114 and 116 are 
attached to opposite sides of the proximal steering spring 102 to enable 
bending in a second plane (shown by arrows 118 in FIG. 10A). As FIG. 10A 
shows, the small diameter wire coils 104 and 106 may themselves be 
contained within the larger diameter steering coil 34 within the catheter 
body 14. 
Instead of steering wires 108/110 and 114/116, either or both springs 100 
and 102 could be attached to preshaped wires (not shown) to assume a 
desired curvature, to thereby bend the respective spring in the manner 
shown in FIG. 4. Alternatively, the compound steering assembly 28(4) may 
includes a third, preshaped wire section (not shown), like that shown in 
FIG. 4 located, either proximally or distally to the bendable springs 100 
and 102. In these arrangements, an external slidable sleeve (not shown) is 
used to selectively straighten the preshaped wire when desired. In this 
way, complex bends can be formed in the distal region in at least 3 
different planes, or, alternatively, two bending locations can be provided 
in a single plane with another bending location being provided in an 
orthogonally separate plane. 
FIG. 11 shows an alternative embodiment of a compound steering assembly, 
designated 28(5), that reduces stiffness of the proximal section. The 
compound steering assembly 28(5) includes two side-to-side guide coils 120 
and 122. A distal element 124 is soldered between the distal ends of the 
guide coils 120 and 122, thereby collectively forming a distal bendable 
section 30. A PET retaining sleeve 126 preferably holds the guide coils 
120 and 122 together orthogonal to plane of the distal element 124. 
Distal steering wires 128 and 130 are attached to opposite sides of the 
distal element 124. The steering wires 128 and 130 pass through the guide 
coils 120 and 122 and into the main guide coil 34 within the catheter body 
14 for attachment to a control element on the handle. By applying tension 
to a steering wire 128 and 130, the distal element 124 and guide coils 120 
and 22 bend as a unified structure in the direction of the tensioned 
steering wire. 
A proximal steering wire 132 is soldered to a transverse edge 134 of the 
distal element 124. The proximal steering wire 132 also extends into the 
main guide coil 34 within the catheter body 14 for attachment to another 
control element on the handle. By applying tension to the proximal 
steering wire 132, the distal element 124 and guide coils 120 and 122 bend 
as a unified structure in a direction orthogonal to the direction 
controlled by the distal steering wires 128 and 130. A second proximal 
steering wire (not shown) could be soldered to the opposite transverse 
edge of the distal element 124 for bi-directional steering. 
FIGS. 12 and 13 show another embodiment of a compound steering assembly, 
designated 28(6) that embodies features of the invention. The steering 
assembly 28(6) includes a preformed proximal section 136, which maintains 
a predefined curve, thereby forming a bend in the distal region 16. The 
distal end of the preformed proximal section 136 carries a ferrule 138. 
The ferrule 138 includes a notch 140. A bendable distal spring 142 fits 
within the notch 140. 
The distal spring 142 includes two oppositely attached steering wires 144 
and 146. Bi-directional bending of the spring 142 is thereby provided. 
Alternatively, a single steering wire could be provided for single 
directional bending. 
A sleeve (not shown) made of Kevlar polyester or Kevlar Teflon or plain 
polyester preferable encircles the junction of the distal spring 142 and 
the ferrule 138 to strengthen the junction. Further details concerning the 
sleeve and the attachment of the spring to the distal end of the proximal 
section are contained in U.S. Pat. No. 5,257,451, which is incorporated 
herein by reference. 
As shown in FIGS. 12 and 13, the notched ferrule 138 holds the distal 
spring 142 in a plane that is generally orthogonal to the plane of the 
preshaped bend of the preformed proximal section 136. The distal spring 
142 therefore bends in two cross-plane directions, to the right and to the 
left of the proximal section 136 (as arrows 148 in FIG. 13 show). Still, 
it should be appreciated that the notched ferrule 138 can be rotated to 
hold the distal spring 142 in any desired angular relationship with the 
preshaped proximal section 136. 
For example, FIGS. 14 and 15 show the notch 140 of the ferrule 138 has been 
rotated to orient the distal spring 142 in generally the same plane as the 
preformed proximal section 136. In this arrangement, the distal spring 142 
is supported for bi-directional, in-plane bending, upward and downward of 
the preformed proximal section (as arrows 150 in FIG. 15 show). 
The proximal section 136 may be preformed into any desired curve, simple 
(as FIGS. 12 and 13 and FIGS. 14 and 15 show) or complex (as FIG. 16 
shows, without a distal spring 142 attached). 
In the illustrated simple and complex curve embodiments, the proximal 
section 136 preferably comprises a braid tube 152 made of polyamide with 
wire braid, which is thermally formed into the desired shape. The 
preshaped proximal tube 152 preferably contains within it a guide coil 
154, through which the steering wires 144/146 for the distal spring 142 
pass. The steering wires 144/146 may also be preshaped like the proximal 
section to prevent straightening the preformed proximal section. 
In the illustrated and preferred embodiments shown in FIGS. 12 and 13 and 
FIGS. 14 and 15, a flatwire 156 lends additional support to the preformed 
proximal section 136. The flatwire 156 is formed in a preshaped curve 
matching corresponding to the proximal section 136. The flatwire 156 is 
preferably bonded to the exterior of the proximal tube 152. Also 
preferably, an exterior polyester shrink tube 158 encloses the flatwire 
156 and proximal tube 152 to hold them intimately together. The polyester 
shrink tube 158 can also serve this purpose without first bonding the 
flatwire 156 to the proximal tube 152. The assembly of the flatwire 156 
and shrink tube 158 as just described can also be used in association with 
the complex curve shown in FIG. 16. 
In an alternative embodiment (see FIGS. 17 and 18), a compound steering 
assembly, designated 28(7) includes a proximal section 160 comprising a 
guide coil 166 that does not have a preset curvature. In this embodiment, 
the steering assembly 28(7) includes a flatwire 162 preshaped into the 
desired curve. The precurved flatwire 162 includes a bracket 164 at its 
distal end designed to receive and support the guide coil 166. The bracket 
164 is spot welded to the guide coil 166, thereby holding the guide coil 
166 in a bent condition corresponding to the curve of the flatwire 162. A 
heat shrink polyester tube (not shown) preferably encircles the flatwire 
162 and guide coil 166 to hold them together. The preformed proximal 
section 136 is thereby formed. 
The compound steering assembly 28(7) includes a notched ferrule 138 like 
that shown in the preceding FIGS. 12 to 16. The ferrule 138 is spot welded 
to the distal end of the guide coil 166 (see FIG. 18) to receive and 
support a distal bendable spring 142 and steering wires 144 and 146, in 
the manner previously shown in FIGS. 12 to 16. As before described, the 
notch 140 of the ferrule 138 can be rotated to orient the distal spring 
142 in any desired orientation, either orthogonal to the curve axis of the 
preformed proximal section (as FIG. 18 and preceding FIGS. 12 and 13 
show), or in plane with the curve axis of the preformed proximal section 
(as preceding FIGS. 14 and 15 show), or any desired angular relationship 
in between. 
Instead of using a preformed braid tube 152 and/or a flatwire 156/162 to 
preform the proximal section 136 in the manner above described, the 
proximal section 136 may take the form of a malleable tube, which can be 
bent by the physician into the desired simple or complex curvature. 
As FIG. 16 represents, the preformed proximal section 136 may be shaped in 
any simple 2-dimensional or complex 3-dimensional shape. Virtually any 
curvature can be selected for the proximal section end, provided that the 
curvature permits unimpeded movement of the steering wires 144/146 for the 
bendable distal spring 142. Furthermore, the stiffness of the preformed 
proximal section 136 is controlled so that it readily yields for 
straightening during introduction, either through the vasculature or a 
guide sheath. 
In vivo experiments demonstrate that the walls of the vasculature 
themselves provide enough force to straighten the proximal section 136 
made according to the invention, to thereby enable easy advancement of the 
distal region 16 of the catheter body 14 through the vasculature. Guide 
sheaths may also be used, if desired. 
Entry of the distal region 16 of the catheter body 14 into the desired body 
cavity frees the proximal section 136, and it assumes its predefined shape 
as previously described. The physician may now further manipulate the 
distal region 16 by rotating the catheter body 14 and/or bending the 
distal spring 142 to locate the ablation and/or sensing element(s) 18 at 
the desired tissue location(s). 
The various compound steering assemblies 28(1) to 28(7) that the invention 
provides make it possible to locate the ablation and/or mapping 
electrode(s) at any location within the body cavity. With prior 
conventional catheter designs, various awkward manipulation techniques 
were required to position the distal region, such as prolapsing the 
catheter to form a loop within the atrium, or using anatomical barriers 
such as the atrial appendage or veins to support one end of the catheter 
while manipulating the other end, or torquing the catheter body. While 
these techniques can still be used in association with the compound 
assemblies 28(1) to 28(7), the compound bendable assemblies 28(1) to 28(7) 
significantly simplify placing electrode(s) at the desired location and 
thereafter maintaining intimate contact between the electrode(s) and the 
tissue surface. The compound assemblies 28(1) to 28(7) make it possible to 
obtain better tissue contact and to access previously unobtainable sites, 
especially when positioning multiple electrode arrays. 
Compound bendable assemblies 28(1) to 28(7) which provide a proximal curved 
section orthogonal to the distal steering plane allow the physician to 
access sites which are otherwise difficult and often impossible to 
effectively access with conventional catheter configurations, even when 
using an anatomic barrier as a support structure. For example, to place 
electrodes between the tricuspid annulus and the cristae terminalis 
perpendicular to the inferior vena cava and superior vena cava line, the 
distal tip of a conventional the catheter must be lodged in the right 
ventricle while the catheter is torqued and looped to contact the anterior 
wall of the right atrium. Compound bendable assemblies 28(1) to 28(7) 
which can provide a proximal curved section orthogonal to the distal 
steering plane greatly simplify positioning of electrodes in this 
orientation. Compound bendable assemblies 28(1) to 28(7)which provide a 
proximal curved section orthogonal to the distal steering plane also 
maintain intimate contact with tissue in this position, so that 
therapeutic lesions contiguous in the subepicardial plane and extending 
the desired length, superiorly and/or inferiorly oriented, can be 
accomplished to organize and help cure atrial fibrillation. 
A transeptal approach will most likely be used to create left atrial 
lesions. In a transeptal approach, an introducing sheath is inserted into 
the right atrium through the use of a dilator. Once the dilator/sheath 
combination is placed near the fossa ovalis under fluoroscopic guidance, a 
needle is inserted through the dilator and is advanced through the fossa 
ovalis. Once the needle has been confirmed to reside in the left atrium by 
fluoroscopic guidance of radiopaque contrast material injected through the 
needle lumen, the dilator/sheath combination is advanced over the needle 
and into the left atrium. At this point, the dilator is removed leaving 
the sheath in the left atrium. 
A left atrial lesion proposed to help cure atrial fibrillation originates 
on the roof of the left atrium, bisects the pulmonary veins left to right 
and extends posteriorly to the mitral annulus. Since the lesion described 
above is perpendicular to the transeptal sheath axis, a catheter which can 
place the distal steering plane perpendicular to the sheath axis and 
parallel to the axis of the desired lesion greatly enhances the ability to 
accurately place the ablation and/or mapping element(s) and ensure 
intimate tissue contact with the element(s). To create such lesions using 
conventional catheters require a retrograde procedure. The catheter is 
advanced through the femoral artery and aorta, past the aortic valve, into 
the left ventricle, up through the mitral valve, and into the left atrium. 
This approach orients the catheter up through the mitral valve. The 
catheter must then be torqued to orient the steering plane parallel to the 
stated lesion and its distal region must be looped over the roof of the 
left atrium to position the ablation and/or mapping element(s) bisecting 
the left and right pulmonary veins and extending to the mitral annulus. 
This awkward technique often fails to create adequate tissue contact 
necessary for therapeutic lesions. 
Preformed guiding sheaths have also been employed to change catheter 
steering planes. However, preformed guiding sheaths have been observed to 
straighten in use, making the resulting angle different than the desired 
angle, depending on the stiffness of the catheter. Furthermore, a guiding 
sheath requires a larger puncture site for a separate introducing sheath, 
if the guiding sheath is going to be continuously inserted and removed. 
Additional transeptal punctures increase the likelihood for complications, 
such as pericardial effusion and tamponade. 
While various preferred embodiments of the invention have been shown for 
purposes of illustration it will be understood that those skilled in the 
art may make modifications thereof without departing from the true scope 
of the invention as set forth in the appended claims. 
For example, as FIGS. 19A to 19C show a compound loop assembly 167 carried 
at the distal end of a catheter body 14. The loop assembly 167 comprises 
at least two loop splines 168 and 170. 
The loop spline 168 carries an array of ablation elements 172. According to 
the features of the invention described above, the loop spline 168 
includes a proximal section 174 that is preformed into a desired curvature 
to access additional planes. 
Since the loop spline 168 may be formed from memory elastic materials, the 
spline 168 may be preformed into any desired shape through mechanically 
forming the spline 168 and thermally forming the spline 168 in that shape. 
Preshaped braid tubing or other support may also be included to help 
maintain the shape of the proximal spline bend 174, as previously 
described. 
As FIGS. 19B and 19C show, the other spline 170 of the loop structure 167 
may be retracted or advanced to decrease or increase the loop diameter to 
affect desired tissue contact and ablation element location. 
The two splines 168 and 170 may be fabricated from a single wire made of 
nickel titanium or other memory elastic material. Alternatively, the two 
splines 168 and 170 may be fabricated from two or more wires which are 
connected by a distal tip at a common point. One spline may be attached to 
the catheter body, or two splines may be attached to the catheter body 
with another stylet to manipulate the preshaped loop, or both splines may 
be maneuvered. 
Various features of the invention are set forth in the following claims.