Steerable electrode catheter

A steerable catheter includes control handle having a generally tubular housing with a longitudinal slot therein in which an axially or longitudinally movable two-part slideblock resides, and a generally cylindrical, rotatably mounted thumbwheel surrounding a distal portion of the tubular housing, for controlling the axial translation of the slideblock. The pullwire passes into the distal end of the control handle and is only secured to the proximal part of the two-part slideblock so as to prevent the user from placing the pullwire under compression. A tip radius adjusting wire is attached to and extends distally from a slide actuator in the control handle into and through the main catheter shaft portion. The free distal end of the tip radius adjusting wire is selectably Iocatable at different positions. The radius of curvature of the tip portion, when deflected, depends upon how far distally into the deflectable tip portion the radius adjusting wire has been advanced by the user. The electrode catheter thus has a deflectable tip whose radius of curvature is adjustable over a relatively wide range.

FIELD OF THE INVENTION 
This invention relates to steerable catheters. More particularly, the 
invention relates to a manually controllable actuator handle of particular 
utility in controlling a deflectable electrode catheter tip of the type 
used for endocardial catheter recording, mapping, ablating and other 
surgical procedures. 
BACKGROUND OF THE ART PERTAINING TO THE INVENTION 
The clinical role of endocardial catheter recording and mapping is to 
direct ablation, surgical, and drug therapies in the treatment of 
supraventricular tachycardia, ventricular tachycardia, atrial flutter, 
atrial fibrillation and other arrhythmias. The success and advancement of 
current therapies is dependent upon the development and use of more 
precise localization techniques which will allow accurate anatomical 
determination of abnormal conductive pathways and other arrhythmogenic 
sites. Historically, the electrophysiologist has had to compromise between 
placing the catheter in the place of greatest clinical interest and areas 
which are anatomically accessible. 
Open heart surgery to perform electrophysiological recording and mapping 
has largely been supplanted by cardiac catheterization performed under 
local anesthesia in the electrophysiology lab. Prior art catheter 
placement has been generally restricted to areas which can be repeatedly 
accessed by the electrophysiologist. These areas include the HRA (high 
right atrium), the RVA (right ventricular apex), the RVOT (right 
ventricular outflow tract), the coronary sinus and the HIS bundle. To 
obtain meaningful information about additional placement sites, the number 
of electrograms recorded over a given area may be increased, and the 
precise position of the electrode array of the distal tip portion of the 
catheter may be varied. Some of these additional sites include atrial 
sites above the tricuspid and mitral valves, ventricular sites 
circumferential to the mitral and tricuspid valve leaflets, distal areas 
of the coronary sinus and great cardiac vein, the AV nodal area and the 
left ventricle, to name a few. 
One area of advancement in improving localization techniques and accessing 
additional recording sites includes the use of steerable catheters. One 
type of prior art steerable catheter offers improved maneuverability to 
specific, otherwise inaccessible sites by providing catheters shaped 
specifically to access a particular site. Although perhaps useful for some 
less inaccessible sites, the use of this type of catheter is limited, not 
very practical, and not helpful in reaching sites requiring active 
articulation during placement. Three such pre-shaped catheters are 
described in U.S. Pat. Nos. 3,503,385 issued to Stevens, 3,729,008 issued 
to Berkovits, and 4,860,769 issued to Forgerty, each of which is 
incorporated herein by reference. 
Another type of prior art steerable catheter attempts to improve placement 
maneuverability by providing catheters having deflecting tips. These 
catheters include a relatively soft and flexible distal tip portion of a 
certain length attached to a proximal shaft made from a relatively stiffer 
material. Generally, the tip may be selectively deflected but only in a 
prescribed arc, i.e., the tip bends in one planar direction, with the bend 
having a fixed, predetermined radius of curvature. Some examples of 
deflecting tip catheters are described in U.S. Pat. Nos. 4,920,980 issued 
to Jackowski, 4,960,411 issued to Buchbinder, and 4,960,134 issued to 
Webster, each of which is also incorporated herein by reference. In 
devices of this type, a pullwire attached to the distal tip portion at or 
near the tip is pulled proximally while the catheter shaft is restrained, 
thus causing the tip to deflect. Alternatively, the pullwire is restrained 
while the shaft portion is advanced distally, producing the same effect. 
Various means are known for causing the tip to bend in a predetermined 
plane and direction. 
A disadvantage of the above-described preformed and deflecting tip type 
catheters is that the tip of the catheter in each case may be deflected or 
steered only in a prescribed configuration which cannot be altered during 
its placement. That is, the steerable tip has a radius of curvature which 
is fixed, thus restricting the accessibility of the distal tip to certain 
anatomical sites without additional significant efforts of the 
electrophysiologist maneuvering the catheter exteriorly of the patient, 
and some sites may not be accessible at all. Such excessive maneuvering of 
the catheter exteriorly of the patient is difficult, frustrating, time 
consuming and inefficient to the physician performing a delicate 
procedure, and is thus inherently more risky for the patient undergoing 
that procedure. Most serious is the increased exposure of the patient, 
physicians and technicians to dangerous X-ray radiation which is used for 
fluoroscopic examination during procedures of this type. 
Many of the desired sites require that the catheter traverse paths having 
many sharp bends and be able to negotiate multiple changes of direction 
through any or all of the three perpendicular planes of movement. Four-way 
steerable catheters have been developed in an attempt to provide a 
catheter with the above-described multi-planar maneuverability. As 
examples, such four-way steerable catheters are described in U.S. Pat. 
Nos. 3,470,876 issued to Barchilon, and 4,921,482, 4,998,916 and 5,037,391 
issued to Hammerslag, each of which is also incorporated herein by 
reference. While such four-way steerable catheters may be improvements 
over two-way steerable catheters of this general type, the four-way 
steerable devices similarly suffer the disadvantage that the tips can 
deflect in only one predetermined configuration, that is, having a fixed, 
predetermined radius of curvature. 
As a result of the above described disadvantage of prior art steerable 
catheters, the electrophysiologist must obtain and maintain not one but a 
set of similar steerable electrode catheters for use during any single 
clinical evaluation of a patient. For example, the user will have on hand 
a catheter having a steerable tip having a small radius of curvature; 
another with a medium radius of curvature and a third with a relatively 
large radius of curvature. While this availability of differently radiused 
tips is beneficial, it is often not known by the electrophysiologist which 
size will be required at any given moment during a diagnostic or 
therapeutic intracardiac procedure. Moreover, similar tip placements may 
require different radiused tips from one individual to another, even those 
of the same general body size and mass. When it is discovered by the 
electrophysiologist that a catheter then placed in a patient has an 
incorrectly radiused tip for the required procedure, the catheter must be 
completely withdrawn from the patient (through whichever one of the 
femoral, subclavian, jugular or brachial approaches was used), and a new 
properly radiused electrode catheter tip must be reintroduced into the 
heart. This substitution may take up to two hours or more to complete, 
including the time required to precisely reposition the electrode tip. 
Moreover, the initially selected, but improperly sized catheter must 
generally be discarded, never having been actually used for its intended 
purpose, as such devices are intended as "single use only" devices, for a 
variety of safety reasons. Steerable catheters are relatively expensive 
devices, and this waste of an otherwise good device is especially 
troublesome. 
Deflectable catheter tips of the type just described are generally 
resiliently biased to some degree to return to a straight configuration 
when not acted upon by the various prior art mechanisms for causing tip 
deflection. Another drawback with such catheters, as a result of this 
resiliency, is the sometimes undesired tendency of the tip to return to an 
undeflected position, or to merely change the amount of deflection, during 
the course of the electrophysiological procedure. 
Furthermore, it is frequently necessary to rotate the entire catheter tip 
portion by applying torque to the catheter shaft by rotating the entire 
control handle. Some prior art catheters include steering control 
mechanisms or actuators which are located at a single particular radial 
location on the control handle. In use, however, when such handles are 
rotated, the electrophysiologist often loses a degree of control over the 
device, as the steering control mechanism is rotated to some position 
which is less easily manipulated. 
OBJECTS OF THE INVENTION 
The object of the invention is to provide an improved steerable electrode 
catheter which overcomes the foregoing problems and difficulties in the 
use of existing steerable electrode catheters. 
Another object of the invention is to provide a control handle for a 
steerable catheter which maintains the deflectable catheter tip in its 
deflected position until the user changes the set amount of deflection. 
A further object is to provide a steerable catheter tip having a variable 
radius of curvature, which radius of curvature can be varied during a 
procedure. 
A still more specific object of the invention is to provide an improved 
control handle for use with a steerable catheter which is of a particular 
utility for endocardial catheter recording. 
A still further specific object is to provide a control handle which can 
apply tension to a deflectable tip pullwire, but which is incapable of 
placing the pull cable under compression, and which is easy to use and 
relatively inexpensive to manufacture. 
Yet still another object of the invention is to provide a steerable 
catheter control handle with which a tip deflection may be controlled 
regardless of the angular position of the handle about its longitudinal 
axis in the user's hand. 
SUMMARY OF THE INVENTION 
A steerable catheter includes a control handle, a main catheter shaft and a 
deflectable catheter distal tip portion. The catheter distal tip portion 
has an off-access lumen through which a pullwire extends, connecting the 
steering control mechanism of the control handle to a point near the 
distal end of the flexible tip portion. The proximal end of the main 
catheter shaft is secured to the distal end of the handle. The control 
handle includes a generally tubular housing having a longitudinal slot 
therein in which an axially or longitudinally movable two-part slideblock 
resides, and a generally cylindrical, rotatably mounted thumbwheel 
surrounding a distal portion of the tubular housing, for controlling the 
axial translation of the slideblock. The pullwire passes into the distal 
end of the control handle and is secured to the proximal part of the 
two-part slideblock. 
Extending outwardly from each side of the longitudinal slot and integral 
with the lateral portions of the distal part of the slideblock is a single 
external helical thread or projection, i.e., one thread or helical "wing" 
on each lateral side of the distal part. The cylindrical thumbwheel is 
rotatably and coaxially mounted on the generally tubular housing, 
surrounding the longitudinal housing slot in which the slideblock is held. 
Internal helical threads on the cylindrical thumbwheel engage the external 
threads or projections protruding from the sides of the slideblock distal 
portion. Upon rotation of the thumbwheel by the user's thumb, or thumb in 
combination with one or more other fingers, the two-part slideblock is 
caused to travel proximally within the control handle housing, thus 
placing the pullwire in tension and pulling the pullwire proximally. 
Accordingly, the deflectable tip is caused to assume a deflected or bent 
configuration, due to the relatively softer material from which the tip 
portion is constructed, as compared to the main catheter shaft. 
In order to prevent the user from placing the pullwire under compression, 
which compression can cause the pullwire to kink and ultimately fracture, 
the two parts of the slideblock are not joined together. Only the distal 
portion of the slideblock carries the external threads or projections. The 
pullwire passes through the distal part of the slideblock, however, and is 
secured only to the proximal part thereof. In this manner, the distal part 
of the slideblock can draw the pullwire proximally when the thumbwheel is 
rotated in the appropriate direction. But upon reversal of the thumbwheel, 
the distal part slides freely distally over the pullwire. Only the natural 
resiliency of the distal tip portion acts to return that tip portion to 
its undeflected condition. 
A tip radius adjusting means comprises a relatively stiff shaft, spring, 
tube or similar member, as compared to the stiffness of the distal tip 
portion of the catheter. The shaft is preferably a wire or a wire within a 
spring which is attached to and extends distally from a slide actuator in 
the control handle into and through the main catheter shaft portion. The 
free distal end of the tip radius adjusting wire is selectably located at 
different positions, ranging from proximal to the boundary or junction 
between the main catheter shaft and the distal tip portion, to any more 
distal position within the relatively soft, deflectable tip portion, 
within the axial limit of its travel as controlled by the slide actuator. 
The radius of curvature of the tip portion, when deflected, depends upon 
how far distally into the deflectable tip portion the adjusting wire has 
been advanced by the user. In this way, the electrode catheter according 
to the invention has a deflectable tip whose radius of curvature is 
adjustable over a relatively wide range. 
Once a radius of curvature has been selected by the electrophysiologist, 
deflection or steering of the catheter distal tip portion is thus 
accomplished without axial movement of any external control handle parts, 
allowing the catheter to be more easily held in its relative positions 
with respect to the surgical site. The handle is also generally tubular 
and symmetrical about its longitudinal axis, thus allowing rotation about 
that axis by the electrophysiologist without affecting either the desired 
curvature of the catheter tip portion or the physician's access to the 
cylindrical thumbwheel. Mechanical advantage achieved by employing the 
above described screw thread arrangement allows for precise movement of 
the deflectable tip with minimum effort and reduces the possibility of 
accidental axial movement of the pullwire caused, for example, by 
resiliency of the tip portion. In this way, frictional resistance provides 
a passive locking mechanism of the tip deflection. 
Other objects and features of the present invention will become apparent 
from the following detailed description of the preferred embodiment 
considered in conjunction with the accompanying drawings. It is to be 
understood, however, that the drawings are designed solely for the 
purposes of illustration and not as a definition of the limits of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 depicts a preferred embodiment of the steerable electrode catheter 
10 of the present invention. The steerable electrode catheter comprises a 
control handle 20, an elongated flexible main catheter shaft 40, and a 
relatively soft steerable or deflectable tip portion 60. As described 
below, an electrophysiologist manipulates the tip portion 60 by means of 
the control handle and control wires which pass from the handle through 
the main shaft to the tip portion assembly. Generally speaking, the device 
may be described as an insulated electric conductor for use during 
electrophysiology studies for temporary intracardiac electrocardiographic 
recording, mapping, stimulation and/or therapy, including intracardiac 
ablation. 
The tip portion 60 may be provided with a number of conductive ring 
electrodes 62 (three shown in FIG. 1 )and a conductive tip or cap 
electrode 64, all of which are mechanically secured to the tip portion 60 
at desired positions. The ring electrodes 62 and cap electrode 64 are 
preferably made of platinum. The ring electrodes 62 preferably range from 
two millimeters to four millimeters in length and are either 6 French or 7 
French in size, depending upon the specific intended use of the catheter, 
although other sizes are also commonly employed. Spacing between the 
electrodes may range from one millimeter to one centimeter, again 
depending upon the particular type of electrode catheter. It will be 
readily understood by those skilled in the art that these details, 
including the many possible variations thereto, concerning the 
construction and location of the conductive electrodes 62,64 are entirely 
conventional and well known in the field of cardiac electrode catheters. 
The proximal end of the catheter 10 is preferably provided with a cable 
connector 30 for electrical connection to a recording device (not shown) 
or some other device for capturing electrical signals sensed by the ring 
electrodes 62 and cap electrode 64. Such a recording device (not shown) 
may also include means for delivering electrical energy through the 
catheter conductive electrodes to cardiac tissue as desired, for pacing, 
diagnostic stimulation or therapeutic ablation or some other purpose, such 
as might be involved in medical research. The manner and details of 
construction of the connector 30 are not pertinent to the present 
invention, but it is preferred that the connector 30 have a knurled or 
textured surface for ease of gripping or manipulation by the physician, 
who will generally be wearing one (and possibly two) medical gloves on his 
or her hands. The connector 30 is secured to the handle 20 by a length of 
hollow, relatively flexible catheter shaft material 34 or other tubular 
stock. A strain relief 31 is preferably provided at the junction between 
the interconnecting shaft 34 and the connector 30, as is customary. It is 
also preferred that a similar strain relief 21 is provided at the junction 
of shaft 34 and the proximal end of the control handle 20, and another 
strain relief 22 is provided at the junction of the catheter main shaft 40 
and the distal end of the control handle 20 to which the main shaft 40 is 
fixedly secured, such as by bonding. 
As will be readily apparent, fine electrical conductors, such as wires (not 
shown), are electrically connected to each of the ring electrodes 62 and 
cap electrode 64. The ring electrodes 62 are preferably welded to their 
respective conductors, and the cap electrode 64 is preferably soldered to 
its conductive wire. These signal wires (not shown) pass through an 
internal bore or lumen in the tip portion 60, through an internal bore or 
lumen in the main shaft 40, into and through the control handle 20 as will 
be described in more detail below, and through the interconnecting shaft 
34 for ultimate electrical connection, for example by crimping or 
soldering, to respective conductive contacts (not shown) of the connector 
30. The signal wires are preferably individually electrically insulated 
and therefore may advantageously pass through and share a single lumen. 
As further depicted in FIG. 1, the control handle 20, which will be 
described in detail below, generally comprises a tubular, substantially 
axially symmetric housing 23 has a distal end 29 and a proximal end 28 and 
a longitudinal axis therethrough, the housing axis being substantially/ 
coaxial with the proximal end of main shaft 40 and the distal end of 
interconnecting shaft 34. The tubular housing 23 nearer its proximal end 
28 preferably has a plurality of longitudinal indentations or grooves 24 
for ease of gripping the device. A cylindrical, coaxially rotatably 
mounted thumbwheel 25 is positioned on the housing 23 near its distal end 
29, for manipulation of the steerable tip portion 60, by rotation of the 
thumbwheel 25 about its longitudinal axis, to be explained below. The 
thumbwheel 25 is advantageously provided with a plurality of evenly 
spaced, longitudinally oriented grooves 35 for improving the user's 
ability to rotate the thumbwheel 25. In use, when the control handle 20 is 
held in one's hand, the tubular housing 23 is held in the palm with four 
fingers wrapped therearound, and the thumbwheel 25 is rotated by the 
user's thumb. Alternatively, the user may cradle or hold the housing 23 
with just three fingers in order to more precisely rotate the thumbwheel 
25 with both the thumb and index finger. 
Also, generally, the control handle 20 is provided with a slide actuator 26 
which travels proximally and distally in a longitudinal slot 27 in the 
tubular housing 23, located substantially proximally of the thumbwheel 25 
and in the general area of the longitudinal grooves 24 in the housing 23 
outer surface. The slide actuator 26 is attached to a relatively stiff 
shaft 42, preferably a relatively stiff wire or wire within a spring, 
which passes distally through the control handle and into the main 
catheter shaft 40. The shaft 42 may also comprise a hypotube within the 
catheter shaft 40 secured to a wire extending from the handle into the 
shaft 40. For ease of description, the radius adjustment member 42 will be 
referred to hereafter as a wire. 
In the main catheter shaft 40, the wire 42 (shown in phantom lines in FIG. 
1) has a free distal end 50. When the slide actuator 26 is in its most 
proximal position in the handle slot 27, the distal end 50 of the wire 42 
extends to the junction 51 between the tip portion 60 and the stiffer, 
main catheter shaft 40. In this position, the tip portion 60 will be 
deflected (by rotation of thumbwheel 25) into a configuration having a 
relatively large radius of curvature. By advancing the slide actuator 26 
distally, the user advances the wire 42 past the junction 51 into the 
softer distal tip portion 60. When the tip 60 is then deflected, the 
deflected tip configuration will have a relatively smaller radius of 
curvature, as explained below in more detail in connection with FIG. 3. 
The overall length of the main shaft 40 and flexible tip portion combined 
preferably ranges from about 60 to 130 centimeters. The particular length 
selected for use in a given situation is purely a matter of physician 
preference, based upon medical judgment, training, the intended procedure 
to be performed and the anatomy of the individual patient. 
Referring now to FIG. 2, the construction of control handle 20 is described 
in detail. Reference numerals identified in connection with FIG. 1 are 
consistently used to refer to the same components in FIG. 2 and in FIGS. 
3-6. In FIG. 2, certain elements, such as strain reliefs 21,22 are not 
illustrated for the sake of clarity. 
The proximal end 28 of the handle 20 comprises an end cap 52 having a 
reduced diameter plug section 58 fitted with a sealing O-ring 59. In 
manufacture, end cap 52 is adhesively bonded or sealed to tubular housing 
23 of the handle 20. A substantially axial bore 67 passes through the end 
cap 52 for accommodating passage of the electrically conductive signal 
wires connecting the ring and tip electrodes 62,64 to the electrical 
connector 30 of the device 10. A relatively flexible sheath 38 is secured 
to the distal end of the plug section 58 for guiding the fine electrically 
conductive wires from one end of the control handle to the other and into 
catheter main shaft 40, without exposing the delicate signal wires to 
potentially damaging mechanical movement of the internal parts of the 
control handle. Positioning of the sheath 38 within the central cavity of 
the tubular housing 23 is maintained by a lower longitudinal groove 95 
formed in the proximal part 90 of a two-part slideblock and a 
corresponding lower longitudinal groove 85 in the distal part 80 of the 
slideblock, as seen more clearly in FIGS. 5 and 6, and as will be further 
described below. 
Referring to FIGS. 2 and 4, slide actuator 26 is axially slidably supported 
in longitudinal groove 27 formed in the tubular housing 23 of the control 
handle 20. Radius of curvature adjustment wire 42 is secured, for example, 
by set screw 43, to the interior end of the slide actuator 26. In a 
similar manner to the positioning of wire sheath 38, wire 42 is also 
protected from accidental engagement with moving parts within the control 
handle 20 by resting in an upper longitudinal groove 93 of proximal part 
90 of the slideblock and corresponding upper longitudinal groove 83 of the 
distal part 80 of the two-part slideblock, as seen more clearly in FIGS. 5 
and 6. Adjustment wire 42 extends from the slide actuator 26 distally 
through the interior of the control handle tubular housing 23 and into the 
main catheter shaft 40, as described hereinabove. 
At the distal end of the control handle 20, the generally cylindrical, 
fluted, axially rotatable thumbwheel 25 is supported on the housing 23 by 
circumferential shoulder 36 on the outer surface of the housing wall. The 
structure and operation of the thumbwheel 25 will be described in greater 
detail below. 
Distal of the housing portion supporting the thumbwheel 25 is a reduced 
diameter sealing seat 56 in which one or more annular spacers 78 and a 
resilient rubber O-ring 57 are snugly held in place. The spacers 78 serve 
in the manufacturing and assembly process to finely adjust the initial or 
baseline torque required to rotate the thumbwheel 25. 
A tip deflection indicator ring 45 is supported by the threaded distal end 
portion 77 of the tubular housing 23, and rests against the sealing O-ring 
57 and the distal-most annular face of the cylindrical thumbwheel 25. The 
indicator ring 45 comprises an inner, annular ring 49 supported by and 
connected to an outer annular ring 48, the rings 49,48 being separated by 
an annular space 46. A distally protruding flat tab (not shown) is 
preferably provided on the distal-most annular face of the thumbwheel 25 
and slidably mates into the annular groove 46. By virtue of the 
construction of the indicator ring 45, as illustrated in FIG. 7, the 
annular groove or slot 46 ensures that the thumbwheel 25 can travel only 
approximately one full revolution about the handle axis, due to the 
interference between the thumbwheel flat tab (not shown) and the 
connecting support structure attaching the inner annular ring 49 to the 
outer ring 48 of indicator ring 45. The outer annular ring 48 is further 
provided with a through hole 99 as seen in FIGS. 2 and 7 so that the 
protruding flat tab (not shown) may be visually observed when the 
thumbwheel 25 is rotated to a particular position. That position is 
selected to be the fully relaxed or undeflected position of the distal tip 
portion 60 of the electrode catheter 10. In this way, the user can be 
assured, for example, during retraction of the electrode catheter 10 
through the vascular approach, that the distal tip is in its undeflected 
state. Without an indicator, such assurance is not always possible even 
under direct fluoroscopic inspection. 
An internally threaded end cap 54 completes the overall assembly of the 
control handle 20. The end cap 54 fits over the catheter main shaft 40 
which is adhesively bonded to the tubular housing 23. In actual 
manufacture, the threaded end cap 54 at the distal end 29 of the control 
handle 20 is also sealed and adhesively secured to the control handle 
tubular housing 23. 
Now referring to FIG. 2 in conjunction with FIGS. 5 and 6, it is seen that 
a two-part slideblock comprises a distal part 80 and a proximal part 90. 
Both the distal part 80 and proximal part 90 are mounted in a longitudinal 
slot within the interior of control handle housing 23. The deflection tip 
pullwire 70 passes through the central through holes 86 and 96, 
respectively, of the distal part 80 and proximal part 90 of the 
slideblock. While the distal part 80 slides freely on pullwire 70, the 
proximal part 90 is releasably secured to the pullwire 70 by a rotatable 
pin 97 supported within a lateral bore through part 90, which can be 
rotated via a through hole 98 in the tubular housing 23 of the handle 20. 
As previously mentioned, both the distal part 80 and proximal part 90 of 
the slideblock include upper longitudinal grooves 83,93 and lower 
longitudinal grooves 85,95 for permitting passage of the radius of 
curvature adjusting wire 42 and the conductive wire protecting sheath 38 
therearound, respectively, without causing any mechanical interference 
therewith. In this described embodiment, threaded nylon-tipped set screws 
91,92 are mounted to the distal face of the proximal part 90 for 
engagement with the rotatable pin 97 to lock the pin 97, and thus the 
pullwire 70, in position in the slideblock. 
As is seen in FIG. 2, the arrangement of the radius adjusting wire 42 
within the housing 23 causes the wire 42 to navigate a relatively bent 
pathway at the distal end of the handle 20. An alternative, preferred 
embodiment for attachment of the wire 42 to the slide actuator 26 is now 
described. In this alternative preferred embodiment, the slide actuator 26 
extends slightly further radially inwardly toward the housing longitudinal 
axis, and the radial position of the actuator 26 is rotated 90 degrees 
away from the viewer with respect to the radial position shown in FIG. 2. 
Next, the left-most hole 81 in the distal part 80 of the slideblock is 
modified to be a through hole, and the nylon-tipped set screw 91 of the 
proximal part 90 of the slideblock is supplanted by a through hole. The 
rotating pin 97 is also cut down to two-thirds of its original length. Now 
the radius adjusting wire 42 can pass through the slideblock in a more 
direct, straighter path from the slide actuator 26 into the main catheter 
body 40, thus avoiding the abovementioned potential disadvantage. 
The distal part 80 of the slideblock includes helically angled, laterally 
disposed external threads or wings 82,84. When mounted within the tubular 
housing 23 of the handle 20, the wings 82,84 engage and travel within the 
internal helical thread 72 of the cylindrical thumbwheel 25. Accordingly, 
upon rotation of the thumbwheel 25 in a first direction, the distal 
portion 80 of the slideblock is forced to travel proximally, thus pushing 
the proximal portion 90 of the slideblock in a proximal direction. This 
places tension on pullwire 70 and causes deflection of the tip portion 60 
of the catheter. The mechanical advantage achieved by this 
rotation-to-axial translation provides a passive resistance or passive 
lock of sufficient frictional force so as to prevent the tip deflection 
angle from changing without further manipulation of the thumbwheel 25 by 
the user. 
In certain prior art deflectable tip type steerable catheters, upon the 
user's desire to relax or straighten the deflectable portion, the pullwire 
70 is advanced in the opposite direction from that which caused deflection 
of the tip. It has been discovered that in the case where deflection is 
caused by placing tension on the pullwire, it is not desirable to place 
the pullwire in compression. While relatively stiff, the pullwire is 
subject to buckling and subsequent cold fracture when repeatedly and 
successively place under tension and compression. Accordingly, the 
proximal part 90 of the two-part slideblock according to the invention has 
no similar external threads or wings corresponding to the helically 
disposed wings 82,84 of the distal part of the slideblock. Thus, upon 
counter rotation of the thumbwheel 25, the distal part 80 travels distally 
until the indicator ring 45 signifies that the tip is in a fully relaxed 
position as described hereinabove. At that point, natural resiliency of 
the distal portion 60 will tend to straighten out the tip and will place 
the pullwire 70 under some tension. Even though very slight, the amount of 
tension is sufficient to avoid buckling and fracture of the pullwire 70. 
In addition, withdrawing the catheter from the anatomical site under 
investigation will also tend to straighten out the catheter for ease of 
withdrawal. 
The variable radius of curvature feature of the invention is now described 
in connection with FIGS. 2 and 3. Selectable distance D is determined by 
the user's positioning of the slide actuator 26 on the control handle 20. 
In the distal-most position of slide actuator 26, the free end 50 of 
adjusting wire 42 extends into the softer flexible length of the distal 
tip portion beyond the junction 51 between that tip portion and relatively 
stiffer main catheter shaft 40, as shown in the upper portion of FIG. 3: 
In an alternative preferred embodiment, the free end 50 is slightly 
proximal of the junction 51 when the slide actuator 26 in its 
proximal-most position, in order to create a more stepped transition in 
stiffness from the main shaft 40 to the soft tip portion 60. The stiffest 
portion would be the main shaft 40 with the adjusting wire 42 therein; 
somewhat less stiff would be the main catheter shaft 40 without the 
adjusting wire 42, and least stiff would be the soft tip portion 60 alone. 
Returning to FIGS. 2 and 3, upon proximal sliding action of the slide 
actuator 26 by the user, the free end 50 is brought back to a position 
substantially near the junction 51 between the softer and relatively 
stiffer portions of the catheter, as shown in the lower portion of FIG. 3. 
Because the tip portion 60 will bend substantially only in areas where it 
is relatively soft, presence of the adjusting wire 42 serves to define an 
effective length of flexible soft material of the distal tip portion 60. 
Bending of the tip generally begins only at the transition point between 
relatively stiff and relatively softer materials. Since the throw or 
length of travel of the two-part slideblock is the same in any case, a 
smaller length of relatively soft material is caused to bend with a 
sharper radius of curvature when the pullwire 70 (not shown in FIG. 3) is 
retracted proximally. Thus, distal tip portion can be curved with a small 
radius to maneuver within a small cavity. 
On the other hand, when the adjusting wire 42 is positioned so that its 
free end 50 is substantially coincident with or proximal to the boundary 
or junction 51 between the relatively stiffer material of the main 
catheter shaft 40 and the distal tip portion 60, a substantially long, 
soft, flexible segment of the distal tip portion 60 is defined. Here, when 
the pullwire 70 is selectively retracted in the proximal direction, the 
distal end of the tip portion 60 bends about the junction 51 to create a 
substantially larger radius of curvature. This allows the 
electrophysiologist to bend the flexible portion of the distal tip 60 a 
further distance from the longitudinal axis of the catheter main shaft 40 
at the junction 51. In this way, the user may conveniently reach a more 
distant anatomical site for electrophysiological recording, mapping, 
ablation, etc. 
Thus, as illustrated by FIG. 3, both the radius of curvature and the degree 
of deflection of the distal portion 60 are easily selectable by the user's 
manipulation of the thumbwheel 25 in conjunction with the slide actuator 
26 of the control handle 20. The more the pullwire is retracted 
proximally, the larger the deflection angle of the distal tip will be. The 
further distally the adjusting wire 42 is telescoped passed the junction 
51 between the relatively soft tip portion 60 and relatively stiff 
catheter main shaft 40, the smaller the radius of curvature will be. Thus, 
the electrophysiologist can vary the deflection of the distal tip 60 to 
maneuver in both small and large cavities, and may more easily reach both 
relatively near and more distant sites. 
A presently preferred embodiment of the invention, without the radius of 
curvature adjustment feature, is commercially available from C. R. Bard, 
Inc., assignee of the presently described inventions, and is identified as 
a BARD ELECTROPHYSIOLOGY EP.RTM.XT.TM. Steerable Catheter, which is a 
radiopaque flexible insulated electrode catheter constructed of a 
polyurethane main shaft and all solid platinum electrodes. 
The following are preferred materials for use in making the present 
invention. 
The ring electrodes 62 and tip electrode 64 are pure (99%) platinum. The 
electrode wires are 0.005" diameter copper wire, with approximately 0.001" 
thick insulation thereon. The soft tip portion 60 is made of KJ-5 
polyurethane, supplied by USCI Division of C. R. Bard, Inc. The main 
catheter shaft 40 is also made of KJ-5 polyurethane, reinforced with a 
wire braid. The main shaft 40 may also be stiffened with 
tetrafluoroethylene (TEFLON) tubing, 0.059" O.D..times.0.038" I.D., or 
acrylic/polyurethane (ISOPLAST) tubing, 0.059" O.D..times.0.026" I.D. The 
pullwire is 304 Stainless Steel, 0.008" diameter. The control handle 20 is 
molded from modified polyphenylene oxide (NORYL), as are most of the 
handle subcomponents. The thumbwheel is molded acetal (DELRIN). The 
proximal part 90 of the slideblock is 304 Stainless Steel, as are the 
spacers 57. The guide tube 38 is acrylic/polyurethane, 0.049" 
O.D..times.0.026" I.D. The O-rings 59,77 are silicone 0.50" 
I.D..times.0.070" diameter cross section. The connector 30 is molded 
polybutylene terepthalate and includes gold-plated copper terminals. 
While there have been shown and described fundamental novel features as 
applied to a preferred embodiment thereof, it will be understood that 
omissions and substitutions and changes in the form of details of the 
disclosed device, and in its manner of assembly and operation, may be made 
by those skilled in the art without departing from the spirit of the 
invention. It is the intention, therefore, to be limited only as indicated 
by the scope of the claims appended hereto. 
Illustratively, although the steerable catheter of the present invention is 
expressly disclosed for use in sensing electrical signals in body tissues 
and applying electric signals to such tissues, a catheter so designed may 
be readily and suitably modified for use in the transfer of fluids (liquid 
or gas) into or out of a patient. In such an alternate embodiment, the 
electrical contacts, the conductive wires and the electrical connector may 
be eliminated. Instead, appropriate through holes or lumens may be 
provided in the catheter's tip portion and appropriate fluid transfer 
apparatus connected to the proximal end of the lumens so as to provide 
irrigation or aspiration capabilities. Similarly, optical fibers may be 
provided instead of, or in addition to, electrical conductors. In such an 
embodiment one or more optical fibers may be connected to a light source, 
such as a laser, while one or more other optical fibers are connected to a 
video camera and/or similar viewing or recording devices. Alternatively, a 
longitudinally movable rigid cable equipped with various manipulatable 
devices may be extendable distally through a bore or lumen in the 
catheter's tip portion for removal of patient tissue for biopsy, or for 
use in other surgical procedures such as removal or destruction of 
atherosclerotic plaque or other diseased body tissue. Any one or more of 
these alternative embodiments may be combined with another for a 
particular use contemplated or intended for a tip deflectable, steerable 
catheter. 
Finally, as will be readily apparent to those skilled in the art the 
dimensions stated relate to one particular catheter size and are disclosed 
solely by way of example and should not, therefore, be understood as an 
intended limitation on the scope of the invention.