Rail catheter ablation and mapping system

An ablation system for ablating cardiac tissue within a chamber of the human heart including a guiding introducer system, a rail, one end of which is contained within the guiding introducer system, and an ablation catheter system which is supported by the guiding introducer system. The guiding introducer system may be a single or multiple guiding introducers. The ablation system may include a slotted sheath which passes over the rail which supports the ablation catheter. A process is disclosed for ablation of cardiac tissue to form a linear lesion utilizing a rail catheter ablation and mapping system which includes a guiding introducer, a rail and an ablation catheter system advanced over the rail.

FIELD OF INVENTION 
This invention relates to a rail catheter ablation and mapping system 
designed to map and ablate specific locations within chambers of a human 
heart. In addition, it relates to a process for mapping and ablating 
cardiac tissue utilizing a rail catheter ablation and mapping system to 
form linear lesions within chambers of a human heart. 
BACKGROUND 
Catheters have been in use for medical procedures for many years. Catheters 
can be used for medical procedures to examine, diagnose and treat while 
positioned at a specific location within the body which is otherwise 
inaccessible without more invasive procedures. During these procedures a 
catheter is inserted into a vessel located near the surface of a human 
body and is guided to a specific location within the body for examination, 
diagnosis and treatment. For example, one procedure utilizes a catheter to 
convey an electrical stimulus to a selected location within the human 
body. Another procedure utilizes a catheter with sensing electrodes to 
monitor various forms of electrical activity in the human body. 
Catheters are used increasingly for medical procedures involving the human 
heart. Typically, the catheter is inserted in an artery or vein in the 
leg, neck or arm of the patient and threaded, sometimes with the aid of a 
guidewire or introducer, through the vessels until a distal tip of the 
catheter reaches the desired location for the medical procedure in the 
heart. 
A typical human heart includes a right ventricle, a right atrium, a left 
ventricle and a left atrium. The right atrium is in fluid communication 
with the superior vena cava and the inferior vena cava. The 
atrioventricular septum separates the right atrium from the right 
ventricle. The tricuspid valve contained within the atrioventricular 
septum provides communication between the right atrium and the right 
ventricle. On the inner wall of the right atrium, where it is connected 
with the left atrium, is a thin-walled, recessed portion, the fossa 
ovalis. Medical procedures are frequently performed in the left atrium 
using transseptal procedures performed through the interatrial septum. 
Present in the wall of the left atrium are the entrances to the four 
pulmonary veins: the right superior, the left superior, right inferior and 
left inferior pulmonary veins. The mitral valve contained in the 
atrioventricular septum provides communication between the left atrium and 
the left ventricle. 
In the normal heart, contraction and relaxation of the heart muscle 
(myocardium) takes place in an organized fashion as electro-chemical 
signals pass sequentially through the myocardium from the sinoatrial (SA) 
node to the atrioventricular (AV) node and then along a well defined route 
which includes the His-Purkinje system into the left and right ventricles. 
Sometimes abnormal rhythms occur in the heart which are referred to 
generally as arrhythmia. Abnormal arrhythmias which occur in the atria are 
referred to as atrial arrhythmia. Three of the most common atrial 
arrhythmia are ectopic atrial tachycardia, atrial fibrillation and atrial 
flutter. Atrial fibrillation is the most common of all sustained cardiac 
arrhythmias. While it is present in less than one percent of the general 
population, it has been estimated that at least 10 percent of the 
population over 60 is subject to atrial fibrillation. Although frequently 
considered to be an innocuous arrhythmia, atrial fibrillation can result 
in significant patient discomfort and even death because of a number of 
associated problems, including: an irregular heart rate which causes 
patient discomfort and anxiety, loss of synchronous atrioventricular 
contractions which compromises cardiac hemodynamics resulting in varying 
levels of congestive heart failure, and stasis of blood flow, which 
increases the likelihood of thromboembolism. 
Efforts to alleviate these problems in the past have included significant 
usage of pharmacological treatments. While pharmacological treatments are 
sometimes effective, in some circumstances drug therapy has had only 
limited effectiveness and is frequently plagued with side effects, such as 
dizziness, nausea, vision problems and other difficulties. 
An increasingly common medical procedure for the treatment of certain types 
of cardiac arrhythmia is catheter ablation. The use of catheters for 
ablating specific locations within the heart has been disclosed, for 
example in U.S. Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 
5,281,217. 
The use of RF energy with an ablation catheter contained within a 
transseptal sheath for the treatment of W-P-W in the left atrium is 
disclosed in Swartz, J. F. et al. "Radiofrequency Endocardial Catheter 
Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites" 
Circulation Vol. 87, pgs. 487-499 (1993). 
Ablation of a specific location within the heart requires the precise 
placement of the ablation catheter within the heart. One procedure used to 
place ablation catheters at a specific location in the heart utilizes a 
guiding introducer or a pair of guiding introducers. Ablation procedures 
using guiding introducers for treatment of atrial arrhythmia have been 
disclosed in U.S. Pat. Nos. 5,497,774, 5,427,119, 5,575,166, 5,640,955, 
5,564,440 and 5,628,316. Lesions are produced in the heart tissue as an 
element of these procedures. 
Placement of catheters at particular locations in a human body is sometimes 
accomplished using guide wires. For example, U.S. Pat. No. 5,163,911 
discloses a catheter system utilizing a guidewire to guide a working 
catheter within the vasculature to perform medical procedures. U.S. Pat. 
No. 5,209,730 discloses an over-the-wire balloon dilation catheter for use 
within a vessel of the heart. A similar extendable balloon on a wire 
catheter system is disclosed in U.S. Pat. No. 5,338,301. 
A different type of ablation catheter is disclosed in U.S. Pat. No. 
5,482,037, which discloses an electrode catheter for insertion into a 
cavity of the heart. U.S. Pat. Nos. 5,487,385 and 5,575,810 disclose 
ablation systems which are utilized for mapping and ablation procedures 
within the right atria of the heart. 
Conventional ablation procedures utilize a single distal electrode secured 
to the tip of an ablation catheter. Increasingly, however, cardiac 
ablation procedures utilize multiple electrodes affixed to the catheter 
body. 
The ablation catheters commonly used to perform these ablation procedures 
produce scar tissue at particular points in the cardiac tissue by physical 
contact of the cardiac tissue with an electrode of the ablation catheter. 
One difficulty in obtaining an adequate ablation lesion using conventional 
ablation catheters is the constant movement of the heart, especially when 
there is an erratic or irregular heart beat. Another difficulty in 
obtaining an adequate ablation lesion is caused by the inability of 
conventional catheters to obtain and retain uniform contact with the 
cardiac tissue across the entire length of the ablation electrode surface. 
Without such continuous and uniform contact, any ablation lesions formed 
may not be adequate. 
Effective ablation procedures are sometimes quite difficult because of the 
need for an extended linear lesion, sometimes as long as about 3 inches to 
5 inches (approximately 8 cm. to 12 cm.). To produce such a linear lesion 
of this length within an erratically beating heart is a difficult task. 
One process for the production of linear lesions in the heart by use of an 
ablation catheter is disclosed in U.S. Pat. Nos. 5,487,385, 5,582,609 and 
5,676,662. In addition, a process for the production of a series of linear 
lesions in the atria for the treatment of atrial arrhythmia is disclosed 
in U.S. Pat. No. 5,575,766. 
To form linear lesions within the heart using a conventional ablation tip 
electrode requires the utilization of procedures such as a "drag burn". 
During this procedure, while ablating energy is supplied to the ablating 
electrode, the ablating electrode is drawn across the tissue to be 
ablated, producing a line of ablation. Alternatively, a series of points 
of ablation are formed in a line created by moving the ablating electrode 
incremental distances across the cardiac tissue. The effectiveness of 
these procedures depends on a number of variables including the position 
and contact pressure of the ablating electrode of the ablation catheter 
against the cardiac tissue, the time that the ablating electrode of the 
ablation catheter is placed against the tissue, the amount of coagulum 
that is generated as a result of heat generated during the ablation 
procedure and other variables associated with a beating heart, especially 
an erratically beating heart. Unless an uninterrupted track of ablated 
cardiac tissue is created, unablated cardiac tissue or incompletely 
ablated cardiac tissue may remain electrically active, permitting the 
continuation of the reentry circuit which causes the arrhythmia. Thus, new 
devices are necessary for the production of linear lesions in the heart. 
SUMMARY OF INVENTION 
The present invention is a rail catheter ablation and mapping system for 
ablation procedures in the human heart which, in a preferred embodiment, 
includes an inner and an outer guiding introducer, a rail, an ablation 
catheter, and a slotted sheath. One end of the rail is secured to the 
outer guiding introducer. The rail is advanced out of the guiding 
introducers. The ablation catheter is extended through a lumen of the 
slotted sheath. The slotted sheath with ablation catheter inside is 
extended from the guiding introducers over the rail to form a loop to map 
and ablate cardiac tissue. 
Also disclosed is a rail caetheter ablation and mapping system which 
includes a single guiding introducer, a rail, a slotted sheath, and an 
ablation catheter. One end of the rail is secured to the guiding 
introducer. The rail is advanced out of the guiding introducer. The 
ablation catheter is extended through a lumen of the slotted sheath. The 
slotted sheath with ablation catheter inside is extended from the guiding 
introducer over the rail to form a loop to map and ablate cardiac tissue. 
The ablation procedures may be performed by use of an ablation catheter 
containing a single electrode which may be formed from a series of coils. 
As an alternative, the ablation catheter includes a series of electrodes. 
Either of these ablation catheters preferably performs the ablation 
procedure through slots of the slotted sheath with a flushing system 
utilized within the slotted sheath and/or within the ablation catheter to 
cool and flush the electrode during the ablation procedure. 
Also disclosed is a rail catheter ablation and mapping system which 
includes a guiding introducer system, a rail, and an ablation catheter 
which includes one or more electrodes contained in a lumen of the ablation 
catheter. A plurality of openings are provided in the surface of the 
ablation catheter. A system for introduction of a conductive media through 
the lumen of the ablation catheter is also provided which passes the 
conductive media through the openings to conduct the ablating energy to 
the tissue to be ablated. 
Also disclosed is a rail catheter ablation and mapping system which 
includes a guiding introducer system, a rail and an ablation catheter with 
flexible electrodes. 
A process for ablation of cardiac tissue to form linear lesions in a 
chamber of a human heart is also disclosed. During the procedure, a 
guiding introducer system, with a rail secured to the guiding introducer, 
is advanced through the vasculature of the human body into the chamber of 
the heart. The rail is extended from the guiding introducer. A slotted 
sheath is then extended through a lumen of the guiding introducer over the 
rail. The ablation catheter passes through a lumen in the slotted sheath. 
As the slotted sheath containing an ablation catheter passes over the 
surface of the cardiac tissue, it maps and/or ablates the cardiac tissue.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The rail catheter ablation and mapping system (10) of the present invention 
as shown in FIGS. 1 and 2 includes a guiding introducer system (11), 
comprising preferably an inner guiding introducer (12) and an outer 
guiding introducer (14), each with proximal and distal ends and each 
containing a lumen (13, 15) extending lengthwise substantially through 
each of the guiding introducers, a rail (16), and an ablation system (18) 
passing through the lumen (13) of the inner guiding introducer (12). In 
the first embodiment of the invention, as shown in FIGS. 3 and 11, the 
ablation system (18) consists of an ablation catheter (20) passing through 
a lumen (33) of a slotted sheath (22). 
In a second embodiment of the present invention, as shown in FIGS. 4, 5 and 
6, the rail catheter ablation and mapping system (100) includes a guiding 
introducer system (102), which is preferably an inner guiding introducer 
(104) and an outer guiding introducer (106), a rail (108), and an ablation 
catheter (110) containing at least two lumens (112, 114). The ablation 
catheter (110) includes a plurality of openings (116) through the surface 
(122) of the ablation catheter (110), an electrode (118) contained within 
one of the lumen (114) of the ablation catheter (110) and a system (not 
shown) for introduction of a conductive media into one of the lumen (114) 
of the ablation catheter (110). 
In a third alternative embodiment, as shown in FIGS. 7 and 10, the rail 
catheter ablation and mapping system (200) includes a guiding introducer 
system (202), which is preferably an inner guiding introducer (204) and 
outer guiding introducer (206), a rail (208), and an ablation catheter 
(210) which passes over rail (208). 
In a fourth alternative embodiment shown in FIG. 8, the rail catheter 
ablation and mapping system (300) includes a single guiding introducer 
(302), a rail (304), and an ablation catheter system (306) which passes 
over the rail (304). 
The introducer or introducers utilized with the rail catheter systems of 
the present invention can be any conventional guiding introducer with a 
sufficient inner diameter to accommodate the rail catheter ablation system 
and introduce the ablation system into a chamber of the human heart in 
which the ablation procedure is to be performed, preferably the left 
atrium (17), as shown in FIG. 1. In a preferred embodiment, the 
introducers are precurved inner and outer guiding introducers, such as 
those sold by Daig Corporation under the names AMAS 1-2 outer and AMAS 3-4 
inner. 
Medical practitioners normally monitor the introduction of a catheter and 
its progress through the vascular system by fluoroscope. However, such 
fluoroscopes do not easily identify the specific features of the heart in 
general and the particular structures of individual chambers of the human 
heart in specific, thus making placement of the rail catheter ablation and 
mapping systems (10, 100, 200, 300) within the heart difficult. Placement 
is also complicated when the heart is beating resulting in the ablation 
system (18, 110, 210) moving within the chamber as blood is pumped through 
the heart throughout the procedure. Utilization of preferably a precurved 
inner guiding introducer and precurved outer guiding introducer, with the 
rail catheter ablation systems (18, 110, 210) makes placement of the 
ablation system at the correct location in the heart is made easier. In 
addition, use of the rail catheter ablation and mapping systems (10, 100, 
200, 300) results in more positive tissue contact which permits the 
formation of better ablation lesions. 
In a preferred embodiment, as shown in FIGS. 1 and 2, an inner and outer 
guiding introducer (12, 14) are used in combination. When using an inner 
(12) and outer (14) guiding introducer, the outer diameter of the inner 
guiding introducer (12) is generally only slightly smaller than the inner 
diameter of the outer guiding introducer (14) so that the two introducers 
can be used together. In a preferred embodiment, the rail (16) passes 
between the inner (12) and outer (14) guiding introducers. Thus, the 
difference in diameter between the inner diameter of the outer guiding 
introducer (14) and the outer diameter of the inner guiding introducer 
(12) must be sufficient to accommodate the rail (16) without interfering 
with the operation of the guiding introducer system (11). In a preferred 
embodiment, the difference in diameter should be between 1 and 3 French 
(one French unit equals 1/3 of a millimeter), about 0.01 inch to about 
0.04 inch (about 0.3 mm. to about 1 mm.). 
By utilizing different curvatures for the distal portions (62) of the inner 
(12) and outer (14) guiding introducer and by rotating and extending the 
inner guiding introducer (12) in relation to the outer guiding introducer 
(14), the overall shape of the guiding introducer system (11) can be 
modified to support the ablation system (18). Not only can the use of a 
pair of guiding introducers (12, 14) in combination provide varying 
overall shapes for the guiding introducer system (11) than when using a 
single guiding introducer, but the use of a pair of guiding introducers 
(12, 14) is also helpful in the operation of the rail (16), as will be 
discussed in more detail. When a pair of introducers (12, 14) are 
utilized, in one preferred embodiment when the ablation procedure is 
performed transseptally in the left atrium, the preferred inner (12) and 
outer (14) guiding introducers are AMAS 1-2 outer introducer and AMAS 3-4 
inner introducer, produced by Daig Corporation. 
In an alternative embodiment, instead of utilizing an inner (12) and outer 
(14) guiding introducer of the guiding introducer system (11), a single 
precurved guiding introducer (302) can be utilized as an element of the 
rail catheter ablation and mapping system (300), as shown in FIG. 8. 
The guiding introducers utilized with the guiding introducer system contain 
a first section (60) as shown in FIGS. 2 and 9 which is generally an 
elongated, hollow straight section of sufficient length for introduction 
in the patient and for manipulation from the point of insertion to the 
specific desired location within the heart. Continuous with the distal end 
of this first section of the guiding introducer is a precurved, distal 
portion (62) of the guiding introducer as shown in FIGS. 2 and 9. The 
choice of curvature of this precurved distal portion depends on the choice 
of location within the heart for the ablation procedure. For example, when 
the ablation procedure occurs in the left atrium using a transseptal 
approach, the preferred guiding introducers are AMAS guiding introducers 
manufactured by Daig Corporation. The overall curvature of the various 
guiding introducers can be modified by use of various straight or curved 
sections to achieve the desired shape for the guiding introducers. In 
addition, the choice of the guiding introducer or guiding introducer 
system can be modified to place the rail catheter ablation and mapping 
system (10, 100, 200, 300) at various locations within the chambers of the 
heart. Examples of acceptable guiding introducers are those disclosed, for 
example, in U.S. Pat. Nos. 5,427,119, 5,497,774, 5,575,766, 5,640,955, 
5,564,440, 5,628,316, and 5,656,028, as well as other precurved guiding 
introducers sold by Daig Corporation. 
An important design feature of the guiding introducer (302) or pair of 
guiding introducers (12, 14) when used for an ablation procedure is that 
they provide a stable platform supported by the cardiac anatomy to permit 
the ablation system (18, 110, 210) and the rail (16) to be extended from 
the guiding introducer (302) or inner and outer guiding introducers (12, 
14) to circumscribe the inner surface of the chamber of the heart in which 
the medical procedure occurs. The guiding introducer (302) or pair of 
guiding introducers (12, 14) also provide stable support for the ablation 
system (18, 110, 210) to perform the ablation procedure within the heart 
without the need for repeated repositioning. 
The distal tip of the guiding introducers may be, and generally are, 
tapered to form a good transition with a dilator. The guiding introducers 
may be made of any material suitable for use in humans, which has a memory 
or permits distortion from, and subsequent substantial return to, the 
desired three dimensional or complex multi-planar shape. For purpose of 
illustration and not limitation, the internal diameter of the guiding 
introducers may vary from about 6 to about 14 French (about 0.07 inch to 
about 0.20 inch) (about 2.0 mm. to about 5.0 mm.). Such guiding 
introducers can accept dilators from about 6 to about 14 French (0.07 inch 
to about 0.20 inch) (about 2.0 mm. to about 5.0 mm.) and appropriate guide 
wires. Obviously, if larger or smaller dilators and catheters are used in 
conjunction with the guiding introducers of the present invention, 
modification can be made in the size of the guiding introducers. 
The guiding introducer (12) preferably also contains one or a plurality of 
radiopaque tip marker bands near the distal tip. Various modifications may 
be made in the shapes by increasing or decreasing the size of the tip 
markers or adding additional tip markers. 
The guiding introducer (12) also preferably contains one or a plurality of 
vents (64, 214) near the distal tip of the guiding introducers, preferably 
3 or 4 vents, as shown in FIGS. 2 and 7. The vents are preferably located 
no more than about 2 to about 3 inches (about 5 cm. to about 8 cm.) from 
the distal tip of the guiding introducers and more preferably about 0.1 
inch to about 2.0 inches (about 0.2 cm. to about 5.0 cm.) from the distal 
tip. The size of the vents should be in the range of about 0.02 inch to 
about 0.06 inch (about 0.05 cm. To about 0.15 cm.) in diameter. The vents 
are generally designed to prevent air emboli from entering the guiding 
introducers due to the withdrawal of a catheter contained within the 
guiding introducers in the event the distal tip of one of the guiding 
introducers is occluded. 
Variances in size and shape of the guiding introducers are also intended to 
encompass guiding introducers used with pediatric hearts. While pediatric 
ablation procedures are generally not performed on children less than 
about 2 years of age, under extreme situations, such ablation procedures 
may be conducted. These procedures may require reductions in the size and 
shape of the guiding introducers. 
The configuration of the rail (16) is an important aspect of the invention. 
The purpose of the rail (16) is to provide a guide and support for the 
ablation system (18, 110, 210) while the ablation and/or mapping 
procedures are being performed within the chamber of the heart. To provide 
this support, the rail (16) must be flexible enough not to injure the 
inner surface of the chamber of the heart in which it is used, while still 
retaining sufficient structural integrity to support the ablation system 
(18, 110, 210) as it traverses around the inner surface of the chamber of 
the heart to perform the ablation procedure. 
In order to achieve the preferred curvature and performance of the rail 
(16), in a preferred embodiment, the rail (16) is constructed of a super 
elastic metal alloy material, such as a nickel-titanium alloy, such as a 
NiTiNol.RTM. material. Such super elastic material is more preferably a 
shape memory alloy with a transformation temperature below that of the 
human body temperature. Alternatively, the shape memory alloy may also 
have a transformation temperature above that of the human body. In this 
alternative utilization, an electric current is applied to the shape 
memory alloy material to convert it into a super elastic state. When such 
super elastic, shape memory alloy is utilized, rail (16) retains its 
curvature when exiting the outer guiding introducer (14) through the slot 
or opening (30) near the distal end (31) of the outer guiding introducer 
(14), as shown in FIGS. 2 and 9, while still retaining sufficient 
flexibility to support the ablation system (18, 110, 210) as it 
circumscribes the inner surface of the heart chamber in which the ablation 
procedure is performed. 
In a preferred embodiment, the cross section of the rail is preferably 
rectangular in shape, as shown in FIG. 12B. The rail (16) preferably is 
about 0.02 inch to about 0.04 inch (about 0.05 cm. to about 0.1 cm.) in 
width and from about 0.005 inch to about 0.02 inch (about 0.01 cm. to 
about 0.05 cm.) in thickness. As the preferred rail (16) is a flattened 
wire, it is resistant to bending laterally while still retaining 
sufficient flexibility to form a loop when extended away from the outer 
guiding introducer (14) by advancing the ablation system (18, 110, 210) 
over the rail (16). The rail (16) should be of sufficient length so that 
it can be fully extended into the chamber of the heart to be ablated and 
back out the proximal end of the guiding introducer system (11), exiting 
at point (19) as shown in FIG. 2. Thus, it should be at least about 60 
inches (152 cm.) in length. 
One end (24) of the rail (16) is preferably secured in place as shown in 
FIG. 9. The manner of securing end (24) of the rail (16) in place and the 
location where the rail (16) is secured is not critical. In one preferred 
embodiment, end (24) of the rail (16) is secured to the hub (28) at the 
proximal end (26) of the outer guiding introducer (14). End (24) of the 
rail (16) is secured in place by conventional means, such as with 
adhesives. Alternatively, one end of the rail (16) may be secured by 
conventional securing methods to one of the guiding introducers within a 
distal portion of the guiding introducer (not shown). In another 
alternative embodiment (not shown), neither end of the rail is secured in 
place and both ends pass through a lumen or lumens of the guiding 
introducer(s) and/or ablation system (18, 110, 210) and exit at the 
proximal end of the guiding introducer(s) and/or ablation system (18, 110, 
210). 
When end (24) of the rail (16) is secured in place at the proximal end (26) 
of the outer guiding introducer (14), as shown in FIG. 9, the remaining 
portion of the rail (16) extends through the lumen (15) of the outer 
guiding introducer (14) between the inside surface of the outer guiding 
introducer (14) and the outside surface of the inner guiding introducer 
(12) to a location near the distal end (31) of the outer guiding 
introducer (14). The rail (16) then exits through an opening or slot (30) 
provided in the surface of the outer guiding introducer (14). In a 
preferred embodiment, the opening or slot (30) extends at least about 20 
degrees, and preferably as much as 180 degrees, around the circumference 
of the outer guiding introducer (14). Opening or slot (30) permits the 
rail (16) to be moved laterally in relation to the outer guiding 
introducer (14) to adjust the position of the ablation system (18, 110, 
210) while in use in the heart. 
In order to substantially circumscribe the inner surface of a chamber of a 
human heart, the rail (16), preferably is angled outwardly from the outer 
guiding introducer (14) at an angle of approximately 60 to 180 degrees and 
more preferably from about 80 to 100 degrees as it exits the outer guiding 
introducer (14) through the opening or slot (30) as shown in FIG. 9. 
In a preferred embodiment, as shown in FIG. 9, the rail (16) extends 
through the lumen (15) of the outer guiding introducer (14), out the 
opening or slot (30) and then loops back through a lumen (23) within the 
slotted sheath (22) as is shown in FIG. 11. However, the rail need not 
extend through the entire length of the slotted sheath (22) and may exit 
through the side of the slotted sheath (22) at a location (25) proximal 
from the distal end (40) of the slotted sheath (22). The rail then runs 
along the side of the ablation catheter (18, 110, 210) through the lumen 
(13) of the inner guiding introducer (12) until it exits the proximal end 
of the inner guiding introducer (12). 
The ablation catheters (18, 110, 210) is preferably a n elongated catheter 
made of materials suitable for use in humans, such as nonconductive 
polymers. Exemplary polymers used for the production of the catheter body 
include those well known in the art such as polyurethanes, polyether-block 
amides, polyolefins, nylons, polytetrafluoroethylene, polyvinylidene 
fluoride, and fluorinated ethylene propylene polymers and other 
conventional materials. 
The ablation catheters (18, 110, 210) preferably are flexible near its 
distal end (34) for at least 7 inches (18 cm.). While the more proximal 
portion of the ablation catheters (18, 110, 210) are preferably stiffer 
than the distal end, the stiffness of the ablation catheters (18, 110, 
210) may be consistent over their entire length. Enhanced stiffness is 
generally provided to the ablation catheters (18, 110, 210) by 
conventional catheter forming procedures, such as by braiding a portion of 
the ablation catheter (20), or by use of higher durometer catheter 
materials. 
The ablation catheter (18, 110, 210 ) should be sufficiently flexible so 
that its distal portion can pass smoothly through the lumen (33) within 
the slotted sheath (22) as shown in FIG. 11. However, the ablation 
catheter (20) should also be sufficiently stiff so that it can be advanced 
through the lumen (33) of the slotted sheath (22) without undue 
difficulty. 
The length of the ablation catheters (18, 110, 210) is preferably from 
about 20 to about 60 inches (about 50 cm. to about 150 cm.). The diameter 
of the catheter is within ranges known in the industry, preferably, from 
about 4 to 16 French (about 0.05 inch to about 0.2 inch) (about 1.3 mm to 
about 5.2 mm) and more preferably from about 6 to 8 French (about 0.07 to 
about 0.1 inch) (about 1.8 mm to about 2.4 mm). 
There are several alternative ablation systems. The ablation catheter (210) 
may contain a series of ring electrodes (37), as shown in FIG. 7, without 
a tip electrode. This ablation catheter (210) is introduced over the rail 
(16) of the guiding introducer system (11), as shown in FIG. 7. 
Alternatively, the ablation system may consist of a conventional ablation 
catheter with a tip electrode (36) and a series of ring electrodes (37). 
The ring electrodes (37) may be rigid or flexible, circumferential or 
directional. The body of the ablation catheter (210) preferably contains 
one or more lumens extending through the catheter body from its proximal 
end to or near its distal end. Preferably, sufficient lumens are present 
in the catheter body to accommodate wires for one or more sensing and/or 
ablating electrodes. Thermosensing devices, such as thermocouples (not 
shown), may also be attached to the ablation catheter (20). 
Alternatively a single tip electrode (46) may be used. The ablating tip 
electrode (46) may be rounded and secured to the distal tip of the 
ablation catheter (20) by conventional means. 
The preferred source for energy generated through the ablating electrodes 
is radiofrequency energy, although other sources for energy can also be 
utilized including direct current, laser, ultrasound and microwave. The 
electrodes may monitor electrical activity within the heart. 
In an alternative embodiment, the ablating electrode of the ablation 
catheter may be a tip coil electrode (46) secured at or near the distal 
tip (34) of the ablation catheter (20), as shown in FIGS. 3 and 11. This 
coil electrode (46) is preferably at least about 0.15 inch (0.4 cm.) in 
length. It is preferably formed from wire coils with a cross-section of 
about 0.005 inch (0.013 cm.), which are secured to the outside surface of 
the ablation catheter (20) by conventional methods, such as adhesives. In 
order to cool the coil electrode (46) during use, cooling fluid is 
introduced through the lumen (33) of the slotted sheath (22) and the lumen 
(39) of the ablation catheter so that the fluid can flow around and 
through the coils of the coil electrode (46) while the ablation procedure 
is proceeding. 
In a preferred embodiment, the ablation catheter (20) is advanced and 
withdrawn within lumen (33) of the slotted sheath (22) as shown in FIG. 
11. The preferred slotted sheath (22) of the present invention is 
disclosed in application Ser. No. 08/757,832, filed Nov. 27, 1996, owned 
by the common assignee, which disclosure is incorporated herein by 
reference. Once the slotted sheath (22) is properly positioned over the 
rail (16) in the cardiac chamber as shown in FIG. 1, the ablation catheter 
(20) is advanced within the lumen (33) of the slotted sheath (22) to 
ablate the cardiac tissue to form an ablation track or lesion. 
Openings (38) are provided in the body (27) of the slotted sheath (22) to 
form a longitudinal line extending from near the distal tip (40) of the 
slotted sheath (22) proximally as shown in FIGS. 3 and 11. The number of 
individual openings (38) provided in the body (27) of the slotted sheath 
(22) is at least 3. The overall length of the flexible portion of the body 
(27) of the slotted sheath (22) containing the openings (38) is generally 
about the same length as the desired linear lesion to be formed, 
preferably from about 3 inches to about 5 inches (approximately 8 cm. to 
about 12 cm.). 
The openings (38) in the body (27) of the slotted sheath (22) are 
preferably from about 0.010 inch to about 0.050 inch (about 0.025 cm. to 
about 0.127 cm.) in diameter. The shape of the openings (38) is not 
critical, but preferably, they are longer than they are wide. Referring to 
FIG. 11, a bridge (42) of sheath material exists between individual 
openings (38). The width of the bridge (42) of material should not be 
greater than about 0.05 inch (approximately 0.2 cm.). Located at the 
distal tip (40) of the slotted sheath (22) is the opening (44) through 
which the rail (16) extends through the slotted sheath (22). The structure 
of the slotted sheath (22) should be sufficiently flexible so that it can 
circumscribe the inner surface of the chamber of the heart, as shown in 
FIG. 1, yet stiff enough to support the ablation catheter (20) and rail 
(16) contained within lumens (33, 23) of the slotted sheath (22). 
In an alternative preferred embodiment, instead of using an ablation 
catheter (20) advanced within a slotted sheath (22), the rail catheter 
ablation and mapping system (100) may utilize an ablation catheter (110) 
such as is disclosed in application Ser. No. 08/897,300, filed Jul. 21, 
1997, owned by the common assignee and incorporated herein by reference, 
as shown in FIG. 6. The ablation catheter (110) of this system (100) 
contains a plurality of lumens (112, 114), one lumen (112) of which is 
used to receive the rail (16) as shown in FIGS. 12A and 12B. One or more 
electrodes (118) are located within a lumen (114) of the ablation catheter 
(110). A series of openings (116) are provided in the outer surface (122) 
of the ablation catheter (110), which extend from the outer surface (122) 
into the lumen (114) containing the electrodes (118). A system (not shown) 
is provided for the introduction of a conductive media into the lumen 
(114), which media conductively contacts the electrode (118) and then 
passes out through the openings (116) in the surface (122) of the ablation 
catheter (110). The electrode (118) utilized in one preferred embodiment, 
as shown in FIG. 6, constitutes one or more coiled electrodes extending 
along the length of the lumen (114) inside the ablation catheter (110). 
The conductive media is forced out of the openings (116) in the ablation 
catheter (110). The electrode (118) does not directly contact the cardiac 
tissue to be ablated. Instead, the conductive media conducts the energy, 
preferably radiofrequency energy, from the electrode (118) to the surface 
of the cardiac tissue to be ablated. As the impedance of the conductive 
media is maintained at a level less than that of the impedance of the 
cardiac tissue, the cardiac tissue will heat up as the ablation procedure 
proceeds. If sufficient energy is conducted to the tissue by the 
conductive media for a sufficient period of time, a satisfactory ablation 
lesion will be formed. 
In order to produce an adequate lesion, the flow of the conductive media 
should occur through all or substantially all of the openings (116) along 
the length of the ablation catheter (110). Any structural system which 
controls the flow of the conductive media through these openings (116) is 
consistent with this invention. Several such systems are disclosed in 
application Ser. No. 08/897,300, filed Jul. 21, 1997, which disclosure is 
incorporated into this application by reference. 
Instead of utilizing a coiled electrode (118), as shown in FIG. 6, other 
electrode systems can be utilized, including a coated tubular body, a 
conductive filter element, and the utilization of a chemical ablative 
element. Each of these systems is disclosed in application Ser. No. 
08/897,300, filed Jul. 21, 1997, which systems are incorporated by 
reference into this application. 
FIG. 7 discloses another alternative rail catheter ablation and mapping 
system (200). This system (200) includes a guiding introducer system (11), 
which is preferably an inner guiding introducer (12) and an outer guiding 
introducer (14), an ablation catheter (210) and a rail (16). The inner 
(12) and outer (14) guiding introducers and the rail (16) are similar to 
those previously discussed. The ablation catheter (210) may have a 
plurality of electrodes (37). However, no slotted sheath is utilized with 
this embodiment. The ablation catheter (210) is first extended over the 
rail (16) to isolate the cardiac tissue from the rail (16). Flushing may 
be provided through catheter (210) to flow out and around the electrodes 
(37) for cooling during ablation. In this embodiment, the rail (208) with 
catheter (210) is then extended from the guiding introducers (12, 14) to 
circumscribe the chamber of the heart. 
In operation, a modified Seldinger technique for inserting hemostasis 
introducers for vascular access is normally used for the insertion of the 
associated dilators and hemostasis introducers into the body. The 
appropriate vessel is accessed by needle puncture. The soft flexible tip 
of an appropriately sized guidewire is inserted through and a short 
distance beyond the needle into the vessel. Firmly holding the guidewire 
in place, the needle is removed. A hemostasis introducer with a dilator is 
then inserted into the vessel over the guidewire. A long guidewire is then 
inserted into the vessel through the hemostasis introducer and advanced 
into the right atrium. A transseptal introducer is then advanced into the 
right atrium through the hemostasis introducer and over the guidewire. A 
conventional transseptal technique is used for approach into the left 
atrium of the heart. The guidewire is used to provide a path from the left 
atrium transseptally back through the hemostasis valve after the 
transseptal technique has been performed. 
The system (11), as assembled in FIG. 13, is then introduced over the 
guidewire. With the guidewire in place, a dilator (50) is advanced over 
the guidewire within the appropriate inner (12) and outer (14) guiding 
introducers. The rail (16) exits through the opening (30) in the outer 
guiding introducer (14) and loops around through an opening (48) in the 
dilator (50). The rail (16) then extends down the length of the dilator 
(50) and out its proximal end (52). The dilator (50), inner (12) and outer 
(14) guiding introducers and rail (16) form an assembly to be advanced 
together over the guidewire into the appropriate chamber of the heart. 
After insertion of the assembly into the appropriate chamber of the heart, 
the guidewire is withdrawn. Once the dilator (50), inner (12) and outer 
(14) guiding introducers, and rail (16) are in position in the appropriate 
chamber of the heart, the inner guiding introducer (12) is rotated 180 
degrees and the dilator (50) is withdrawn. The slotted sheath (22) of the 
ablation system (18) is then advanced over the rail (16) into the inner 
guiding introducer (12). The catheter ablation system (18) is advanced 
over the rail (16) through the distal tip (29) of the inner guiding 
introducer (12) until the distal tip (40) of the slotted sheath (22) 
approaches the opening or slot (30) in the outside surface of the side of 
the outer guiding introducer (14), as shown in FIGS. 1 and 2. The ablation 
catheter system (18) is then advanced out of the distal end (29) of the 
inner guiding introducer (12) such that it contacts the wall of the heart. 
The distal tip (29) of the inner guiding introducer (12) is advanced away 
from the distal tip (31) of the outer guiding introducer (14), as shown in 
FIG. 1, until the distal tip (29) of the inner guiding introducer (12) 
approaches the opposite side of the chamber of the heart in which the 
ablation procedure is to be performed. The distal tip (31) of the outer 
guiding introducer (14) is retained at or near the opening into the 
chamber of the heart. By this process, a loop of the slotted sheath (22) 
over the rail (16) can be formed that circumscribes the entire surface of 
the chamber of the heart as shown in FIG. 1. The specific placement of the 
ablation system (18) on the surface of the chamber of the heart can be 
adjusted by rotating, advancing or withdrawing the inner guiding 
introducer (12) in relation to the outer guiding introducer (14). 
After the desired location for ablation is determined, the ablation 
catheter (20) is positioned within the slotted sheath (22). In a preferred 
embodiment, as the ablation catheter (20) is advanced, it first senses the 
electrical activity of that chamber of the heart along the pathway created 
by the rail (16) located within the slotted sheath (22). Once the proper 
location for the ablation procedure is determined, the ablation catheter 
(20) utilizing energy, preferably radiofrequency energy, performs the 
ablation procedure in the heart and forms a linear lesion by dragging the 
ablation catheter (20) through the slotted sheath (22). For the catheters 
(110, 210) the procedure for use is the same as the procedures using the 
slotted sheath(22). Because of the rail (16), the slotted sheath system 
(18) or the ablation catheter (110, 210) can maintain tissue contact in 
the cardiac chamber throughout the ablation procedure, making the 
formation of linear lesions significantly easier. Thermosensing devices, 
such as thermocouples, may also be secured to the ablation catheter to 
determine whether sufficient energy has been applied to the tissue to 
create an adequate linear lesion. 
Alternatively, an ablation catheter can be advanced over the rail (16) to 
create a linear lesion, such that the rail (16) is in direct contract with 
the tissue. The rail (16) in this embodiment provides a linear track for 
the catheter (110, 210) to slide over. 
After the ablation procedure is completed, a sensing electrode may be used 
to determine if the arrhythmia has been eliminated at the particular 
location within the heart. Additional ablation lesions or tracks may then 
be produced, if necessary, using the ablation catheter (18, 110, 210) at 
the same or different locations within the heart. 
Pharmacological treatments may also be used in combination with ablation 
procedures to relieve the atrial arrhythmia. 
This rail catheter ablation and mapping system (10, 100, 200, 300) provides 
several improvements over conventional ablation systems, including 
steerable catheters. This rail catheter ablation and mapping system (10, 
100, 200, 300) allows ablation catheters to maintain positive contact with 
the cardiac tissue to be ablated to form linear lesions that are 
contiguous and continuous. These systems also allow the ablation catheter 
system (18, 110, 210) to be firmly placed against the tissue to be 
ablated. When used with a guiding introducer system, preferably an inner 
and outer guiding introducer, a stable platform for the rail and ablation 
system (18, 110, 210) is created to maintain positive contact with the 
cardiac tissue to be ablated. The rail catheter ablation and mapping 
system (10, 100, 200, 300) also permits a single positioning of the 
ablation catheter for the creation of a linear ablation lesion without the 
need for continuous repositioning of the ablation catheter. Because the 
rail is preferably rectangular in shape, it is flexible to conform to the 
contours of the cardiac tissue to be ablated while still maintaining 
lateral stiffness to retain the rail catheter ablation and mapping system 
(10, 100, 200, 300) at the correct location for formation of the linear 
lesions. The use of a flushing system around the rail and the electrodes 
prevents formation of coagulum during the ablation procedure. 
It will be apparent from the foregoing that while particular forms of the 
invention have been illustrated and described, various modifications can 
be made without departing from the spirit and scope of the invention.