Medical instrument positioning tool and method Number:6,802,840 from the United States Patent and Trademark Office (PTO) owispatent A system and method for positioning a medical instrument at a desired biological target tissue site is provided. The system includes an elongated sheath having a deflectable distal end configured to deflect or otherwise position at least a portion of a medical instrument during a surgical procedure allowing for the placement of the deflected portion adjacent or proximate to a predetermined target tissue surface. The positioning system may be incorporated into the medical instrument. The medical instrument may be an ablation system.<H positioning, instrument, Medical, instrum, 6802840.html, Patent, pto, 6802840

Title: Medical instrument positioning tool and method

Abstract: A system and method for positioning a medical instrument at a desired biological target tissue site is provided. The system includes an elongated sheath having a deflectable distal end configured to deflect or otherwise position at least a portion of a medical instrument during a surgical procedure allowing for the placement of the deflected portion adjacent or proximate to a predetermined target tissue surface. The positioning system may be incorporated into the medical instrument. The medical instrument may be an ablation system.

Patent Number: 6,802,840 Issued on 10/12/2004 to Chin, et al.

Inventors: Chin; Sing Fatt (Fremont, CA); Berube; Dany (Fremont, CA); Mody; Dinesh I. (Pleasanton, CA); Norris; Nancy (Fremont, CA)
Assignee: AFx, Inc. (Santa Clara, CA)

Appl. No.: 09/872,652

Filed: June 1, 2001

Current U.S. Class: 606/41 ; 606/45

Field of Search: 606/41,46,47-50 600/585 604/528 607/101-102

References Cited [Referenced By]

U.S. Patent Documents


4073287	February 1978	Bradley et al.
4476872	October 1984	Perlin
4611604	September 1986	Botvidsson et al.
4641649	February 1987	Walinsky et al.
4643186	February 1987	Rosen et al.
5044375	September 1991	Bach et al.
5246438	September 1993	Langberg
5314466	May 1994	Stern et al.
5344441	September 1994	Gronauer
5370644	December 1994	Langberg
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5800494	September 1998	Campbell et al.
6161543	December 2000	Cox et al.
6237605	May 2001	Vaska et al.
6245062	June 2001	Berube et al.
6287302	September 2001	Berube
6309388	October 2001	Fowler
6311692	November 2001	Vaska et al.
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6474340	November 2002	Vaska et al.
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Foreign Patent Documents


WO 94/02204	Feb., 1994	WO
WO 98/17187	Apr., 1998	WO

Other References

CH. Durney and M.F. Iskander, "Antennas for Medical Applications" Chapter 24, pp. 24-2, 24-27, 24-28, 24-29, and 24-58. .
Cox et al., "The Surgical Treatment of Atrial Fbrilation" Thorac Cardiovasc Surg , 402-426, 569-592 (1991). .
Gauthier, "A Microwave Ablation Instrument With Flexible Atenna Assembly and Method", U.S. patent application No. 09/484,548, filed Jan. 18, 2000. .
Danny Berube, Electrode Arrangement for Use in a Medical Instrument, U.S. patent application No. 09/484,548 filed Jan. 18, 2000..

Primary Examiner: Gibson; Roy D.
Attorney, Agent or Firm: Fenwick & West LLP

Parent Case Text

This application is a Continuation-in-Part of U.S. patent application Ser. No. 09/751,472, filed Dec. 29, 2000, which is incorporated herein by reference, in its entirety.

Claims

What is claimed is:

1. A device to position a medical instrument during a surgical procedure, comprising: a handle; a guide sheath operably attached to the handle and having a deflectable distal end comprising a sharp tip translatable from a position external to the distal end to a position within at least a portion of the deflectable distal end; an activation means for slidably controlling the translatable sharp tip; and a deflection means for deflecting the distal end of the guide sheath, wherein tissue is dissected by the translatable sharp tip creating an opening through which at least a portion of the medical instrument can be advanced and positioned adjacent a target tissue site.

2. The device of claim 1, wherein the guide sheath is configured to slidably receive a portion of a medical instrument along a longitudinal axis of the deflectable distal end.

3. The device of claim 2, wherein the guide sheath is malleable.

4. The device of claim 2, wherein the guide sheath is slidably attached to the handle.

5. The device of claim 2, wherein the deflection means comprises an attachment point allowing for the deflection of the deflectable distal end along at least one plane.

6. The device of claim 5, wherein the attachment point comprises one or more nodes on the distal end of the elongated sheath and one or more matching recesses on the proximal end of the deflectable distal end which are configured to accept the one or more nodes.

7. The device of claim 5, wherein the attachment point comprises one or more pins, the one or more pins defining a fulcrum about which the deflectable distal end rotates.

8. The device of claim 1, wherein the deflection means comprises one or more components, alone or in combination, selected from the group consisting of pull wires, springs of various shapes and configurations, sliders, switches, or motors.

9. The device of claim 8, wherein the activation means is part of the deflection means, the operation of the deflection means and the activation means being performed in one controlled movement by a surgeon performing the surgical procedure.

10. The device of claim 9, wherein the deflection means is at least partially located within the handle.

11. The device of claim 1 wherein the deflection means deflects the deflectable distal end from about 0.degree. to about 180.degree..

12. The device of claim 1 herein the medical instrument is an ablation system.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates, generally, to ablation instrument systems that use ablative energy to ablate internal bodily tissues. More particularly, to preformed guide apparatus which cooperate with energy delivery arrangements to direct the ablative energy in selected directions along the guide apparatus.

2. Description of the Prior Art

It is well documented that atrial fibrillation, either alone or as a consequence of other cardiac disease, continues to persist as the most common cardiac arrhythmia. According to recent estimates, more than two million people in the U.S. suffer from this common arrhythmia, roughly 0.15% to 1.0% of the population. Moreover, the prevalence of this cardiac disease increases with age, affecting nearly 8% to 17% of those over 60 years of age.

Atrial arrhythmia may be treated using several methods. Pharmacological treatment of atrial fibrillation, for example, is initially the preferred approach, first to maintain normal sinus rhythm, or secondly to decrease the ventricular response rate. Other forms of treatment include drug therapies, electrical cardioversion, and RF catheter ablation of selected areas determined by mapping. In the more recent past, other surgical procedures have been developed for atrial fibrillation, including left atrial isolation, transvenous catheter or cryosurgical ablation of His bundle, and the Corridor procedure, which have effectively eliminated irregular ventricular rhythm. However, these procedures have for the most part failed to restore normal cardiac hemodynamics, or alleviate the patient's vulnerability to thromboembolism because the atria are allowed to continue to fibrillate. Accordingly, a more effective surgical treatment was required to cure medically refractory atrial fibrillation of the Heart.

On the basis of electrophysiologic mapping of the atria and identification of macroreentrant circuits, a surgical approach was developed which effectively creates an electrical maze in the atrium (i.e., the MAZE procedure) and precludes the ability of the atria to fibrillate. Briefly, in the procedure commonly referred to as the MAZE III procedure, strategic atrial incisions are performed to prevent atrial reentry circuits and allow sinus impulses to activate the entire atrial myocardium, thereby preserving atrial transport function postoperatively. Since atrial fibrillation is characterized by the presence of multiple macroreentrant circuits that are fleeting in nature and can occur anywhere in the atria, it is prudent to interrupt all of the potential pathways for atrial macroreentrant circuits. These circuits, incidentally, have been identified by intraoperative mapping both experimentally and clinically in patients.

Generally, this procedure includes the excision of both atrial appendages, and the electrical isolation of the pulmonary veins. Further, strategically placed atrial incisions not only interrupt the conduction routes of the common reentrant circuits, but they also direct the sinus impulse from the sinoatrial node to the atrioventricular node along a specified route. In essence, the entire atrial myocardium, with the exception of the atrial appendages and the pulmonary veins, is electrically activated by providing for multiple blind alleys off the main conduction route between the sinoatrial node to the atrioventricular node. Atrial transport function is thus preserved postoperatively as generally set forth in the series of articles: Cox, Schuessler, Boineau, Canavan, Cain, Lindsay, Stone, Smith, Corr, Change, and D'Agostino, Jr., The Surgical Treatment Atrial Fibrillation (pts. 1-4), 101 THORAC CARDIOVASC SURG., 402-426, 569-592 (1991).

While this MAZE III procedure has proven effective in ablating medically refractory atrial fibrillation and associated detrimental sequelae, this operational procedure is traumatic to the patient since this is an open-heart procedure and substantial incisions are introduced into the interior chambers of the Heart. Consequently, other techniques have been developed to interrupt atrial fibrillation restore sinus rhythm. One such technique is strategic ablation of the atrial tissues through ablation catheters.

Most approved ablation catheter systems now utilize radio frequency (RF) energy as the ablating energy source. Accordingly, a variety of RF based catheters and power supplies are currently available to electrophysiologists. However, radio frequency energy has several limitations including the rapid dissipation of energy in surface tissues resulting in shallow "burns" and failure to access deeper arrhythmic tissues. Another limitation of RF ablation catheters is the risk of clot formation on the energy emitting electrodes. Such clots have an associated danger of causing potentially lethal strokes in the event that a clot is dislodged from the catheter. It is also very difficult to create continuous long lesions with RF ablation instruments.

As such, catheters which utilize other energy sources as the ablation energy source, for example in the microwave frequency range, are currently being developed. Microwave frequency energy, for example, has long been recognized as an effective energy source for heating biological tissues and has seen use in such hyperthermia applications as cancer treatment and preheating of blood prior to infusions. Accordingly, in view of the drawbacks of the traditional catheter ablation techniques, there has recently been a great deal of interest in using microwave energy as an ablation energy source. The advantage of microwave energy is that it is much easier to control and safer than direct current applications and it is capable of generating substantially larger and longer lesions than RF catheters, which greatly simplifies the actual ablation procedures. Such microwave ablation systems are described in the U.S. Pat. No. 4,641,649 to Walinsky; U.S. Pat. No. 5,246,438 to Langberg; U.S. Pat. No. 5,405,346 to Grundy, et al.; and U.S. Pat. No. 5,314,466 to Stern, et al, each of which is incorporated herein by reference.

Most of the existing microwave ablation catheters contemplate the use of longitudinally extending helical antenna coils that direct the electromagnetic energy in all radial directions that are generally perpendicular to the longitudinal axis of the catheter. Although such catheter designs work well for a number of applications, such radial output is inappropriate when the energy needs to be directed toward the tissue to ablate only.

Consequently, microwave ablation instruments have recently been developed which incorporate microwave antennas having directional reflectors. Typically, a tapered directional reflector is positioned peripherally around the microwave antenna to direct the waves toward and out of a window portion of the antenna assembly. These ablation instruments, thus, are capable of effectively transmitting electromagnetic energy in a more specific direction. For example, the electromagnetic energy may be transmitted generally perpendicular to the longitudinal axis of the catheter but constrained to a selected radial region of the antenna, or directly out the distal end of the instrument. Typical of these designs are described in the U.S. patent application Ser. No. 09/178,066, filed Oct. 23, 1998; and Ser. No. 09/333,747, filed Jun. 14, 1999, each of which is incorporated herein by reference.

In these designs, the resonance frequency of the microwave antenna is preferably tuned assuming contact between the targeted tissue or blood and a contact region of the antenna assembly extending longitudinally adjacent to the antenna longitudinal axis. Hence, should a portion of, or substantially all of, the exposed contact region of the antenna not be in contact with the targeted tissue or blood during ablation, the resonance frequency will be adversely changed and the antenna will be untuned. As a result, the portion of the antenna not in contact with the targeted tissue or blood will radiate the electromagnetic radiation into the surrounding air. The efficiency of the energy delivery into the tissue will consequently decrease which in turn causes the penetration depth of the lesion to decrease.

This is particularly problematic when the microwave antenna is not in the blood pool, or when the tissue surfaces are substantially curvilinear, or when the targeted tissue for ablation is difficult to access, such as in the interior chambers of the Heart. Since these antenna designs are generally relatively rigid, it is often difficult to maneuver substantially all of the exposed contact region of the antenna into abutting contact against the targeted tissue. In these instances, several ablation instruments, having antennas of varying length and shape, may be necessary to complete just one series of ablations.

SUMMARY OF THE INVENTION

Accordingly, a system for ablating a selected portion of a contact surface of biological tissue is provided. The system is particularly suitable to ablate cardiac tissue, and includes an elongated ablation sheath having a preformed shape adapted to substantially conform a predetermined surface thereof with the contact surface of the tissue. The ablation sheath defines an ablation lumen extending therethrough along an ablation path proximate to the predetermined surface. An elongated ablative device includes a flexible ablation element which cooperate with an ablative energy source which is sufficiently strong for tissue ablation. The ablative device is formed and dimensioned for longitudinal sliding receipt through the ablation lumen of the ablation sheath for selective placement of the ablative device along the ablation path created by the ablation sheath. The ablation lumen and the ablative device cooperate to position the ablative device proximate to the ablation sheath predetermined surface for selective ablation of the selected portion.

Accordingly, the ablation sheath in its preshaped form functions as a guide device to guide the ablative device along the ablation path when the predetermined surface of the ablation sheath properly contacts the biological tissue. Further, the cooperation between the ablative device and the ablation lumen, as the ablative device is advanced through the lumen, positions the ablative device in a proper orientation to facilitate ablation of the targeted tissue during the advancement. Thus, once the ablation sheath is stationed relative the targeted contact surface, the ablative device can be easily advanced along the ablation path to generate the desired tissue ablations.

In one embodiment, the ablative device is a microwave antenna assembly which includes a flexible shield device coupled to the antenna substantially shield a surrounding area of the antenna from the electromagnetic field radially generated therefrom while permitting a majority of the field to be directed generally in a predetermined direction toward the ablation sheath predetermined surface. The microwave antenna assembly further includes a flexible insulator disposed between the shield device and the antenna. A window portion of the insulator is defined which enables transmission of the directed electromagnetic field in the predetermined direction toward the ablation sheath predetermined surface. The antenna, the shield device and the insulator are formed for manipulative bending thereof, as a unit, to one of a plurality of contact positions to generally conform the window portion to the ablation sheath predetermined surface as the insulator and antenna are advanced through the ablation lumen.

In another embodiment, to facilitate alignment of the ablative device assembly in the ablation lumen, the ablative device provides a key device which is slidably received in a mating slot portion of the ablation lumen. In still another embodiment, the system includes a guide sheath defining a guide lumen formed and dimensioned for sliding receipt of the ablation sheath therethrough. The guide sheath is pre-shaped to facilitate positioning of the ablation sheath toward the selected portion of the contact surface when the ablation sheath is advanced through guide lumen.

The ablation sheath includes a bendable shape retaining member extending longitudinally therethrough which is adapted to retain the preformed shape of the ablation sheath once positioned out of the guide lumen of the guide sheath.

The ablative energy is preferably provided by a microwave ablative device. Other suitable tissue ablation devices, however, include cryogenic, ultrasonic, laser and radiofrequency, to name a few.

In another aspect of the present invention, a method for treatment of a Heart includes forming a penetration through a muscular wall of the Heart into an interior chamber thereof; and positioning a distal end of an elongated ablation sheath through the penetration. The ablation sheath defines an ablation lumen extending along an ablation path therethrough. The method further includes contacting, or bringing close enough, a predetermined surface of the elongated ablation sheath with a first selected portion of an interior surface of the muscular wall; and passing a flexible ablative device through the ablation lumen of the ablation sheath for selective placement of the ablative device along the ablation path. Once these events have been performed, the method includes applying the ablative energy, using the ablative device and the ablation energy source, which is sufficiently strong to cause tissue ablation.

In one embodiment, the passing is performed by incrementally advancing the ablative device along a plurality of positions of the ablation path to produce a substantially continuous lesion. Before the positioning event, the method includes placing a distal end of a guide sheath through the penetration, and then positioning the distal end of the ablation sheath through the guide lumen of the guide sheath.

In still another embodiment, before the placing event, piercing the muscular wall with a piercing sheath. The piercing sheath defines a positioning passage extending therethrough, The placing the distal end of a guide sheath is performed by placing the guide sheath distal end through the positioning passage of the piercing sheath.

In yet another configuration, the positioning the distal end event includes advancing the ablation sheath toward the first selected portion of the interior surface of the muscular wall through a manipulation device extending through a second penetration into the Heart interior chamber independent from the first named penetration.

In another embodiment, a system for ablating tissue within a body of a patient is provided including an elongated rail device and an ablative device. The radial device is adapted to be positioned proximate and adjacent to a selected tissue region to be ablated within the body of the patient. The ablative device includes a receiving passage configured to slideably receive the rail device longitudinally therethrough. This enables the ablative device to be slideably positioned along the rail substantially adjacent to or in contact with the selected tissue region. The ablative device, having an energy delivery portion which is adapted to be coupled to an ablative energy source, can then be operated to ablate the selected tissue region.

In this configuration, the ablative device is adapted to directionally emit the ablative energy from the energy delivery portion. A key assembly cooperates between the ablative device and the rail member, thus, to properly align the directionally emitted ablative energy toward the tissue region to be ablated. This primarily performed by providing a rail device with a non-circular transverse cross-sectional dimension. The receiving passage of the ablative device further includes a substantially similarly shaped non-circular transverse cross-section dimension to enable sliding of the ablative device in a manner continuously aligning the directionally emitted ablative energy toward the tissue region to be ablated as the ablative device advances along the rail device.

BRIEF DESCRIPTION OF THE DRAWINGS

The assembly of the present invention has other objects and features of advantage which will be more readily apparent from the following description of the best mode of carrying out the invention and the appended claims, when taken in conjunction with the accompanying drawing, in which:

FIGS. 1A and 1B are fragmentary, top perspective views, partially broken-away, of the ablation system constructed in accordance with the present invention, and illustrating advancement of a bendable directional reflective microwave antenna assembly through an ablation lumen of a ablation sheath.

FIGS. 2A-2D is series of fragmentary, side elevation views, in partial cross-section, of the Heart, and illustrating advancement of the ablation system of present invention into the left atrium for ablation of the targeted tissue.

FIG. 3 is a fragmentary, side elevation view, in partial cross-section, of the Heart showing a pattern of ablation lesions to treat atrial fibrillation.

FIGS. 4A and 4B are a series of enlarged, fragmentary, top perspective view of a pigtail ablation sheath of the ablation system of FIGS. 2C and 2D, and exemplifying the ablation sheath being advanced into one of the pulmonary vein orifices.

FIG. 5 is a front schematic view of a patient's cardiovascular system illustrating the positioning of a trans-septal piercing sheath through the septum wall of the patient's Heart.

FIG. 6 is a fragmentary, side elevation view, in partial cross-section, of another embodiment of the ablation sheath of the present invention employed for lesion formation.

FIG. 7 is a fragmentary, side elevation view, in partial cross-section, of yet another embodiment of the ablation sheath of the present invention employed for another lesion formation.

FIG. 8 is an enlarged, front elevation view, in cross-section, of the ablation system of FIG. 1 positioned through the trans-septal piercing sheath.

FIG. 9 is an enlarged, front elevation view, in cross-section, of the ablation sheath and the antenna assembly of the ablation system in FIG. 8 contacting the targeted tissue.

FIG. 10 is a n enlarged, front elevation view, in cross-section, of the antenna as sembly taken substantially along the plane of the line 10--10 in FIG. 9.

FIG. 11 is a diagrammatic top plan view of an alternative embodiment microwave ablation instrument system constructed in accordance with one embodiment of the present invention.

FIG. 12 is an enlarged, fragmentary, top perspective view of the ablation instrument system of FIG. 11 illustrated in a bent position to conform to a surface of the tissue to be ablated.

FIGS. 13A-13D is a series of side elevation views, in cross-section, of the ablation sheath of the present invention illustrating advancement of the ablation device incrementally through the ablation sheath to form plurality of overlapping lesions.

FIG. 14A is a fragmentary, side elevation view of a laser-type ablation device of the present invention.

FIG. 14B is a front elevation view of the laser-type energy delivery portion taken along the plane of the line 14B--14B in FIG. 14A.

FIG. 15A is a fragmentary, side elevation view of a cryogenic-type ablation device of the present invention.

FIG. 15B is a front elevation view of the cryogenic-type energy delivery portion taken along the plane of the line 15B--15B in FIG. 15A.

FIG. 16 is a fragmentary, side elevation view, in cross-section, of an ultrasonic-type ablation device of the present invention.

FIG. 17 is an enlarged, fragmentary, top perspective view of an alternative embodiment ablation sheath having an opened window portion.

FIG. 18 is a fragmentary, side elevation view of an alternative embodiment ablation assembly employing a rail system.

FIG. 19 is a front elevation view of the energy delivery portion of the ablation rail system taken along the plane of the line 19--19 in FIG. 18.

FIGS. 20A-20C are cross-sectional views of alternative key systems in accordance with the present invention.

FIG. 21 is a fragmentary, diagrammatic, front elevation view of a torso applying one embodiment of the present invention through a minimally invasive technique.

FIG. 22 is a top plan view, in cross-section of the fragmentary, diagrammatic, top plan view of the torso of FIG. 21 applying the minimally invasive technique.

FIGS. 23A-B are side elevation views of a positioning tool used in accordance with the present invention.

FIG. 23C is an end elevation view of a positioning tool used in accordance with the present invention.

FIG. 23D is an end elevation view of an alternative embodiment of a positioning tool used in accordance with the present invention.

FIG. 23E is a side elevation view of an alternative embodiment of a positioning tool used in accordance with the present invention.

FIG. 24 is a side view of another alternative embodiment of a positioning tool used in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention will be described with reference to a few specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications to the present invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. It will be noted here that for a better understanding, like components are designated by like reference numerals throughout the various Figures.

Turning generally now to FIGS. 1A-2D, an ablation system, generally designated 20, is provided for transmurally ablating a targeted tissue 21 of biological tissue. The system 20 is particularly suitable to ablate the epicardial or endocardial tissue 40 of the heart, and more particularly, to treat medically refractory atrial fibrillation of the Heart. The ablation system 20 for ablating tissue within a body of a patient includes an elongated flexible tubular member 22 having at least one lumen 25 (FIGS. 1A, 1B, 8 and 9) and including a pre-shaped distal end portion (E.g., FIGS. 2C, 6 and 7) which is shaped to be positioned adjacent to or in contact with a selected tissue region 21 within the body of the patient. An ablative device, generally designated 26, is configured to be slidably received longitudinally within the at least one lumen 25, and includes an energy delivery portion 27 located near a distal end portion of the ablative device 26 which is adapted to be coupled to an ablative energy source (not shown).

The ablative device is preferably provided by a microwave ablation device 26 formed to emit microwave energy sufficient to cause tissue ablation. As will be described in greater detail below, however, the ablative device energy may be provided by a laser ablation device, a Radio Frequency (RF) ablation device, an ultrasound ablation device or a cryoablation device.

The tubular member 22 is in the form of an elongated ablation sheath having, in a preferred embodiment, a resiliently preformed shape adapted to substantially conform a predetermined contact surface 23 of the sheath with the targeted tissue region 21. In another embodiment, the ablation sheath is malleable. Yet, in another embodiment, the ablation sheath is flexible. The lumen 25 of the tubular member extends therethrough along an ablation path proximate to the predetermined contact surface. Preferably, as will be described in more detail below, the ablative device 26 includes a flexible energy delivery portion 27 selectively generating an electromagnetic field which is sufficiently strong for tissue ablation. The energy delivery portion 27 is formed and dimensioned for longitudinal sliding receipt through the ablation lumen 25 of the ablation sheath 22 for selective placement of the energy delivery portion along the ablation path. The ablation lumen 25 and the ablative device 26 cooperate to position the energy delivery portion 27 proximate to the ablation sheath 22 predetermined contact surface 23 of the sheath for selective transmural ablation of the targeted tissue 21 within the electromagnetic field when the contact surface 23 strategically contacts or is positioned close enough to the targeted tissue 21.

Accordingly, in one preferred embodiment, the pre-shaped ablation sheath 22 functions to unidirectionally guide or position the energy delivery portion 27 of the ablative device 26 properly along the predetermined ablation path 28 proximate to the targeted tissue region 21 as the energy delivery portion 27 is advanced through the ablation lumen 25. By positioning the energy delivery portion 27, which is preferably adapted to emit a directional ablation field, at one of a plurality of positions incrementally along the ablation path (FIGS. 1A and 1B) in the lumen 25, a single continuous or plurality of spaced-apart lesions can be formed. In other instances, the antenna length may be sufficient to extend along the entire ablation path 28 so that only a single ablation sequence is necessary.

While the method and apparatus of the present invention are applicable to ablate any biological tissue which requires the formation of controlled lesions (as will be described in greater detail below), this ablation system is particularly suitable for ablating endocardial or epicardial tissue of the Heart. For example, the present invention may be applied in an intra-coronary configuration where the ablation procedure is performed on the endocardium of any cardiac chamber. Specifically, such ablations may be performed on the isthmus to address atrial flutter, or around the pulmonary vein ostium, electrically isolating the pulmonary veins, to treat medically refractory atrial fibrillation (FIG. 3). This procedure requires the precise formation of strategically placed endocardial lesions 30-36 which collectively isolate the targeted regions. By way of example, any of the pulmonary veins may be collectively isolated to treat chronic atrial fibrillation. The annular lesion isolating one or more than one pulmonary vein can be linked with another linear lesion joining the mitral valve annulus. In another example, the annular lesion isolating one or more than one pulmonary vein can be linked with another linear lesion joining the left atrium appendage.

In a preferred embodiment, the pre-shaped ablation sheath 22 and the sliding ablative device 26 may applied to ablate the epicardial tissue 39 of the Heart 40 as well (FIG. 12). An annular ablation, for instance, may be formed around the pulmonary vein for electrical isolation from the left atrium. As another example, the lesions may be created along the transverse sinus and oblique sinus as part of the collective ablation pattern to treat atrial fibrillation for example.

The application of the present invention, moreover, is preferably performed through minimally invasive techniques. It will be appreciated, however, that the present invention may be applied through open chest techniques as well.

Briefly, to illustrate the operation of the present invention, a flexible pre-shaped tubular member (i.e., ablation sheath 22) in the form of a pigtail is shown in FIGS. 2C and 2d which is specifically configured to electrically isolate a pulmonary vein of the Heart 40. The isolating lesions are preferably made on the posterior wall of the left atrium, around the ostium of one, or more than one of a pulmonary vein.

In this example and as illustrated in FIGS. 4A and 4B, a distal end of the pigtail-shaped ablation sheath or tubular member 22 is positioned into the left superior pulmonary vein orifice 37 from the left atrium 41. As the ablation sheath 22 is further advanced, a predetermined contact surface 23 of the ablation sheath is urged adjacent to or into contact with the endocardial surface of the targeted tissue region 21 (FIGS. 2D and 4B). Once the ablation sheath 22 is properly positioned and oriented, the ablative device 26 is advanced through the ablation lumen 25 of the ablation sheath 22 (FIGS. 1A and 1B) which moves the energy delivery portion 27 of the ablative device along the ablation path. When the energy delivery portion 27 is properly oriented and positioned in the ablation lumen 25, the directional ablation field may be generated to incrementally ablate (FIGS. 13A-13D) the epicardial surface of the targeted tissue 21 along the ablation path to isolate the Left Superior Pulmonary Vein (LIPV)

Accordingly, as shown in FIGS. 13A-13D, as the energy delivery portion 27 is incrementally advanced through the lumen 25, overlapping lesion sections 44-44'" are formed by the ablation field which is directional in one preferred embodiment. Collectively, a continuous lesion or series of lesions can be formed which essentially three-dimensionally "mirror" the shape of the contact surface 23 of the ablation sheath 22 which is positioned adjacent to or in contact with the targeted tissue region. These transmural lesions may thus be formed in any shape on the targeted tissue region such as rectilinear, curvilinear or circular in shape. Further, depending upon the desired ablation lines pattern, both opened and closed path formation can be constructed.

Referring now to FIGS. 2A, 2D and 5, a minimal invasive application of the present invention is illustrated for use in ablating Heart tissue. By way of example, a conventional trans-septal piercing sheath 42 is introduced into the femoral vein 43 through a venous cannula 45 (FIG. 5). The piercing sheath is then intravenously advanced into the right atrium 46 of the Heart 40 through the inferior vena cava orifice 47. These piercing sheaths are generally resiliently pre-shaped to direct a conventional piercing device 48 toward the septum wall 50. The piercing device 48 and the piercing sheath 42 are manipulatively oriented and further advanced to pierce through the septum wall 50, as a unit, of access into the left atrium 41 of the Heart 40 (FIG. 2A).

These conventional devices are commonly employed in the industry for accessing the left atrium or ventricle, and have an outer diameter in the range of about 0.16 inch to about 0.175 inch, while having an inner diameter in the range of about 0.09 inch to about 0.135 inch.

Once the piercing device 48 is withdrawn from a positioning passage 51 (FIG. 8) of the piercing sheath 42, a guide sheath 52 of the ablation system 20 is slidably advanced through the positioning passage and into a cardiac chamber such as the left atrium 41 thereof (FIG. 2B). The guide sheath 52 is essentially a pre-shaped, open-ended tubular member which is inserted into the coronary circulation to direct and guide the advancing ablation sheath 22 into a selected cardiac chamber (i.e., the left atrium, right atrium, left ventricle or right ventricle) and toward the general direction of the targeted tissue. Thus, the guide sheath 52 and the ablation sheath 22 telescopically cooperate to position the predetermined contact surface 23 thereof substantially adjacent to or in contact with the targeted tissue region.

Moreover, the guide sheath and the ablation sheath cooperate to increase the structural stability of the system as the ablation sheath is rotated and manipulated from its proximal end into ablative contact with the targeted tissue 21 (FIG. 2A). As the distal curved portions of the ablation sheath 22, which is inherently longer than the guide sheath, is advanced past the distal lumen opening of the guide sheath, these resilient curved portions will retain their original unrestrained shape.

The telescopic effect of these two sheaths is used to position the contact surface 23 of the ablation sheath 22 substantially adjacent to or in contact with the targeted tissue. Thus, depending upon the desired lesion formation, the same guide sheath 52 may be employed for several different procedures. For example, the lesion 30 encircling the left superior pulmonary vein ostium and the Left Inferior Pulmonary Vein Ostium (RIPVO) lesion 31 (FIG. 3) may be formed through the cooperation of the pigtail ablation sheath 22 and the same guide sheath 52 of FIGS. 2B and 2D, while the same guide sheath may also be utilized with a different ablation sheath 22 (FIG. 4) to create the long linear lesion 34 as shown in FIG. 3.

In contrast, as illustrated in FIG. 7, another guide sheath 52 having a different pre-shaped distal end section may be applied to direct the advancing ablation sheath 22 back toward the in the left and right superior pulmonary vein orifices 53, 55. Thus, several pre-shaped guide sheaths, and the corresponding ablation sheaths, as will be described, cooperate to create a predetermined pattern of lesions (E.g., a MAZE procedure) on the tissue.

In the preferred embodiment, the guide sheath 52 is composed of a flexible material which resiliently retains its designated shape once external forces urged upon the sheath are removed. These external forces, for instance, are the restraining forces caused by the interior walls 56 of the trans-septal piercing sheath 42 as the guide sheath 52 is advanced or retracted therethrough. While the guide sheath 52 is flexible, it must be sufficiently rigid so as to substantially retain its original unrestrained shape, and not to be adversely influenced by the ablation sheath 22, as the ablation sheath is advanced through the lumen of the guide sheath. Such flexible, biocompatible materials may be composed of braided Pebax or the like having an outer diameter formed and dimensioned for sliding receipt longitudinally through the positioning passage 51 of the trans-septal piercing sheath 42. The outer dimension is therefore preferably cylindrical having an outer diameter in the range of about 0.09 inch to about 0.145 inch, and more preferably about 0.135", while having an inner diameter in the range of about 0.05 inch to about 0.125 inch, and more preferably about 0.115". This cylindrical dimension enables longitudinal sliding receipt, as well as axial rotation, in the positioning passage 51 to properly place and advance the guide sheath 52. Thus, the dimensional tolerance between the cylindrical-shaped, outer peripheral wall of the guide sheath 52 and the interior walls 56 of the trans-septal piercing sheath 42 should be sufficiently large to enable reciprocal movement and relative axial rotation therebetween, while being sufficiently small to substantially prevent lateral displacement therebetween as the ablation sheath 22 is urged into contact with the targeted tissue 21. For example, the dimensional tolerance between the transverse cross-sectional periphery of the interior walls 56 of the positioning passage 51 and that of the substantially conforming guide sheath 52 should be in the range of about 0.005 inches to about 0.020 inches.

To increase the structural integrity of the guide sheath 52, metallic braids 57 are preferably incorporated throughout the sheath when the guide sheath is molded to its preformed shape. These braids 57 are preferably provided by 0.002" wires composed of 304 stainless steel evenly spaced about the sheath.

Once the guide sheath 52 is properly positioned and oriented relative the trans-septal sheath 42, the ablation sheath 22 is advanced through a guide lumen 54 (FIG. 8) of the guide sheath 52 toward the targeted tissue. Similar to the pre-shaped guide sheath 52, the ablation sheath 22 is pre-shaped in the form of the desired lesions to be formed in the endocardial surface of the targeted tissue 21. As best viewed in FIGS. 2D, 6 and 7, each ablation sheath 52 is adapted facilitate an ablation in the targeted tissue 21 generally in the shape thereof. Thus, several pre-shaped ablation sheaths cooperate to form a type of steering system to position the ablation device about the targeted tissue. Collectively, a predetermined pattern of linear and curvilinear lesions (E.g., a MAZE procedure) can be ablated on the targeted tissue region.

Again, similar to the guide sheath 52, the ablation sheath 22 is composed of a flexible material which resiliently retains its designated shape once external forces urged upon the sheath are removed. These external forces, for instance, are the restraining forces caused by the interior walls 59 defining the guide lumen 54 of the guide sheath 52 as the ablation sheath 22 is advanced or retracted therethrough. Such flexible, biocompatible materials may be composed of Pebax or the like having an outer diameter formed and dimensioned for sliding receipt longitudinally through the guide lumen 54 of the ablation sheath 22. As mentioned, the inner diameter of the guide lumen 54 is preferably in the range of about 0.050 inch to about 0.125 inch, and more preferably about 0.115", while the ablation sheath 26 has an outer diameter in the range of about 0.40 inch to about 0.115 inch, and more preferably about 0.105".

The concentric cylindrical dimensions enable longitudinal sliding receipt, as well as axial rotation, of the ablation sheath 22 in the guide lumen 54 to properly place and advance the it toward the targeted tissue 21. Thus, the dimensional tolerance between the cylindrical-shaped, outer peripheral wall of the ablation sheath 22 and the interior walls 59 of the guide lumen 54 of the guide sheath 52 should be sufficiently large to enable reciprocal movement and relative axial rotation therebetween, while being sufficiently small to substantially prevent lateral displacement therebetween as the ablation sheath 22 is urged into contact with the targeted tissue 21. For example, the dimensional tolerance between the transverse cross-sectional periphery of the guide lumen 54 and that of the substantially conforming energy delivery portion 27 should be in the range of about 0.001 inches to about 0.005 inches.

As above-indicated, the pre-shaped ablation sheath 22 facilitates guidance of the ablative device 26 along the predetermined ablation path 28. This is primarily performed by advancing the energy delivery portion 27 of the ablative device 26 through the ablation lumen 25 of the ablation sheath 22 which is preferably off-set from the longitudinal axis 78 thereof. As best viewed in FIGS. 8 and 9, this offset positions the energy delivery portion 27 relatively closer to the predetermined contact surface 23 of the ablation sheath 22, and hence the targeted tissue 21. Moreover, when using directional fields such as those emitted from their energy delivery portion 27, it is important to provide a mechanism for continuously aligning the directional field of the energy delivery portion 27 with the tissue 21 targeted for ablation. Thus, in this design, the directional field must be continuously aligned with the predetermined contact surface 23 of the ablation sheath 22 as the energy delivery portion 27 is advanced through the ablation lumen 25 since the ablation sheath contact surface 23 is designated to contact or be close enough to the targeted tissue.

If the directional field is not aligned correctly, for example, the energy may be transmitted into surrounding fluids and tissues designated for preservation rather than into the targeted tissue region. Therefore, in accordance with another aspect of the present invention, a key structure 48 (FIGS. 1, 8 and 9) cooperates between the ablative device 26 and the ablation lumen 25 to orient the directive energy delivery portion 27 of the ablative device continuously toward the targeted tissue region 21 as it is advanced through the lumen. This key structure 48, thus, only allows receipt of the energy delivery portion 27 in the lumen in one orientation. More particularly, the key structure 48 continuously aligns a window portion 58 of the energy delivery portion 27 substantially adjacent the predetermined contact surface 23 of the ablation sheath 22 during advancement. This window portion 58, as will be described below, enables the transmission of the directed ablative energy from the energy delivery portion 27, through the contact surface 23 of the ablation sheath 22 and into the targeted tissue region. Consequently, the directional ablative energy emitted from the energy delivery portion will always be aligned with the contact surface 23 of the ablation sheath 22, which is positioned adjacent to or in contact with the targeted tissue region 21, to maximize ablation efficiency. By comparison, the ablation sheath 22 is capable of relatively free rotational movement axially in the guide lumen 54 of the guide sheath 52 for maneuverability and positioning of the ablation sheath therein.

As mentioned, the transverse cross-sectional dimension of the energy delivery portion 27 is configured for sliding receipt in the ablation lumen 25 of the ablation sheath 22 in a manner positioning the directional ablative energy, emitted by the energy delivery portion, continuously toward the predetermined contact surface 23 of the ablation sheath 22. In one example, as shown in FIGS. 8 and 9, the transverse peripheral dimensions of the energy delivery portion 27 and the ablation lumen 25 are generally D-shaped, and substantially similar in dimension. Thus, the window portion 58 of the insulator 61, as will be discussed, is preferably semicylindrical and concentric with the interior wall 62 defining the ablation lumen 25 of the ablation sheath 22. It will be appreciated, however, that any geometric configuration may be applied to ensure unitary or aligned insertion. As another example, one of the energy delivery portion and the interior wall of the ablation lumen may include a key member and corresponding receiving groove, or the like. Such key and receiving groove designs, nonetheless, should avoid relatively sharp edges to enable smooth advancement and retraction of the energy delivery portion in the ablation lumen 25.

This dimension alignment relationship can be maintain along the length of the predetermined contact surface of the ablation sheath 22 as the energy delivery portion 27 is advanced through the ablation lumen whether in the configuration of FIGS. 2, 6, 7 or 12. In this manner, a physician may determine that once the predetermined contact surface 23 of the ablation sheath 22 is properly oriented and positioned adjacent or in contact against the targeted tissue 21, the directional component (as will be discussed) of the energy delivery portion 27 will then be automatically aligned with the targeted tissue as it is advanced through the ablation lumen 25. Upon selected ablation by the ablative energy, a series of overlapping lesions 44-44'" (FIGS. 13A-13D) or a single continuous lesion can then be generated.

It will further be appreciated that the dimensional tolerances therebetween should be sufficiently large to enable smooth relative advancement and retraction of the energy delivery portion 27 around curvilinear geometries, and further enable the passage of gas therebetween. Since the ablation lumen 25 of the ablation sheath 22 is closed ended, gases must be permitted to flow between the energy delivery portion 27 and the interior wall 62 defining the ablation lumen 25 to avoid the compression of gas during advancement of the energy delivery portion therethrough. Moreover, the tolerance must be sufficiently small to substantially prevent axial rotation of the energy delivery portion in the ablation lumen 25 for alignment purposes. The dimensional tolerance between the transverse cross-sectional periphery of the ablation lumen and that of the substantially conforming energy delivery portion 27, for instance, should be in the range of about 0.001 inches to about 0.005 inches.

To further facilitate preservation of the fluids and tissues along the backside of the ablation sheath 22 (i.e., the side opposite the contact surface 23 of the sheath), a thermal isolation component (not shown) is disposed longitudinally along, and substantially adjacent to, the ablation lumen 25. Thus, during activation of the ablative device, the isolation component and the directive component 73 of the energy ablation portion 27 cooperate to form a thermal barrier along the backside of the ablation sheath.

For instance, the isolation component may be provided by an air filled isolation lumen extending longitudinally along, and substantially adjacent to, the ablation lumen 25. The cross-sectional dimension of the isolation lumen may be C-shaped or crescent shaped to partially surround the ablation lumen 25. In another embodiment, the isolation lumen may be filled with a thermally refractory material.

In still another embodiment, a circulating fluid, which is preferably biocompatible, may be disposed in the isolation lumen to provide to increase the thermal isolation. Two or more lumens may be provided to increase fluid flow. One such biocompatible fluid providing suitable thermal properties is saline solution.

Similar to the composition of the guide sheath 52, the ablation sheath 22 is composed of a flexible bio-compatible material, such as PU Pellethane, Teflon or polyethylent, which is capable of shape retention once external forces acting on the sheath are removed. By way of example, when the distal portions of the ablation sheath 22 are advanced past the interior walls of the guide lumen 54 of the guide sheath 52, the ablation sheath 22 will return to its preformed shape in the interior of the Heart.

To facilitate shape retention, the ablation sheath 22 preferably includes a shape retaining member 63 extending longitudinally through the distal portions of the ablation sheath where shape retention is necessary. As illustrated in FIGS. 1, 8 and 9, this retaining member 63 is generally extends substantially parallel and adjacent to the ablation lumen 25 to reshape the predetermined contact surface 23 to its desired pre-shaped form once the restraining forces are removed from the sheath. While this shape-memory material must be sufficiently resilient for shape retention, it must also be sufficiently bendable to enable insertion through the guide lumen 54 of the guide sheath 52. In the preferred form, the shape retaining member is composed of a superelastic metal, such as Nitinol (NiTi). Moreover, the preferred diameter of this material should be in the range of 0.020 inches to about 0.050 inches, and more preferably about 0.035 inches.

When used during a surgical procedure, the ablation sheath 22 is preferably transparent which enables a surgeon to visualize the position of the energy delivery portion 27 of the ablative device 26 through an endoscope or the like. Moreover, the material of ablation sheath 22 must be substantially unaffected by the ablative energy emitted by the energy delivery portion 27. Thus, as will be apparent, depending upon the type of energy delivery portion and the ablative source applied, the material of the tubular sheath must exhibit selected properties, such as a low loss tangent, low water absorption or low scattering coefficient to name a few, to be unaffected by the ablative energy.

As previously indicated, the ablation sheath 22 is advanced and oriented, relative to the guide sheath 52, adjacent to or into contact with the targeted tissue region 21 to form a series of over-lapping lesions 44-44'", such as those illustrated in FIGS. 3 and 13A-13D. Preferably, the contact surface 23 of the pre-shaped ablation sheath 22 is negotiated into physical contact with the targeted tissue 21. Such contact increases the precision of the tissue ablation while further facilitating energy transfer between the ablation element and the tissue to be ablated, as will be discussed.

To assess proper contact and positioning of the contact surface 23 of the ablation sheath 22 against the targeted tissue 21, at least one positioning electrode, generally designated 64, is disposed on the exterior surface of the ablation sheath for contact with the tissue. Preferably a plurality of electrodes are positioned along and adjacent the contact surface 23 to assess contact of the elongated and three dimensionally shaped contact surface. These electrodes 64 essentially measure whether there is any electrical activity (or electrophysiological signals) to one or the other side of the ablation sheath 22. When a strong electrical activation signal is detected, or inter-electrode impedance is measured when two or more electrodes are applied, contact with the tissue can be assessed. Once the physician has properly situated and oriented the sheath, they may commence advancement of the energy delivery portion 27 through the ablati