Low temperature lesion formation apparatus, systems and methods Number:7,160,290 from the United States Patent and Trademark Office (PTO) owispatent Low temperature lesion formation apparatus, systems and methods. The apparatus includes a base member and an inflatable element carried by the base member.<H temperature, apparatus, Low, temperature, 7160290.html, Patent, pto, 7160290

Title: Low temperature lesion formation apparatus, systems and methods

Abstract: Low temperature lesion formation apparatus, systems and methods. The apparatus includes a base member and an inflatable element carried by the base member.

Patent Number: 7,160,290 Issued on 01/09/2007 to Eberl, et al.

Inventors: Eberl; Greg (Sunnyvale, CA), Swanson; David K. (Campbell, CA)
Assignee: Boston Scientific Scimed, Inc. (Maple Grove, MN)

Appl. No.: 11/278,694

Filed: April 5, 2006

Current U.S. Class: 606/21 ; 606/20; 606/22; 606/23

Current International Class: A61B 18/02 (20060101)

Field of Search: 606/20-23

References Cited [Referenced By]

U.S. Patent Documents


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Foreign Patent Documents


WO-02/38052	May., 2002	WO

Primary Examiner: Peffley; Michael
Assistant Examiner: Toy; Alex
Attorney, Agent or Firm: Henricks, Slavin & Holmes LLP

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 10/842,183, filed May 10, 2004, which is incorporated herein by reference.

Claims

We claim:

1. An apparatus, comprising: an inflatable cryogenic element; and a base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration where the inflatable cryogenic element is located inwardly of the base member and the base member is located outwardly of the inflatable cryogenic element, and is bendable into a non-loop configuration.

2. An apparatus as claimed in claim 1, wherein the inflatable cryogenic element includes an inlet and an outlet.

3. An apparatus as claimed in claim 2, wherein the inflatable cryogenic element defines longitudinal ends and the inlet and outlet are each associated with a respective one of the longitudinal ends.

4. An apparatus as claimed in claim 2, further comprising: an infusion lumen associated with the inlet; and a ventilation lumen associated with the outlet.

5. An apparatus as claimed in claim 1, further comprising: a support structure located within the inflatable cryogenic element.

6. An apparatus as claimed in claim 5, wherein the support structure comprise a coil.

7. An apparatus as claimed in claim 1, further comprising: a longitudinally movable insulation sleeve.

8. An apparatus as claimed in claim 1, wherein the inflatable cryogenic element comprises an outer tube and an inner tube located within the outer tube.

9. An apparatus as claimed in claim 8, further comprising: a support structure located within the inner tube.

10. An apparatus as claimed in claim 8, wherein the outer tube includes an inlet and an outlet and the inner tube includes an inlet and an outlet, the apparatus further comprising: first infusion and ventilation lumens respectively associated with the outer tube inlet and outlet; and second infusion and ventilation lumens respectively associated with the inner tube inlet and outlet.

11. An apparatus, comprising: an inflatable cryogenic element: and an insulative base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, and is bendable into a non-loop configuration.

12. An apparatus as claimed in claim 11, wherein the insulative base member has a thermal conductivity of less than about 0.002 w/cm-K.

13. An apparatus, comprising: an inflatable cryogenic element; and a base member, including a foam member and a reinforcing member that is pre-shaped into a loop configuration and is bendable into a non-loop configuration, that carries the inflatable cryogenic element.

14. An apparatus comprising: a base member that defines a surface, is pre-shaped into a loop configuration, and is bendable into a non-loop configuration; and an inflatable cryogenic element, defining a longitudinal axis and a perimeter extending around the longitudinal axis, carried by and; flattened against the base member surface such that a substantial portion of the perimeter is adjacent the base member surface.

15. An apparatus, comprising: an inflatable cryogenic element defining a length, a width, a height, and a width to height ratio that is at least 2 to 1; and a base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, and is bendable into a non-loop configuration.

16. An apparatus, comprising: an inflatable cryogenic element; a base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, is bendable into a non-loop configuration, and defines longitudinal end portions; and a connector associated with the longitudinal end portions of the base member.

17. An apparatus as claimed in claim 16, wherein the connector comprises first and second portions that respectively extend longitudinally beyond the first and second longitudinal ends of the base member.

18. An apparatus, comprising: an inflatable cryogenic element; a base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, is bendable into a non-loop configuration, and defines a longitudinally extending lumen; and a longitudinally movable stylet positionable within the longitudinally extending lumen, the stylet being configured to maintain the base member in the non-loop orientation when within the longitudinally extending lumen.

19. An apparatus as claimed in claim 18, wherein the base member and stylet define respective lengths and the stylet is at least as long as the base member.

20. An apparatus as claimed in claim 18, wherein the longitudinally movable stylet is configured to maintain the base member in a substantially straight orientation when within the longitudinally extending lumen.

21. A system, comprising: a source of cryogenic fluid; and an apparatus including an inflatable cryogenic element adapted to be operably connected to the source of cryogenic fluid, and an insulative base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, and is bendable into a non-loop configuration.

22. A system as claimed in claim 21, wherein the insulative base member comprises a foam member and a reinforcing member that is pre-shaped into the loop configuration.

23. A system as claimed in claim 21, wherein the inflatable cryogenic element defines a longitudinal axis and a perimeter extending around the longitudinal axis; the insulative base member defines a surface; and and the inflatable cryogenic element is flattened against the insulative base member surface such that a substantial portion of the perimeter is adjacent the insulative base member surface.

24. A system as claimed in claim 21, wherein the source of cryogenic fluid includes an inlet and an outlet; the inflatable cryogenic element includes an infusion lumen adapted to be connected to the outlet and a ventilation lumen adapted to be connected to the inlet.

25. A system as claimed in claim 21, further comprising: a support structure located within the inflatable cryogenic element.

Description

BACKGROUND OF THE INVENTIONS

1. Field of Inventions

The present inventions relate generally to devices for performing therapeutic operations on body tissue.

2. Description of the Related Art

There are many instances where therapeutic elements must be positioned adjacent to body tissue. One instance involves the formation of therapeutic lesions to the treat cardiac conditions such as atrial fibrillation, atrial flutter and arrhythmia. Therapeutic lesions, which may also be used to treat conditions in other regions of the body such as the prostate, liver, brain, gall bladder, uterus, breasts, lungs and other solid organs, are typically formed by ablating tissue.

Cryogenic cooling devices are one example of the devices that have been used to form lesions in tissue. During the cryo-ablation of soft tissue (i.e. tissue other than blood, bone and connective tissue), ice crystals disrupt cell and organelle membranes and it is the disruption that kills the tissue. A cryogenic element, such as a balloon or hollow metal tip, is carried on the distal end of a catheter or surgical probe (referred to herein collectively as "probes"), placed in contact with tissue and cooled to a temperature that will cause tissue death. The cryogenic element may be cooled by a variety of techniques. One technique employs the Joule-Thompson ("JT") effect. Here, cryogenic cooling occurs as a result of a rapid decrease of gas pressure that occurs within the therapeutic element. Pressurized cryogenic fluid, such as liquid nitrous oxide, is directed into the therapeutic element where it undergoes rapid phase change and a rapid expansion of the gas from a high-pressure to a lower pressure state. The reaction is endothermic and produces temperatures as low as minus 70.degree. C. at the therapeutic element. In some instances, the cryogenic fluid is pre-cooled in order to increase the cooling power delivered to the targeted tissue. The cryogenic element may also be cooled by directing super-cooled fluid through the catheter or surgical probe to the cryogenic element. Here, the temperature at the therapeutic element can be as low as minus 100.degree. C. when it enters the patient.

The present inventors have determined that conventional cryogenic cooling devices are susceptible to improvement. For example, the present inventors have determined that conventional cryogenic cooling devices can damage non-target tissue near the tissue in which the therapeutic lesions are being formed. The present inventors have also determined that it can be difficult to achieve good tissue contact with conventional cryogenic devices because they are relatively turgid. Some conventional cryogenic cooling devices are susceptible to leaks, which can result in the release of toxic chemicals (e.g. perfluorocarbons) into the patient's blood stream during endocardial procedures. Additionally, the inventors herein have determined that the manner in which temperature is monitored during cryogenic lesion formation procedures.

SUMMARY OF THE INVENTIONS

An apparatus in accordance with one invention herein includes a base member, an inflatable cryogenic element carried by the base member and a connector, associated with at least one of the base member and the inflatable cryogenic element, adapted to maintain the inflatable cryogenic element in the looped orientation. A system in accordance with one invention herein includes such an apparatus and a source of cryogenic fluid. A method in accordance with one invention herein includes the steps of positioning an apparatus including an inflatable cryogenic element in a looped orientation around a tissue structure, securing at least two portions of the apparatus relative to one another to maintain the looped orientation and directing cryogenic fluid through the inflatable cryogenic element.

An apparatus in accordance with one invention herein includes an inflatable cryogenic element and a base member that carries the inflatable cryogenic element, is pre-shaped into a loop configuration, and is bendable into a non-loop configuration. A system in accordance with one invention herein includes such an apparatus and a source of cryogenic fluid. A method in accordance with one invention herein includes the steps of bending an apparatus including an inflatable cryogenic element into a looped orientation around a tissue structure with a pre-shaped portion of the apparatus, maintaining the apparatus in the looped orientation and directing cryogenic fluid through the inflatable cryogenic element.

An apparatus in accordance with one invention herein includes an inflatable cryogenic apparatus configured to be removably secured to a first clamp member and a temperature sensor apparatus configured to be removably secured to a second clamp member. A clamp in accordance with one invention herein includes first and second clamp members, an inflatable cryogenic apparatus carried by the first clamp member, and a temperature sensor apparatus carried by the second clamp member. Systems in accordance with inventions herein include a source of cryogenic fluid and the apparatus or the clamp. A method in accordance with one invention herein includes the steps supplying cryogenic fluid to a cryogenic apparatus on the first opposing surface and measuring temperature on the second opposing surface.

An apparatus in accordance with one invention herein includes a base member configured to be removably secured to a clamp member and an inflatable cryogenic element, carried by the base member, defining a longitudinal axis and a non-circular inflated shape in a cross-section perpendicular to the longitudinal axis. A clamp in accordance with one invention herein includes a cryogenic apparatus including an inflatable cryogenic element defining a longitudinal axis and a non-circular inflated shape in a cross-section perpendicular to the longitudinal axis.

A method in accordance with one invention herein includes the steps of positioning a resilient inflatable cryogenic element adjacent to tissue, inflating the resilient inflatable cryogenic element with cryogenic fluid and maintaining pressure within the resilient inflatable cryogenic element below about 100 mm Hg. A system in accordance with one invention herein includes a source of cryogenic fluid and resilient inflatable cryogenic element adapted to be operably connected to the source of cryogenic fluid. The pressure within the resilient inflatable cryogenic element is maintained below about 100 mm Hg when the source of cryogenic fluid supplies the cryogenic fluid to the resilient inflatable cryogenic element.

An apparatus in accordance with one invention herein includes a resilient inflatable cryogenic apparatus configured to be removably secured to a clamp member and to operate at a maximum internal pressure of about 100 mm Hg. A clamp in accordance with one invention herein includes a resilient inflatable cryogenic apparatus configured to operate at a maximum internal pressure of about 100 mm Hg.

A surgical probe in accordance with one invention herein includes a relatively short shaft, an inflatable cryogenic element defining an exterior surface, and at least one temperature sensor on the exterior of the inflatable cryogenic element.

A method in accordance with one invention herein includes the steps of positioning an inflatable cryogenic element on the tissue structure with a temperature sensor between a portion of the inflatable cryogenic element and a portion of the tissue surface, supplying cryogenic fluid to the inflatable cryogenic element, and measuring tissue temperature with the temperature sensor.

A surgical probe in accordance with one invention herein includes a relatively short shaft and a resilient inflatable cryogenic element, carried by the relatively short shaft, and configured to operate at a maximum internal pressure of about 100 mm Hg. A system in accordance with one invention herein includes such a surgical probe. A method in accordance with one invention herein includes the steps of positioning a resilient inflatable cryogenic element on the tissue structure with a surgical probe, inflating the resilient inflatable cryogenic element with cryogenic fluid and maintaining pressure within the resilient inflatable cryogenic element below about 100 mm Hg.

There is a wide variety of advantages associated with the present inventions. By way of example, but not limitation, and as described in detail below, at least some of the present inventions prevent damage to non-target tissue near the tissue in which the therapeutic lesions are being formed. As described in detail below, at least some of the present inventions achieve superior tissue contact because they are relatively resilient. As described in detail below, at least some of the present inventions are especially useful in applications outside the blood stream (such as epicardial applications) where leaks are less likely to harm the patient. As described in detail below, because at least some of the present inventions are configured to operate at relatively low pressure, the volume of cryogenic fluid that is lost in the unlikely event of a leak will be lower than conventional devices which operate at high pressure. As described in detail below, at least some of the present inventions provide superior temperature monitoring capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description of preferred embodiments of the inventions will be made with reference to the accompanying drawings.

FIG. 1 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 2 is a section view taken along line 2--2 in FIG. 1.

FIG. 3 is a section view taken along line 3--3 in FIG. 1.

FIG. 4 is a perspective view showing a surgical system including the lesion formation apparatus illustrated in FIG. 1.

FIG. 4A is perspective view showing a continuous lesion formed around the pulmonary veins.

FIG. 5 is a section view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 6 is a section view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 7 is a section view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 8 is a section view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 8A is a section view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 8B is a partial side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 8C is a partial section view taken along line 8C--8C in FIG. 8B.

FIG. 8D is a side view of the lesion formation apparatus illustrated in FIG. 8B in a loop orientation.

FIG. 9 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 10 is a section view taken along line 10--10 in FIG. 9.

FIG. 11 is a section view taken along line 11--11 in FIG. 9.

FIG. 12 is a partial section view taken along line 12--12 in FIG. 11.

FIG. 13 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 14 is a section view taken along line 14--14 in FIG. 13.

FIG. 15 is a section view taken along line 15--15 in FIG. 13.

FIG. 16 is a partial section view taken along line 16--16 in FIG. 15.

FIG. 17 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 18 is a section view taken along line 18--18 in FIG. 17.

FIG. 19 is a partial section view taken along line 19--19 in FIG. 17.

FIG. 20 is a section view taken along line 20--20 in FIG. 19.

FIG. 21 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 22 is a top view of a portion of the lesion formation apparatus illustrated in FIG. 21.

FIG. 23 is a bottom view of a portion of the lesion formation apparatus illustrated in FIG. 21.

FIG. 24 is a side view of the lesion formation apparatus illustrated in FIG. 21 in a looped orientation.

FIG. 25 is a side view of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 26 is a section view taken along line 26--26 in FIG. 25.

FIG. 27 is a side view of a portion of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 28 is a side view of a portion of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 29 is a section view taken along line 29--29 in FIG. 28.

FIG. 29A is a side view of a portion of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 29B is a section view taken along line 29B--29B in FIG. 29A.

FIG. 30 is a side view of a portion of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 31 is a side view of a portion of the lesion formation apparatus illustrated in FIG. 30.

FIG. 32 is a side view of a portion of a lesion formation apparatus in accordance with a preferred embodiment of a present invention.

FIG. 33 is a perspective view of a surgical system in accordance with a preferred embodiment of a present invention.

FIG. 34 is a plan view of a tissue coagulation assembly in accordance with a preferred embodiment of a present invention.

FIG. 35 is a section view taken along line 35--35 in FIG. 34.

FIG. 36 is a section view taken along line 36--36 in FIG. 34.

FIG. 37 is a section view taken along line 37--37 in FIG. 34.

FIG. 38 is an enlarged view of a portion of the tissue coagulation assembly illustrated in FIG. 34.

FIG. 39 is a section view taken along line 39--39 in FIG. 38.

FIG. 40 is a section view taken along line 40--40 in FIG. 38.

FIG. 40A is a section view taken along line 40A--40A in FIG. 38.

FIG. 41 is a plan view of a clamp in accordance with a preferred embodiment of a present invention.

FIG. 42 is a section view taken along line 42--42 in FIG. 41.

FIG. 43 is a top view of a portion of the clamp illustrated in FIG. 41.

FIG. 44 is a perspective view of a surgical system in accordance with a preferred embodiment of a present invention.

FIG. 45 is a section view taken along line 45--45 in FIG. 44.

FIG. 46 is a section view taken along line 46--46 in FIG. 44.

FIG. 47 is a section view taken along line 47--47 in FIG. 44.

FIG. 48 is a section view taken along line 48--48 in FIG. 44.

FIG. 49 is a section view taken along line 49--49 in FIG. 44.

FIG. 50 is a section view taken along line 50--50 in FIG. 44.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.

The detailed description of the preferred embodiments is organized as follows:

I. Introduction

II. Exemplary Lesion Formation Apparatus Capable of Being Secured Around an Organ

III. Exemplary Clamp Based Lesion Formation Apparatus

IV. Exemplary Probe Based Lesion Formation Apparatus

The section titles and overall organization of the present detailed description are for the purpose of convenience only and are not intended to limit the present inventions.

I. Introduction

This specification discloses a number of structures, mainly in the context of cardiac treatment, because the structures are well suited for use with myocardial tissue. Nevertheless, it should be appreciated that the structures are applicable for use in therapies involving other types of soft tissue. For example, various aspects of the present inventions have applications in procedures concerning other regions of the body such as the prostate, liver, brain, gall bladder, uterus, breasts, lungs, and other solid organs.

II. Exemplary Lesion Formation Apparatus Capable of Being Secured Around an Organ

A lesion formation apparatus 100 in accordance with a preferred embodiment of a present invention is illustrated in FIGS. 1 3. The illustrated embodiment includes an inflatable cryogenic element 102 carried on a base member 104 and a connector device 106 that may be used to position the longitudinal ends of the inflatable cryogenic element adjacent to one another. A fluid transmission space 108 is defined within the inflatable cryogenic element 102. The exemplary lesion formation apparatus 100 also includes an infusion lumen 110 and a ventilation lumen 112 that extend a short distance into the longitudinal ends of the inflatable cryogenic element 102. The infusion and ventilation lumens 110 and 112, which are in communication with the fluid transmission space 108, are held in place with adhesive material 114. The adhesive material 114 also seals the longitudinal ends of the inflatable cryogenic element 102. Each of these elements is discussed in greater detail below.

As illustrated for example in FIG. 4, the lesion formation apparatus 100 is connected to a cryogenic fluid supply and control apparatus 200 in a surgical system 10. The cryogenic fluid supply and control apparatus 200, which may be used in combination with any of the other lesion formation apparatus described herein, includes housing 202, a fluid outlet port 204, a fluid inlet port 206 and an electrical connector 208. The fluid outlet port 204 may be coupled to the infusion lumen 110 by a tube 210, and the fluid inlet port 206 may be coupled to the ventilation lumen 112 by a tube 212. As discussed below with reference to FIGS. 30 32, the electrical connector 208 may be used to connect the cryogenic fluid supply and control apparatus 200 to, for example, a connector that is associated with temperature sensors and/or a valve, in those instances where the apparatus includes the temperature sensors and/or a valve.

The lesion formation apparatus 100 may be positioned around portions of organs during lesion formation procedures performed with the surgical system 10. For example, one method of treating focal atrial fibrillation with the lesion formation apparatus 100 involves the creation of transmural lesions around the pulmonary veins. Lesions may be created around the pulmonary veins individually, in pairs, or, as is illustrated in FIG. 4A, a single transmural epicardial lesion L may be created around all four of the pulmonary veins PV. Such a lesion may be formed by positioning the lesion formation apparatus 100 around the pulmonary veins PV in the manner illustrated in FIG. 4. The connector device 106 may be used to secure the longitudinal ends of the inflatable cryogenic element 102 in close proximity to one another. Although there is a slight space between the ends of the inflatable cryogenic element 102 in FIG. 4 in order to more clearly show various elements of the illustrated embodiment, the ends would typically be in contact with one another or slightly overlap in actual use. Cryogenic fluid from the cryogenic fluid supply and control apparatus 200 is then passed through the inflatable cryogenic element 102, by way of the infusion and ventilation lumens 110 and 112, to form the lesion.

The inflatable cryogenic element 102 illustrated in FIGS. 1 3 is preferably formed from a thin tube 116. Referring more specifically to FIGS. 2 and 3, the tube 116 may be flattened against the base member 104 and secured to the base member with adhesive 118. Flattening the tube 116 and securing it to the base member 104 in this manner prevents the tube from buckling when pulled into a loop, increases the amount of surface area that will be in contact with tissue when the inflatable cryogenic element 102 is pressurized (or "inflated"), improves contact stability when the inflatable cryogenic element is pressurized, and minimizes folding and twisting of the cryogenic element when it is deflated. Flattening the tube 116 and securing it to the base member 104 in this manner also increases the strength of the bond between the tube and the base member and minimized the profile (i.e. the height in the orientation illustrated in FIGS. 1 3) of the lesion formation apparatus 100. Additionally, in those instances where the base member 104 is formed from insulating material (discussed below), this configuration insures that about one-half of the inflatable cryogenic element 102 will be thermally isolated from tissue.

The exemplary tube 116 is preferably formed from material that is relatively high in thermal conductivity. A suitable temperature gradient across the wall of the tube is about 2.degree. C. or less. The tube material should also result in an inflatable cryogenic element 102 that has a burst pressure rating which exceeds the operating pressures within the inflatable cryogenic element. In the illustrated implementations for example, and assuming that liquid perfluorocarbon will be supplied to the inflatable cryogenic element 102 at a rate of 300 ml/min. and a temperature of minus 100.degree. C., a suitable burst pressure rating would be about 760 mm Hg (1 atmosphere). Another important consideration is tear resistance because the inflatable cryogenic element 102 will be subjected to forces that could result in tearing (and leaks) when the lesion formation apparatus 100 is deployed around a body structure. For example, the inflatable cryogenic element 102 will be subjected to relatively large tearing forces when deployed around the inferior pulmonary veins in the posterior aspect to the heart. The present inventors have determined that inflatable cryogenic elements with a burst pressure rating of about 3800 mm Hg (5 atmospheres) will not tear under these conditions. Accordingly, a suitable burst pressure rating is about 3800 mm Hg (5 atmospheres).

In one mode of operation, the inflatable cryogenic element 102 may be supplied with liquid cooling fluid in such a manner that, as the liquid cooling fluid flows through the inflatable cryogenic element, the pressure within the cryogenic element will be less than about 100 mm Hg, which results in a resilient cryogenic element. Such a resilient cryogenic element is softer and less traumatic to tissue than turgid cryogenic elements (i.e. those whose internal pressure is greater than 100 mm Hg). It is also able to better conform to tissue. It should also be noted that there are a variety of ways to achieve the relatively low pressures (i.e. less than 100 mm Hg) within the inflatable cryogenic element 102. For example, configuring the infusion and ventilation lumens 110 and 112 such that the cross-sectional area of the infusion lumen is less than that of the ventilation lumen is one way to produce a low pressure within the inflatable cryogenic element 102.

Although the present inventions are not limited to any particular materials, suitable materials for the inflatable cryogenic element 102 include biaxially oriented polyethylene terephthalate (PET), Nylon, and Pebax.RTM. heat shrink tubing. The wall of such tubing will typically be about 0.001 inch to 0.0005 inch thick. Conductive polymer mixtures (such as 25% graphite filled Pebax.RTM. 2533), which allow for thicker walls while maintaining adequate levels of heat transfer, are other examples of suitable materials. Semi-compliant, compliant and elastomeric materials may also be employed. Here, thicknesses of about 0.004 inch to 0.008 inch would be required to compensate for stretching.

In addition to supporting the inflatable cryogenic element 102, the base member 104 in the illustrated embodiment functions as an insulation device to protect non-target tissue adjacent to the target tissue from the cryogenic element. The exemplary base member 104 is a flexible device that, as illustrated in FIGS. 2 and 3, is generally rectangular in cross-section. However, a wide variety of alternative configurations are possible. Such configurations include, but are not limited to, the configurations illustrated in FIGS. 5 8. Referring first to FIG. 5, the base member 104a includes a groove 120 which receives a portion of the cryogenic element 102. Such a configuration provides a relatively low profile, reduces the possibility that the cryogenic element will separate from the base member, provides additional lateral insulation, and reduces the likelihood that the cryogenic element will collapse. The exemplary base member 104b illustrated in FIG. 6 wraps around the sides of the cryogenic element 102 in order to prevent the ablation of tissue that is laterally adjacent to the target tissue. Alternatively, the sides of the base member may simply extend laterally beyond the sides of the cryogenic element 102. Turning to FIG. 7, the exemplary base member 104c is a composite formed from a number of layers of different materials. Such composites can be configured for superior twist resistance or pre-shaped to aid the physician during the positioning process.

The exemplary base member 104d illustrated in FIG. 8 includes a plurality of reinforcing members 122, such as straight or pre-shaped polymer, composite or metal members, that prevent twisting of the lesion formation apparatus 100, hold a shaped lesion formation apparatus straight for introduction, or provide lumens for temperature sensor wires or other elements. Alternatively, as illustrated in FIG. 8A, the exemplary base member 104e simply includes a plurality of lumens 123.

Base members may also perform specific functions within a lesion formation apparatus. As illustrated for example in FIGS. 8B 8D, a base member 104f in the lesion formation apparatus 100h includes a pre-shaped reinforcing member 122a (e.g. a thin strip of Nitinol) with a pre-shaped loop configuration and a removable stylet 122b (e.g. a steel rod) that is straight and rigid enough to overcome the bending forces applied by pre-shaped reinforcing member 122a. The removable stylet 122b is carried within a tube 122c that defines a longitudinally extending lumen within the base member 104f. Absent the presence of the removable stylet 122b, the base member 104f, with its pre-shaped reinforcing member 122a, will bend the lesion formation apparatus 100h into a loop and will maintain the loop during lesion formation procedures.

In the illustrated embodiment, the longitudinal ends of the cryogenic element 102 overlap slightly in order to insure that the lesion formed thereby will be a complete circle. Alternatively, pre-shaped reinforcing member 122a may be configured such that the longitudinal ends abut one another, or such that there is a gap between the longitudinal ends, if the intended application so requires. Additionally, although the illustrated reinforcing member has a substantially circular shape, any shape suitable for the intended application may be employed. Finally, a pre-shaped reinforcing member and stylet may be incorporated into any of the lesion formation apparatus described herein with reference to FIGS. 1 32.

During use, the removable stylet 122b will be in place within the tube 122c prior to deployment of the associated lesion formation apparatus. The removable stylet 122b will be withdrawn in the direction of arrow A as the apparatus is advanced in a direction tangential to the target tissue structure, thereby allowing the pre-shaped reinforcing member 122a to bend the apparatus into a loop shape around the target structure. The stylet 122b is preferably slightly longer than the base member 104f is order to provide a free end that may be grasped by the physician. The stylet 122b may, in some instances, have a slight curvature where applications so require.

In addition to bending the lesion formation apparatus 100h into the bent orientation illustrated in FIG. 8D, the pre-shaped reinforcing member 122a will maintain the lesion formation apparatus in the bent orientation during lesion formation procedures. As such, the connector device 106 need not be used (although it may be used if desired) to maintain the lesion formation apparatus in the loop orientation. The end portions 126 and 128 may still be used, however, to pull the lesion formation apparatus around a tissue structure as it is being positioned for a procedure.

In other alternative base member configurations, the cross-sectional shape (in the orientation illustrated in FIGS. 5 8) may be varied. For example, instead of the rectangular cross-sectional shape illustrated in FIGS. 1 3, the cross-sectional base members may be thicker, thinner, circular, semi-circular, triangular, or any other shape that is suitable for the intended use. Base members in accordance with the present inventions may also be hollow (e.g. molded hollow bodies) or have a plurality of small channels formed therein.

Although the present inventions are not limited to any particular materials, suitable materials for the base members 104 104d include flexible polymer (elastomer) open and closed cell foams. In those instance where open cell foams are used, the base member may include a sealing skin (not shown) to prevent fluid absorption. Flexible thermoplastics and thermoset polymers may also be employed. The base members are also preferably insulating and, in some instances, transfer heat at a rate of 0.33 w/cm.sup.2 of exposed surface area, which is low enough to prevent freezing. A typical thermal conductivity for an insulator is less than about 0.002 w/cm-K. Foams having a thickness of about 2 mm will provide this level of insulation, as will thin (e.g. 0.8 mm) balloons filed with a gas such as CO.sub.2. In addition to protecting adjacent tissue from the extremely lower temperatures associated with the inflatable cryogenic element 102, an insulating base member makes the lesion formation apparatus "one directional" in that heat transfer to the cryogenic element will take place on the surface opposite the base member. Such an arrangement is more efficient that one in which the heat transfer can take place along the entire perimeter of the cryogenic element 102.

As illustrated in FIGS. 1 4, the exemplary connector device 106 is a relatively thin, flexible elongate device that includes a main portion 124 and a pair of end portions 126 and 128. The main portion 124 is secured to the base member 104, preferably along the entire length of the base member. The end portions 126 and 128, which extend from the longitudinal ends of base member 104, may be used to pull the lesion formation apparatus 100 into the orientation illustrated in FIG. 4 and then tied onto a knot 130 to hold the lesion formation apparatus in place. The end portions 126 and 128 may also be provided with knots, beads, eyelets and/or any other closure mechanism that can be used to hold the end portions (as well as the longitudinal ends of the inflatable cryogenic element 102 and base member 104) in the orientation illustrated in FIG. 4. It should be noted that the connector device 106 is preferably, although not necessarily, secured to the side of the base member 104 opposite the inflatable cryogenic element 102, as opposed to in between the base member and cryogenic element. Such an arrangement isolates the cryogenic element 102 from the pulling stresses associated with the introduction, positioning and securing of the lesion formation apparatus 100.

Although the present inventions are not limited to any particular materials, one suitable material for the connector device 106 is thin (e.g. about 0.005 inch to 0.025 inch) woven fabric ribbon. This material is relatively soft and will not slice through tissue during use. Other suitable materials include polymer films and cords. The main portion 124 may be secured to the base member 104 with a flexible adhesive (not shown) such as polyurethane or a Polycin.RTM. and Vorite.RTM. mixture.

The exemplary infusion and ventilation lumens 110 and 112 (FIGS. 1 and 3) will typically extend about 3 mm to 10 mm into the respective longitudinal ends of the inflatable cryogenic element 102 and are provided with polycarbonate Luer connectors 132 and 134 that may be used to connect the infusion and ventilation lumens to a source of cryogenic fluid by way of, for example, the tubes 210 and 212 (FIG. 4). Depending on the type of cryogenic cooling that is desired, the infusion and ventilation lumens may be used to supply and ventilate super-cooled fluid, such as liquid perfluorocarbon that has been cooled to a suitably low temperature such as minus 100.degree. C., or to supply liquid nitrous oxide and ventilate the gas that results from the expansion within the inflatable cryogenic element 102. Other suitable connectors include stopcocks, valves, check valves, T or Y-fittings adapted for purging/flushing or temperature monitoring. In order to withstand the extremely cold temperatures associated with cryogenic cooling, the infusion and ventilation lumens 110 and 112 are preferably formed from materials such as Tygon.RTM., C-Flex.RTM., or a polyurethane polymer. The infusion and ventilation lumens 110 and 112 may also be insulated for improved performance and safety.

As noted above, adhesive material 114 (FIG. 3) may be used to secure the infusion and ventilation lumens 110 and 112 in place, as well as to seal the longitudinal ends of the inflatable cryogenic element 102. Suitable adhesives include flexible UV activated adhesives such as Loctite.RTM. 3321 and 3021. Alternatively, the infusion and ventilation lumens 110 and 112 may be secured in place and the ends of the inflatable cryogenic element 102 sealed by heat curing or RTV polyurethane. The adhesive 118 is preferably a Vorite.RTM. and polycin polyurethane blend.

The overall dimensions of lesion formation apparatus in accordance with the present inventions will, of course, depend on the intended application. In one exemplary implementation that is suitable for forming epicardial lesions around the pulmonary veins, the inflatable cryogenic element 102 is about 15 cm to 30 cm in length. The aspect ratio, i.e. the width to thickness (or height) ratio, is about 2 3 to 1. Typically, in the orientation illustrated in FIG. 3, the width inflatable cryogenic element 102 is about 4 mm to 12 mm and the thickness is about 1 mm to 4 mm, when secured to the base member 104 in the manner illustrated in FIG. 3. The length and width of the base member 104 corresponds to that of the cryogenic element 102 in the exemplary implementation, i.e. the base member is about 15 cm to 30 cm in length and about 4 mm to 12 mm wide. The thickness, which depends on the materials, will typically be about 1 mm to 7 mm. With respect to the exemplary connector device 106, the width will correspond to that of the base member 104 and, accordingly, is about 4 mm to 12 mm. The end portions 126 and 128 extend about 15 cm to 60 cm from the longitudinal ends of the cryogenic element.

Another exemplary lesion formation apparatus is generally represented by reference numeral 100a in FIGS. 9 12. The lesion formation apparatus 100a is substantially similar to the lesion formation apparatus 100 described above with reference to FIGS. 1 8 and similar elements are represented by similar reference numerals. Here, however, the inflatable cryogenic element 102a includes a support structure 136. A variety of different support structures may be employed. In the illustrated embodiment, for example, the support structure is a spiral coil extends from a point slightly inside one longitudinal end of the inflatable cryogenic element 102a (i.e. about 1 mm to 4 mm) to a point slightly inside the other longitudinal end. The support structure 136, which includes short, linear longitudinal end portions 138 that are held in place by the adhesive 114, may be formed from a thin wire, such as a Nitinol wire that is about 0.016 inch in diameter. The overall diameter of the support structure 136 itself will depend on the intended application. In epicardial applications such as that illustrated in FIG. 4, the diameter will typically be about 2 mm to 4 mm. Aluminum, stainless steel, copper or silver wires may also be used in order to improve heat transfer from the tissue to the fluid. Thin layers of adhesive 114 are also deposited within the lateral edges of the tube 116 in order to prevent draping or bagging.

There are a number of advantages associated with the use of a support structure such as the support structure 136. For example, the support structure insures that the fluid transmission space 108 will have a substantially constant cross-sectional area. A coil-type support structure (e.g. the support structure 136) will also create secondary flow within the transmission space, which increases thermal efficiency. Coil-type support structures also create ridges that may help the associated lesion formation apparatus engage soft or fatty substrates for thermal transmission, provide anchoring stability and increase contact surface area.

Another exemplary lesion formation apparatus is generally represented by reference numeral 100b in FIGS. 13 16. The lesion formation apparatus 100b is substantially similar to the lesion formation apparatus 100a described above with reference to FIGS. 9 12 and similar elements are represented by similar reference numerals. Here, however, the inflatable cryogenic element 102b has a relatively non-compliant inner region and a relatively compliant outer region. The relatively compliant outer region allows the lesion formation apparatus 100b to conform to tissue, thereby insuring good tissue contact, and also acts a barrier in the event of any leakage from the inner region.

In the exemplary implementation illustrated in FIGS. 13 16, the outer region of the inflatable cryogenic element 102b includes an outer fluid transmission space 109 that is defined by a thin outer tube 117, while the inner region includes an inner fluid transmission space 108 that is defined by a thin inner tube 116b located within the outer tube. The outer fluid transmission space 109 is connected to a source of thermally conductive media by infusion and ventilation lumens 111 and 113, and the inner fluid transmission space 108 is connected to a source of cryogenic fluid by the infusion and ventilation lumens 110 and 112. The shape of the inner fluid transmission space 108 is generally maintained by the support structure 136, which also prevents the outer tube 117 from occluding the inner tube 116b.

The outer tube 117 is preferably formed from thin (e.g. about 0.002 inch), compliant (or elastomeric) and thermally conductive material such as unrecovered PET or polyurethane rubber. The longitudinal ends of the outer tube 117 are sealed around the inner tube 116b and the infusion and ventilation lumens 111 and 113 with adhesive 114. The outer tube 116b is flattened against the base member 104 and secured to the base member with adhesive 118. The inner tube 116b may be formed from a relatively non-complaint material, such as recovered PET, that is heat shrunk onto the support structure 136. Adhesive 114 is also used to seal the longitudinal ends of the inner tube 116b around the infusion and ventilation lumens 110 and 112. Stopcocks 133 and 133 are provided on the inlet lumens 110 and 111, and stopcocks 135 and 135 are provided on the outlet lumens 112 and 113. The stopcocks may be used to exclude air bubbles from purged, filled spaces and to prevent fluid leaka