Not Applicable
The invention relates to catheters, and more particularly to cryosurgical catheters used for tissue ablation.
Many medical procedures are performed using minimally invasive surgical techniques, wherein one or more slender implements are inserted through one or more small incisions into a patient""s body. With respect to ablation, the surgical implement can include a rigid or flexible structure having an ablation device at or near its distal end that is placed adjacent to the tissue to be ablated. Radio frequency energy, microwave energy, laser energy, extreme heat, and extreme cold can be provided by the ablation device to kill the tissue.
With respect to cardiac procedures, a cardiac arrhythmia can be treated through selective ablation of cardiac tissue to eliminate the source of the arrhythmia. A popular minimally invasive procedure, radio frequency (RF) catheter ablation, includes a preliminary step of conventional electrocardiographic mapping followed by the creation of one or more ablated regions (lesions) in the cardiac tissue using RF energy. Multiple lesions are frequently required because the effectiveness of each of the proposed lesion sites cannot be predetermined due to limitations of conventional electrocardiographic mapping. Often, five lesions, and sometimes as many as twenty lesions may be required before a successful result is attained. Usually only one of the lesions is actually effective; the other lesions result in unnecessarily destroyed cardiac tissue.
Deficiencies of radio frequency ablation devices and techniques have been overcome by using cold to do zero degree or ice mapping prior to creating lesions, as taught in U.S. Pat. Nos. 5,423,807; and 5,281,213; and 5,281,215. However, even though combined cryogenic mapping and ablation devices permit greater certainty and less tissue damage than RF devices and techniques, both the cryogenic and the RF devices are configured for spot or roughly circular tissue ablation.
Spot tissue ablation is acceptable for certain procedures. However, other procedures can be more therapeutically effective if multiple spot lesions along a predetermined line, or a single elongate or linear lesion is created in a single ablative step. Radio frequency ablation devices are known to be able to create linear lesions by dragging the ablation tip along a line while it is active. However, no cryogenic devices are known that are optimized for, or which are even minimally capable of, creating an elongate lesion.
According to one aspect, the present invention provides a medical device having a body which includes a fluid transport member disposed within the body. An outer member substantially surrounds the fluid transport member. A chamber is formed between the outer member and the fluid transport member. A means to vary the relative distance between the outer membrane and the fluid transport member is included.
As another aspect, the present invention provides a medical device which has a thermally transmissive region, and an axially off-set fluid path thermally coupled to at least a portion of the thermally transmissive region. The axially off-set fluid path is adjacent to an inner surface of the thermally transmissive region.
yet another aspect, the present invention provides a medical device having a body which includes a thermally transmissive region disposed on the surface of the body and a rotatable fluid transport member thermally coupled to the thermally transmissive region. The rotatable fluid transport member has at least one segment that is proximally positionable to an inner surface of the thermally transmissive region.
According to a further aspect, the present invention provides a medical device having a body which includes a thermally transmissive region disposed on the surface of the body, a support slide disposed within the body and proximal to the thermally transmissive region, and a flexible fluid transport member slidably mounted to the support slide.
According to yet another aspect, the present invention provides a method of treating a selected portion of tissue. An appropriate medical device having a fluid transport path and a thermally transmissive region disposed therein is provided. The medical device is located within the selected portion of tissue. A flexible member which substantially surrounds the thermally transmissive region is inflated. The fluid transport path is moved to a selected portion of the flexible member. A thermally active fluid is circulated within the fluid transport path to deliver a medically effective amount of thermal energy to the selected portion of tissue.
According to still yet another aspect, the present invention provides a method of delivering a medically efficacious amount of energy to a selected tissue using a medical device having a thermally transmissive region, an expandable membrane substantially surrounding the thermally transmissive region and a thermal fluid path thermally coupled to the thermally transmissive region. At least a portion of the thermally transmissive region is positioned adjacent to the selected tissue. The selected tissue is compressed by activating the expandable membrane. The thermal fluid path is moved to a position proximal to an inner surface of the expandable membrane. A thermally active fluid is circulated within the thermal fluid path which transfers a therapeutic amount of energy to the selected tissue.
In yet another aspect, the present invention provides a method of treating a tissue using a medical device which has a thermally transmissive region and an axially off-center fluid path thermally coupled to the thermally transmissive region. At least a portion of the thermally transmissive region is positioned proximal to the tissue to be treated. The axially off-center fluid path is positioned closest to the portion of the thermally transmissive region which is proximal to the tissue to be treated. An energetic fluid is circulated within the axially off-center fluid path.
According to still another aspect, the present invention provides a method of treating a selected tissue which uses a medical device that has a thermally transmissive region, an expandable member substantially surrounding the thermally transmissive region and a moveable fluid path thermally coupled to the thermally transmissive region. The expandable member is expanded against the selected tissue. The moveable fluid path is moved in a direction towards the selected tissue. An energetic fluid is circulated within the moveable fluid path to deliver a medically effective amount of thermal energy to the selected tissue.
In yet a further aspect, the present invention provides a method of treating a selected tissue which utilizes a medical device with a body, a fluid transport member disposed within the body, an outer member substantially surrounding the fluid transport member, a chamber disposed between the outer member and the fluid transport member; and a means to vary a relative distance between the outer member and the fluid transport member. The medical device is positioned to contact the selected tissue. The outer member is expanded by injecting a bio-compatible fluid into the chamber. The relative distance between the fluid transport member and the outer member is decreased until a selected distance is reached. A thermally active fluid is injected into the fluid transport member for a medically effective period of time.