Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-02-08
2003-04-01
Milano, Michael J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
Reexamination Certificate
active
06540767
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to filters for use inside blood vessels. More particularly, the present invention relates to thrombus filters which can be securely affixed at a selected location in the vascular system and removed when no longer required.
BACKGROUND OF THE INVENTION
There are a number of situations in the practice of medicine when it becomes desirable for a physician to place a filter in the vascular system of a patient. One of the most common applications for vascular filters is the treatment of Deep Venous Thrombosis (DVT). Deep Venous Thrombosis patients experience clotting of blood in the large veins of the lower portions of the body. These patients are constantly at risk of a clot breaking free and traveling via the inferior vena cava to the heart and lungs. This process is known as pulmonary embolization. Pulmonary embolization can frequently be fatal, for example when a large blood clot interferes with the life-sustaining pumping action of the heart. If a blood clot passes through the heart it will be pumped into the lungs and may cause a blockage in the pulmonary arteries. A blockage of this type in the lungs will interfere with the oxygenation of the blood causing shock or death.
Pulmonary embolization may be successfully prevented by the appropriate placement of a thrombus filter in the vascular system of a patient's body. Placement of the filter may be accomplished by performing a laparotomy with the patient under general anesthesia. However, intravenous insertion is often the preferred method of placing a thrombus filter in a patient's vascular system.
Intravenous insertion of a thrombus filter is less invasive and it requires only a local anesthetic. In this procedure, the thrombus filter is collapsed within a delivery catheter. The delivery catheter is introduced into the patients vascular system at a point which is convenient to the physician. The delivery catheter is then fed further into the vascular system until it reaches a desirable location for filter placement. The thrombus filter is then released into the blood vessel from the delivery catheter.
In the treatment of Deep Venous Thrombosis, a thrombus filter is placed in the inferior vena cava of a patient. The inferior vena cava is a large vessel which returns blood to the heart from the lower part of the body. The inferior vena cava may be accessed through the patient's femoral vein.
Thrombus filters may be placed in other locations when treating other conditions. For example, if blood clots are expected to approach the heart and lungs from the upper portion of the body, a thrombus filter may be positioned in the superior vena cava. The superior vena cava is a large vessel which returns blood to the heart from the upper part of the body. The superior vena cava may by accessed through the jugular vein, located in the patient's neck.
Once placed inside a blood vessel, a thrombus filter acts to catch and hold blood clots. The flow of blood around the captured clots allows the body's lysing process to dissolve the clots.
SUMMARY OF THE INVENTION
The present invention pertains to a thrombosis filter which can be securely affixed at a selected location in the vascular system of a patient and removed when no longer required. In a first embodiment, the thrombosis filter includes a strut formation, a wire formation, and a body portion. The body portion includes a plurality of apertures. The strut formation includes a plurality of struts each having a fixed end and a free end. The fixed ends of the struts are each fixably attached to the body portion of the thrombus filter inside the apertures; one strut radiating from each aperture.
The wire formation is comprised of a plurality of wires. Each wire has a fixed end and a free end. The fixed ends of the wires are fixably attached to the body portion of the thrombus filter. The struts radiate away from the proximal end of the body portion in a proximal direction such that the strut formation is generally conical in shape. Likewise, the wires radiate away from the distal end of the body portion in a distal direction such that the wire formation is generally conical in shape.
When the thrombosis filter is disposed in a blood vessel, the wire formation acts to capture blood clots. The generally conical shape of the wire formation serves to urge captured blood clots toward the center of the blood flow. The flow of blood around the captured clots allows the body's natural lysing process to dissolve the clots. The struts are formed of a shape memory material. At about body temperature, the struts assume an extended shape and engage the walls of the blood vessel. At a selected temperature, other than body temperature, the struts assume a contracted shape. This contracted shape causes the struts to contract inside the apertures of the body portion.
Various techniques can be used to alter the temperature of the struts causing them to retract. Suitable techniques for warming the thrombosis filter include applying electromagnetic energy to a portion of the thrombosis filter (e.g. laser light delivered by an optical fiber), and inducing an electrical current through a portion of the thrombosis filter. In a preferred embodiment, the struts are cooled by introducing a relatively cool fluid into the blood vessel proximate the thrombosis filter. After the struts are retracted, the thrombosis filter can be readily pulled into the lumen of a removal catheter.
A second embodiment of the thrombosis filter includes a generally cylindrical anchoring portion and a generally conical filtering portion terminating at a body member. The filtering portion includes a plurality of elongated strands. The strands of the filtering portion are arranged in an interwoven pattern to create cells. The interwoven pattern of strands enables the filtering portion to trap or capture blood clots. The conical shape of the filtering portion urges captured blood clots toward the center of the blood flow. The flow of blood around the captured blood clots allows the body's natural lysing process to dissolve the clots.
The strands extend beyond the filtering portion to create the anchoring portion. The strands are formed from a shape memory alloy. The shape memory alloy construction of the thrombosis filter allows it to change shape in response to a change in temperature. At about body temperature, the thrombosis filter assumes an extended shape. At a selected temperature other than body temperature, the thrombosis filter assumes a contracted shape. When the thrombosis filter assumes a contracted shape the anchor portion of the thrombosis filter disengages the walls of the blood vessel. When it is desirable for the thrombosis filter to be removed from a blood vessel, a physician may selectively heat or cool the thrombosis filter causing it to assume the contracted shape. Various techniques can be used to change the temperature of the thrombosis filter. In a preferred embodiment, the thrombosis filter is cooled by introducing a relatively cold fluid into the blood vessel proximate the thrombosis filter. Once the thrombosis filter assumes a contracted shape, it may be pulled in the lumen of a removal catheter.
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DeVries Robert B.
DiMatteo Kristian
Proskoczilo Bernedette
Walak Steven E.
Crompton Seager & Tufte LLC
Ho (Jackie ) Tan-Uyen T.
Milano Michael J.
Sci-Med Life Systems, Inc.
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