Method and device for retrieving embolic coils

A method and device are disclosed for retrieving embolic coils used for treating an aneurysm of a patient. The method comprises the steps of providing a wire device that is pushable through a microcatheter and has a flexible distal portion comprising distal collapsible arms with a latch member carried by one of the arms. The microcatheter is introduced into a patient's vessel leading to the aneurysm. The wire device, distal end first, is introduced into the microcatheter whereby the arms collapse while they are within the microcatheter. The distal end of the wire device is pushed through the microcatheter whereby the arms open when they extend out of the distal end of the microcatheter. The latch member is manipulated so that it engages an embolic coil to be retrieved. The latch-engaged embolic coil and wire device are withdrawn through the catheter, whereby the arms become collapsed as the arm is withdrawn through the catheter, securing the latch and the embolic coil.

FIELD OF THE INVENTION

The present invention concerns a novel method and device for retrieving embolic coils used for treating an aneurysm of a patient.

BACKGROUND OF THE INVENTION

A well known method of treating an aneurysm of a vessel wall includes the placement of a number of detachable embolic coils within the aneurysm. Multiple coils are employed during the procedure in an effort to completely embolize the vessel defect. Typically, a deployment device is used to introduce the coils, one by one, via a microcatheter, into the aneurysm. Occasionally during a procedure, an earlier introduced coil may become displaced from the aneurysm and protrude into the parent vessel. This coil protrusion can have a disastrous effect on the patient. Because the embolic coil is in the blood flow, thrombus begins to form around the coil which can potentially occlude the vessel initiating an ischemic attack or the clot may break off, flow distal and occlude other vessels leading to ischemia in another part of the brain. Therefore it is imperative that the misplaced coil be removed.

Certain prior art coil retrieval devices use a loop or snare configuration to try to lasso the misplaced coil. Since the misplaced coil is sometimes a loop, the physician often has difficulty trying to lasso these coils which may add to the procedure time and cause potential complications.

It is, therefore, an object of the invention to provide a novel method for retrieving embolic coils.

It is a further object of the invention to provide a method and device for retrieving embolic coils in which the embolic coils are secured in a retrieval device and prevented from becoming dislodged.

Another object of the present invention is to provide a tool for the physician to enable the physician to rapidly retrieve a misplaced embolic coil.

A further object of the present invention is to provide a pushable wire device for retrieving embolic coils that is simple in operation and relatively easy to manufacture.

Other objects and advantages of the present invention will become apparent as the description proceeds.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method is disclosed for retrieving embolic coils used for treating an aneurysm. The method comprises the steps of providing a wire device that is pushable through a microcatheter and has a flexible distal portion comprising a distal collapsible arm with a latch member carried by the arm. A microcatheter is introduced into a patient's vessel leading to the aneurysm. The wire device is introduced into the microcatheter whereby the arm collapses while it is within the microcatheter. The distal end of the wire device is pushed through the microcatheter whereby the arm opens when it extends out of the distal end of the microcatheter. The latch member is manipulated so that it engages an embolic coil to be retrieved. The latch-engaged embolic coil and the wire device are withdrawn through the catheter whereby the arm becomes collapsed as the arm is withdrawn through the catheter.

In the illustrative embodiment, the flexible distal portion comprises a pair of distal collapsible arms with a latch member carried by at least one of the arms.

In the illustrative embodiment, the wire device has a stiffer proximal portion than the distal portion. A portion of the collapsible arm is radiopaque and the arm and latch are formed from a composition comprising nitinol.

In accordance with the illustrative embodiment, a medical device is provided for retrieving embolic coils implanted in a patient. The medical device of the illustrative embodiment comprises a wire device that is pushable through a microcatheter and has a flexible distal portion comprising a pair of distal collapsible arms with an angled latch member carried by one of the arms.

A more detailed explanation of the invention is provided in the following description and claims, and is illustrated in the accompanying drawings.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

Referring toFIG. 1, an embolic coil retrieval system10is shown therein. System10includes a microcatheter12formed of a polymeric material as is known in the art, the proximal end14of which comprises a luer connector. Except for the proximal end of the microcatheter12, the remaining portions of the microcatheter are preferably uniform. Although no limitation is intended, as a specific example, the inner diameter of the catheter is preferably between 0.010 inch and 0.025 inch, and the outer diameter of the catheter is preferably between 0.030 inch and 0.050 inch.

Positioned within microcatheter12is a wire device16, which wire device16has pushability with respect to the catheter so that it can be manipulated like a guidewire. The proximal portion18of the wire device16is generally uniform but the wire device becomes tapered at a distal portion20which connects to a headpiece22including a pair of arms24,26. Proximal portion18of the wire device16is stiffer than the distal headpiece portion22which includes arms24and26. Arm24carries a latch member28that extends at an angle with respect to the arm24and toward the proximal end of arm24.

Arms24and26are collapsible and are shown inFIG. 1in their collapsed position within the microcatheter.

Although there are numerous equivalent ways in which the wire device16can be fabricated, as a preferred example the wire device is laser cut from a rod of nitinol measuring 0.018 inch in diameter. Nitinol is a superelastic alloy comprised of nickel and titanium. The wire device has a greater length than the length of the microcatheter so that it can be delivered through the lumen of the microcatheter to engage and retrieve an embolic coil30(FIGS. 3A,3B and4). The length of each portion of the wire device16varies by necessity according to the length of the vasculature to be navigated.

Although no limitation is intend, as a specific example the proximal portion18of the wire device16may have a diameter of between about 0.014 inch and 0.016 inch. The intermediate tapered portion20of the wire element16is tapered by grinding so that its diameter decreases from between about 0.014 inch and 0.016 inch to about 0.005 inch at the distal end of the tapered portion.

Although no limitation is intended, in the illustrative embodiment headpiece22is cut by laser from a tube of nitinol having a 0.018 inch diameter. Arms24and26are each preferably between 0.006 inch and 0.007 inch in width and between 5.0 mm and 10.0 mm in length. Latch element28is preferably between about 0.002 inch and 0.003 inch in width and between about 2.0 mm and 3.0 mm in length. Latch element28is preferably integrally struck from arm24as seen most clearly inFIG. 2.

Headpiece22is preferably attached to tapered portion20by soldering. Each of the arms24,26has an end projection32that preferably is about 0.002 inch wide, although no limitation is intended. The opening range of the arms24,26is preferably between 1.5 mm and 4.5 mm, depending upon the size of the vessel34.

Projections32are formed at the distal end of each arm for the attachment of the radiopaque platinum marker coils36. The diameter of these projections32is reduced from that of the remainder of the arms so that once the marker coils36are affixed, their outer diameter will be substantially the same as the outer diameter of the remainder of the arms.

A radiopaque marker coil36is attached to each of the projections32and a radiopaque marker coil38is attached to latch element28. A marker coil44is also attached to headpiece22, proximal of arms24and26. The marker coils may be attached by soldering. Alternatively, instead of soldering marker coils the device may be radiopacified by means of electroplating or ion deposition. Further, some or all of wire device16may be formed from polymers such as polycarbonate or nylon or other equivalent materials.

In the construction of arms24and26, a tube of nitinol is cut so that the arms are oriented opposite to each other and are arcuate in shape. The arms are heat treated while in the open configuration so that they remain outwardly biased when they are not constrained by the lumen of the catheter12. After the arms are cut by laser from the nitinol tube, latch element28, which may also be slightly arcuate in shape, is cut from the central portion of arm24. Latch element28is heat treated while the arms are oriented in their open configuration. The latch element is angulated downward so that its distal end40is oriented toward a proximal portion of the opposing arm26. Latch element28does not contact opposing arm26when the arms24,26are in their open configuration.

The operation for retrieving an embolic coil using the wire device16is illustrated inFIGS. 3A,3B, and4. First, microcatheter12is introduced into the patient's vessel34, to a location where the distal end42of microcatheter12is adjacent to coil30but at a sufficient distance therefrom so that the arms of the wire device can be extended. Wire device16is then introduced into the catheter and is pushed through the catheter with the arms being collapsed as illustrated inFIG. 3A. In its collapsed position, the distal end40of latch element28engages arm26.

As illustrated inFIG. 3B, when headpiece22is moved to a position past the distal end of42of catheter12, the arms will spring open. The physician, holding the proximal end of wire element16, can manipulate the arms and associated latch so that it will engage coil30and hook onto coil30. As illustrated inFIG. 4, the physician can then withdraw the wire element16, which will cause the arms to collapse under the forces provided by the lumen of the microcatheter acting upon the outside surfaces of the arms. In this manner, distal end40of latch element28will engage arm26to secure a portion of coil30whereby the coil will move into the microcatheter and be withdrawn via the proximal end of the microcatheter. Although it is preferred that distal end40of latch element28engage arm26when the arms are collapsed, distal end40may be closely adjacent arm26instead of engaging it so long as the space between distal end40and arm26is less than the outer diameter d of the helix that forms embolic coil30(seeFIG. 3A).

As a result of the latch construction of the present invention, the embolic coils can be engaged and latched in a manner that prevents their dislodgement once the latch is engaged. This is in contrast to prior art coil retrieval devices in which a loop is used and the physician attempts to lasso the misplaced coil. Using the present invention, the physician is provided with an easier ability to grasp a coil that may be in a loop configuration, without the coil having an opportunity to become dislodged from the retrieval device.

Although an illustrative embodiment of the invention has been shown and described, it is to be understood that various modifications and substitutions may be made by those skilled in the art without departing from the novel spirit and scope of the present invention.