Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-08-02
2001-11-20
Chaudhuri, Olik (Department: 2814)
Surgery
Instruments
Internal pressure applicator
Reexamination Certificate
active
06319268
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to blood filter and associated devices for temporary placement in a blood vessel to capture embolic material, and more particularly to a hollow vessel insertion device with an adjustable filter apparatus for placement in a blood vessel to carry blood to the vessel and to entrap embolic material in the vessel, for example when delivering blood to the aorta from a bypass-oxygenator system during cardiac surgery. The present invention also relates to methods for protecting a patient from embolization that may be caused by procedures, such as incising, clamping and unclamping, which may dislodge atheromatous material from an artery.
BACKGROUND
During cardiac surgery, it is often necessary to introduce a cannula into an artery or other blood vessel. For example, an arterial cannula is typically introduced into the aorta to deliver blood from a bypass-oxygenator system. Such a cannula generally includes a proximal end for receiving blood from a bypass-oxygenator machine, a distal end for entry into an artery and a lumen extending between the proximal and distal ends.
One concern with such procedures is that calcified plaque or other embolic material may be dislodged, particularly when clamping or unclamping arteries such as the aorta. See Barbut et al., “Cerebral Emboli Detected During Bypass Surgery Are Associated With Clamp Removal,”
Stroke ,
25(12):2398-2402 (1994), which is incorporated herein by reference in its entirety. Such embolic material may travel downstream, possibly becoming lodged in another portion of the blood vessel or possibly reaching a vital organ, such as the brain, where the material can cause substantial injury to the patient.
For this reason, some arterial cannulas may include a blood filter device attached directly to them. For example, an expandable filter device may be mounted on the distal end of a cannula, allowing the filter to capture any loose embolic material once the cannula is introduced into the vessel. Generally, such devices include an expandable frame, such as an inflation seal or an umbrella frame, and a filter mesh attached to the frame, the mesh being adapted to capture embolic material of a predetermined minimum size. The frame may be attached externally to the distal end, or alternatively, it may be retractably deployed from a lumen within the cannula.
The use of a cannula with such a filter device, however, may not be as effective as desired. For example, because the filter is generally attached to the distal end of the cannula, the filter may be exposed within the vessel for the entire duration of the procedure, sometimes several hours. Because of the length of time of most cardiac procedures, the filter mesh may eventually become clogged due to thrombus formation or buildup of embolic material, preventing the device from effectively capturing additional material and/or possibly impairing blood flow through the filter. If the filter is retractable, it may be closed within the vessel when it becomes clogged, but this prevents capture of embolic material throughout the remainder of the procedure.
Accordingly, there is a need for a filter device for use with an arterial cannula or other hollow vessel insertion device, such as an introducer, that minimizes the exposure of the filter within a blood vessel, thereby reducing the risk of clogging the filter mesh. Certain types of self-expanding modular filter devices have been described in U.S. Pat. No. 5,846,260, which is incorporated herein by reference in its entirety. However, there is a need for a modular filter apparatus with a filter that can be adjusted to fit various sizes of vessels. The exterior of such a device should optimally conform to the size and shape of the inner lumen of the vessel through which the emboli may pass to reduce the possibility of emboli escape around the exterior of the filter. The size of such a filter should be either self-adjusting or adapted to external operation to adjust the size to fit the vessel in which the filter resides. Further, there is a need for associated devices such as vessel sizing tools, expandable obturators, cannula liners and blood filtering system indexing/locking devices to assist in the use of the blood filtering system.
SUMMARY OF THE INVENTION
The present invention is directed to a modular adjustable blood filter device and a delivery system for intermittently introducing the filter device into a blood vessel during an extended surgical procedure and to methods for using such a device. The present invention is also directed to a hollow vessel insertion device, such as an introducer or an arterial cannula, with modular filter device for temporary placement in a blood vessel to carry blood to the vessel and to entrap embolic material in the vessel, for example when delivering blood to the aorta from a bypass-oxygenator system during cardiac surgery.
Generally, an embodiment of a blood filtering system includes a modular filter apparatus and a hollow vessel insertion device, such as an arterial cannula or an introducer, capable of receiving the filter for capturing embolic material in a blood vessel. The insertion device may be a stand-alone device, or may be part of a blood filtering system with the modular filtering apparatus. When the insertion device and the filter are used together, certain embodiments include indexing and locking mechanisms to assure proper alignment of the filter in the device. These indexing/locking mechanisms may also be included when the insertion device is used with other apparatuses, for example obturators.
When a cannula is used, it has a distal end adapted to enter an artery, a proximal end adapted to receive blood from a bypass oxygenator machine, and a lumen that extends from the proximal end to the distal end. The cannula can be a hybrid of extruded, drawn or welded metal tubing and molded or machined plastics, or could be made entirely of metal or of plastic. The cannula also includes a port for receiving the modular filter apparatus. The port may be attached to or integrally formed on the outer surface of the cannula, the inner surface of the cannula, such as a lumen parallel with the main cannula lumen, possibly on the front (downstream area), back (upstream area) or side of the cannula. Preferably, a side port is located adjacent the distal end of the cannula, for example above a suture flange thereon. More preferably, the side port extends diagonally from the outer surface to facilitate directing the filter device towards the distal end of the cannula. A passage extends from the side port to the lumen in the cannula, or alternatively, may extend distally from the side port along a wall of the cannula to an outlet on or adjacent the distal end of the cannula. The side port may include a hemostatic valve across the passage to provide a fluid-tight seal, yet allow a modular filter cartridge to be received in and removed from the side port. The cannula may also include a cannula liner to prevent the escape of blood from the outlet.
The filter apparatus includes a shaft with an adjustable filter frame disposed about the distal end of the shaft. The frame is adjustable between a contracted condition and an enlarged condition. The filter also includes a frame sizing mechanism and a filter mesh coupled to the frame for capturing embolic material. The filter apparatus may be a stand-alone device or may be removably insertable into the arterial cannula or introducer. Upon insertion through the cannula into the artery, the frame sizing mechanism adjusts the diameter of the filter frame to conform to the inner lumen of the vessel.
Embodiments of the modular filter apparatus include a semi-rigid shaft with some embodiments having a handle on the shaft proximal end. The frame may be metal, plastic, gel or foam or any combination thereof The filter mesh pore size ideally ranges from 40 to 120 microns, but other sizes may be used depending on the clinical need. The mesh may be plastic, fibrous, or metal, polyester, nylon, Teflon(k, or the like, and
Addis Bruce S.
Ambrisco William M.
Maahs Tracy D.
Murphy Richard O.
Turovskiy Roman
Chaudhuri Olik
Embol-X Inc.
Lyon & Lyon LLP
Trinh (Vikki) Hoa B.
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