Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Having plurality of parallel lumens
Reexamination Certificate
2000-01-26
2001-06-05
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Having plurality of parallel lumens
C623S001160
Reexamination Certificate
active
06241764
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an improved vascular graft system, and in particular to a stented vascular graft system incorporating improved stents and drafts designed to provide flow transfer from an aortic source to a branch flow path for coronary bypass procedures. In accordance with the present invention, graft material is appropriately secured to the stent structure so as to facilitate this step in the coupling of the graft system to the vasculature of the patient, thereby expediting the surgical procedure while at the same time reducing the number of suturing steps necessary in the procedure. The features of the present invention are set forth in greater detail hereinafter.
Coronary bypass surgery has become a common procedure, and is normally indicated for conditions requiring replacement and/or reconfiguration due to blockage of the coronary blood flow within a patient. Apparatus and techniques are also disclosed herein for selectively monitoring the flow through a graft. The present invention involves use of a stented graft, and particularly wherein the stent is utilized to receive the graft and also for modifying the flow pattern through coupling to relevant portions of the vasculature. Two forms of stented grafts are utilized in a typical surgical procedure, with a first form being employed for introduction into a coronary artery downstream from a blockage site, and with the second form of stented graft being employed to couple the distal end of the graft network to a point of relatively lower flow pressure, and to serve as a terminus for the grafted structure. In the second form of stented graft, means are provided for suturing the stent to a selected location, typically at the right atrium or superior vena cava. The utilization of stented grafts facilitates and expedites the procedure while reducing the number of necessary steps, all of this being achieved without compromising the efficacy of the overall procedure.
In a typical bypass procedure, a section of the vascular system in a patient's body that has become impaired or inoperative through disease or other defect may be treated so as to improve flow to those portions previously being given an inadequate or limited supply of blood. In order to create the graft network, biocompatible graft material may be employed, such as, for example, Gortex™, with this being a polytetrafluoroethylene-based material normally being accepted by the patient's body. Thus, such graft material is frequently and typically utilized in bypass as well as in other procedures such as, for example, as a joint reinforcing material, such as a brace interposed across the knee.
Because of the physical properties of the biocompatible graft material, stent suturing, while possible, is frequently difficult to complete. The procedure is one which requires great dexterity, and when done at the site, is frequently in a zone with limited accessibility. In the design of the stent portion of the stented grafts, a certain degree of axial offset is provided in order to more fully and completely expose a portion of the stent to which a graft must be applied during the surgical procedure. Because of this greater accessibility and visibility, the stented graft device of the present invention is highly desirable.
Coronary bypass procedures are frequently undertaken with patients whose coronary arteries have been partially or almost completely blocked, thereby impeding and disrupting the proper flow of blood through the vascular system. While bypass procedures have been undertaken for some period of time, one meticulous and time consuming step is that of suturing the vascular graft elements. The time required for completing each such suture is reduced significantly through providing a pre-attached or stented graft in accordance with the present invention.
As a further feature of the present invention, means can be provided in combination with the vascular assembly for monitoring blood flow through various branches of the graft configuration. In particular, flow rate monitoring may be achieved through utilization of devices functioning in response to temperature variations resulting by introducing a temperature energy signal into the bloodstream, and measuring and/or detecting the thermal response at a downstream location. Another technique suitable for use in connection with the present invention is based upon the use of ultrasonic signals, wherein the system comprises one or more signal generators in communication with the blood flow (transducers) along with detection means, normally an array transducer exposed to the signal. Doppler techniques may be employed to determine flow rate and volume. Such systems are known in the art, with a thermal response system being disclosed in U.S. Pat. No. 5,989,192, and with ultrasonic systems being disclosed in U.S. Pat. Nos. 5,967,989; 5,807,258 and 5,588,436.
In order to evaluate the condition of an individual graft, determinations of flow velocity and overall blood volume provide a good indicator. A determination of pressure differentials between opposed ends of a graft will provide valuable information as well. Obviously, as deposits collect along the interior wall of a graft, pressure differentials will increase along with a corresponding decrease in velocity and flow volume. The utilization of the stented grafts in accordance with the present invention reduces some of the potential for buildup within certain other graft structures, this being accomplished by tailoring the configuration of the flow channel through the stent so as to preserve flow patterns, and also preserve and/or reduce the tendency for any increase in the Reynold's number within the blood flow through the graft network.
SUMMARY OF THE INVENTION
In accordance with the present invention, a family of stented grafts are provided for each bypass procedure. In addition to the terminal stent to be described hereinafter, at least one branch stent is provided for each procedure, with the branch stent comprising biocompatible material and including a feature for cross-flow from the supply channel which communicates with the aorta to a location in the coronary artery where flow correction is needed. This location is typically downstream of the blockage necessitating the bypass procedure. These stent devices are typically dual lumen with a cross-flow channel being provided between the lumens, thus permitting a portion of the blood from the main supply to be utilized for flow to the blockage site. In the dual lumen structure, a relatively large diameter lumen is employed for that portion of the graft which is in direct communication with the aorta, with the second lumen typically being of somewhat lesser overall diameter and being designed for insertion into a slit formed in the coronary artery requiring bypass. For many applications, a lumen diameter of approximately 2 mm. is desirable and useful, although lumens of slightly larger and/or smaller diameter may be appropriately considered.
The stented grafts also include a terminal or distal stent structure which is designed to be coupled directly to the terminus of the graft network, such as at the right atrium or superior vena cava. This terminal member includes a biocompatible body having a channel or bore therethrough which is provided with a suture flange at one end, and with a graft being secured to the other. As indicated above, the configuration of the bore is such that the flow rate is maintained consistent with that through the balance of the supply network, with the Reynold's number being held well within the laminar area.
In each instance, the graft material is pre-attached to the stent and is of a length which is more than ample for the contemplated use. Thus, the surgeon is able to cut the graft to a desired and required length in the course of the procedure, while at the same time, not having to disturb the integrity of the previously prepared secure junction between the stent and the graft. In the course of the overall procedure, the
CABG Medical, Inc.
Haugen Law Firm PLLP
Snow Bruce
LandOfFree
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