Patent Application
20050149068
The present invention relates generally to medical devices, specifically to a device for excluding the left atrial appendage (LAA) from blood flow in the left atrium, and related procedures.
Embolic stroke is the nation's third leading killer for adults, and is a major cause of disability. There are over 80,000 strokes per year in the United States alone. The most common cause of embolic stroke emanating from the heart is thrombus formation due to atrial fibrillation. Atrial fibrillation is an arrhythmia of the heart that results in a rapid and chaotic heartbeat that produces lower cardiac output and irregular and turbulent blood flow in the vascular system. There are over five million people worldwide with atrial fibrillation, with about four hundred thousand new cases reported each-year. Atrial fibrillation is associated with a 500 percent greater risk of stroke due to the condition. A patient with atrial fibrillation typically has a significantly decreased quality of life due, in large part, to the fear of a stroke, and the pharmaceutical regimen necessary to reduce that risk.
For patients who have atrial fibrillation and develop atrial thrombus therefrom, the clot normally occurs in the left atrial appendage (LAA) of the heart. The LAA is a cavity which looks like a small finger or windsock and which is connected to the lateral wall of the left atrium between the mitral valve and the root of the left pulmonary vein. The LAA normally contracts with the rest of the left atrium during a normal heart cycle, thus keeping blood from becoming stagnant therein, but like the rest of the atrium does not contract in patients experiencing atrial fibrillation due to the discoordinate electrical signals associated with AF. As a result, thrombus formation is predisposed to form in the stagnant blood within the LAA. Blackshear and Odell have reported that of the 1288 patients with non-rheumatic atrial fibrillation involved in their study, 221 (17%) had thrombus detected in the left atrium of the heart. Blackshear J. L., Odell, J. A., Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation, Ann Thorac. Surg., 1996,61(2):755-9. Of the patients with atrial thrombus, 201 (91%) had the atrial thrombus located within the LAA. The foregoing suggests that the elimination or containment of thrombus formed within the LAA of patients with atrial fibrillation would significantly reduce the incidence of stroke in those patients.
Pharmacological therapies for stroke prevention such as oral or systemic administration of blood thinning agents, such as warfarin, coumadin or the like have been inadequate due to serious side effects of the medications (e.g., an increased risk of bleeding) and lack of patient compliance in taking the medication.
As an alternative to drug therapy, invasive surgical procedures for closing the LAA have been proposed. Most commonly, the LAA has been closed or removed in open surgical procedures, typically where the heart has stopped and the chest opened through the sternum. The perceived risks of even a thorascopic surgical procedure often outweigh the potential benefits, and many patients are not suitable candidates for such surgical procedures due to a compromised condition or having previously undergone cardiac surgery. See Lindsay, B. D., Obliteration of the left atrial appendage: A concept worth testing. Ann Thorac. Surg., 1996.61(2):515.
Because of the significant risk and trauma of such procedures, LAA removal occurs almost exclusively when the patient's chest is opened for other procedures, such as coronary artery bypass or valve surgery. For that reason, alternative procedures that do not require opening of the patient's chest, i.e., a large median sternotomy, have been proposed.
For instance, U.S. Pat. No. 5,865,791, to Whayne et al. describes a transvascular approach for closing the LAA. Access is gained via the venous system, typically through a femoral vein, a right internal jugular vein, or a subclavian vein, where a catheter is advanced in an antegrade direction to the right atrium. The intra-atrial septum is then penetrated, and the catheter passed into the left atrium. The catheter is then positioned in the vicinity of the LAA which is then fused closed, e.g., using radiofrequency energy, other electrical energy, thermal energy, surgical adhesives, or the like. The transvascular approach suggested by Whayne et al. is advantageous in that it avoids the need to penetrate the patient's chest but suffers from the need to penetrate the intra-atrial septum, may not provide definitive closure, requires entry into the LAA, which may dislodge a clot and requires injury to the endocardial surface, which may promote thrombus formation.
U.S. Pat. No. 5,306,234 to Johnson describes a thoracoscopic procedure where access to the pericardial space over the heart is achieved using a pair of intercostal penetrations (i.e., penetrations between the patients ribs) to establish both visual and surgical access. While such procedures may be performed while the heart remains beating, they still require deflation of the patient's lung and that the patient be placed under full anesthesia. Furthermore, placement of a chest tube is typically required to reinflate the lung.
U.S. Pat. No. 6,488,689 to Kaplan, et al. discloses another minimally invasive approach to LAA closure where access to the pericardial space overlying the patient's LAA is accomplished through percutaneous penetrations through the patient's skin. Rather than passing through the rib cage, as with the technique disclosed in Johnson, Kaplan, et al. rely on a “sub-xiphoid” approach where the percutaneous penetration is first made beneath the rib cage, preferably between the xiphoid and adjacent costal cartilage. An atrial appendage closure tool is advanced through the penetration, over the epicardial surface (in the pericardial space) to reach a location adjacent to the exterior of the LAA. The closure tool can then be used to close the LAA to prevent the formation of clot and the release of emboli from the atrium. Closure can be effected by positioning a loop of material, such as suture, wire, mesh, tape, or the like, over the appendage and cinch the loop tighter to close the interior of the appendage. Other closure techniques disclosed include suturing, stapling, clipping, fusing, gluing, clamping, riveting, or the like.
Despite these efforts, it would be desirable to provide devices and procedures for closure of the LAA that account for the delicate nature of existing thrombi in the LAA cavity and are less traumatic to the LAA tissue and left atrium.
The present invention desirably provides a left atrial appendage exclusion device comprising a pair of elongated compression members co-extensive with one another and joined together at both ends to form a closed periphery defining an opening therein. The closed periphery may define a lenticular opening or a generally rectangular opening. Preferably, at least one of the compression members has a protrusion facing the opening, and the protrusion may have an angled compression surface. In an alternative embodiment, the invention comprises two compression members that are not joined together at one or more of the two ends but lock in place at the two ends when deployed. For example, either of the two ends may comprise male and female members that can be snapped together to lock-in the end.
In accordance with a further aspect, the present invention provides a left atrial appendage exclusion device comprising a pair of elongated compression members co-extensive with one another and hinged together at one end. The compression members each further includes mating structures on the end opposite the hinged end that mutually engage to form a closed periphery for the exclusion device. Desirably, the compression members are flexible and biased toward each other to minimize the opening within the closed periphery. Again, the closed periphery may define a lenticular opening or a generally rectangular opening. At least one of the compression members preferably has a protrusion facing the opening, and the protrusion may have an angled compression surface.
Another aspect of the invention is a left atrial appendage exclusion device comprising a pair of elongated compression members co-extensive with one another and coupled at both ends to form a closed periphery defining an opening therein. At least one of the compression members has a plurality of piercing members extending into the opening toward the other member for piercing the left atrial appendage and trapping matter therein. The piercing members may be needles, and may be arrayed in a single line. Desirably, the piercing members are provided on both compression members and are offset from one another across the opening.
In another embodiment, a left atrial appendage exclusion device is provided comprising a pair of elongated compression members co-extensive with one another and coupled at both ends to form a closed periphery defining an elevational opening therein, the compression members being non-linear in plan view. The compression members may be molded into the non-linear shape, or may be malleable and manually formed into the non-linear shape. Preferably, the non-linear shape is an arc.
In accordance with one aspect, the present invention provides a method for excluding the cavity of a left atrial appendage from the interior of the left atrium. The method includes providing an exclusion device having a pair of elongated compression members co-extensive with one another and joined together at both ends to form a closed periphery defining an opening therein. The exclusion device is introduced to a location adjacent the left atrial appendage and manipulated to expand the opening. The exclusion device is then advanced such that it surrounds the left atrial appendage without applying compression thereto. Finally, the opening is minimized such that the compression members contact the exterior of the left atrial appendage and exclude the cavity from the interior of the left atrium.
In one embodiment, the compression members are flexible and biased toward each other to minimize the opening within the closed periphery, and the step of manipulating comprises forcing the compression members apart. The compression members may be forced apart by applying an outward force against both compression members from within the opening. Further, the step of minimizing the opening may comprise releasing the outward force applied to the compression members. In a preferred embodiment, the outward force is applied by forceps.
Desirably, the step of advancing the exclusion device comprises advancing the compression members to an outer wall of the left atrium. The method may further include immobilizing a thrombus within the left internal appendage cavity prior to excluding the cavity from the interior of the left atrium. For example, a needle may be used to pierce the left atrial appendage and the thrombus to immobilize it.
In accordance with the present invention, a method for excluding the cavity of a left atrial appendage from the interior of the left atrium is provided that includes providing an exclusion device and introducing it to a location adjacent the left atrial appendage. The exclusion device is manipulated to surround the left atrial appendage adjacent to the exterior wall of the left atrium and compression is applied to the left atrial appendage. The compression is applied so as to start from a location adjacent to the exterior wall of the left atrium and move away from the left atrium to exclude the cavity from the interior of the left atrium while minimizing the extrusion into the left atrium of any existing thrombus within the cavity.
As in the first method, the exclusion device may include a pair of spaced apart compression members and the step of applying compression comprises closing the distance between the compression members. The compression members may be elongated and co-extensive with one another and may or may not be joined or hinged together at one or both ends to form a closed periphery defining an opening therein. Preferably, the compression members are flexible and biased toward each other to minimize the opening within the closed periphery and thus close the distance between the compression members in the absence of an external force. If the compression members are hinged each further includes mating structure on the end opposite the hinged end that mutually engage to form a closed periphery for the exclusion device.
The compression may be applied to the left atrial appendage with a non-planar compressive force on opposite sides of the left atrial appendage. For example, the non-planar compressive force may be applied by opposed ramp surfaces on the exclusion device.
Whatever the configuration, the compression members 30a, 30b are capable of being expanded or opened into the position shown in
It should be noted at this stage that various medical implements are suitable for manipulating the exclusion device 20 within the chest cavity. For example, forceps 40 are shown extending within the opening 32 to contact the inner side of each compression members 30a, 30b. Opening the forceps 40 as seen in
Now with reference to
Finally, the exclusion device 20 is shown in
The exemplary exclusion device 20 includes the aforementioned compression members 30a, 30b that are relatively elongated (by comparison of the length seen in
The opposite end 64 of each of the compression members 30a, 30b is joined to corresponding end 64 of the other compression member using mating structure that mutually engage to form a closed periphery (generally rectangular as shown) for the exclusion device 20. In the illustrated embodiment, the mating structure includes a pair of walls 66a, 66b each of which terminate in a mating rib or tooth 68. Of course, the mating structures can be any number of configurations including multiple ratchet teeth for a variable sized closed periphery, hook and loop fasteners, etc.
In a preferred embodiment, at least one of the compression members 30a, 30b has a protrusion facing the opening 32 that helps prevent migration of the exclusion device 20 after deployment. In the embodiment of
Desirably, the protrusions 70a, 70b are shaped so as to be atraumatic to the exterior tissue of the left atrial appendage LAA. As seen best in
In addition to helping prevent migration of the deployed exclusion device 20, the protrusions 70a, 70b may also help prevent extrusion of any thrombus deposits from within the cavity 22 of the left atrial appendage LAA during deployment. More generally, the present invention contemplates a deployment procedure wherein the left atrial appendage LAA is first squeezed together close to the wall of the left atrium LA and then in a direction away from the atrium; that is, there is a squeezing motion away from the left atrium LA. This can be done in a number of ways, although as seen in
Instead of providing the ramped protrusions 70a, 70b, alternative compression members 80a, 80b may be oriented at an angle with respect to one another as seen in
A further alternative method of squeezing the left atrial appendage LAA from the left atrium LA first is to provide multiple compression members on either side of the appendage. Although not shown in the drawings, a first pair of compression members may be deployed close to the exterior wall the left atrium LA and then a second pair deployed in a direction away from the left atrium. This “stepped” compression moving away from the left atrium LA is essentially what occurs when the angled compression members 80a, 80b of
Alternatively, or in conjunction with the aforementioned deployment technique, any identified thrombus deposits 24 may be immobilized within the left internal appendage cavity 22 prior to excluding the cavity from the interior of the left atrium LA. For example, a pin or needle may be used to pierce into the identified thrombus deposit 24 from the exterior of the left atrial appendage LAA. The deposit 24 may be identified using ultrasound or other methods.
In
Each of the compression members 102a, 102b includes a pair of inner protrusions 114 located near the ends 104, 106 and not in the middle. Again, the protrusions 114 are desirably rounded so as to be atraumatic to the left atrial appendage LAA tissue. Although not shown, the protrusions 114 may also include the ramp surface previously described.
With reference to
In use, the needles 158 pierce the left atrial appendage tissue and help entrap any pieces of blood clots or other such loose matter within the left atrial appendage cavity. The length of the needles 150a should be sufficient to pass through one wall of the left atrial appendage, and the number of needles should create an array of needles when the device is closed that traps all loose clots or plaque. The clots may be pierced and thus captured directly, or the array of needles may function similarly to the baleen filter of some whales. The needles 158 on the upper compression member 152a are shown offset across the opening 156 from those on the lower compression member 152b, although they could be in alignment. Furthermore, a single row of needles 158 is shown on each compression member 152a, 152b, though it should be understood that multiple rows on each might be provided.
a and 10b are the plan and elevation views of an alternative LAA exclusion device 170 that is in many respects similar to the device 150 shown in
a and 11b illustrate, in plan view, use of the non-linear LAA exclusion device 170 to exclude the left atrial appendage. The device 170 is first spread apart and advanced along arrow 180 toward the LAA. Once positioned adjacent to the exterior wall of the left atrium LA, the device 170 is released and permitted to contract, thus closing off the LAA cavity. As can be seen from
Deployment of any of the exclusion devices described herein can be accomplished using an open chest approach, such as a median sternotomy, or with a minimally-invasive approach such as a small thoracotomy or port access procedure. In one exemplary embodiment, deployment will be in a minimally invasive manner, i.e., where access to the pericardial space overlying the patient's left atrial appendage is accomplished through percutaneous penetrations through the patient's skin. Such a technique is disclosed in U.S. Pat. No. 6,488,689 to Kaplan, et al., which is expressly incorporated herein by reference. Rather than passing through the rib cage, as with prior thoracoscopic techniques, a “sub-xiphoid” approach is used in Kaplan, et al. where the percutaneous penetration is first made beneath the rib cage, preferably between the xiphoid and adjacent costal cartilage. An LAA exclusion device of the present invention is then advanced through the penetration, over the epicardial surface (in the pericardial space) to reach a location adjacent to the exterior of the left atrial appendage. The exclusion device can then be used to close the left atrial appendage to prevent the formation of clots and the release of emboli from the atrium.
The degree of compression on the tissue of the left atrial appendage is desirably great enough to cause necrosis or fibrosis along a line across the inner cavity mouth. This creates a block of conduction though the tissue which electrically isolates the left atrial appendage and helps reduce problems associated with atrial fibrillation.
Any of the LAA exclusion devices of the present invention may be coated with one or more biocompatible materials to facilitate long-term implantation. For example, the devices may be coated with an agent that is either synthetic or biological, active or inactive. Active agents include heparin and other anticoagulants, EDGF (endothelium derived growth factor), VGFs (vascular growth factors) or inactive agents like silicone, polyurethane, PTFE (polytetrafluoroethylene) and/or other polymers. Inactive (or inert) agents may have active agents such as those listed above encapsulated therewithin. The coating may be bioresorbable or not.
It will also be appreciated by those of skill in the relevant art that various modifications or changes may be made to the examples and embodiments of the invention described in this provisional application, without departing from the intended spirit and scope of the invention. In this regard, the particular embodiments of the invention described herein are to be understood as examples of the broader inventive concept disclosed in this application.
