The invention relates to prosthesis deployment and more particularly to locating a branch passageway in a human body such as a branch artery prior to prosthesis deployment or locating a passageway in a prosthesis prior to in vivo cannulation thereof.
Tubular prostheses such as stents, grafts, and stent-grafts (e.g., stents having an inner and/or outer covering comprising graft material and which may be referred to as covered stents) have been widely used in treating abnormalities in passageways in the human body. In vascular applications, these devices often are used to replace or bypass occluded, diseased or damaged blood vessels such as stenotic or aneurysmal vessels. For example, it is well known to use stent-grafts, which comprise biocompatible graft material (e.g., Dacron® or expanded polytetrafluoroethylene (ePTFE)) supported by a framework (e.g., one or more stent or stent-like structures), to treat or isolate aneurysms. The framework provides mechanical support and the graft material or liner provides a blood barrier.
Aneurysms generally involve abnormal widening of a duct or canal such as a blood vessel and generally appear in the form of a sac formed by the abnormal dilation of the duct or vessel. The abnormally dilated vessel has a wall that typically is weakened and susceptible to rupture. Aneurysms can occur in blood vessels such as in the abdominal aorta where the aneurysm generally extends below the renal arteries distally to or toward the iliac arteries.
In treating an aneurysm with a stent-graft, the stent-graft typically is placed so that one end of the stent-graft is situated proximally or upstream of the diseased portion of the vessel and the other end of the stent-graft is situated distally or downstream of the diseased portion of the vessel. In this manner, the stent-graft spans across and extends through the aneurysmal sac and beyond the proximal and distal ends thereof to replace or bypass the weakened portion. The graft material typically forms a blood impervious lumen to facilitate endovascular exclusion of the aneurysm.
Such prostheses can be implanted in an open surgical procedure or with a minimally invasive endovascular approach. Minimally invasive endovascular stent-graft use is preferred by many physicians over traditional open surgery techniques where the diseased vessel is surgically opened, and a graft is sutured into position bypassing the aneurysm. The endovascular approach, which has been used to deliver stents, grafts, and stent grafts, generally involves cutting through the skin to access a lumen of the vasculature. Alternatively, lumenar or vascular access may be achieved percutaneously via successive dilation at a less traumatic entry point. Once access is achieved, the stent-graft can be routed through the vasculature to the target site. For example, a stent-graft delivery catheter loaded with a stent-graft can be percutaneously introduced into the vasculature (e.g., into a femoral artery) and the stent-graft delivered endovascularly to a portion where it spans across the aneurysm where it is deployed.
When using a balloon expandable stent-graft, balloon catheters generally are used to expand the stent-graft after it is positioned at the target site. When, however, a self-expanding stent-graft is used, the stent-graft generally is radially compressed or folded and placed at the distal end of a sheath or delivery catheter and self expands upon retraction or removal of the sheath at the target site. More specifically, a delivery catheter having coaxial inner and outer tubes arranged for relative axial movement therebetween can be used and loaded with a compressed self-expanding stent-graft. The stent-graft is positioned within the distal end of the outer tube (sheath) and in front of a stop fixed to distal end of the inner tube. Regarding proximal and distal positions referenced herein, the proximal end of a prosthesis (e.g., stent-graft) is the end closest to the heart (by way of blood flow) whereas the distal end is the end furthest away from the heart during deployment. In contrast, the distal end of a catheter is usually identified as the end that is farthest from the operator, while the proximal end of the catheter is the end nearest the operator. Once the catheter is positioned for deployment of the stent-graft at the target site, the inner tube is held stationary and the outer tube (sheath) withdrawn so that the stent-graft is gradually exposed and expands. An exemplary stent-graft delivery system is described in U.S. patent application Publication No. 2004/0093063, which published on May 13, 2004 to Wright et al. and is entitled Controlled Deployment Delivery System, the disclosure of which is hereby incorporated herein in its entirety by reference.
Although the endovascular approach is much less invasive, and usually requires less recovery time and involves less risk of complication as compared to open surgery, there can be concerns with alignment of asymmetric features of various prostheses in relatively complex applications such as one involving branch vessels. Branch vessel techniques have involved the delivery of a main device (e.g., a graft or stent-graft) and then a secondary device (e.g., a branch graft or branch stent-graft) through a fenestration or side opening in the main device and into a branch vessel.
The procedure becomes more complicated when more than one branch vessel is treated. One example is when an aortic abdominal aneurysm is to be treated and its proximal neck is diseased or damaged to the extent that it cannot support a reliable connection with a prosthesis. In this case, grafts or stent-grafts have been provided with fenestrations or openings formed in their side wall below a proximal portion thereof. The fenestrations or openings are to be aligned with the renal arteries and the proximal portion is secured to the aortic wall above the renal arteries.
To ensure alignment of the prostheses fenestrations and branch vessels, some current techniques involve placing guidewires through each fenestration and branch vessel (e.g., artery) prior to releasing the main device or prosthesis. This involves manipulation of multiple wires in the aorta at the same time, while the delivery system and stent-graft are still in the aorta. In addition, an angiographic catheter, which may have been used to provide detection of the branch vessels and preliminary prosthesis positioning, may still be in the aorta. Not only is there risk of entanglement of these components, the openings in an off the shelf prosthesis with preformed fenestrations may not properly align with the branch vessels due to differences in anatomy from one patient to another. Prostheses having preformed custom located fenestrations or openings based on a patient's CAT scans also are not free from risk. A custom designed prosthesis is constructed based on a surgeon's interpretation of the scan and still may not result in the desired anatomical fit. Further, relatively stiff catheters are used to deliver grafts and stent-grafts and these catheters can apply force to tortuous vessel walls to reshape the vessel (e.g., artery) in which they are introduced. When the vessel is reshaped, even a custom designed prosthesis may not properly align with the branch vessels.
U.S. Pat. No. 5,617,878 to Taheri discloses a method comprising interposition of a graft at or around the intersection of major arteries and thereafter, use of intravenous ultrasound or angiogram to visualize and measure the point on the graft where the arterial intersection occurs. A laser or cautery device is then interposed within the graft and used to create an opening in the graft wall at the point of the intersection. A stent is then interposed within the graft and through the created opening of the intersecting artery.
U.S. patent application Ser. No. 11/276,512 to Marilla, entitled Multiple Branch Tubular Prosthesis and Methods, filed Mar. 3, 2006, and co-owned by the assignee of the present application discloses positioning in an endovascular prosthesis an imaging catheter (intravenous ultrasound device (IVUS)) having a device to form an opening in the side wall of the prosthesis. The imaging catheter detects an area of the prosthesis that is adjacent to a branch passageway (e.g., a renal artery), which branches from the main passageway in which the prosthesis has been deployed. The imaging catheter opening forming device is manipulated or advanced to form an opening in that area of the prosthesis to provide access to the branch passageway. The imaging catheter also can include a guidewire that can be advanced through the opening.
Generally speaking, one challenge in prosthesis (e.g., stent graft) delivery/placement in the vicinity of one or more branch vessels is identifying and locating the position of branch vessels (e.g., arteries). Typically fluoroscopy is used to identify branch vessels. More specifically, fluoroscopy has been used to observe real-time X-ray images of the openings within cardiovascular structures such as the renal arteries during a stent-graft procedure. This approach requires one to administer a radiopaque substance, which generally is referred to as a contrast medium, agent or dye, into the patient so that it reaches the area to be visualized (e.g., the renal arteries). A catheter can be introduced through the femoral artery in the groin of the patient and endovascularly advanced to the vicinity of the renals. The fluoroscopic images of the transient contrast agent in the blood, which can be still images or real-time motion images, allow two dimensional visualization of the location of the renals.
The use of X-rays, however, requires that the potential risks from a procedure be carefully balanced with the benefits of the procedure to the patient. While physicians always try to use low dose rates during fluoroscopy, the duration of a procedure may be such that it results in a relatively high absorbed dose to the patient. Patients who cannot tolerate contrast enhanced imaging or physicians who must or wish to reduce radiation exposure need an alternative approach for defining the vessel configuration and branch vessel location.
Accordingly, there remains a need to develop and/or improve prosthesis deployment apparatus and methods for endoluminal or endovascular applications.
The present invention involves improvements in prosthesis deployment apparatus and methods.
In one embodiment according to the invention, a method of locating a branch vessel in a human patient comprises tracking a sensor moving in a vessel in a first navigational direction (e.g., along a vessel wall); and detecting movement of the sensor in a direction generally orthogonal to the first navigational direction. The detected movement can be monitored to confirm if branch vessel detection occurred.
In another embodiment according to the invention, a method of positioning a tubular prosthesis in a passageway in a human body comprises advancing a tubular prosthesis through a vessel in a patient; obtaining the position in three dimensions of a portion of an opening to a branch vessel; and positioning the proximal end portion of the prosthesis at a predetermined distance from the branch vessel opening portion. In one example, the vessel can be the aorta of the patient and the branch vessel can be a renal artery.
In another embodiment according to the invention, a method of cannulating a bifurcated tubular prosthesis in vivo comprises positioning a bifurcated tubular prosthesis in the aorta of a patient having an ipsilateral leg and a truncated contralateral leg portion; positioning a first sensor in the truncated contralateral leg portion; obtaining the position in three dimensions of the first sensor; advancing a contralateral leg delivery catheter, which has a distal portion and a proximal portion and a second sensor coupled to the distal portion, toward the first sensor position; and monitoring the second sensor position in three dimensions relative to the first sensor position to guide the distal portion of the contralateral leg delivery catheter into the truncated contralateral leg portion.
In another embodiment according to the invention, a prosthesis delivery system comprises a stent-graft delivery catheter having a proximal end portion and a distal end portion; a first sensor coupled to the catheter distal end portion; a flexible member having a fixed end portion and a feeler end portion, the flexible member fixed end portion being secured to the catheter distal end portion; and a second signal sensor coupled to the flexible member feeler end portion and suspended thereby.
In another embodiment according to the invention, a prosthesis delivery system comprises a tubular prosthesis delivery sheath having a proximal end portion and a distal end portion; a tip member having a proximal end portion and a distal end portion, the tip member proximal end portion being releasably coupled to the sheath distal end portion; a first sensor coupled to the tip member; a flexible member having a fixed end portion and a feeler end portion, the flexible member fixed end portion being secured to the tip member; and a second sensor coupled to the flexible member and suspended thereby.
In another embodiment according to the invention, a stent-graft delivery system comprises a stent-graft delivery catheter having a proximal end portion and a distal end portion; a flexible member having a fixed end portion and a feeler end portion, the flexible member fixed end portion being secured to the catheter distal end portion; a first sensor coupled to one of the catheter distal end portion and the flexible member; a signal generator coupled to the other of the catheter distal end portion and the flexible member; and the one of the sensor and signal generator that is coupled to the flexible member being suspended thereby.
In another embodiment according to the invention, a stent-graft delivery system comprises a stent-graft delivery sheath having a proximal end portion and a distal end portion; a tip member having a proximal end portion and a distal end portion, the tip member being releasably coupled to the sheath distal end portion; a flexible member having a fixed end portion and a feeler end portion, the flexible member fixed end portion being secured to the tip member; a first sensor coupled to one of the tip member and the flexible member; a signal generator coupled to the other of the tip member and the flexible member; and the one of the sensor and signal generator that is coupled to the flexible member being suspended thereby and movable relative to the tip member.
According to another embodiment of the invention a probe for locating structure in a patient comprises an elongated member configured for endovascular delivery in a patient, the elongated member having a proximal end portion and a distal end portion; a first sensor coupled to the elongated member distal end portion; a flexible member having a proximal end portion and a distal end portion, the flexible member fixed end portion being secured to the elongated member distal end portion; and a second sensor coupled to the flexible member and suspended thereby.
Other features, advantages, and embodiments according to the invention will be apparent to those skilled in the art from the following description and accompanying drawings.
The following description will be made with reference to the drawings where when referring to the various figures, it should be understood that like numerals or characters indicate like elements.
Regarding proximal and distal positions, the proximal end of the prosthesis (e.g., stent-graft) is the end closest to the heart (by way of blood flow) whereas the distal end is the end farthest away from the heart during deployment. In contrast, the distal end of the catheter is usually identified as the end that is farthest from the operator, while the proximal end of the catheter is the end nearest the operator. Therefore, the prosthesis (e.g., stent-graft) and delivery system proximal and distal descriptions may be consistent or opposite to one another depending on prosthesis (e.g., stent-graft) location in relation to the catheter delivery path.
Embodiments according to the invention facilitate mapping of one or more branch lumens in a patient prior to stent-graft deployment and/or locating a prosthesis lumen position prior to cannulation thereof. Branch lumens emanate from the intersection of a vessel (e.g., the aorta) and other attendant vessels (e.g., major arteries such as the renal, brachiocephalic, subclavian and carotid arteries). According to one embodiment of the invention, one or more sensors, which can be signal devices (e.g., magnetically sensitive, electrically conductive sensing coils, which can be referred to as antenna coils), are coupled to a prosthesis delivery catheter through a flexible member that allows the signal device(s) to move relative to the catheter.
In the case of magnetically sensitive, electrically conductive sensing coils, the coil positions can be located by determining the positions of the coils relative to a plurality of magnetic field sources of known location. Pre-specified electromagnetic fields are projected to the portion of the anatomical structure of interest (e.g., that portion that includes all prospective locations of the coils in a manner and sufficient to induce voltage signals in the coil(s). Electrical measurements of the voltage signals are made to compute the angular orientation and positional coordinates of the sensing coil(s) and hence the location of the vasculature and/or devices of interest. An example of sensing coils for determining the location of a catheter or endoscopic probe inserted into a selected body cavity of a patient undergoing surgery in response to prespecified electromagnetic fields is disclosed in U.S. Pat. No. 5,592,939 to Martinelli, the disclosure of which is hereby incorporated herein by reference in its entirety. Another example of methods and apparatus for locating the position in three dimensions of a sensor comprising a sensing coil by generating magnetic fields which are detected at the sensor is disclosed in U.S. Pat. No. 5,913,820 to Bladen, et al., the disclosure of which is hereby incorporated herein by reference in its entirety.
Referring to
One or more sensors (S1, S2 . . . Sn) are suspended from tapered tip 106. Further, one or more sensors (Sa, Sb . . . Sn) are coupled to the tapered tip and can be secured to or embedded in the tapered tip as will be described in more detail below. Alternatively, sensors (Sa, Sb . . . Sn) can be coupled to the catheter sheath or guidewire lumen along the distal portion of the catheter sheath adjacent to the tapered tip.
When the prosthesis to be delivered is a self-expanding graft or stent-graft (such as stent-graft 200 shown in
Referring to
In the embodiment shown in
Although the flexible members are each shown with three sensors, the number of sensors can vary. For example, a single sensor can be provided at each flexible member feeler end. However, three sensors suspended along a respective flexible member as shown in
In the illustrative embodiment of
Referring to
Each flexible member 116a and 116b can be made from shape memory material and provided with a preshaped memory set configuration such as the configuration shown in
Any suitable electromagnetic field generating and signal processing circuit for locating sensor position in three dimensions can be used (see e.g., U.S. Pat. No. 5,913,820 to Bladen, et al. (supra) regarding magnetically sensitive, electrically conductive sensing coils (e.g., antenna coils)). Referring to
Circuit 300 generally includes three electromagnetic field (EMF) generators 302a, 302b, and 302c, amplifier 304, controller 306, measurement unit 308, and display device 310. Each field generator comprises three electrically separate coils of wire (generating coils) wound about a cuboid wooden former. The nine generating coils are separately electrically connected to amplifier 304, which is able, under the direction of controller 306, to drive each coil individually.
In use, controller 306 directs amplifier 304 to drive each of the nine generating coils sequentially. Once the quasi-static field from a particular generating coil is established, the value of the voltage induced in each sensing coil (S1-S6) by this field is measured by the measurement unit 308, processed and passed to controller 306, which stores the value and then instructs the amplifier 304 to stop driving the present generating coil and to start driving the next generating coil. When all generating coils have been driven, or energized, and the corresponding nine voltages induced into each sensing coil have been measured and stored, controller 306 calculates the location and orientation of each sensor relative to the field generators and displays this on a display device 310. This calculation can be carried out while the subsequent set of nine measurements are being taken. Thus, by sequentially driving each of the nine generating coils, arranged in three groups of three mutually orthogonal coils, the location and orientation of each sensing coil can be determined.
The sensor and generating coil specifications, as well as the processing steps are within the skill of one of ordinary skill of the art. An example of coil specifications and general processing steps that can be used are disclosed in U.S. Pat. No. 5,913,820 to Bladen, et al., the disclosure of which is hereby incorporated herein by reference in its entirety.
Referring to
Prior to the surgical procedure, the patient is scanned using either a CT or MRI scanner to generate a three-dimensional model of the vasculature to be tracked. Therefore, the aorta and branch vessels of interest (e.g., renal arteries) can be scanned and images taken therealong to create a three-dimensional pre-procedural data set for that vasculature and create a virtual model upon which real-time data will be overlayed. This information is stored in the system and is identified and accessible as a historical baseline image. Any portion of the aorta or branch vessels can be provided with fiducial markers (anatomic markers which are considered to provide a reliable reference to a particular body location) that are visible on the pre-procedural images and accurately detectable during the procedure as is known in the art.
The three magnetic field generators are positioned on the operating table to facilitate triangulation of the exact position of each sensor in three-dimensional space using xyz coordinates.
The patient is prepared for surgery and a cut is made down to a femoral artery and a guidewire (by itself or together with a guide catheter) inserted. A contrast agent catheter is delivered through the femoral artery and the vasculature perfused with contrast and a fluoroscopic image including the renal arteries taken. Using the fiducial markers, the processor orients or registers the previously acquired and stored three-dimensional image to the currently presented fluoroscopic X-ray image.
Referring to
The catheter is further advanced and the sensors reach the aneurysm's proximal neck as shown in
In the vicinity of the target location (e.g., the lower renal artery), which the operator can estimate based on the three-dimensional model and the sensor positions, the operator rotates and further advances the catheter to find the lower renal artery, which in this example corresponds to BV2. When a sensor indicates movement in a direction radial outward from tapered tip 106 that exceeds the expected position of the vessel wall, the operator can conclude that the renal artery has been found. Referring to
If the aorta was very tortuous, the catheter may have significantly changed the aorta's configuration during advancement therethrough. In this event, the surgeon has the option to take a fluoroscopic image to confirm the location of the renal artery.
Locating the upper and lower walls of the renal artery provides a guide for the location of the ostium of the renal artery and is related to fiducial markers already present in the anatomy, the stent-graft is positioned at the desired location relative to the three-dimensional model Since the position of the proximal end of stent-graft 200 relative to sensors Sa,b is known, the proximal end of the stent-graft can be positioned at the desired location relative to the renal artery. The catheter is advanced to align sensors Sa,b with S2 while monitoring these sensors on the display and then advances the catheter a distance slightly less than the distance between sensors Sa,b and the stent-graft to align the stent-graft with the proximal neck landing zone. Alternatively, one, two or more sensors can be coupled to the catheter sheath or inner surface of guidewire lumen 110 to indicate the exact position of the proximal end of the stent-graft. Once the stent-graft is in the desired position, the operator holds the guidewire tube 110 and pusher disk 120 stationary and retracts or pulls back sheath 103 (
Referring to
Referring to
Referring to
All catheters are then removed. A flow chart summary of the foregoing procedure is depicted in
The three-dimensional data points used in the procedure can increase accuracy of the surgery as compared to two-dimensional fluoroscopic images. The need for contrast agent also can be eliminated or minimized.
In another embodiment according to the invention, a self-contained proximity based system, which does not require external field generators, identifies when the distance between two or more markers or signal devices increases to indicate the position of a branch vessel such as a renal artery.
Referring to the illustrative example of
In this embodiment a signal or wave generating device or transmitter 528a is secured to the feeler end of flexible member 516a or in the vicinity thereof and a signal or wave generating device or transmitter 528b is secured to the feeler end of flexible member 516b or in the vicinity thereof. A conductor can extend from each signal transmitter along a respective flexible member to lead 540a, which extends from the distal end of the tapered tip and then is incorporated into lead bundle 540 where it extends through the guidewire lumen to a power source (not shown) to actuate signal generators 528a and 528b to generate analog RF or infrared electromagnetic signals or waves.
The embodiment illustrated in
Referring to
In a variation of system 500, signal device 530 can be a signal generator and signal devices 528a,b can be signal receivers. As in the embodiment of
Any of the foregoing embodiments also can be used to obtain three-dimensional data indicative of the opening of branch vessels (e.g. the renal arteries) in applications where there is insufficient proximal neck to anchor the proximal end of the stent-graft. In this case, the stent-graft is positioned across one or both of the branch vessels (e.g., renal arteries) and the acquired position data used to track a steerable piercing catheter having a sensor or signal device coupled to the distal end portion thereof so that the piercing catheter can be guided through the stent-graft and into the either or both branch vessel openings. Alternatively, the stent-graft can include one or more openings, each of which have a recorded position relative to the tapered tip sensor or signal device(s) or one or more sensors attached to the guidewire lumen as described above so that the position of the stent-graft openings can be virtually tracked along the three-dimensional model that has been updated to include the opening position(s).
Any feature described in any one embodiment described herein can be combined with any other feature of any of the other embodiments whether preferred or not.
Variations and modifications of the devices and methods disclosed herein will be readily apparent to persons skilled in the art.