Abstract:
An anchor for a medical implant, a method of manufacturing an anchor, and a delivery system and method for delivering a medical implant, such as for monitoring physiological parameters, for example, for diagnosing and/or monitoring and/or treating cardiovascular diseases, such as CHF and CHD. The anchor includes a base member, arms, legs, features for securing the medical implant to the base member, and features for connecting the anchor to a connector. The anchor has a deployed configuration in which the arms radially project from a first end of the base member and the legs radially project from an opposite end of the base member. When deployed, the arms and legs terminate at extremities that are opposing but not aligned with each other.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/780,604, filed Mar. 10, 2006, and is a continuation-in-part patent application of U.S. patent application Ser. No. 10/898,053, filed Jul. 24, 2004, now U.S. Pat. No. 7,317,951 which claims the benefit of U.S. Provisional Application Nos. 60/489,974, filed Jul. 25, 2003, and 60/491,002, filed Jul. 30, 2003. The contents of these prior applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to implantable medical devices and implant procedures, including devices and procedures used to monitor physiological parameters of the living (e.g., human) body. More particularly, the invention relates to anchors for a medical implant, methods of manufacturing anchors, and methods of placing medical implants, wherein the anchors and methods are suitable for use in procedures performed to diagnose, monitor, and/or treat cardiovascular diseases, including congestive heart failure (CHF) and congenital heart disease (CHD), for example, by monitoring pressures in the left side of the heart. 
     CHF is a condition in which the heart fails to pump efficiently, and currently affects about 4.7 million patients (over 400,000 new patients per year in the U.S.). Estimates are that CHF accounts for about 5 to 10% of all hospitalizations and costs over $38 billion in the U.S. Following diagnosis of CHF, physicians typically monitor disease progression on a continuing basis to better tailor treatment. The best course of action for a tailored treatment involves monitoring pressures of the left side of the heart, particularly left ventricular end diastolic pressure (LVEDP, also known as left ventricular filling pressure) and mean left atrium pressure (MLA). These pressures are recognized as the best parameters for characterizing CHF in patients. Clinical evaluation of LVEDP or MLA is currently limited to cardiac catheterization procedures, which provide a snapshot of pressure data a few times per year at most, carries morbidity, and is expensive. 
     CHD includes various defects of the heart that are typically present at birth. A particularly complex example is a heart that has only one functional ventricle. In order to provide patients with appropriate solutions, multiple surgical procedures are required. These procedures enable the single ventricle to serve as the systemic ventricle, while the lungs receive blood flow via different anastomosis (for example, a Fontan baffle). A key dilemma in the treatment of these patients is the timing of the different surgical stages. The inclination is to perform the surgeries at a younger age. However, if performed too early, the outcome can be dismal. The hemodynamic status and timing of the different surgical stages can be assessed by invasive cardiac catheterization to measure pulmonary artery pressure and resistance. However, as noted above with respect to monitoring CHF patients, cardiac catheterization provides only a single measurement in time and has been associated with morbidity and mortality in CHD patients. 
     Using an implant to monitor pressures of the left side of the heart is very challenging for many reasons, most importantly the potentially fatal outcome of any thrombi caused by the implant. Miniaturized sensors capable of being chronically implanted are gaining particular attention, especially those made produced by MEMS (microelectromechanical systems) technologies. Notable examples include devices disclosed in commonly-assigned U.S. Pat. Nos. 6,926,670 and 6,968,743, and commonly-assigned U.S. patent application Ser. Nos. 10/679,888, 10/679,916, 10/679,926, 10/677,674, and 10/677,694, which collectively have achieved significant advances for the use of implants in diagnosing, monitoring, and/or treating cardiovascular diseases. When adapted to monitor pressure, the devices disclosed in these patent documents generally have two primary components: the implant comprising an implantable telemetric pressure sensor that is batteryless or makes use of a small battery, and a companion hand-held reader. The implant further preferably includes custom electronics for processing the output of the sensor and an antenna for telemetry and, if necessary or desired, for tele-powering the sensor. Telemetry and tele-powering can be achieved via various techniques, including but not limited to magnetic telemetry (including RF), acoustic waves, ultrasonic waves, with the currently preferred technique typically being magnetic telemetry. The reader transmits power to the sensor, and the sensed pressure is in turn transmitted back to the reader. Data collected from the sensor can then be used by a physician to tailor the treatment of the patient. In some cases, the implant may also be configured or adapted to perform additional functions, such as delivering a drug or an electric signal to the muscles/nerves. 
     In view of the foregoing, it can be appreciated that miniaturized implants of the types described above can provide chronic, continuous bio-pressure measurements and support the trend toward home health monitoring. Advancements have also been achieved in regard to the delivery and anchoring of such medical implants within the heart for monitoring heart pressures. Notable examples include delivery and anchoring systems disclosed in commonly-assigned U.S. patent application Ser. No. 10/730,439 and U.S. Patent Application Publication No. 2005/0065589. Nonetheless, further improvements are desired, particularly in regard to the reliability and manufacturability of anchoring systems and the simplicity of their delivery. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an anchor for a medical implant, a method of manufacturing an anchor, and a delivery system and method for delivering a medical implant, such as for monitoring physiological parameters. The invention is particularly directed to implantation of physiologic sensors/actuators for diagnosing and/or monitoring and/or treating cardiovascular diseases, such as CHF and CHD. 
     The anchor of this invention includes a base member, a plurality of arms, a plurality of legs, a feature for securing the medical implant to the base member, and a feature for connecting the anchor to a connector. The base member has an axis and first and second ends in oppositely-disposed first and second directions, respectively, along the axis of the base member. The anchor has a deployed configuration in which the arms radially project from the first end of the base member, and the legs radially project from the second end of the base member. Each arm has a first portion extending in the first direction from the first end of the base member and a second portion extending in the second direction from the first portion thereof. Each leg has a first portion extending in the second direction from the second end of the base member and a second portion extending in the first direction from the first portion thereof. When deployed, the arms and legs terminate at extremities that are opposing but not aligned with each other. 
     A preferred method of manufacturing the anchor of this invention generally entails cutting a unitary body to form the base member, the arms, the legs, and the connecting means, and then deforming the arms, the legs, and the connecting means. 
     The delivery system of this invention includes a catheter assembly containing a catheter, an anchor, and a feature for connecting the anchor to the catheter. The anchor includes a base member with first and second ends in oppositely-disposed first and second directions, arms and legs extending from the base member, and a feature for securing the medical implant to the base member. The connecting feature includes a joint that enables articulating movement of the anchor relative to the catheter in directions transverse to an axis of the catheter. 
     The delivery method of this invention involves coupling an anchor to an end of a catheter and securing the medical implant to the anchor, passing the catheter with the anchor coupled thereto through a sheath, placing an end of the sheath through an internal wall of a human body so that the anchor is positioned within that portion of the sheath within the internal wall, retracting the sheath so as to release a plurality of arms from the anchor that engage a distal surface of the internal wall, and then further retracting the sheath so as to release a plurality of legs from the anchor that engage a proximal surface of the internal wall. 
     In view of the above, it can be seen that the present invention provides an uncomplicated anchor and procedure of placing a variety of implantable medical devices, including those adapted to monitor physiological parameters including pressures within the heart. The configuration of the anchor addresses delivery issues, including delivery method, delivery equipment, implant design, and anchor location, that arise when employing chronically implanted physiologic devices, sensors, and actuators to diagnose and/or monitor and/or treat cardiovascular diseases such as CHF and CHD. Notably, the anchor and its delivery find application in the very challenging application of monitoring the pressure of the left side of the heart. Medical implants that can be placed and anchored in accordance with this invention can operate wirelessly or can be connected to other devices (such as pacemakers) using electrical wires (e.g., pacemaker leads, polymer based flex cables, or wires) or other types of communications means (e.g., ultrasonic, optical, or electrophysiology signals). 
     Other objects and advantages of this invention will be better appreciated from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an implant delivery system in accordance with a first embodiment of this invention. 
         FIGS. 2 and 3  are isolated perspective views of an anchor of the implant delivery system of  FIG. 1 , showing the anchor in both stowed and deployed configurations, respectively. 
         FIG. 4  is an isolated perspective view of a positioning catheter of the implant delivery system of  FIG. 1 . 
         FIG. 5  is a perspective view of the implant delivery system of  FIG. 1 , showing the anchor and its implant retracted into a sheath in preparation for delivering the implant. 
         FIGS. 6 through 11  are perspective views representing procedural steps when placing the anchor and implant of  FIG. 1 . 
         FIG. 12  is a perspective view of an implant delivery system in accordance with a second embodiment of this invention. 
         FIGS. 13 and 14  are isolated perspective views of an anchor of the implant delivery system of  FIG. 12 , showing the anchor in both stowed and deployed configurations, respectively. 
         FIG. 15  is an isolated perspective view of a positioning catheter of the implant delivery system of  FIG. 12 . 
         FIG. 16  is a perspective view of the implant delivery system of  FIG. 12 , showing the anchor and its implant retracted into a sheath in preparation for delivering the implant. 
         FIGS. 17 through 22  are perspective views representing procedural steps when placing the anchor and implant of  FIG. 12 . 
         FIG. 23  is a perspective view representing a manipulator for use with the implant delivery systems of  FIGS. 1 through 22 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 12  depict delivery systems  10  and  100  suitable for delivering and securing a medical implant  12  to a wall, such as a wall of a cardiovascular organ, in accordance with embodiments of the present invention. As a notable example, the wall can be an atrial septum and the implant  12  measures physiological parameters of the heart, such as LVEDP or MLA pressure. The implant  12  may be any one of a variety of types of implants currently known or developed in the future, and the scope of the present invention is not limited in any way by the type and operation of the implant  12 . Implantable devices capable of being delivered with the present invention include but are not limited to devices disclosed in commonly-assigned U.S. Pat. Nos. 6,926,670 and 6,968,743, and commonly-assigned U.S. patent application Ser. Nos. 10/679,888, 10/679,916, 10/679,926, 10/677,674, and 10/677,694. 
     With reference first to the embodiment of  FIGS. 1 through 11 , the implant delivery system  10  is represented as including an anchor  14  in which an implant  12  is secured, a positioning catheter  16  to which the anchor  14  is coupled, and a sheath  18  in which the catheter  16  and its attached anchor  14  are telescopically received. As such, the anchor  14 , catheter  16 , and sheath  18  are all generally coaxial. In the preferred embodiment, the positioning catheter  16  is hollow to enable fluids to be delivered to or removed from the deployment site of the anchor  14 . The sheath  18  can be of any suitable type known in the art or subsequently developed. 
     The anchor  14  is depicted in  FIG. 1  in what will be termed a stowed configuration, meaning the configuration of the anchor  14  while within the sheath  18  ( FIG. 5 ). The stowed configuration is also depicted in the isolated view of the anchor  14  in  FIG. 2 . In contrast,  FIG. 3  depicts the anchor  14  in a deployed configuration, meaning the configuration of the anchor  14  when extended outside the sheath  18  so that appendages of the anchor  14  are allowed to deploy, as described below. As such, though  FIG. 1  shows the anchor  14  in its stowed configuration for illustrative purposes, the position of the anchor  14  outside the sheath  18  would ordinarily result in the deployed configuration shown in  FIG. 3 . 
     In  FIGS. 1 through 3 , the anchor  14  is shown as having an annular-shaped base  20  surrounding the implant  12 . The base  20  has oppositely-disposed first and second ends  22  and  24  corresponding to oppositely-disposed first and second directions along the axis of the base  20 . For convenience, these directions will be referred to as distal and proximal directions, and various structures of the system  10  including the ends  22  and  24  of the base  20  will be described as being distal or proximal, to reflect the orientation of the anchor  14  during an implantation procedure described below, though it should be understood that the invention is not necessarily limited to such an orientation. When stowed ( FIGS. 1 and 2 ), arms  26  and legs  28  extend substantially parallel to the axis of the base  20  from its distal and proximal ends  22  and  24 , respectively. When deployed ( FIG. 3 ), the arms  26  and legs  28  acquire arcuate shapes that preferably lie entirely within angularly spaced radial planes, each containing the axis of the base  20 . The deployed arms  26  generally deploy in the proximal direction to project substantially radially from the base  20 , with a first portion  30  of each arm  26  generally extending in the distal direction from the distal end  22  of the base  20 , and a second portion  32  of each arm  26  generally extending in the proximal direction from the first portion  30 . Each second portion  32  terminates with an extremity or tip  34 , which is generally parallel to the axis of the base  20 , radially offset from the axis. Similarly, each deployed leg  28  projects substantially radially from the base  20 . However, the legs  28  generally deploy in the distal direction (opposite that of the arms  26 ), with a first portion  36  of each leg  28  generally extending in the proximal direction from the proximal end  24  of the base  20 , a second portion  38  of each leg  28  generally extending in the distal direction from its corresponding first portion  36 , and each second portion  38  terminating with an extremity or tip  40  that is generally parallel to but radially offset from the axis of the base  20 . In addition to their direction of deflection, the legs  28  differ from the arms  26  by having a third portion  42  between its second portion  38  and tip  40 , and generally oriented radially relative to the axis of the base  20 , necessitating an additional curve to each leg  28  to orient the tip  40  substantially parallel to the axis of the base  20 . 
     As evident from  FIGS. 1 through 3 , each arm  26  and leg  28  lies in a different radial plane, with the result that the arms  26  and legs  28  are not collinear when stowed and their tips  34  and  40  do not directly oppose each other when deployed, such that a wall into which the anchor  14  is inserted would not be locally compressed by directly opposing arms  26  and legs  28 , as will become evident from  FIG. 11 . Furthermore, the tips  34  and  40  of the arms  26  and legs  28  are capable of piercing a wall in which the anchor  14  is placed, so that the tips  34  and  40  can become embedded in the wall without puncturing the wall. In this manner, the arms  26  and legs  28  cooperate to secure the anchor  14  to a wall (as represented in  FIG. 11 ), so that the anchor  14  is able to resist axial and rotating forces that might dislodge the anchor  14  and its implant  12 . Furthermore, the minimized compressive forces applied by the anchor  14  to the septum of a heart is believed to reduce tissue killed after implantation. The configurations of the arms  26  and legs  28  and their opposing actions also accommodate walls of differing thicknesses. 
       FIGS. 1 through 3  further show the anchor  14  as having retention legs  44  that extend from the proximal end  24  of the base  20  in the proximal direction and parallel to the axis of the base  20 . Each retention leg  44  terminates with a finger  46  that extends radially inward toward the axis of the base  20 . At the distal end  22  of the base  20 , fingers  48  extend radially inward from the circumference of the base  20 . As evident from  FIG. 1 , together the base  20 , retention legs  44 , and fingers  46  and  48  define a cage for the implant  12 , with opposite ends of the implant  12  abutting the fingers  46  and  48 . The implant  12  can be placed within the cage through openings defined by the base  20  or retention legs  44 , and then retained by crimping the appropriate fingers  46  or  48  over the opening. Preferably, the implant  12  is inserted through the base  20  and retained by crimping the base fingers  28 , and the length of the retention legs  44  are sized so that their fingers  46  provide a spring load to positively retain the implant  12  within the cage, so that pulsation effects of the heart or blood flow do not cause movement of the implant  12  that might lead to potentially false signal data. While a cylindrical implant  12  is shown in  FIG. 1 , the functionality of the anchor  14  is not dependent on any particular type of implant, and can be readily adapted to secure a variety of different types of implants with different sensing technologies. Furthermore, though fingers  46  and  48  are preferred for retaining the implant  12 , it should be appreciated that retention of the implant  12  in the anchor  14  can be accomplished in different ways, including without limitation one, more, or any combination of the following methods: cam slot, threading, snapping, snap latch, latch fingers, spring latch, latch fingers with a catheter sheet on top to release the latch, use of one or more guidewires or catheters in order to either latch or release coupling means (such as latching fingers), dissolvable glues, temporary glues, thermal glues, heated shape memory latches, unheated shape memory latches, heated mechanical means, piezoelectric release system, hydraulic coupling systems, pneumatic coupling systems, magnetic coupling systems, etc. 
     As further evident from  FIGS. 1 and 2 , the tips  40  of the legs  28  are configured to couple with a connector  50  when in their stowed position. The connector  50  has a tubular shape sized to be received and secured in the end of the positioning catheter  16 . As shown in  FIG. 4 , the connector  50  is formed to have slots or windows  52  corresponding in number to the legs  28  and sized to receive the tips  40  of the legs  28 . By using the sheath  18  to hold the tips  40  of the legs  28  in their respective windows  52 , as is the case when the positioning catheter  16  and anchor  14  are disposed within the sheath  18  ( FIG. 5 ), the anchor  14  is secured to the catheter  50  through its connector  50 , but can be quickly released by retracting the sheath  18  to expose the legs  28  and thereby release the leg tips  40  from their windows  52 . Another desirable feature of the leg-connector coupling scheme described above is that the tips  40  and windows  52  do not form a rigid joint, but instead create an articulating joint in that the anchor  14  has some freedom of movement in directions transverse to the axis of the catheter  16 . This aspect of the invention facilitates threading the catheter assembly (catheter  16  and anchor  14 ) through a patient&#39;s arterial system. 
     According to a preferred aspect of the invention, the entire anchor  14  can be fabricated as a unitary body, and therefore without resorting to any assembly techniques involving metallurgical joining (e.g., welding, brazing, etc), mechanical joining (e.g., fasteners, threads, latches, deformation, etc.), or bonding (e.g., adhesive), though such assembly methods are within the scope of the invention. As such, the entire anchor  14  can be fabricated from a single preform, such as by cutting the preform to form the base  20 , arms  26 , and legs  28  and  44 , and then deforming the base  20 , arms  26 , and legs  28  and  44  as required to form the anchor  14  shown in  FIGS. 1 through 3 . 
     Many existing medical implantable devices for use in the heart utilize NITINOL®, a “shape memory” nickel-titanium alloy that enables an umbrella-like structure folded inside a catheter for delivery to later automatically expand once outside the catheter for implantation. In a preferred embodiment, the anchor  14  is formed of NITINOL or another suitable shape memory material. According to another preferred aspect, the anchor  14  can be manufactured primarily by laser cutting techniques performed on solid tubes of a shape memory material, rather than primarily using welding techniques as typically done in the prior art. Fabrication of the anchor  14  using laser cutting techniques provides at least two advantages. First, the reliability of the anchor  14  is much higher since its components (base  20 , arms  26 , and legs  28  and  44 ) are integral portions of a single metal piece. Welded joints possess higher risk of failure than that possible with the preferred unitary construction for the anchor  14 . Secondly, the cost of manufacturing can be significantly lower than would be possible if relying primarily on welding to form the anchor  14 . 
     In practice, a NITINOL tube can be cut by laser alone to form an anchor preform. The laser cutting operation can be performed as an automated process based on drawing files using commercial mechanical design software. The tubular-shaped anchor preform is then formed into the desired 3-D structure (i.e., the deployed configuration of  FIG. 3 ) with shape memory by being placed in a mechanical jig and heated to an appropriate temperature to store the shape into the memory of the NITINOL material. After its fabrication, the anchor  14  preferably undergoes chemical passivation in order to reduce the corrosion tendencies of NITINOL in body fluids, and then coated with a suitable biocompatible coating such as parylene. 
     A key parameter of any wireless, implantable system is the communication distance (both tele-powering and telecommunication) between the implant  12  and a remote readout handheld unit. Since the anchor  14  may be formed of a metal such as NITINOL, there exists a potential that such a metallic anchor could adversely affect (reduce) the communication distance between the implant  12  and the handheld unit (not shown) by acting similar to a Faraday cage. Tests performed using metal implants indicated that telemetry communication distances can be reduced by about two-thirds, such that placing an implant using RF/electromagnetic telemetry inside a metal anchor would not be expected to achieve reasonable performance. To overcome this problem, the anchor  14  is configured to avoid the primary causes of reduced communication distances. Attenuation was determined to depend on parameters including the number of metal loops, the orientation of the loops, and whether the loops are arranged in such a manner as to form a mesh or cage. Fewer numbers of metal loops were associated with longer communication distances. Furthermore, metal loops that are arranged in parallel to the implant communication coil (with or without a ferrite core) were found to not adversely affect the communication distance, while metal wires oriented perpendicular to the implant communication coil (with or without a ferrite core) were found to greatly reduce such magnetic fields. The anchor  14  of the present invention comprises a single loop (the base  20 ) which does not form a mesh and is limited to one end of the implant  12 . In the embodiment shown in  FIGS. 1 through 3 , the anchor  14  makes satisfactory use of only six arms  26  and six legs  28 , none of which lie within the same radial plane. Furthermore, from  FIG. 1  it can be appreciated that the size of the cage enclosing the implant  12  and each element (base  20 , retention legs  44 , and fingers  46  and  48 ) forming the cage is minimized and their locations selected (including the base  20  limited to one end of the implant  12 ) so that signals (e.g., data transmission and/or powering) received and transmitted by the implant  12  suffer minimal attenuation. As such, the configuration of the anchor  14  minimizes metal shielding effects, which is beneficial if the implant  12  is wirelessly operated, such as by radio frequency (RF) telemetry, and renders the anchor  14  of this invention practical for use with small implants across long communication distances. The low-profile configuration of the anchor  14  also minimizes the diameter required of the sheath  18  used to delivery the anchor  14  and implant  12 , and advantageously results in the anchor  14  exerting minimal stress on the implant  12 . 
     The anchor  14  may be employed to locate the implant  12  in various places, depending on the physiological parameter of interest. For the tailored treatment of chronic heart failure, LVEDP and/or MLA pressure are of most importance, and therefore the left chambers of the heart or immediately attaching vessels are among preferred locations for the implant  12 . Because the number of implants is not practically limited by the technology, multiple locations for blood pressure measurement are easily established, including all chambers of the heart, major arteries and appendages. The preferred waveforms to monitor for CHF applications are the pressures of the left atrium. The monitored waveforms may include but not limited to complete detailed LA waveform, particularly accurate MLA pressure, real time, and continuous. It should be mentioned that some aspects of the anchor  14  described above will allow pressure measurements of the right atrium (by locating the pressure sensor at the end of the implant  12  facing the right atrium) or both right and left atriums (for example, using two pressure sensors, one at each end of the implant  12 ), or direct differential pressure measurement between the right and left atrium (again, for example, using two pressure sensors, one at each end of the implant  12 ). In addition to or instead of pressure, other parameters can easily be monitored using an implant delivered and placed with the anchor  14 . Such parameters include but are not limited to blood chemistry, oxygen level, etc. For example, a hydrogel film (with selectivity to different elements) can be placed on top of a pressure sensor to measure the presence of elements that cause the hydrogel to expand, thereby applying pressure to the pressure sensor. 
     Thrombogenicity is the primary concern when considering a device for implantation in the left side of the heart, due to the possibility of thrombi reaching the brain. In order to assure such high-level of nonthrombogenicity, the present invention is able to reduce such risks through proper anchor shape, anchor location, and delivery method. Thrombogenesis can be caused by direct chemical interaction with an implant or anchor, and by blood flow turbulence resulting from implant geometry. Regarding the former, the above-noted materials for the anchor  14  are selected to be either biocompatible or covered by biocompatible materials. As to the latter, the present invention provides an anchor configuration and placement capability that greatly reduces protrusion of the implant  12  and anchor  14  into the blood flow path of the left atrium to a minimum level, and also provides a hydrodynamic sensor profile that is minimally disruptive to surrounding blood flow. The implant  12  can be preferably placed with the anchor  14  of this invention at two desirable locations: the atrial septum and left atrial appendage. The atrial septum is believed to be preferable for locating the anchored implant  12 . It should be emphasized that, while the implant may be long length (e.g., lengths greater than ten millimeters), the anchor  14  is configured so that only a small portion (e.g., less than two millimeters) of the implant  12  is exposed to the left side of the heart; the rest of the implant  12  is in the septum wall and the right atrium. The pressure sensor is placed at or near the end side of the implant  12  that is exposed to the left side. A preferred location for the pressure sensor is believed to be on the front flat side of the cylindrical implant  12  shown in the Figures, so that only a small portion of the implant  12  will be above the surface of the left side of the heart. Subsequent cell growth over the top of the small exposed area of the implant  12  will further reduce the risk of thrombogenicity. 
     If placed in the atrial appendage, the implant  12  may be anchored by expanding the anchor  14  and then occluding the appendage. In this case, thrombi formation on the distal end (opposite from sensor) of the occlusion device would not pose a risk to the patient, as evidenced by previous left atrial appendage devices that have been introduced for this very purpose. 
     A reason for preferring placement in the atrial septum is that there exists FDA-approved, commercially-available medical devices for chronic implantation in this location. These devices, for example, are used to occlude atrial septum defects and other vascular holes. The implant  12  can be anchored to the atrial septum with similar techniques as FDA-approved, commercially-available devices such as the AMPLATZER® family of devices commercially available from AGA Medical, or the CardioSEAL commercially available from NMT Medical. These devices have been shown to be suitable for cardiovascular implantation. As a result, one may take advantage of this existing infrastructure, including standard practices of delivering cardiovascular implants. Another advantage of placing the implant  12  within the wall of the atrial septum is that the potential adverse confounding effects of the muscle contraction on the sampled pressure measurements will be considerably reduced. 
     Delivery of the implant  12  with the anchor  14  demands such considerations as safety, minimal invasiveness, suitability as an outpatient procedure, ease of operation, preferable use of existing practices, minimum training for the physician/technician, and the ability to allow multiple tries before deploying and releasing the anchor  14 . As evidenced by  FIG. 1 , the preferred delivery method for the anchor  14  is believed to be by catheter delivery, discussed below in more detail with reference to  FIGS. 6 through 11 . To minimize catheter diameter, the implant  12  is preferably small and thin. Delivery and placement of the anchor  14  is able to make use of standard current practices in the cardiovascular field to reduce both time and cost of R&amp;D and manufacturing, create comfort and confidence in cardiologists, and make FDA process easier. The anchor  14  is configured so that, after it is coupled to the connector  50  of the positioning catheter  16  are placed in the sheath  18 , the diameter of the stowed anchor  14  is equal or as close as possible to the diameter of the original tube from which the preform was laser cut. This approach renders the smallest possible diameter of the catheter  16  and sheath  18 . 
       FIGS. 6 through 11  represent a series of steps depicting the procedure for delivering and implanting the anchor  14  and its implant  12  in a wall, such as the atrial septum  54 . Using a standard cardiology guidewire via a standard procedure (not shown), the sheath  18  is passed through a patient&#39;s arterial system and placed through the atrial septum  54 , after which the catheter  16  with its anchor  14  and implant  12  are passed through the sheath  18  until located within the distal end of the sheath  18  as shown in  FIG. 6 .  FIG. 7  depicts the result of slight retraction of the sheath  18  to the extent that the arms  26  of the anchor  14  are released from the sheath  18  and the shape-memory property of the anchor material causes the arms  26  to deploy in the proximal direction so that the tips  34  of the arms  26  engage and become embedded in the distal surface of the septum  54 . The sheath  18  is then further retracted as sequentially depicted in  FIGS. 8 and 9 , with the latter showing the sheath  18  sufficiently retracted to expose the entire lengths of the legs  28 . As with  FIG. 1 , though  FIG. 9  shows the legs  28  of the anchor  14  in their stowed positions for illustrative purposes, the location of the legs  28  outside the sheath  18  immediately leads to the deployed configuration shown in  FIG. 10 . As with the arms  26 , deployment of the legs  28  results from the shape-memory property of the anchor material causing the tips  40  of the legs  28  to move radially outward and disengage the windows  52  of the connector  50 , and then arcuately travel in the distal direction to engage and become embedded in the proximal surface of the septum  54 . Importantly, because the arms  26  and legs  28  are not collinear when stowed, the tips  34  and  40  of the arms  26  and legs  28  do not directly oppose each other when deployed. Finally, disengagement of the leg tips  40  from the connector  50  uncouples the anchor  14  from the connector  50 , as evident from  FIG. 10 , so that the sheath  18  and positioning catheter  16  can be withdrawn together to leave the sensor  12  implanted in the septum  54  with the anchor  14  as depicted in  FIG. 11 . 
     The delivery system  100  represented in  FIG. 12  is illustrated in  FIGS. 12 through 22  in a manner corresponding to  FIGS. 1 through 11  for the deliver system  10  of  FIG. 1 . In  FIGS. 12 through 22 , consistent reference numbers are used to identify functionally similar structures, but with a numerical prefix (1) added where appropriate to distinguish the embodiment from the previous embodiment of the invention. Because of the commonality of the delivery systems  10  and  100 , only differences between the embodiments will be discussed in any detail, and the detailed description of the delivery system  10  is otherwise incorporated by reference into the following discussion of the delivery system  100 . 
     As evident from comparing  FIGS. 1 through 5  to  FIGS. 12 through 16 , the construction of the delivery system  100  ( FIG. 12 ), the stowed and deployed configurations of its anchor  114  ( FIGS. 13 and 14 , respectively), and the release actions of its arms  126  ( FIG. 14 ) are similar to that for the delivery system  10  of  FIGS. 1 through 11 . The most notable differences between the delivery systems  10  and  100  involve their legs  28  and  128 , including their configurations, the manner in which they connect to their respective connectors  50  and  150 , and the manner in which the legs  28  and  128  deploy. With regard to the last item, whereas the legs  28  of the delivery system  10  deploy primarily by continuously traveling along a substantially arcuate route toward the distal end of the anchor  14 , the legs  128  of the delivery system  100  shown in  FIGS. 12 through 22  have a compound deployment action, in which the legs  128  initially spread radially ( FIGS. 19 and 20 ) and then travel axially in the distal direction until the tips  140  of the legs  128  engage and become embedded in the septum  54  ( FIG. 21 ). 
     The embodiment of  FIGS. 12 through 22  is represented as achieving the above by reconfiguring the legs  128  and connector  150  as shown in  FIGS. 12 through 15 . As evident from  FIGS. 12 ,  13 , and  14 , the legs  128  are configured to have three primary sections: a first portion  136  that generally extends in the proximal direction from the proximal end  124  of the base  120 , a tab  142  at the proximal end of each first portion  136 , and a second portion  138  that extends from the tab  142  in the distal direction. Each first portion  136  is represented as being formed by two parallel bands spaced apart to define a slot  137  within which the corresponding second portion  138  is entirely received when the anchor  114  is in its stowed configuration ( FIGS. 12 and 13 ). Each tab  142  defines a junction that interconnects its corresponding first and second portions  136  and  138 . As evident in  FIG. 14 , the tab  142  serves as a base from which the first and second portions  136  and  138  extend and diverge to define a V-shaped cross-section in a plane coinciding with a radial of the base  120 . Each second portion  138  terminates with an extremity or tip  140 . All members  136 ,  137 ,  138 ,  140 , and  142  of the legs  128  are generally parallel to but radially offset from the axis of the base  120 . As with the previous embodiment, the arms  126  and the second portions  138  of the legs  128  are not collinear when stowed. 
     Each tab  142  defines a circumferentially-extending flange  143  sized and shaped to be received in a slot  152  on the connector  150 , so that axial movement of the anchor  114  relative to the connector  150  is prevented when the anchor  114  is in its stowed configuration ( FIGS. 12 and 13 ). By using the sheath  18  to hold the flanges  143  of the legs  128  in their respective slots  152 , as is the case when the positioning catheter  16  and anchor  114  are disposed within the sheath  18  ( FIG. 16 ), the anchor  114  is secured to the catheter  16  through its connector  150 , but can be quickly released by retracting the sheath  18  to expose the legs  128  and thereby release the flanges  142  from their windows  152 . 
     As evident from  FIGS. 13 and 15 , the connector  150  is an assembly that includes an articulating extension  154  coupled to a tubular base  156  by a number of fingers  158  (for example, by engaging the fingers  158  with windows in the base  156 , corresponding to the windows  52  of the connector  50  in  FIG. 4 ). As with the previous embodiment, this leg-connector coupling scheme does not form a rigid joint, but instead creates an articulating joint in that the extension  154  (and therefore the anchor  114  mounted to the extension  154 ) has some freedom of movement in directions transverse to the axis of the positioning catheter  16 . 
     As with the first embodiment, the anchor  114  further includes retention legs  144  that extend from the proximal end  124  of the base  120  in the proximal direction and parallel to the axis of the base  120 , with each retention leg  144  terminating with a finger  146  that extends radially inward toward the axis of the base  120 . In combination with fingers  148  at the distal end  122  of the base  120 , the base  120 , retention legs  144 , and fingers  146  define a cage for the implant  12 , with opposite ends of the implant  12  abutting the fingers  146  and  148 . Placement of the implant  12  within the cage can be achieved in the same manner as described for the first embodiment. 
       FIGS. 17 through 22  represent a series of steps depicting the procedure for delivering and implanting the anchor  114  and implant  12  in the atrial septum  54  (or other suitable wall). The procedure is similar to that described for the first embodiment, with the sequence of  FIGS. 17 through 22  generally corresponding in sequence to that of  FIGS. 6 through 11 , respectively. As such, after the sheath  18  is passed through a patient&#39;s arterial system and placed through the atrial septum  54 , the catheter  16  with its anchor  114  and implant  112  are passed through the sheath  18  until located within the distal end of the sheath  18  as shown in  FIG. 17 .  FIG. 18  depicts the sheath  18  as having been sufficiently retracted to deploy the arms  126 , resulting in the tips  134  of the arms  126  engaging and becoming embedded in the distal surface of the septum  54 . The sheath  18  is then further retracted as sequentially depicted in  FIGS. 19 and 20 , with the former showing only the second portions  138  of the legs  128  being deployed as a result of moving radially outward.  FIG. 20  shows the sheath  18  as sufficiently retracted to expose the entire lengths of the legs  128 , though with the legs  128  remaining in their stowed positions for illustrative purposes. The transition between  FIGS. 20 and 21  evidence that the sheath  18  has released the first portion  136  and tab  142  of each leg  128 , resulting in their radially outward movement to decouple the flanges  143  from their corresponding slots  152  in the connector  150 . In addition,  FIG. 21  shows the legs  128  as having traveled in the distal direction, causing the tips  140  of the legs  128  to engage and become embedded in the proximal surface of the septum  54 . Importantly, because the arms  126  and legs  128  are not collinear when stowed, the tips  134  and  140  of the arms  126  and legs  128  do not directly oppose each other when deployed. Finally, disengagement of the leg flanges  143  from the connector  150  uncouples the anchor  114  from the connector  150 , as evident from  FIG. 21 , so that the sheath  18  and positioning catheter  16  can be withdrawn together to leave the sensor  12  implanted in the septum  54  with the anchor  114  as depicted in  FIG. 22 . 
       FIG. 23  represents a manipulator  60  for use with the implant delivery systems  10  and  100  of  FIGS. 1 through 22 . The manipulator  60  functions to lock the positioning catheter  16  and sheath  18  together to precisely maintain their axial alignment. A rotational actuator ring  62  is coupled to the sheath  18  and provides precise control of the relatively small axial movements performed by the sheath  18 , which in turn controls the deployment of the arms  26  and  126  and legs  28  and  128  of the anchors  14  and  114 . The actuator ring  62  preferably operates with detents that provide tactile feel feedback to the operator, such that the operator is better informed of the relative positions of the catheter  16  and sheath  18  without visually checking. The handle  64  of the manipulator  60  enables the operator to have positive rotational control of the entire delivery system  10  or  100 , such that the manipulator  60  has both rotational and axial control of the anchors  14  and  114  while threading the delivery systems  10  and  100  through a patient&#39;s arterial system. Finally, the manipulator  60  further includes a fluid port  66  at the end of the handle  64  to enable fluid insertion and withdrawal through the hollow positioning catheter  16 . 
     In view of the manner in which the anchors  14  and  114  are coupled to their connectors  50  and  150  as described above, the operator has the option to retry placing the anchors  14  and  114  and their implants  12  any number of times before deploying the arms  26  and  126  and legs  28  and  128  and final detachment of the anchors  14  and  114  from their catheter  16  by retracting the sheath  18 . The preferred use of a single catheter  16  and single sheath  18  is believed to be uncomplicated and readily within the skills of the ordinary cardiologist. 
     In addition to the delivery and anchoring of wireless implanted medical devices, the anchors  14  and  114  and delivery methods of this invention can be utilized for non-wireless applications. For example, a pressure sensor (or any other type of sensor) located in the left atrium (or elsewhere) can be provided with a communication connection to other medical devices (such as, but not limited to, pacemakers) from the right atrium side of the anchor/implant. Potential communication connections include, but are not limited to, electrical wires, pacemaker leads, flexible cables, optical connectors, ultrasonic pads, and electrophysiology signals. Hermetic electrical connection pads (instead of or in addition to a pressure sensor) can be provided from inside the implant  12  to its exterior. Such pads can be used to provide electrical connections to other medical devices, e.g., pacemakers, or provide electrical connections to other sensors (e.g., blood chemical sensors), which are made independently of implant  12  and anchors  14  and  114 . Preferred locations for these pads are believed to be either of the flat ends of the cylindrical implant  12  shown in the Figures, for locating the pads in the left side, right side, or both sides of the heart. 
     While the invention has been described in terms of preferred embodiments, it is apparent that other forms could be adopted by one skilled in the art. Therefore, the scope of the invention is to be limited only by the following claims.