Abstract:
An implantable, self-contained, user-attachable or detachable telemetry module plugs into an implantable medical device to provide or supplement one or more telemetry functions needed by a patient having certain health conditions. A user-attachable or detachable telemetry module allows a user, such as a physician or other care provider, to select a telemetry module and attach it to a medical device. Various types of telemetry are implemented as various user-attachable or detachable telemetry modules, each providing one or more telemetry functions suitable for a particular patient whose condition imposes a particular demand on telemetry. A care provider selects a user-attachable or detachable telemetry module most suited for the particular patient, which improves healthcare cost efficiency. One example of user-attachable or detachable telemetry module includes a radio-frequency (RF) transmitter-receiver circuit module and a lead carrying an antenna. In one example, the circuit module is away from the implantable medical device and coupled to the implantable medical device through the lead. In another example, the circuit module directly attaches to the implantable medical device.

Description:
TECHNICAL FIELD  
         [0001]    The present system relates generally to implantable medical devices and particularly, but not by way of limitation, to such a device including a telemetry system allowing communication with an external device.  
         BACKGROUND  
         [0002]    Medical devices are implanted in human bodies to perform tasks including, for example, monitoring physiological conditions, diagnosing diseases, treating diseases, or restoring functions of organs or tissues. Examples of such implantable medical devices include cardiac rhythm management systems, neurological stimulators, neuromuscular stimulators, and drug delivery systems. Because such a device may be implanted in a patient and typically remain therein for a long time, even up to the patient&#39;s life expectancy, the size and power consumption of the device are inherently constrained. Consequently, an implantable device may depend on an external system to perform certain functions. A function of a device providing communication between the implantable device and the external system is referred to as telemetry. Examples of specific telemetry functions include programming the implantable device to perform certain monitoring or therapeutic tasks, extracting an operational status of the implantable device, transmitting real-time physiological data acquired by the implantable device, and extracting physiological data acquired by and stored in the implantable device.  
           [0003]    In certain instances, the patient&#39;s health condition may determine the amount of telemetry activity between the implantable device and the external system. For example, an implantable device stabilizing a body function of an already stable patient may need infrequent telemetry during follow-ups. However, an implantable device worn by a very ill patient to treat an unstable, life-threatening condition may need frequent telemetry for monitoring and/or device-reprogramming. The amount of telemetry activity also depends on the type of the implantable device. A self-contained device performing relatively simple tasks may require only infrequent check-ups. A device performing complicated tasks, such as frequent real-time data processing, may require access to an external system having computing capabilities required for the task. Such a device may require frequent or even continuous telemetry.  
           [0004]    One particular example of implantable medical devices is a cardiac rhythm management device implanted in a patient to treat irregular or other abnormal cardiac rhythms by delivering electrical pulses to the patient&#39;s heart. Such rhythms result in diminished blood circulation. Implantable cardiac rhythm management devices include, among other things, pacemakers, also referred to as pacers. Pacers are often used to treat patients with bradyarrhythmias, that is, hearts that beat too slowly or irregularly. Such pacers may coordinate atrial and ventricular contractions to improve the heart&#39;s pumping efficiency. Implantable cardiac rhythm management devices also include devices providing cardiac resynchronization therapy (CRT), such as for patients with congestive heart failure (CHF). CHF patients have deteriorated heart muscles that display less contractility and cause unsynchronized heart contraction patterns. By pacing multiple heart chambers or sites, CRT device restores a more synchronized contraction of the weakened heart muscle, thus increasing the heart&#39;s efficiency as a pump. Implantable cardiac management devices also include defibrillators that are capable of delivering higher energy electrical stimuli to the heart. Such defibrillators may also include cardioverters, which synchronize the delivery of such stimuli to portions of sensed intrinsic heart activity signals. Defibrillators are often used to treat patients with tachyarrhythmias, that is, hearts that beat too quickly. In addition to pacers, CRT devices, and defibrillators, implantable cardiac rhythm management systems also include, among other things, pacer/defibrillators that combine the functions of pacers and defibrillators, drug delivery devices, and any other implantable systems or devices for diagnosing or treating cardiac arrhythmias.  
           [0005]    Typically, an implantable cardiac rhythm management device communicates, via telemetry, with an external device referred to as a programmer. One type of telemetry is based on inductive coupling between two closely-placed coils using the mutual inductance between these coils. This type of telemetry is referred to as inductive telemetry or near-field telemetry because the coils must typically be closely situated for obtaining inductively coupled communication.  
           [0006]    In one example, an implantable device includes a first coil and a telemetry circuit, both sealed in a metal housing (referred to as a “can”). An external programmer provides a second coil in a wand that is coupled to the programmer. During device implantation, a physician evaluates the patient&#39;s condition, sometimes by using the implanted device to acquire real-time physiological data from the patient and communicating the physiological data in real-time to the external programmer for processing and/or display. The physician may also program the implantable device, including selecting a pacing or defibrillation therapy mode and parameters required by that mode based on the patient&#39;s condition and needs. The data acquisition and device programming are both performed via the inductive telemetry. If the patient&#39;s condition is stable after implantation, he or she needs no attention from the physician or other care provider until a scheduled routine follow-up. During a typical routine follow-up, the physician reviews the patient&#39;s history with the implantable device, re-evaluate the patient&#39;s condition, and re-program the implantable device if necessary.  
           [0007]    The inductive telemetry requires the two coils to be closely placed, typically by placing the wand on the body surface over the implantable device. Because the wand is coupled to the programmer using a cable, the inductive telemetry limits the patient&#39;s mobility. This limitation is tolerable for patients requiring infrequent routine follow-ups. However, some patients may be very ill or unstable to such an extent that the device is incapable of adjusting itself to provide adequate therapy in a timely manner. Where the patient&#39;s condition is life-threatening, telemetry must be active constantly to immediately alert a care provider. Using inductive telemetry would constantly restrain the patient who may otherwise enjoy a more active life.  
           [0008]    Alternatively, a far-field radio-frequency (RF) telemetry may substitute for, or supplement to, the inductive telemetry. An RF transceiver in the implantable device is used to communicate with an RF transceiver in the external programmer. With a far-field RF telemetry, the patient is typically free of any body surface attachment that limits mobility. However, RF telemetry typically consumes more energy and requires a larger circuit and battery than inductive telemetry.  
           [0009]    Therefore, the present inventors have recognized that there is a need for a method and apparatus to provide an adequate telemetry to an implantable device to satisfy each individual patient&#39;s needs without increasing the size and/or the cost of the implantable device.  
         SUMMARY  
         [0010]    An implantable, self-contained, user-attachable or detachable telemetry module plugs into an implantable medical device to provide or supplement one or more telemetry functions needed by a patient having certain health conditions. A user-attachable or detachable telemetry module allows a user, such as a physician or other care provider, to select a telemetry module and attach it to a medical device. Various types of telemetry are implemented as various user-attachable or detachable telemetry modules, each providing one or more telemetry functions suitable for a patient whose particular condition imposes particular demands on telemetry. A care provider selects a user-attachable or detachable telemetry module suitable for each individual patient wearing an implantable medical device. This eliminates a need for implantable medical devices having one or more built-in telemetry functions that may never be used or, alternatively, a need for many types of implantable medical devices, each including one possible combination of telemetry and therapeutic functions, and thus improves healthcare cost efficiency.  
           [0011]    In one example, a user-attachable or detachable telemetry module provides for far-field communications between an implantable medical device and a remote external device, for example, capable of communicating over at least a six-foot range. In one example, the user-attachable or detachable telemetry module includes an antenna including a first end and a second end. An RF module, coupled to the first end of the antenna, includes a transmitter and a receiver. An interface connector, coupled to the second end of the antenna, couples the telemetry module to an implantable medical device. In a further example, the RF module is attached to a device body of the implantable medical device via a snap-on connection. In an alternative example, the antenna has one end coupled to the RF module and a free end. The RF module includes an interface connector that allows the RF module to be attached to the implantable medical device with a plug-in connection. Other aspects of the invention will be apparent on reading the following detailed description and viewing the drawings that form a part thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.  
         [0013]    [0013]FIG. 1 is a schematic illustration of an example of portions of an implantable system and portions of an environment in which it is used.  
         [0014]    [0014]FIG. 2 is a schematic illustration of an example of a remote user-attachable or detachable telemetry module coupled to an implantable device by a lead.  
         [0015]    [0015]FIG. 3 is a schematic illustration of an example of a proximal user-attachable or detachable telemetry module coupled to an implantable device by a lead.  
         [0016]    [0016]FIG. 4A is a schematic illustration of an example of a proximal user-attachable or detachable telemetry module, coupled to an implantable device, with an outwardly extending antenna-carrying lead.  
         [0017]    [0017]FIG. 4B is a schematic illustration of another example of a proximal user-attachable or detachable telemetry module, coupled to an implantable device, with an outwardly extending antenna-carrying lead.  
         [0018]    [0018]FIG. 4C is a schematic illustration of one example of a proximal user-attachable or detachable telemetry module within a connector plugged into an implantable device.  
         [0019]    [0019]FIG. 4D is a schematic illustration of one example of a proximal user-attachable or detachable telemetry module within a connector, plugged into an implantable device, with an outwardly extending antenna-carrying lead.  
         [0020]    [0020]FIG. 5 is a schematic/block diagram showing an example of a circuit of a user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIGS. 2 and 3.  
         [0021]    [0021]FIG. 6A is a schematic/block diagram showing an alternative example of a circuit of the user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIGS. 2 and 3.  
         [0022]    [0022]FIG. 6B is a schematic/block diagram showing another alternative example of a circuit of the user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIGS. 2 and 3.  
         [0023]    [0023]FIG. 7 is a schematic/block diagram showing an example of a circuit of the user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIG. 4.  
         [0024]    [0024]FIG. 8A is a schematic/block diagram showing an alternative example of a circuit of the user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIG. 4.  
         [0025]    [0025]FIG. 8B is a schematic/block diagram showing another alternative example of a circuit of the user-attachable or detachable telemetry module coupled to an implantable device, such as shown in FIG. 4. 
     
    
     DETAILED DESCRIPTION  
       [0026]    In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.  
         [0027]    This document discusses, among other things, an implantable, user-attachable or detachable telemetry module connecting to an implantable medical device to provide communication between the implantable device and a remote external device. The present methods and apparatuses will be described in applications involving implantable cardiac rhythm management systems such as pacemakers, CRT devices, cardioverter/defibrillators, and pacer/defibrillators. However, it is understood that the present methods and apparatuses may be employed in other types of implantable medical devices, including, but not being limited to, neurological stimulators, neuromuscular stimulators, drug delivery systems, and various types of physiological signal monitoring devices.  
         [0028]    As already discussed, a patient&#39;s condition may determine a suitable type of telemetry, in additional to an implantable device having suitable type of therapeutic functions. To minimize size and maximize longevity of the implantable device, the type of telemetry should be selected based on the patient&#39;s needs. There is no typical one-to-one correspondence between a suitable type of telemetry and suitable type of therapeutic functions. For example, a patient having a bradyarrhythmia may need a pacer with either inductive telemetry or far-field RF telemetry, depending on whether his condition requires routine follow-ups or frequent monitoring. Similarly, a patient having a tachyarrhythmia may need a defibrillator with either inductive telemetry or far-field RF telemetry. Thus, a patient&#39;s condition should determine any possible combination of a suitable type of telemetry and an implantable device having suitable type of therapeutic functions.  
         [0029]    It is possible to include two or more types of telemetry in one implantable device. A suitable type of telemetry may be selected by programming the implantable device. This approach allows implantable devices to be categorized by therapeutic function or functions (e.g., pacers, CRT devices, defibrillators, pacer/defibrillators, and drug delivery devices), as they typically are at the present time. However, it is cost inefficient and may result in a device size unsuitable for implantation. Another possibility is to produce implantable devices categorized by predetermined combinations of therapeutic function or functions and telemetry type or types. This approach allows each implantable device to be efficiently used but requires maintenance of an inventory that is cost inefficient and confusing. In addition to cost inefficiency, both approaches have a potential to confuse physicians and other care providers with a complicated device selection and/or programming process.  
         [0030]    A user-attachable or detachable telemetry module provides a solution to these problems by allowing a user to select a suitable telemetry device and combine it with an implantable device having suitable type of therapeutic functions. The user-attachable or detachable telemetry module allows a user, such as a physician or other care provider or other person outside the factory that manufactures the implantable device, to select a suitable telemetry module and attach it to a medical device to provide the medical device with telemetry.  
         [0031]    [0031]FIG. 1 is a schematic illustration of an example of portions of an implantable system  100  and portions of an environment in which it is used. In this example, system  100  is an implantable cardiac rhythm management system including, among other things, an implantable device  105  and a remote external device  125 . Implantable device  105  is implanted within a body  120  of a patient and coupled to the patient&#39;s heart  115  by a lead system  110 . Examples of implantable device  105  include pacemakers, CRT devices, cardioverter/defibrillators, and pacer/defibrillators. Remote external device  125  provides a user interface for system  100 . The user interface allows a physician or other care provider to interact with implantable device  105  through a wireless telemetry link  190 . Telemetry link  190  provides for communications between implantable device  105  and remote external device  125 . In one example, telemetry link  190  provides for bi-directional communications between implantable device  105  and remote external device  125 . In another example, telemetry link  190  provides for uni-directional communications from implantable device  105  to remote external device  125 . In an alternative example, telemetry link  190  provides for uni-directional communications from remote external device  125  to implantable device  105 . In the example of FIG. 1, telemetry link  190  is provided by an external telemetry module  145  within or coupled to remote external device  125  and an implantable telemetry module  135  coupled to implantable device  105 . In one example, implantable telemetry module  135  is coupled to implantable device  105  (for example, outside the facility that manufactures the implantable device  105 ) using a user-attachable connector, and is therefore referred to as a user-attachable telemetry module. In one example, implantable telemetry module  135  is coupled to implantable device  105  (e.g., at the factory or elsewhere) using a detachable connector, and is therefore referred to as a detachable telemetry module.  
         [0032]    External telemetry module  145  includes, among other things, an external RF module  140  and an antenna  141 . In one example, antenna  141  is a quarter-wavelength antenna suitable for far-field telemetry. External RF module  140  includes a transmitter and a receiver. The transmitter generates an RF carrier signal and modulates it with data being transmitted, such as to implantable device  105 . The modulated signal is amplified by an amplifier and emitted though antenna  141 . The receiver receives through antenna  141  a modulated RF signal, such as from implanted user-attachable or detachable telemetry module  135  and demodulates the signal to recover data transferred from implantable device  105 .  
         [0033]    Implanted user-attachable or detachable telemetry module  135  includes, among other things, an RF module  130  and a lead  131 . In one example, lead  131  carries an antenna, such as a quarter-wavelength antenna suitable for far-field telemetry. RF module  130  includes a transmitter and a receiver. The transmitter generates an RF carrier signal and modulates it with data being transmitted to remote external device  125 . The modulated signal is amplified by an amplifier and emitted though the antenna. The receiver receives, through the antenna, a modulated RF signal coming from external telemetry module  145  and demodulates the signal to recover data transferred from remote external device  125 .  
         [0034]    In one example, telemetry link  190  is a far-field telemetry link. A far-field, also referred to as the Fraunhofer zone, refers to the zone in which a component of an electromagnetic field produced by the transmitting electromagnetic radiation source decays substantially proportionally to 1/r, where r is the distance between an observation point and the radiation source. Accordingly, far-field refers to the zone outside the boundary of r=λ/2π, where λ is the wavelength of the transmitted electromagnetic energy. In one example, a communication range of far-field telemetry link  190  (a distance over which data is capable of being wirelessly communicated) is at least six feet but can be as long as allowed by the particular communication technology. Unlike a near-field inductive telemetry link using a wand close to device  105  and electrically connected to remote external device  125 , using the far-field telemetry link of this example, no cable from body  120  to external telemetry module  145  is needed.  
         [0035]    User-attachable or detachable telemetry module  135  includes one or more user 15  attachable connectors to allow physical and electrical connection to implantable device  105 . In one example, the user-attachable connectors are detachable after attachment. In the example of FIG. 1, the one or more user-attachable or detachable connectors are coupled to one end of lead  131 . RF module  130  is coupled to the other end of lead  131 . A physician determines therapeutic and telemetry functions suitable for a particular patient and accordingly selects a particular type of implantable device  105  from among a plurality of types and a particular type of user-attachable or detachable telemetry module  135  among a plurality of types. In one example, user-attachable telemetry module  135  is coupled to implantable device  105  before or during an implantation operation. In another example, user-attachable telemetry module  135  is coupled to implantable device  105  in a manufacturing or assembly site, however, it is configured to be capable of being attached by a user outside the manufacturing facility.  
         [0036]    [0036]FIG. 2 is a schematic illustration of an example of user-attachable or detachable telemetry module  135  coupled to implantable device  105 . In this example, implantable device  105  is an implantable cardiac rhythm management device such as a pacer, a CRT device, a cardioverter/defibrillator, or a pacer/defibrillator. Lead system  110 , including leads  110 A and  110 B, couples implantable device  105  to heart  115  to allow monitoring of electrical signals from heart  115  and delivering electrical stimulation to heart  115 . User-attachable or detachable telemetry module  135  provides telemetry for implantable device  105 .  
         [0037]    Implantable device  105  includes a device body  200  and a header  210 . Device body  200  includes a pulse generator having an energy source, such as one or more batteries, and an electronic circuit. In this example, the pulse generator is contained within a metal housing (“can”) and hermetically sealed, with wire feedthroughs allowing access to outside of the can. Header  210  is permanently attached to device body  200  and includes the wire feedthroughs and one or more electromechanical connectors  232 . In the example of FIG. 2, implantable device  105  is coupled to two regions of heart  115  by two leads,  110 A and  110 B. Header  210  includes two lead connectors  232 A and  232 B for mechanically securing lead system  110 A and  110 B into implantable device  105  and electrically coupling these leads to the electronic circuit within the can. One example of lead connectors  232 A and  232 B, each including a socket into which a lead having a conducting pin terminal (shown as  233 A/ 233 B) is inserted, is discussed in Bradshaw et al. U.S. Pat. No. 5,545,188 (“the Bradshaw patent”), entitled “CARDIAC PACEMAKERS WITH COLLET-TYPE LEAD CONNECTOR,” assigned to Intermedics, Inc., which is incorporated herein by reference in its entirety.  
         [0038]    In the example of FIG. 2, header  210  further includes at least one connector  232 C into which a mating portion of user-attachable or detachable telemetry module  135  is plugged into implantable device  105 . Connector  232 C also provides for electrical coupling between user-attachable or detachable telemetry module  135  and the electronic circuit of implantable device  105 . Using this electrical connection, data is communicated from header  210  to user-attachable or detachable telemetry module  135 , and vice versa. One suitable example of connectors  232 C and  233 C is discussed in the Bradshaw patent.  
         [0039]    In the example of FIG. 2, user-attachable or detachable telemetry module  135  includes RF module  130  and lead  131 . RF module  130  includes a far-field RF telemetry circuit. In one example, the far-field RF telemetry circuit is capable of wirelessly transmitting and receiving data over a range of at least six feet. The telemetry circuit is contained within a hermetically sealed housing, with wire feedthroughs allowing electrical connection between RF module  130  and lead  131 . Lead  131  carries, among other things, an antenna that provides for RF signal emission and reception. Lead  131  also provides electrical and mechanical coupling between RF module  130  and implantable device  105 . In this example, lead  131  extends from RF module  130  and terminates at male connector  233 C, which is plugged into female connector  232 C.  
         [0040]    In one example, after selecting a combination of a particular type of implantable device  105  and a particular type of user-attachable or detachable telemetry module  135  suitable for a patient, user-attachable or detachable telemetry module  135  is coupled to implantable device  105  using matching connectors  233 C and  232 C before or during implantation. In another example, a suitable combination of one type of implantable device  105  and one type of user-attachable or detachable telemetry module  135 , pre-assembled in a manufacturing or assembly site, is selected for the patient before implantation. In one example, if a different type of telemetry is desired after implantation, user-attachable or detachable telemetry module  135  can be detached from implantable device  105  by separating connectors  233 C and  232 C. A different user-attachable or detachable telemetry module  135  can then be coupled to implantable device  105 , which need not be replaced.  
         [0041]    [0041]FIG. 3 is a schematic illustration of an alternative example of user-attachable or detachable telemetry module  135  coupled to implantable device  105 . In this example, an additional mechanical fixture  355  physically attaches RF module  130  onto implantable device  105 . In one example, mechanical fixture  355  includes one or more screws to unite components  360  and  350 , respectively attached to device body  200  and RF module  130 . In another example, mechanical fixture  355  includes two snap-on components  360  and  350 . In a further example, the snap-on connection is reinforced with one or more screws.  
         [0042]    Fixing RF module  135  onto device body  105  provides control over the physical placement of lead  131 . This obtains consistent orientation of the antenna in lead  131 , in relation to each patient&#39;s implantable device  105 . This may also prevent implantable device  105  from acting as a shield attenuating the RF signals transceived by the antenna in lead  131 . Mechanical fixture  355  may also provide for an electrical connection between the housings of device body  200  and RF module  130 , thus forming a common electrical ground, if desired. In an alternative example, components  360  and  350  include wire feedthroughs allowing access to the electronic circuit within device body  200  and RF module  130 , respectively. Components  360  and  350  also include conductive pins and/or receptacles such that mechanical fixture  355  also allows for electrical connection, in addition to mechanical connection, between implantable device  105  and RF module  130 .  
         [0043]    [0043]FIGS. 4A, 4B,  4 C, and  4 D are schematic illustrations of yet another example of user-attachable or detachable telemetry module  135  coupled to implantable device  105 . In the example illustrated in FIG. 4A, RF module  130  physically attaches onto header  210 , such as by using at least one pair of plug-in connectors  432  and  433 , which are associated with header  210  and RF module  130 , respectively. Lead  131  extends from RF module  130  and carries the antenna. In the example of FIG. 4A, the antenna includes an elongated conductor. Alternative examples of the antenna include a monopole antenna, a dipole antenna, a patch antenna, and a slot antenna.  
         [0044]    Connectors  432  and  433  include one or more pins and the same number of corresponding receptacles to allow user-attachable or detachable telemetry module  135  to be connected to and disconnected from implantable device  105  as needed. Additional features, such as one or more screws, may be used to provide or reinforce the connection provided by connectors  432  and  433 .  
         [0045]    In an alternative example illustrated in FIG. 4B, connector  432  is included in device body  200 . RF module  130  physically attaches onto device body  200 .  
         [0046]    In another alternative example illustrated in FIG. 4C, RF module  130  and the antenna are both constructed entirely within connector  433 . In one example, one or more set screws are used to provide or reinforce the connection between connectors  432  and  433 . In an additional example, the one or more set screws are also used to provide electrical connection(s) for power and/or data transmission between RF module  130  and device body  200  provided for by connectors  432  and  433 .  
         [0047]    In another alternative example illustrated in FIG. 4D, RF module  130  is constructed entirely within connector  433 . Lead  131  extends from RF module  130  and carries the antenna.  
         [0048]    In a further example, if a different type of telemetry is desired after implantation, user-attachable or detachable telemetry module  135  can be detached from implantable device  105  by separating connectors  433  and  432 . A different user-attachable or detachable telemetry module  135  can then be coupled to implantable device  105 , which need not be replaced.  
         [0049]    [0049]FIG. 5 is a schematic/block diagram showing an example of a circuit of user-attachable or detachable telemetry module  135  electrically and mechanically coupled to implantable device  105  by connectors  232 C and  233 C. In this example, implantable device  105  is an implantable cardiac rhythm management device including device body  200  and header  210 . Header  210  is permanently attached to device body  200 . Device body  200  includes an electronic circuit  505  and an energy source  506 , coupled to circuit  505 , to provide circuit  505  with power required for its operation. Device body  200  is housed in a conductive housing  508  and hermetically sealed. Housing  508  is exposed to body tissue after the implantation. Energy source  506  includes one or more batteries. Circuit  505 , electrically coupled to heart  115  through lead system  110  and header  210 , includes functional modules that monitors physiological activities of a patient and delivers one or more types of therapy to heart  115  of the patient through lead system  110 . Such functional modules are known in the art of cardiac rhythm management using implantable devices. Examples of such functional modules are discussed in Langer et al. U.S. Pat. No. 4,407,288, entitled “IMPLANTABLE HEART STIMULATOR AND STIMULATION METHOD,” assigned to Mieczyslaw Mirowski, which is incorporated herein by reference in its entirety.  
         [0050]    In the example shown in FIG. 5, lead system  110  includes leads  110 A and  110 B, each including two ends. One end is coupled to one or more electrodes in contact with heart  115 . The other end is coupled to a conductive pin connector,  233 A or  233 B, which is inserted into a corresponding receptacle connector,  232 A or  232 B, of header  210 . In this way, an electrical continuity is formed between heart  115  and circuit  505 .  
         [0051]    Circuit  505  is programmed to provide one or more monitoring and/or therapeutic functions suitable for each individual patient. User-attachable or detachable telemetry module  135  provides one means of programming circuit  505  by sending it commands and parameters. Each command causes circuit  505  to perform one or more functions. Examples of such functions include acquiring physiological data, performing at least one self-diagnostic test for a device operational status, and/or delivering at least one therapy. The parameters are required to define and control how each function is performed. For example, if the function is to deliver a pacing therapy, the parameters may include, among other things, a pacing mode, a maximum pacing rate, a minimum pacing rate, and values needed to quantitatively define a stimulus waveform.  
         [0052]    User-attachable or detachable telemetry module  135  transfers data from circuit  505  to remote device  125 . This may include, for example, transmitting real-time physiological data acquired by circuit  505 , extracting physiological data acquired by and stored in circuit  505 , extracting therapy history data stored in circuit  505 , and extracting data indicating an operational status of circuit  505 .  
         [0053]    In one example, circuit  505  includes a telemetry circuit that is independent from that in user-attachable or detachable telemetry module  135 . For example, circuit  505  may include an inductive telemetry circuit providing for near-field telemetry used in regularly scheduled routine follow-ups in a physician&#39;s office, and user-attachable or detachable telemetry module  135  provides for far-field telemetry for communicating over a long distance, such as notifying a physician of an urgent situation for a patient who is at home. Alternatively, user-attachable or detachable telemetry module  135  exclusively provides all telemetry for implantable device  105 .  
         [0054]    In the example shown in FIG. 5, user-attachable or detachable telemetry module  135  includes RF module  130  and lead  131 . RF module  130  includes an energy source  599 , a receiver  570 , and a transmitter  580 . In one example, RF module  130  is housed in a conductive housing  538  and hermetically sealed. Housing  538  is exposed to body tissue after the implantation. Energy source  599  includes one or more batteries and supplies power to receiver  570  and transmitter  580 . Receiver  570  includes an amplifier  574  and a demodulator  572 . Amplifier  574  includes an input that is coupled to an antenna  131 C, carried in lead  131 , through a capacitor  539  that decouples a dc component of RF telemetry signal  534  and a transmitter/receiver switch (TR switch)  576 . Signal  534  includes either an incoming signal  534 A that is to be received or an outgoing signal  534 B that is transmitted by the user-attachable or detachable telemetry module  135 . Signal  534 A is amplified by amplifier  574  and demodulated by demodulator  572  to result in an incoming component  532 A of binary data  532 . In one example, signal  534 A is an RF signal amplitude-modulated with binary data, and demodulator  572  is an envelope detector. In an alternative example, signal  534 A is an RF signal frequency-modulated with binary data, and demodulator  572  is frequency demodulator. In another alternative example, signal  534 A is an RF signal phase-modulated with binary data, and demodulator  572  is a phase demodulator. Data  532 A is passed to the implantable device  105  by using antenna  131  C, which also functions as a conductor providing for wired data transmission between RF module  130  and implantable device  105 . An RF choke (RFC)  536 A, between the output of demodulator  572  and antenna  131  C, prevents RF telemetry signal  534  and any noise received by antenna  131 C from interfering with the operation of RF module  130 .  
         [0055]    Transmitter  580  includes an RF carrier generator  582 , a modulator  584 , and an amplifier  586 . RF carrier generator  582  includes an oscillator generating a carrier signal for far-field data transmission, such as over a telemetry range of at least six feet. Modulator  584  includes a carrier input coupled to the output of RF carrier generator, and a signal input electrically connected to implantable device  105  through the wire of antenna  131 C and through RFC  536 A. Data  532  includes an outgoing component  532 B that is conducted from implantable device  105  via a wired connection. In one example, modulator  584  is an amplitude modulator by which the RF carrier is modulated by data  532 B to result in an amplitude-shift keyed RF signal. In an alternative example, modulator  584  is a frequency modulator by which the RF carrier is modulated by data  532 B to result in a frequency-shift keyed RF signal. In another alternative example, modulator  584  is a phase modulator by which the RF carrier is modulated by data  532 B to result in a phase-shift keyed RF signal. The modulator outputs a modulated RF signal that is amplified by amplifier  586  to result in signal  534 B, which is transmitted to, through capacitor  539  and TR switch  576 , antenna  131 C and emitted from antenna  131 C.  
         [0056]    In one example, telemetry link  190  allows data transmission in two directions (e.g., from external remote device  125  to implantable device  105 , and from implantable device  105  to external remote device  125 ) using time-sharing coordinated with a handshake or other protocol. In one example, data is transmitted in one direction at a time over telemetry link  190 , controlled by TR switch  576 . In a first state, TR switch  576  couples receiver  570  to antenna  131  C to allow data transmission from external remote device  125  to implantable device  105 . In a second state, TR switch  576  couples transmitter  580  to antenna  131 C to allow data transmission from implantable device  105  to external device  125 .  
         [0057]    Implantable device  105  includes RFC  537 C, between connector  232 C and circuit  505 , to prevent RF telemetry signal  534  and any noise received by antenna  131 C from interfering with operation of circuit  505 .  
         [0058]    [0058]FIGS. 6A and 6B are schematic/block diagrams showing an alternative example of a circuit of user-attachable or detachable telemetry module  135  coupled to implantable device  105 , in which RF module  130  does not include an energy source, but is instead energized by energy source  506  within implantable device  105 . In the example illustrated in FIG. 6A, in addition to antenna  131  C, lead  131  also carries conductors  131 D and  131 E for energy transmission. RF module  130  is coupled to conductors  131 D and  131 E through RFCs  536 D and  536 E, which prevent RF energy present in lead  131  from interfering with operation of RF module  130 . In this example, additional connector pairs  232 D- 233 D and  232 E- 233 E are used to couple conductors  131 D and  131 E, respectively, to energy source  506 , through header  210 . RFCs  537 D and  537 E are placed between connector  232 D and  232 E, respectively, and energy source  506  to prevent RF energy present in lead  131  from interfering with operation of circuit  505 .  
         [0059]    In the example illustrated in FIG. 6B, lead  131  carries only antenna  131  C that is also utilized for transmitting data  532  between user-attachable or detachable telemetry module  135  and implantable device  105  and for transmitting power VCC from implantable device  105  to user-attachable or detachable telemetry module  135 . In this example, RF module  130  further includes a VCC modulation-demodulation circuit  679 . To transmit data  532 B from implantable device  105  to user-attachable or detachable telemetry module  135  via conductor  131 C, circuit  505  modulates VCC with data  532 B. Circuit  679  demodulates the data-modulated VCC to recover both data  532 B and VCC. Housing  508  of device body  200  is connected to a circuit ground of device body  200 . Housing  538  of RF module  130  is connected to a circuit ground of RF module  130 . To transmit data  532 A from user-attachable or detachable telemetry module  135  to implantable device  105 , circuit  679  modulates VCC with data  532 A. Circuit  505  demodulates the data-modulated VCC to recover data  532 A. Housing  508  and housing  538  form a common ground through body tissue for closing a loop of the power transmission. In one example, VCC is amplitude modulated by either data  532 A or  532 B. Circuit  679  includes a low-pass filter and a voltage regulator to recover VCC. In a further example, VCC is on-off modulated by either data  532 A or  532 B.  
         [0060]    [0060]FIG. 7 is a schematic/block diagram showing an example of a circuit of user-attachable or detachable telemetry module  135  coupled to implantable device  105 , in which RF module  130  directly plugs into header  210  through a pair of connectors  432  and  433 . Connector pair  432 - 433  include connector pair  432 C and  433 C to provide for electrical connection allowing data  532  to flow between RF module  130  and circuit  505 . Lead  131  carries antenna  131  C and extends from RF module  130 , but is not directly coupled to implantable device  105 .  
         [0061]    [0061]FIGS. 8A and 8B are a schematic/block diagrams showing an alternative example of a circuit of user-attachable or detachable telemetry module  135  coupled to implantable device  105 , in which RF module  130  directly plugs into header  210  through a pair of connectors  432  and  433 . In the example illustrated in FIG. 8A, connectors pair  432 - 433  includes connector pair  432 C and  433 C, to provide for electrical connection allowing data  532  to flow between RF module  130  and circuit  505 , and connector pairs  432 D- 433 D and  432 E- 433 E to allow energy transmission from energy source  506  to RF module  130 . Lead  131  still carries antenna  131 C and extends from RF module  130 , but is not directly coupled to implantable device  105  and does not carries conductors for energy transmission.  
         [0062]    In the example illustrated in FIG. 8B, connectors pair  432 - 433  includes connector pair  432 C and  433 C to provide for electrical connection allowing data  532  to flow between RF module  130  and circuit  505  and to allow energy transmission from energy source  506  to RF module  130 , in a way that is previously discussed for the example of FIG. 6B. In this example, VCC is modulated by data  532  so that only one pair of connectors,  432 C and  433 C, are needed. Housing  508  and housing  538  closed a ground loop for power transmission.  
         [0063]    It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the implantable device can be any implantable medical device having an active electronic circuit. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”