Patent Publication Number: US-2006017575-A1

Title: Alert system and method for an implantable medical device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
      This application claims the benefit of U.S. Provisional Application No. 60/589,250 filed Jul. 20, 2004 for “Alert System And Method For An Implantable Medical Device” by J. Willenbring, J. VanDanacker, P. Krause, J. Masoud, J. Ball, H. Vitense, S. McAdams, and D. Hooper.  
     INCORPORATION BY REFERENCE  
      U.S. Provisional Application No. 60/589,250 filed Jul. 20, 2004 for “Alert System And Method For An Implantable Medical Device” by J. Willenbring, J. VanDanacker, P. Krause, J. Masoud, J. Ball, H. Vitense, S. McAdams, and D. Hooper is hereby incorporated by reference in its entirety.  
      U.S. Non-Provisional application Ser. No. ______ (Atty. Dkt. P-20168.00) filed on even date for “Alert System And Method For An Implantable Medical Device” by J. Willenbring, J. VanDanacker, P. Krause, J. Masoud, J. Ball, H. Vitense, S. McAdams, and D. Hooper is hereby incorporated by reference in its entirety.  
      U.S. Non-Provisional application Ser. No. 10/727,008 filed Dec. 3, 2003 for “Method And Apparatus For Detecting Change In Intrathoracic Electrical Impedance” by Robert W. Stadler, et al. is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates to implantable medical devices, and more particularly to an alert system for an implantable medical device.  
      During the latter portion of the twentieth century, it became common to implant medical devices to provide therapy for a vast number of medical conditions. Such devices included electrical stimulation devices, pain control devices, and drug delivery systems. Additionally and as these devices became more complex, it became necessary to monitor both their operation and the patient&#39;s condition.  
      At the same time, patients with implantable medical devices (IMDs) have come to expect a fuller life post-implant. These expectations often include few, if any, restrictions on their lifestyle. Thus, patients expect a great degree of mobility while their medical condition is being monitored and/or treated by the IMD and their physician. Semi-annual or annual in-office checkups for the IMD and the patient limits the frequency of monitoring. Moreover, the patient feels that he or she must remain close to the care giver&#39;s clinic or the hospital where checkups take place. Further, emergency situations may sometimes occur which, in the mind of the elderly patient, demand a very close proximity to the attending care giver. Going to the clinic for frequent check-ups may impose a considerable burden on the patient as well as an overall increase in the cost of healthcare. Accordingly, some IMDs are equipped with a communication system that connects to an interface in such a manner that it is transparent to the patient and yet provides the medical data required by the care giver.  
      Until recently, data transmission systems within IMDs were only capable of transferring data over a very small distance. Recent advances in wireless telemetry systems, often utilizing radio frequency (RF) systems, have opened the door to a whole host of new technologies. These technologies are reducing the burden on patients to perform routine tasks and are allowing patients to live with greater freedom and fewer restrictions on their lifestyle. However, there still exist multiple ways in which wireless telemetry systems can be utilized to further enhance the freedom of patients and the quality of care that they receive.  
      Patient interaction is often required in prior IMDs at the occurrence of an event. For example, an alarm system creates an audible alarm to alert the patient to the occurrence of an event. The patient then must either initiate a transfer of data to the care giver over the telephone or like systems or must immediately contact a care giver who can assess the situation. A patient who is relying on the therapy of an IMD can become very distressed when an audible alarm in the IMD begins to sound. Conversely, an audible alarm may not be heard by the patient, depending on the patient&#39;s hearing and environment.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention relates to an alert system and method for informing and communicating to a preceptor (e.g. patient; care giver; or interested party) the occurrence and termination of an event related to a patient. The system generally includes an implantable medical device implanted within a patient. Specifically, the implantable medical device includes means for detecting the occurrence and termination of the event, and a means for transmitting an alert signal and an end alert signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates an embodiment of the alert system of the present invention.  
       FIG. 2  is a block diagram of an IMD of the alert system of the present invention.  
       FIG. 3  is a block diagram of a monitor of the alert system of the present invention.  
       FIG. 4  is a block diagram of a patient management network of the alert system of the present invention.  
       FIG. 5  is a block diagram of patient management web clients of the alert system of the present invention.  
       FIG. 6  is an exemplary flow diagram illustrating a method of sending an alert signal from the IMD upon the occurrence of an event satisfying alert criteria.  
       FIGS. 7 and 8  are exemplary screen shots of a user interface allowing the care giver to select clinical management alert settings.  
       FIGS. 9 and 10  are exemplary screen shots of a user interface allowing the care giver to select lead/device integrity alert settings.  
       FIG. 11  is an exemplary flow diagram illustrating a method of sending an alert signal when an event occurs and an all-clear signal when an event terminates.  
       FIG. 12  is a more detailed embodiment utilizing an alert signal and an end alert signal.  
       FIG. 13  shows an alternate communications system by which alert signals may be transmitted to a medical support network. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  illustrates an embodiment of alert system  20  of the present invention, which communicates between patient P and care giver C. Alert system  20  includes implantable medical device (“IMD”)  24  within patient P, monitor  26 , private network  27 , patient management network  28 , and patient management web clients  30  including patient browser  30   a  that is capable of displaying patient website  31   a  and care giver browser  30   b  that is capable of displaying care giver website  31   b.    
      IMD  24  is, for example, a device such as a pacemaker or defibrillator that is implanted within patient P and is capable of providing cardiac therapies. These therapies may include providing pacing pulses or defibrillation shocks to the heart of patient P. IMD  24  also records useful data such as, for example, without limitation, data related to the condition of patient P, therapy delivery, device performance and functionality and periodically provides information to care giver C. IMD  24  also provides self-monitoring of the system operation (such as lead impedance data, high-voltage capacitor charge times, battery capacity, etc.). In addition, IMD  24  is capable of detecting the occurrence of an event that satisfies predefined alert criteria. The alert criteria may pertain to a clinically-relevant event or a result of self-diagnosis of the IMD that may be necessary, for example, to inform the patient or an interested person. Once an event has been detected that satisfies an alert criterion, IMD  24  is capable of providing a perceptible alert. A patient alert is a patient notification of a triggered alert criteria via an audible tone vibration, or other perceptible communication directed to the patient from IMD  24  or monitor  26 . A silent alert is a notification of a triggered alert criteria via alert system  20 , which is not perceptible to the patient.  
      Monitor  26  is an instrument, such as Medtronic&#39;s CareLink monitor, intended for use in a patient&#39;s home that is capable of receiving data from the patient&#39;s implanted device via telemetry and transmitting this information via phone lines or other communication platforms to private network  27  which transfers the data to patient management network  28 . Private network  27  is, for example, the IP Link service from MCI, which provides a private, secure, and reliable connection.  
      Patient management network  28  utilizes secure computer servers that collect, process and store data sent from monitor  26 . This information is available to patient P and care giver C through e.g., patient management web clients  30 . Patient management web clients  30  are computer systems with a browser capable of viewing web pages on the World Wide Web. At least two patient management web clients  30  are provided: a patient browser  30   a  and a care giver browser  30   b . Patient P can access data and other information on patient website  31   a  via patient browser  30   a . Care giver C can access data and other information on care giver website  31   b  via care giver browser  30   b.    
      There are three follow-up scenarios in which care giver C can interact with IMD  24  to monitor the condition of patient P and IMD  24 : standard follow-up, remote follow-up, and ambulatory follow-up. Standard follow-up is a scheduled face-to-face interaction between patient P and care giver C in order to check the patient&#39;s health and the functioning of IMD  24 . Typically, the standard follow-up occurs every three to six months. Alert system  20  of the present invention reduces the number of standard follow-ups that need to take place. The remote follow-up is a scheduled electronic transmission of the data stored in IMD  24  to care giver C in order to check the health of patient P and the functioning of the patient&#39;s IMD  24 . Similar to the standard follow-up, the remote follow-up typically occurs every three to six months depending upon the patient&#39;s medical condition. The remote follow-up is enabled by use of monitor  26  and patient management network  28 . The ambulatory follow-up is an unscheduled and IMD-initiated electronic transmission of the data stored in IMD  24  to care giver C in order to alert care giver C to the occurrence of an event that satisfies the alert criteria and allow care giver C to check the health of patient P and the functioning of the patient&#39;s IMD  24 . It has been found that standard follow-ups are time consuming, and inconvenient for both patient P and care giver C. Ambulatory follow-ups, however, can be provided by alert system  20  of the present invention to provide many benefits.  
      Communication between the various components of alert system  20  will now be described. Either upon the detection of an event satisfying an alert criterion, or at a scheduled time, IMD  24  is interrogated by monitor  26  over a wireless telemetry system utilizing radio frequency (RF) signals. This interrogation provides data from IMD  24  to monitor  26 . Monitor  26  communicates the data to patient management network  28  over a standard telephone system from the home of patient P and through private network  27 . Data is then displayed to care giver C or patient P using patient management web clients  30  utilizing the standard world-wide web (“WWW”) secured communication protocol (e.g. SSL).  
       FIG. 2  is a block diagram of IMD  24  of alert system  20 . Although it is recognized that alert system  20  can be used with any type of implantable medical device, a specific example will now be provided in which IMD  24  is an implantable cardioverter defibrillator. IMD  24  includes leads  42 , pacing circuitry  44 , defibrillation circuitry  46 , sensors  48 , control processor  50 , telemetry processor  52 , transmitter circuitry  54 , receiver circuitry  56 , antenna  58 , speaker drive circuitry  60 , speaker  62 , and memory  64 . Control processor  50  is the primary controller for IMD  24  and thus control processor  50  controls the overall operation of IMD  24 .  
      Control processor  50  controls pacing circuitry  44  and defibrillation circuitry  46  to provide therapeutic electrical pulses to leads  42 . Leads  42  are preferably implanted within the heart of patient P and provide an electrically conductive path for the pulses to selected locations within the heart. In addition, leads  42  can be used by sensors  48  to detect cardiac signals in the heart. These cardiac signals are conducted through leads  42 , detected by sensors  48 , and then provided to control processor  50 . If desired, control processor  50  can save the signals in memory  64 , which is preferably a type of random access memory (RAM) or flash memory.  
      Control processor  50  is capable of analyzing the cardiac signals received from sensors  48  and determining whether an event has occurred which satisfies an alert criterion. In addition, control processor  50  is capable of monitoring the condition of IMD  24  to determine whether an event has occurred which satisfies an alert criterion. If control processor  50  determines that such an event has occurred, it then decides, based upon care giver selectable alert settings, what type of an alert should be provided. If the care giver selectable alert settings instruct control processor  50  to provide a patient alert, an alert signal is generated and sent to speaker drive circuitry  60 . Speaker drive circuitry  60  provides the necessary electrical signal to speaker  62  to create an audible sound which alerts patient P to the occurrence of the event.  
      Alternatively, if care giver selectable alert settings instruct control processor  50  to provide a silent alert, then control processor  50  instructs telemetry processor  52  to transmit a wireless telemetry signal. Telemetry processor  52  then controls transmitter circuitry  54  to create a radio frequency (RF) signal that is transmitted wirelessly over antenna  58 . This signal alerts monitor  26  ( FIG. 3 ) that IMD  24  is initiating communication, provided that monitor  26  is within the telemetry range of IMD  24 . In this way, IMD  24  is capable of initiating communication with monitor  26  to inform monitor  26  of the occurrence of an event that satisfies the alert criteria. Further detail of the communication between IMD  24  and monitor  26  will be provided with reference to  FIG. 3 .  
      IMD  24  could be utilized to provide an alert signal in response to any detectable event as well as the absence of any detectable event. In one embodiment there are six types of events, the occurrence of which care giver C may choose to be notified of. The six types of events relate to therapy delivery, arrhythmias, heart failure, system integrity, cardiac ischemia, and edema.  
      Therapy delivery events occur when IMD  24  provides a therapy to patient P. These therapies may include electrical stimulation, defibrillation, drug delivery, or the delivery of other agents. The alert criterion may specify, for example, that an alert should be sent for all therapies, an initial therapy, an unsuccessful therapy, a successful therapy, an attempt at providing a therapy, a delayed or aborted therapy, only after a predetermined number of therapies, a defibrillation therapy that was not able to be delivered due to an unsuccessful attempt to charge its delivery capacitor, or a defibrillation therapy that was not successfully delivered due to a short circuit present in its delivery pathway. In addition, the alert criterion may specify, for example, that an alert should be sent for a change in percentage of pacing, a change in rate responsive therapy, a change in use of therapies, or a newly detected need for a therapy.  
      Arrhythmic events may include, for example, a new atrial or ventricular tachycardia, a new atrial or ventricular fibrillation, a non-sustained tachycardia, an atrioventricular nodal reentry tachycardia, a premature ventricular contraction, a detected episode with no therapy programmed, a change in duration of episodes, a frequency of episodes, a rate of arrhythmia, and a presence of rapid atrial conduction to ventricle, or when there is no intrinsic rhythm detected (asystole).  
      Heart failure events may include edema triggers, pressure data triggers (for example, data from an implantable hemodynamic monitor such as the Medtronic Chronicle® device), heart rate variability, activity, and nocturnal heart rate changes. Edema, for example, has been found to be a strong indicator of heart failure, and can be used to detect heart failure before any other symptoms are detectable by the patient. Intra-thoracic impedance relates the volume of fluid between a pair of electrodes and thus pulmonary edema (e.g., measuring the impedance between an electrode disposed within a chamber or major vessel (e.g., superior vena cava) of a heart and an surface electrode disposed in a housing, or “can,” of IMD  24  or the conductive surface of the can itself. This impedance measurement can be used to detect the amount of fluid in the lungs, and the onset of pulmonary edema. The reader should note that while the term “transthoracic impedance” is used within this document, it should be interpreted as “intra-thoracic” or “inter-thoracic” impedance (e.g., impedance measured between in-dwelling electrodes disposed in or about the thoracic cavity of a subject). The impedance measurements may occur among one or more subcutaneous electrodes, endocardial electrodes, epicardial electrodes, pericardial electrodes and the like. Furthermore, while the generic term “edema” is oftentimes employed in this document, the term should be interpreted as relating more to pulmonary edema than to peripheral edema, although the onset of one form of edema can precipitate onset or increase in severity of the other form of edema.  
      System integrity events are events which indicate an abnormal functioning of IMD  24 . System integrity events may include a memory failure (such as with RAM), a power-on reset (POR), a charge circuit timeout, an elective replacement indicator (ERI), device hardware failure, EEPROM failure, device initialization failure, multiple microprocessor failure, capture threshold changes, sensing threshold changes, presence of far-field R wave oversensing, myopotentials, electromechanical interference (EMI), T-wave oversensing, pacemaker modes of VOO or DOO on for more than a predetermined amount of time, device detection off or therapy off, device has not had telemetry session in a predetermined amount of time, no superior vena cava lead when active can is off, and an excessive number of non-physiologic ventricular or atrial intervals.  
      An ischemia event is a deficiency of blood in tissue, usually due to functional constriction or actual obstruction of a blood vessel. An example of an ischemia event is cardiac/myocardial ischemia which is a deficiency of blood supply to areas of heart tissue.  
       FIG. 3  is a block diagram of monitor  26  of alert system  20  of the present invention. Monitor  26  includes short-range (e.g., programming head) communication system  70 , longer-range wireless communication system  72 , patient alerts  74 , control switches  76 , digital signal processor (“DSP”)  78 , real-time clock (“RTC”)  80 , memory  82 , modem  84 , and power supply  86 . Short-distance communication system  70  includes antenna  88 , receiver circuitry  90 , and transmitter circuitry  92 . Wireless communication system  72  includes wireless antenna  94 , wireless transmitter circuitry  96 , and wireless receiver circuitry  98 . Patient alerts include speaker  100 , speaker drive  102 , light-emitting diodes (LEDs)  104 , and LED drive  106 . Control switches  76  include start switch  108 , and reset  110 . Memory  82  includes SDRAM  112  and flash  114 . Modem  84  includes digital data access arrangement (“digital DAA”)  116 , isolation  118 , line side DAA  120 , RJ11 ports  122  and  124 , tone/pulse select  126 , and prefix select  128 . Power supply  86  includes DC power  130 , reverse polarity protection  132 , overcurrent protection  134 , digital voltage power supplies  136 , and DC outputs  138  and  140 .  
      Monitor  26  is located within the home or in the vicinity of where patient P is present. In addition, multiple monitors could be located at different places to allow communications with IMD  24  through any one of the monitors. Monitor  26  is capable of longer-distance wireless communication with IMD  24  via wireless communication system  72 . Short-distance communication system  70  is also provided to enable communication with implantable medical devices which utilize the short-distance head-based communication systems.  
      Antenna  88  of short-distance communication system  70  is preferably a dual opposing coil RF read head which is used to transmit data during downlinks and receive data during uplinks. Short-distance receiver circuitry  90  amplifies, filters, and digitizes the received data signal before sending it to DSP  78 . Short-distance transmitter circuitry  92  receives logic level signals from DSP  78  and converts them to a higher current drive signal for RF read head antenna  88 . Transmitter circuitry  92  properly tunes the antenna to the appropriate frequency for transmission. Short-distance transmitter circuitry  92  is also capable of being disabled to isolate it from antenna  88  so that it does not affect the receive circuitry during receive mode.  
      Wireless communication system  72  provides the capability of communicating with IMD  24  using wireless telemetry with RF signals. Wireless antenna  94  includes two separate antennas to provide spatial diversity. It is tuned to a nominal wireless telemetry carrier frequency with sufficient bandwidth to accommodate the entire medical implant communication service (“MICS”) 402-405 MHz band. Wireless transmitter circuitry  96  generates the RF downlink transmission to IMD  24  in the 403-405 MHz MICS band. Wireless receiver circuitry  98  receives and demodulates the RF uplink transmission to IMD  24  in the 402-405 MHz MICS band.  
      Patient alerts  74  include speaker  100  coupled to speaker drive  102  and LEDs  104  coupled to LED drive  106 . Speaker drive and LED drive are both controlled by DSP  78 . Speaker drive  102  and speaker  100  serve two functions: to generate tones to indicate an error or alert condition, and to make modem  84  audible. Speaker drive  102  multiplexes an audible tone from DSP  78  and the modem audio. Speaker drive  102  also has the ability to take a logic level signal as an input and drive the speaker at a high enough current to meet audio sound pressure level requirements. LEDs  104  are used as visual indicators to give status indications to patient P or (care giver C) during an interrogation and modem connection. LEDs  104  also alert patient P to power status and completion of uploaded data to the server. Light from LEDs  104  is transferred to a user interface overlay via injection molded optical light pipes. LED drive  106  accepts a logic signal from DSP  78  or digital DM  116  and drives LEDs  104  at a higher current. Switches  76  provide buttons which allow patient P to interact with monitor  26 . Switches  76  include start switch detection  108  and reset  110 . Start switch  108  allows patient P to instruct monitor  26  to begin an interrogation of IMD  24 . Reset  110  allows patient P to reset monitor  26  to factory defined settings.  
      DSP  78  is responsible for the majority of the functions of monitor  26 . It encodes and transmits data for both short-distance and wireless downlink transmissions, and decodes digitized data from the corresponding receiver circuitry  90  or  98  during uplink transmissions. DSP  78  is also used to implement a soft modem and directly interfaces with digital DAA  116  to send data out on a phone line. DSP  78  also runs the TCP/IP, PPP, and HTTP client software on top of the modem software. All user interface functions are handled by DSP  78  including control of patient alerts  74 , as well as reading the status of tone/pulse select switch  126  and prefix select switch  128 .  
      Real-time clock  80  is provided in monitor  26  to keep track of the time. Both IMD  24  and monitor  26  keep track of the time so that communication can take place at predetermined times. In order to save battery power in IMD  24 , the telemetry system of IMD  24  does not remain active at all times. Instead, IMD  24  and monitor  26  have predefined communication times during which routine communication can take place. However, as described above, alert system  20  also includes the capability of IMD  24  initiated communication at any time in which an event is detected which satisfies the alert criteria.  
      Memory  82  includes SDRAM  112  and flash  114 . SDRAM  112  is used to store interrogation data from IMD  24  as well as program code and other program-related data. Flash  114  is used to store program data and any parameters that need to be stored in non-volatile memory (e.g. phone numbers). DSP  78  boots from flash  114 .  
      Modem  84  includes digital DAA  116 , isolation  118 , line side DAA  120 , RJ-11 jacks  122  and  124 , tone/pulse select switch  126 , and prefix select switch  128 . Digital DAA  116  along with DSP  78  and line side interface  120  form a complete V.34 modem. As described above, DSP  78  is used to implement a soft modem and directly interfaces with digital DAA  116  to send data out on a phone line. DSP  78  also runs the TCP/IP, PPP, and HTTP client software on top of the modem software. DSP  78  also reads the status of tone/pulse select switch  126  and prefix select switch  128 . Tone/pulse select switch allows patient P to select whether dialing modem  84  should use tone or pulse dialing. Prefix select switch  128  allows patient P to select whether a prefix needs to be dialed to access an outside line, such as a number 9. Digital DAA  116  interfaces with DSP  78  through a serial interface and contains all of the control registers for modem  84  such as termination settings, clock phase-locked loop (“PLL”) settings, etc. Digital DAA  116  also includes an audio output (not shown) that is coupled to speaker drive  102  that multiplexes the modem audio and the tones generated from DSP  78 . Line side DM  120  is connected directly to the phone line via RJ-11 jacks  122  and  124 . Line side DAA  120  generates DTMF signals that allow it to communicate over a telephone system to private network  27 , as well as providing several other necessary functions (overload protection, programmable terminations to generate an off-hook condition for various countries, 2 to 4 wire conversion, etc.). Modem  84  isolates the line side from the other components of monitor  26  through capacitive isolation barrier  118 .  
      Power supply  86  provides DC power to monitor  26 . Power supply  86  includes DC power source  130 , reverse polarity protection  132 , overcurrent protection  134 , digital voltage power supplies  136 , and DC outputs  138  and  140 . The function of power supply  86  should be easily understood by one skilled in the art and therefore will not be described in further detail.  
      Monitor  26  is a portable interrogation and data transfer tool used with IMD  24 . Monitor  26  offers the capabilities to patient P, care giver C, and service personnel of remote interrogations, data processing, reporting and follow-up to be performed when the patient is at home and the care giver is in the clinic or a location that has web-enabled capability. This remote feature allows for reduced travel and waiting time, providing prompt care to patients and better efficiencies to care givers. It also enables care givers to better manage patients and still maintain the quality of care that is warranted in the marketplace. Furthermore, monitor  26  allows field representatives to increase their productivity, provide equal or better service to existing and new customers worldwide, and control costs for providing the services. The increased productivity is obtained by reducing the time required for manufacturer-assisted follow-up. Monitor  26  performs four primary functions: it interrogates IMD  24  and stores the data, it collaborates with patient management network  28  to confirm the establishment of a connection with patient management network  28 , it performs any required file translation functions necessary for data transfer, and it executes the data file transfer and then collaborates with patient management network  28  to confirm that the data file transfer was successful. Although the preferred embodiment of the present invention utilizes monitor  26 , it is recognized that other devices could also be used to perform the function of monitor  26 . Examples of such devices include a telemetry transponder/repeater, a cell phone, or a Bluetooth-enabled or WiFi-enabled communication device.  
      Now that the structure of IMD  24  and monitor  26  have been described, the communications between IMD  24  and monitor  26  will be described. As explained above, care giver C and IMD  24  interact for standard follow-up, remote follow-up, and ambulatory follow-up. Of these, a remote follow-up and an ambulatory follow-up utilize monitor  26  as one of the communication links between IMD  24  and care giver C. An ambulatory follow-up occurs only when IMD  24  detects the occurrence of an event that satisfies the alert criteria and must be communicated to care giver C. A remote follow-up, on the other hand, is scheduled and expected by both IMD  24  and monitor  26 , and therefore is initiated by monitor  26 . This procedure also satisfies current FCC regulations for implantable medical device operating in the MICS band to initiate communications only if a “medical implant event” occurs. (Title 47 of the Code of Federal Regulations, Part 95.628.) The FCC has further defined the event as an occurrence that necessitates data exchange in order to maintain patient safety.  
      In any event, once communication has been established, monitor  26  performs an interrogation of IMD  24 . Control processor  50  of IMD  24  reads the desired data from memory  64  and then provides it to telemetry processor  52 . Telemetry processor  52  and transmitter circuitry  54  transform the data to an RF signal that is wirelessly transmitted by antenna  58  to monitor  26 . Monitor  26  receives the wireless transmission of data through antenna  94  and wireless receiver circuitry  98 . Receiver circuitry  98  then provides the data to DSP  78  which stores the data in SDRAM  112 . After all desired data has been received, the communication between monitor  26  and IMD  24  is closed.  
       FIG. 4  is a block diagram of patient management network  28  of alert system  20  of the present invention. Patient management network  28  (“PMN”) includes device data input and interpretation  150 , device data storage  152 , web presentation services  154 , user/web data storage  156 , and core services  158 . Device data input and interpretation  150  includes PMN device data input  160  and PMN device data conversion  162 . Web presentation services  154  include device data presentation  164  and PMN content services  166 . Core services  158  include PMN security  168 , PMN print framework  170 , PMN presentation framework  172 , and PMN administration/operational support  174 .  
      Patient management network  28  utilizes a series of secure computer servers that collect, process and store data sent from monitor  26 . This data is then made available to patient P and care giver C through Internet accessible websites that are personalized for their particular needs. The patient and care giver websites will be described in further detail with reference to  FIG. 5 .  
      After monitor  26  has completed a full interrogation of IMD  24 , it then transfers the data over a telephone line to private network  27 . One example of private network  27  is MCI&#39;s IP Link private network. Private network  27  allows monitor  26  to remotely access patient management network  28  over a private, secure, and reliable connection utilizing the hypertext transfer protocol (“HTTP”). Patient management network, which consists of a series of secure computer servers, receives the data from monitor  26  (over the private network) and into device data input and interpretation  150 , and more specifically through PMN device data input  160  which preferably includes a dedicated router. The data is then processed by PMN device data conversion  162  and stored in device data storage  152 . For example, further processing is performed by web presentation services  154  to turn the raw device data into viewable portable document format (“PDF”) documents, graphs, tables, etc. and also to create client and patient personalized websites which are accessed by patient browser  30   a  and care giver browser  30   b . This data is then stored in user/web data storage  156 . Additionally, core services  158  are performed by patient management system  28  to provide PMN security  168 , PMN framework  170 , PMN presentation framework  172 , and PMN administration/operational support  174 .  
       FIG. 5  is a block diagram of patient management web clients  30  of alert system  20  of the present invention. Patient management web clients  30  include patient computer  176  running patient browser  30   a , and care giver&#39;s personal digital assistant (“PDA”)  177  or care giver computer  178  both capable of running care giver browser  30   b . Patient browser  30   a  is used by patient P to access the patient website  31   a  from patient management network  28  through the world-wide web. Care giver browser  30   b  is used by care giver C to access the care giver website  31   b.    
      Patient and care giver websites  31   a  and  31   b  are both generated by patient management network  28 . Patient website  31   a  includes: general information modules (not related to the patient&#39;s IMD data) concerning the patient&#39;s device and their disease; general (“wire feed”) news items or articles containing information on medical topics of interest; psychosocial support modules designed to meet the needs of specific patient groups; access to a personalized “storefront” of products designed to meet the patient&#39;s needs; a virtual on-line community of “friends and family” that can share information and experiences with the patient; and views of IMD  24  data supplied from the device data level. Care giver website  31   b  includes the following capabilities: creation and maintenance of a patient list with various features for customization on a patient-specific basis; customized updates on products, clinical trials and research in addition to the provision of general (“wire-feed”) news items or articles containing information on medical topics of interest; a route for care givers to access technical services; views of stored IMD data and alerts supplied from the device data level; and means for posting information on the site that their patients can read.  
      Now that the structure of alert system  20  has been described, further detail will be provided as to the operation of alert system  20  of the present invention.  
       FIG. 6  is an exemplary flow diagram illustrating a method of sending an alert signal from IMD  24  upon the occurrence of an event satisfying the alert criteria. The method is intended only as an exemplary embodiment. IMD  24  begins by monitoring for the occurrence of an event (step  180 ). Once an event is detected (step  182 ), the system decides who should first be notified of the occurrence of the event based upon predefined alert criteria. This step is preferably performed by IMD  24 , but may also be performed by monitor  26  or patient management network  28 . If IMD  24  decides to attempt a silent alert to care giver C (step  184 ), IMD  24  wirelessly transmits an alert signal to monitor  26 . If monitor  26  receives the alert signal, monitor  26  performs a full interrogation of IMD  24 , as defined above, and closes the session. Monitor  26  then transfers the data to patient management network  28 , which informs the care giver of the occurrence of the event. The system then determines whether the silent alert was successfully communicated to the care giver (step  186 ).  
      Various methods of determining the success of the silent alert may be used. For example, monitor  26  can provide a verification signal to IMD  24  after monitor  26  has successfully transferred the data to patient management network  28 , care giver C can provide a verification signal to patient management network  28  which is then sent through alert system  20  to IMD  24 , or success can be defined as a successful transfer of data from IMD  24  to monitor  26  which would require no verification signal. If alert system  20  determines that the silent alert has been received (step  188 ), it knows that care giver C will take the necessary corrective action (step  190 ). If alert system  20  determines that the silent alert has failed (step  192 ) (for example, if no verification signal is received in a predetermined amount of time), then IMD  24  assumes that the alert was not successfully communicated to care giver  30 . As a result, IMD  24  repeats the attempted transmission a predetermined number of times (steps  182 ,  184 ,  186 , and  192 ). Since the most frequent cause of a failed transmission is that IMD  24  is not in range of monitor  26 , it is preferable to wait for a specified amount of time, such as three hours, before retrying the transmission. For example, IMD  24  will continue attempting communication every three hours for up to three days for a total of twenty four times.  
      If repeated attempts to transmit the alert signal are unsuccessful, IMD  24  will then switch to the backup alarm. In the exemplary embodiment, the backup alarm is the patient alert that includes speaker drive  60  and speaker  62 . Thus, after repeated unsuccessful attempts to wirelessly transmit the alert signal (steps  182 ,  184 ,  186 , and  192 ), an alert signal is sent to the patient alert (step  194 ). Once the patient has received the alert signal ( 196 ), patient P contacts care giver C (step  198 ) to inform him or her of the occurrence of an event. In an exemplary embodiment, alert system  20  will continue to provide the patient alert periodically until alert system  20  verifies that the patient alert has been received. To do so, alert system  20  detects when a full interrogation of IMD  24  has been taken place, and recognizes at that point that the patient alert has been received and that care giver C will take the appropriate corrective action (step  190 ).  
      In alternate embodiments, the patient alert may also be triggered by other situations in which the wireless transmission is considered a failure, such as: when the alert signal is not received by monitor  26 , when the interrogation of IMD  24  by monitor  26  does not complete, when patient management network  28  does not receive the interrogated data, when the care giver does not acknowledge an alert after being informed by patient management network  28 , or when the care giver does not log in to care giver website  31   b  via care giver browser  30   b  and check the patient&#39;s data after being alerted by patient management network  28 .  
      The present invention inherently includes software control (i.e., instructions performed by at least one computer processor) and, as applicable, the methods herein that are susceptible of being stored on a computer readable medium or being sent as control signals to affect a technical result are expressly disclosed and claimed herein.  
      Alert system  20  of the present invention provides a user interface in which care giver C can set the care giver selectable alert settings of alert system  20  to perform as desired. These settings define the alert criteria that are used by IMD  24  (or patient management network  28 ) to determine whether or not an alert should be sent, and whether a silent alert of a patient alert should be sent. Thus, alert system  20  provides care giver C with a user interface in which he or she can select which events should initiate a silent alert, a patient alert, both alerts, or no alert at all. Table 1 is an exemplary list of care giver selectable alert conditions. It includes the alert name, a description of the alert, and the programmable condition parameters available for that alert.  
               TABLE 1                          Care Giver Selectable Alert Conditions                                 PROGRAMMABLE       ALERT       CONDITION       NAME   DESCRIPTION   PARAMETERS               Lead   A measured lead impedance   Independently       Impedance   trend value has exceeded the   enabled for each       Out of   acceptable range set for the   lead: If enabled,       Range   lead.   Minimum and               Maximum               Impedances.       Low   The elective-replacement-   Enable/disable       Battery   indicator (ERI) battery voltage       Voltage   condition occurs for three           consecutive days, excluding           days when high voltage           charges took place.       Excessive   Charging performance of   Enable/disable       Charge   device has met ERI indicator       Time   for charge time.       VT/VF   A ventricular tachyarrhythmia   Enable/disable       Therapies   occurred which required       Exhausted   delivery of all enabled           therapies for the zone and           failed to terminate the           arrhythmia.       Number of   The programmable number of   Enable/Disable       Ventric-   shocks, or more, were   and Number of       ular   delivered for a single VT/VF   Shocks       CV or   episode.       Defibril-       lation       Shocks       VF   The device is not in session   Enable (High       Therapy   and six hours have elapsed   Urgency Only)/       Disabled   since the last programming   Disable           and one or more of the           following conditions still exist:           VF detection has been           disabled, or more than two VF           Therapies have been disabled,           or FVT is enabled to ‘via VF’           and more than two FVT           therapies have been disabled.       High   The measured threshold for   Independently       Threshold   the chamber is at 5 V for 1 day.   Enabled for each               paced chamber       AT/AF   The cumulative time that the   Enable/Disable:       Burden   patient has been in AT/AF in a   Time in AT/AF           given day (since midnight) has   Threshold           exceeded the acceptable           duration as set by the care           giver.       Fast V   The patient has a mean   Enable/Disable:       Rate   ventricular rate while in AT/AF   Ventricular Rate       during   that has exceeded the   while in AT/AF       AT/AF   acceptable rate threshold, and   Threshold and           AT/AF has occurred for a   Min. Time in           minimum, cumulative duration   AT/AF Threshold           as selected by the care giver           (may be a different duration           than AT/AF Burden duration).           Determined on a per day           basis.       Thoracic   The fluid index exceeded the   Enable/Disable,       Fluid   threshold, indicating possible   Threshold, Alert       Overload   thoracic fluid accumulation in   Time       Alert   the patient.                  
 
      Alert system  20  not only allows care giver C to enable or disable the alert conditions, but also allows care giver C to select the response to each condition. If care giver C selects the alert mode to be “audible,” the alert method is set as a patient alert. If care giver C selects the alert mode to be “silent,” the alert method will be a silent alert. Finally, if the user selects the alert mode to be “audible+silent,” both methods of notification will be used.  
      Additionally, a number of abnormalities always produce a notification and cannot be disabled by care giver C. These relate to catastrophic conditions requiring immediate follow-up and are shown in Table 2.  
               TABLE 2                          Non-Programmable Alert Conditions                                 PROGRAMMABLE               CONDITION       ALERT NAME   DESCRIPTION   PARAMETERS               Power-On   A POR has occurred   No selectable       Reset (POR)       parameters       CPU Lockout   The device has entered the   No selectable           CPU Lockout state   parameters       Charge Time-   An attempt to charge the high   No selectable       out   voltage therapy capacitors   parameters           has aborted due to a time-out       Incorrectly   The case electrode is   No selectable       Configured   disabled as a high voltage   parameters       Defibrillation   therapy electrode and there is       System   no acceptable impedance for           a defibrillation pathway       Permanent   The programmed pacing   No selectable       Asynchronous   mode was asynchronous at   parameters       Mode   midnight of the device clock,           and still asynchronous at the           alert alarm time                  
 
       FIGS. 7-10  are exemplary screen shots of user interface  210  allowing care giver C to select care giver selectable alert settings.  FIGS. 7 and 8  show clinical management alert settings and  FIGS. 9 and 10  show lead/device integrity alert settings.  FIG. 7  shows the dual-column clinical management alert settings that are available when “Patient Home Monitor” is set to “Yes” (enabled).  FIG. 8  shows the single-column clinical management alert settings that are available when “Patient Home Monitor” is set to “No” (disabled). Similarly,  FIGS. 9 and 10  show the lead/device integrity alert settings that are available when “Patient Home Monitor” is set to “Yes” or “No”. User interface  210  provides a plurality of menus and sub-menus through which care giver C can select the desired alert settings. User interface  210  may be provided to care giver C in a number of different embodiments. In a first exemplary embodiment, user interface  210  is provided on a programmer for IMD  24 . A programmer for an implantable medical device is well known in the art and typically includes a computer-like system having a display and input devices such as a keyboard. The programmer also includes a communication device such as an RF head or a wireless telemetry system which allows the programmer to program IMD  24 . In this embodiment, user interface  210  is displayed on the display of the programmer, such that care giver C is able to select the desired alert settings. After care giver C has selected the desired settings, the programmer programs the settings into IMD  24 .  
      In a second exemplary embodiment, user interface  210  is provided by patient management system  28 . In this embodiment, user interface  210  is displayed to care giver C as a part of care giver website  31   b . Care giver C is able to select the desired alert settings through care giver website  31   b  and then save them to patient management network  28 . Patient management network  28  then initiates communication through private network  27 , and monitor  26  to IMD  24  where the care giver selectable alert settings are stored in IMD  24 .  
      To select the desired settings, care giver C first selects the type of settings that he or she wishes to set: Clinical Management Alerts ( FIGS. 7 and 8 ) or Lead/Device Integrity Alerts ( FIGS. 9 and 10 ). Clinical Management Alerts relate to events involving the condition of patient P, while Lead/Device Integrity Alerts relate to events involving the condition of IMD  24  and attached leads.  
      The user interface provides the option of enabling or disabling care giver-selectable settings for the interaction between IMD  24  and monitor  26  altogether. This feature accommodates those patients that do not have a monitor. Care giver C selects whether monitor  26  should be enabled or disabled by selecting the “Patient Home Monitor” field and selecting “Yes” or “No.” If care giver C selects “Yes” then care giver-selectable silent alert options are enabled ( FIGS. 7 and 9 ). If care giver C selects “No” then all silent alert options are disabled ( FIGS. 8 and 10 ).  
      The desired settings are then selected from the menu and sub-menus as desired. For example, if care giver C wants to be alerted to an atrial tachycardia within patient P that exceeds a certain duration or exceeds a certain rate, care giver C would select the option that reads “AT/AF Burden and Rate Settings . . . ” Care giver C would then be provided with a sub-menu in which he or she could select the type of alert desired, the urgency of the alert, and the duration or heart rate at which the alert would trigger. In addition, care giver C is also able to select the specific time of the day in which a patient alert (“device tone”) is provided by selecting “Alert Time . . . ” Alert settings for Lead/Device Integrity Alerts are similarly chosen through the menus as shown in  FIGS. 9 and 10  and additional sub-menus.  
       FIG. 11  is an exemplary flow diagram illustrating a method of sending an alert signal when an event occurs and an end alert signal when an event terminates. This method of providing alert signals allows a care giver to be notified not only of when an event begins, but also when that same event comes to an end.  
      The process of detecting an event and sending an alert signal remains the same as that previously described. IMD  24  monitors for the occurrence of an event (step  202 ). Once an event is detected (step  204 ), IMD  24  transmits a silent alert to the care giver (step  206 ). If the silent alert is unsuccessful, IMD  24  retries the transmission a predetermined number of tries (step  208 ). If the silent alert is still unsuccessful, IMD  24  activates the patient alert (step  210 ).  
      At this point, either the silent alert has been sent to care giver C, or the patient alert has been provided to alert patient P. IMD  24  then continues monitoring this event to detect the end of the event (steps  212  or  214 ). Meanwhile, if a patient alert was provided (step  210 ), this alert can be repeated periodically (step  216 ) to ensure that patient P has become aware of the occurrence of the event. When the end of the event is detected, IMD  24  transmits an end alert signal (step  218 ) in the same way that the alert signal was previously transmitted. If the transmission of the end alert signal is unsuccessful, IMD  24  retries the transmission (step  220 ). When the end alert signal is successfully transmitted, care giver C is notified that the event has terminated, in the same way that care giver C was notified of the occurrence of the event.  
      In an embodiment of the present invention, sensors  48  of IMD  24  (shown in  FIG. 2 ) include a transthoracic impedance sensor. The transthoracic impedance sensor is used to measure the impedance between a lead in a chamber of the heart and the can of IMD  24 . This impedance measurement can be used to detect the amount of fluid in the lungs, and the onset of edema. Edema has been found to be a strong indicator of heart failure, and can be used to detect heart failure before any other symptoms are detectable by the patient. Once edema has been detected, care giver C may choose to make use of one of a number of possible therapies. These therapies may include electrical stimulation from IMD  24  or medications.  
      The onset of edema can be detected by measuring the transthoracic impedance and comparing this to a threshold value or a normal range of values. The threshold value can be selected by a user, or set dynamically by IMD  24 . The dynamic settings are provided by monitoring the patient over a period of time and determining the normal fluctuations in transthoracic impedance. The normal range, or a minimum threshold value is then calculated.  
      In any event, IMD  24  continues to monitor the transthoracic impedance, to determine whether the therapy is successful. If the therapy is successful, IMD  24  will detect a decrease in the transthoracic impedance, which indicates that the amount of fluid in the lungs has been reduced. Once the impedance measurement is reduced below a predetermined threshold value, IMD  24  provides end alert signal to the physician to inform the physician that the therapy has been successful.  
       FIG. 12  shows a more detailed embodiment utilizing an alert signal and an end alert signal. This embodiment is described with reference to a transthoracic impedance sensor to detect the onset and termination of edema. However, it is recognized that the embodiment is equally useful and applicable for sensing any other detectable event. For example, care givers will likely find the present invention particularly useful for monitoring events in which the time between onset and termination of the event is a relatively long period of time, such as one day or more. Detectable events such as reduced transthoracic impedance, out of range blood pressure, glucose level excursions, neurological events, empty reservoir in a drug infusion device, out of range electrolytes or protein levels are all examples of detectable events in which a physician will not only want to know when the event occurs, but also when the event terminates, often as a result of drugs or other therapies, or interaction from the patient or a care giver. It is also recognized that mathematical calculations may be performed on any, or a combination of, sensed levels or events, the result of these calculations being compared to a threshold value or range of values to determine whether an event has occurred or terminated.  
      The method begins with the fluid alert condition not met (step  230 ). At this point a sustained low impedance flag in IMD  24  is set to “0” to indicate that the transthoracic impedance is above a threshold value. Fluid calculations are then performed periodically (step  232 ). For example, the fluid calculations may be performed daily at a predetermined time such as 5:00 p.m. Alternatively, in order to account for daily fluctuations in transthoracic impedance these measurements may be taken periodically throughout the day, for example twenty measurements may be spread out through the day between a period of noon until 5:00 p.m.  
      At the end of the period the measurements are compared to a threshold value set by care giver C. If the transthoracic impedance is below the predetermined threshold value the sustained low impedance flag is set to “1” to indicate that the fluid alert condition has been met (step  234 ). If the transthoracic impedance is not below the predetermined threshold value the sustained low impedance flag stays set at “0” and IMD  24  continues to monitor the patient for future occurrences. If the fluid alert condition has been met (step  234 ), IMD  24  then begins the process of sending a silent alert. This process begins with IMD  24  uplinking its device identification code (ID) to monitor  26  (step  236 ). The device ID may also include a medical event uplink code to indicate to monitor  26  that a medical event has occurred. The device ID informs monitor  26  that IMD wishes to communicate with it. Alternatively, a communication session can be scheduled in advance such that monitor  26  initiates the communication between IMD  24  and monitor  26 . In any event, monitor  26  performs a full interrogation of IMD  24  by transmitting an open session command, receiving device data including data about the occurrence of the event, and then transmitting a close session command (step  238 ). If both the open session and close session commands are received by IMD  24 , IMD  24  recognizes that the silent alert transmission was successful (step  240 ).  
      In another embodiment of the invention, IMD  24  includes a successful session bit. The successful session bit is turned ON (set to “1”) after monitor  26  successfully transmits the alert. When monitor  26  successfully transmits the alert, monitor  26  initiates communication with IMD  24  to program the successful session bit ON to inform IMD  24  that the alert has been successfully transmitted.  
      If IMD  24  did not receive both the open session and close session commands (step  238 ) (or if the successful session bit in IMD  24  has not been programmed ON by monitor  26 ), IMD  24  begins the silent alert retry process (steps  242 - 246  , and  236 - 238 ) in which IMD  24  retries transmission periodically (for example every three hours) for maximum number of attempts (such as twenty-four) or a maximum amount of time (such as three days). If the retry process is unsuccessful for a predetermined maximum number of attempts (step  242 ) IMD  24  recognizes that the silent alert transmission failed (step  248 ). As a result, IMD  24  stores an observation note that will inform care giver C, upon the next follow-up, that a silent alert was attempted and was unsuccessful.  
      IMD  24  then provides a patient alert (steps  250 - 256 ) to inform patient P that the fluid alert condition has been met. At this point IMD  24  verifies that the fluid alert condition is still met (step  250 ) and verifies that the fluid alert alarm indicator has not been cleared (step  252 ). If the fluid alert condition is not still met (step  250 ) IMD  24  returns to monitoring patient P for a future event (step  230 ). If IMD  24  determines that the fluid alert condition has still been met (step  250 ) and that the fluid alert alarm indicator has not been cleared (step  252 ), it then provides a patient alert such as a high urgency backup tone (step  254 ). This alert may be provided immediately or at the programmed “fluid alert time.” IMD  24  then continues with the patient alert retry process (steps  250 - 256 ). The retry process will repeatedly perform fluid calculations (step  256 ), determine whether the fluid alert condition is still met, whether the fluid alert alarm indicator has been cleared, and provide the patient alert if necessary.  
      After providing either a silent alert (step  240 ) or a patient alert (steps  250 - 256 ), IMD  24  begins monitoring for the end of the event. To do so, IMD  24  determines whether the fluid alert condition is unmet (in other words whether the sustained low impedance flag has returned to “0”) (step  258 ). If the event has not terminated, IMD  24  continues to monitor for the termination of the event by performing fluid calculations (step  260 ) and determining whether the fluid alert condition has been unmet (step  258 ). When the termination of the event is detected (such that the sustained low impedance flag is set to “0”) IMD  24  begins the process of sending a silent end alert signal.  
      To transmit a silent end alert signal, IMD  24  uplinks its device ID (step  262 ) to monitor  26 . Monitor  26  then recognizes that IMD  24  wishes to communicate with it and performs a full interrogation of IMD  24 . Alternatively, a communication session can be scheduled in advance, such that monitor  24  initiates the communication between IMD  24  and monitor  26 . In any event, monitor  26  transmits an open session command, receives the interrogation data including data about the end of the event, and transmits a close session command (step  264 ). If IMD  24  receives both the open session and close session commands (or if the successful session bit has been programmed ON), IMD  24  recognizes that the silent end alert signal was successfully received and IMD  24  returns to monitoring for the occurrence of the next event (step  230 ). If both the open session and close session commands are not received by IMD  24  (step  264 ) (or the successful session bit has not been programmed ON), IMD  24  again begins a retry process (steps  262 - 270 ) in which the transmission is retried periodically (such as every three hours) for a maximum number of attempts (such as twenty-four) or a maximum amount of time (such as three days). If the retry process (steps  262 - 270 ) is unsuccessful, such that the silent end alert is not transmitted successfully, IMD  24  recognizes that the transmission of the silent end alert was not successful (step  272 ). IMD  24  then makes an observation note for the care giver, such that a caregiver will be informed upon the next follow-up that the silent end alert transmission was attempted but was not successful (step  272 ). IMD  24  then returns to monitoring for the occurrence of the next event (step  230 ).  
      In an embodiment of the invention, monitor  26  includes an LED to provide a visual indicator to patient P of the occurrence of an event. The LED is turned on when monitor  26  receives the silent alert. After the event terminates, and monitor  26  receives the silent end alert signal, the LED is turned off to indicate that the event has terminated.  
       FIG. 13  shows an alternate communications system by which alert signals may be transmitted to a medical support network. IMD  280  is shown as being an implantable medical device, but could alternately be external rather than implantable. External device  282  is portable and carried with patient P and communicates with IMD  280  by wireless signals. External device  282  communicates with communications link transceiver  284  by wireless signals. Transceiver  284 , in turn, communicates with medical support network  288  via telephone lines  286 . Any of a number of forms of communication of data may be used. External device  282  may also communicate with medical support network  288  via communications link satellite  290 . Once an alert is received by medical support network  288 , care giver C is notified.  
      Although alert system  20  of the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. The inventors have contemplated many changes which will be readily understood by one skilled in the art. For example, the alert system includes a number of patient alert methods including a speaker in IMD  24  and a speaker and LED&#39;s in monitor  26 . Other known types of patient alerts may also be used including muscle stimulation, vibration, or olfactory stimulation (in an external device such as monitor  26 ). Furthermore, multiple patient alerts may be provided such that care giver C can select the most desired alert for the particular event. Similarly, various means of alerting the care giver (or any other person) are contemplated. An alert may be provided to a device worn or nearby a care giver such as a telemetry enabled watch, home PC, public access transponder, WiFi/Bluetooth network, telephone, pager, cell phone, or displayed on a programmer during the next interrogation. Alternatively, the alert could be provided to a call center from monitor  26  or patient management network  28 , the call center having an operator who would contact the care giver. The alerts may include all information from the interrogation of IMD  24 , or it may be simply a message informing care giver C to check care giver website  31   b . Furthermore, a silent alert may be provided to alert patient P of the occurrence of an event in the same way that a silent alert is provided to alert care giver C of the occurrence of an event.  
      The exemplary embodiments of the invention store the care giver-selectable alert settings in memory  64  of IMD  24 . It is recognized that the alert settings may also be stored in other locations such that other methods may be utilized. For example, care giver-selectable alert settings can be stored only on patient management network  28 . In this embodiment, IMD  24  would send an alert signal to monitor  26  upon the occurrence of any possible event. Monitor  26  would then transfer the alert to patient management network  28 . Patient management network  28  would then inform care giver C of the event only if the settings for that particular alert had been programmed ON. In another exemplary embodiment, the care giver-selectable alert settings are again stored on patient management network  28 . IMD  24  then provides an alert signal frequently (preferably more than one per day) and the patient management network  28  would inform care giver C only if an event were detected which matched an event that was programmed ON in the care giver-selectable alert settings. Although these embodiments reduce the amount of memory needed on IMD  24  (or increase the amount of memory available for other data storage), they also decrease the longevity of the battery of IMD  24  by requiring more frequent transmission of data.  
      Furthermore, the alert system  20  is capable of providing an alert when an event is detected by IMD  24 . It is recognized that this alert may be provided for any event which can be detected by IMD  24 , or any other device in the system, or a system in communication with any device in the system. The event may include an event internal to IMD  24  , within patient P, or external to patient P. Sensors capable of detecting the event may include any known sensor such as cardiac sensors, blood sensors, neurological sensors, a global positioning system receiver, microphones, magnetic sensors, pressure sensors, temperature sensors, impact sensors, electric or magnetic field sensors, vibration sensors, chemical sensors, light sensors, radiation sensors, etc. In addition, control processor  50  can be utilized to perform calculations, check for patterns, or otherwise process data and provide an alert based upon a predetermined criterion. Thus, it should be understood that the alert system of the present invention provides enormous possibilities for improving the safety of patients, increasing the quality of care that they receive, and increasing their quality of life.