System for patient alerting associated with a cardiac event

A system for the detection of cardiac events occurring in a human patient is provided. At least two electrodes are included in the system for obtaining an electrical signal from a patient's heart. An electrical signal processor is electrically coupled to the electrodes for processing the electrical signal and a patient alarm is further provided and electrically coupled to the electrical signal processor. The patient alarm generates an escalating sensory alarm signal over a predetermined time period subsequent to the electrical signal processor if the processor detects a cardiac event. The patient alarm may be further applied to a pacemaker or defibrillator system.

FIELD OF USE

This invention is in the field of implantable medical device systems that monitor a patient's cardiovascular condition.

BACKGROUND OF THE INVENTION

Heart disease is the leading cause of death in the United States. A heart attack (also known as an acute myocardial infarction (AMI)) typically results from a thrombus (i.e., a blood clot) that obstructs blood flow in one or more coronary arteries. AMI is a common and life-threatening complication of coronary artery disease. Coronary ischemia is caused by an insufficiency of oxygen to the heart muscle. Ischemia is typically provoked by physical activity or other causes of increased heart rate when one or more of the coronary arteries is narrowed by atherosclerosis. AMI, which is typically the result of a completely blocked coronary artery, is the most extreme form of ischemia. Patients will often (but not always) experience chest discomfort (angina) when the heart muscle is experiencing ischemia. Those with coronary atherosclerosis are at higher risk for AMI if the plaque becomes further obstructed by thrombus.

The current treatment for a coronary artery narrowing (a stenosis) is the insertion of a drug-eluting stent such as the Cypher™ sirolimus-eluting stent from Cordis Corporation or the Taxus™ paclitaxel-eluting stent from the Boston Scientific Corporation. The insertion of a stent into a stenosed coronary artery is a reliable medical treatment to eliminate or reduce coronary ischemia and to prevent the complete blockage of a coronary artery, which blockage can result in an AMI.

Acute myocardial infarction and ischemia may be detected from a patient's electrocardiogram (ECG) by noting an ST segment shift (i.e., voltage change). However, without knowing the patient's normal ECG pattern, detection from a standard 12 lead ECG can be unreliable.

Fischell et al. in U.S. Pat. Nos. 6,112,116, 6,272,379 and 6,609,023 describe implantable systems and algorithms for detecting the onset of acute myocardial infarction and providing both patient alerting and treatment. The Fischell et al. patents describe how the electrical signal from inside the heart (which is called an “electrogram”) can be used to determine various states of myocardial ischemia.

The Reveal™ subcutaneous loop Holter monitor sold by Medtronic, Inc., uses two case electrodes spaced about 3 inches apart to record electrocardiogram information. Recording can be triggered automatically when arrhythmias are detected or upon patient initiation using an external device. The Reveal is designed to record electrogram data only and does not include a patient alerting capability. The Reveal also does not have the capability to measure or alert the patient if there is an ST segment shift. In fact, the Reveal's high pass filtering and electrode spacing preclude accurate detection of changes in the low frequency aspects of the heart's electrical signal such as the ST segment of the electrogram.

While pacemakers and Implantable Cardioverter Defibrillators (ICDs) monitor the patient's electrogram, they do not currently detect ST segment changes nor provide patient alerting.

The term “medical practitioner” shall be used herein to mean any person who might be involved in the medical treatment of a patient. Such a medical practitioner would include, but is not limited to, a medical doctor (e.g., a general practice physician, an internist or a cardiologist), a medical technician, a paramedic, a nurse or an electrogram analyst. Although the masculine pronouns “he” and “his” are used herein, it should be understood that the patient, physician or medical practitioner could be a man or a woman. A “cardiac event” includes an acute myocardial infarction, ischemia caused by effort (such as exercise) and/or an elevated heart rate, bradycardia, tachycardia or an arrhythmia such as atrial fibrillation, atrial flutter, ventricular fibrillation, and premature ventricular or atrial contractions (PVCs or PACs respectively).

It is generally understood that the term “electrocardiogram” is defined as the heart's electrical signals sensed by means of skin surface electrodes that are placed in a position to indicate the heart's electrical activity (depolarization and repolarization). An electrocardiogram segment refers to a portion of electrocardiogram signal that extends for either a specific length of time, such as 10 seconds, or a specific number of heart beats, such as 10 beats. A beat is defined as a sub-segment of an electrogram or electrocardiogram segment containing exactly one R wave. As used herein, the PQ segment of a patient's electrocardiogram or electrogram is the typically straight segment of a beat of an electrocardiogram or electrogram that occurs just before the R wave and the ST segment is a typically straight segment that occurs just after the R wave.

Although often described as an electrocardiogram (ECG), the electrical signal from the heart as measured from electrodes within the body is properly termed an “electrogram”. As defined herein, the term “electrogram” is the heart's electrical signal voltage as sensed from one or more implanted electrode(s) that are placed in a position to indicate the heart's electrical activity (depolarization and repolarization). An electrogram segment refers to a portion of the electrogram signal for either a specific length of time, such as 10 seconds, or a specific number of heart beats, such as 10 beats. For the purposes of this specification, the terms “detection” and “identification” of a cardiac event have the same meaning.

A heart signal parameter is defined to be a measured or calculated value created during the processing of one or more beats of the electrogram (or electrocardiogram). Heart signal parameters include the following: ST deviation (ST segment average value minus PQ segment average value), ST shift (ST deviation compared to a baseline average ST deviation), average signal strength, T wave peak height, T wave average value, T wave deviation, QRS complex width, number of PVCs per unit time, heart rate and R-R interval.

SUMMARY OF THE INVENTION

The present invention system for the detection of coronary ischemia (including AMI) as described herein shall be called the “Guardian” system. The Guardian system detects cardiac events using an implanted sub-system called a “cardiosaver system” which is designed to detect cardiac events including arrhythmias and coronary ischemia. A “cardiac event” can be an acute myocardial infarction, ischemia caused by effort (such as exercise) and/or an elevated heart rate, bradycardia, tachycardia or an arrhythmia such as atrial fibrillation, atrial flutter, ventricular fibrillation, and premature ventricular or atrial contractions (PVCs or PACs respectively). The present invention cardiosaver system is designed to detect ischemia (including AMI) by identifying ST segment changes in a positive direction (ST elevation) or negative direction (ST depression).

The cardiosaver system includes electrodes placed to advantageously sense electrical signals from the heart that is the electrogram. The electrodes can be placed within the heart and/or subcutaneously. The implanted portion of the Guardian system is the cardiosaver system as described by Fischell et al. in U.S. Pat. Nos. 6,112,116, 6,272,379 and 6,609,023, each of these patents being incorporated herein by reference. The Guardian system also includes external equipment that can include a physician's programmer and an external alarm device also described in the Fischell et al. patents.

The present invention is a cardiosaver system that utilizes techniques for patient alerting designed to ensure the patient knows what is happening without startling the patient, which could cause an unwanted rise in heart rate at the time of a cardiac event when it is important to remain calm.

In the Fischell et al. patents mentioned above, the concept of internal and external alarm signals is discussed, including the technique of using different patterns of sound, vibration or electrical tickle to assist the patient in differentiating between an emergency (major or critical) alarm where immediate medical attention is needed and a “see your doctor” alert where an appointment should be scheduled as soon as convenient.

The present invention alerting system improves upon the Fischell et al. concepts by using alert escalation techniques that will communicate the emergency alarm, see doctor alert and/or other patient alert messages without startling or scaring the patient. One embodiment of the present invention uses an increasing amplitude of vibration over time from an internal alarm signal within the implanted cardiosaver. For example, the vibration amplitude might increase over a period of several minutes until it reaches a pre-set level. The escalating amplitude technique can also be applied if the internal alarm uses an electrical tickle or other means of alerting the patient. Also the present invention Guardian system may include an increasing amplitude for the external alarm signal generated by the external alarm system mentioned by Fischell et al. The external alarm signal can be a sound, vibration or visual display with sound being the preferred embodiment.

It is also envisioned that not only can the amplitude of the internal and/or external alarm signals be increased over time, but the pattern and frequency of the signal might change. For example, the internal alarm might use sets of three successive vibrations with a short time between vibrations within a set and a longer time between sets where the time between sets of vibrations might decrease over time. The time between vibrations within a set might also decrease as the alert escalates. Another example might have the external alarm signal using a tone or tone sequence that increases in the pitch of the tones as the alert escalates. Finally, if a visual display using sets of light flashes is used as the external alarm signal, then the escalation might include the brightness of the flashes, an increase in the number of the flashes within a set, a decrease in the time between sets and a change in the color of the flashes.

For the purposes of this invention, the term “alarm signal” refers to the complete signal internally or externally generated to alert the patient to the detection of a cardiac event. An alarm signal will continue until a timer turns it off after a pre-set time period (e.g., 5 minutes) or an alarm silence command is provided to the source generating the alarm. A typical alarm signal will be made up of a sequence of short (less than 10 seconds long) alerting signals. The alerting signals may be produced in sets with an inter-set time interval defined as the time interval between sets of alerting signals and the intra-set time interval defined as the time between alerting signals within a set of alerting signals.

So in summary, the present invention is an implanted system for the detection of cardiac events having any combination of internal alarm signals and external alarm signals where, over the initial period of patient alerting, the alarm signals escalate by any or all of the following:a) An increase in amplitude of alerting signals over time;b) An increase in the number of alerting signals per set;c) A decrease in the time between alerting signals within a set;d) A decrease in the time between sets of alerting signals;e) A change in the frequency (vibrational frequency, sound pitch, color) of the alerting signals; and,f) An increase in the frequency, length and/or amplitude of each alerting signal within a set (including a set of one alerting signal).

Another embodiment of the present invention is an implanted ischemia detection device with patient alerting that also includes pacemaker circuitry to pace the patient's heart as needed. Still another embodiment is an implanted ischemia detection device with patient alerting that includes Implantable Cardiac Defibrillator (ICD) circuitry to defibrillate the patient's heart as needed. Yet another embodiment is an implanted ischemia detection device with patient alerting that includes a combination of pacemaker and ICD circuitry.

It is also envisioned that there could be an escalating pattern where the number of alerting signals in each set increases while the length of each alerting signal decreases.

It is also envisioned that the escalation of alerting might involve the sequencing of internal and external alarms. For example, the external alarm signal might begin first as people who are used to phones ringing are less likely to be startled by external alerting sounds. After a preset period of time, the internal alarm signal might begin. Neither, either or both the external and internal alarm signals in such a sequential activation might use one or more alarm signals that escalate by the means described above.

Thus it is an object of this invention to have a Guardian system that can alert a patient to the detection of a cardiac event without causing a startle response.

Another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates over time.

Still another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by increasing amplitude over time.

Still another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by increasing frequency over time.

Yet another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by decreasing the time between alerting signals within sets of the alarm signal.

Yet another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by decreasing the time between sets of alerting signals within the alarm signal.

Yet another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by increasing the number of alerting signals within sets of the alarm signal.

Yet another object of this invention is to have a Guardian system that can alert a patient to the detection of a cardiac event where the alarm signal escalates by increasing the frequency, length and/or amplitude of each alerting signal with a set (including a set of one alerting signal).

Yet another object of the present invention is to have a Guardian system with an implanted component having the capability to generate an internal alarm signal and an external alarm system capable of generating an external alarm signal where the patient alert initiates the external alarm signal before the internal alarm.

Yet another object of the present invention is to have a Guardian system with an implanted component having the capability to generate an internal alarm signal and an external alarm system capable of generating an external alarm signal where the patient alert initiates the internal alarm signal before the external alarm.

These and other objects and advantages of this invention will become obvious to a person of ordinary skill in this art upon reading of the detailed description of this invention including the associated drawings as presented herein.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates one embodiment of the Guardian system10consisting of an implanted cardiosaver system5and external equipment7. The cardiosaver system5includes a cardiosaver11, an antenna6and an electrode4that is part of a lead2. The cardiosaver11includes electronic circuitry that can detect a cardiac event such as an acute myocardial infarction or arrhythmia and can warn the patient when a cardiac event occurs. The cardiosaver11can store the patient's electrogram for later readout and can send and receive wireless signals3to and from the external equipment7via the implanted antenna6and the external antenna25. The functioning of the cardiosaver system5will be explained in greater detail with the assistance ofFIG. 2.

The cardiosaver system5has at least one lead2with at least one electrode4. In fact, the cardiosaver system5could utilize as few as one lead or as many as three and each lead could have as few as one electrode or as many as eight electrodes. The lead2inFIG. 1could advantageously be placed subcutaneously or through the patient's vascular system with the electrode4being placed into the apex of the right ventricle. For example, the lead2could be placed in the right ventricle or right atrium or the superior vena cava similar to the placement of leads for pacemakers and ICDs. The metal case of the cardiosaver11could serve as an indifferent electrode with the electrode4being the active electrode. Alternately, the lead2inFIG. 1could be placed through the patient's vascular system with the electrode4being placed into the apex of the left ventricle.

The lead2could advantageously be placed subcutaneously at any location where the electrode4would provide a good electrogram signal indicative of the electrical activity of the heart. Again for the lead2, the case of the cardiosaver11of the cardiosaver system5could be an indifferent electrode and the electrode4would be the active electrode. Although the Guardian system10described herein can readily operate with only two electrodes, or one electrode and the case of the cardiosaver being the other electrode, it is envisioned that multiple electrodes used in monopolar or bipolar configurations could be used.

FIG. 1also shows the external equipment7that consists of an external alarm transceiver20, a physician's programmer18, a pocket PC12, an emergency room diagnostic system16and the equipment14in a remote diagnostic center. The external equipment7provides the means to interact with the cardiosaver system5. These interactions include programming the cardiosaver11, retrieving data collected by the cardiosaver system5, and handling alarms generated by the cardiosaver11. It should be understood that the cardiosaver system5could operate with some but not all of the external equipment7.

The external alarm transceiver20includes a battery21, an alarm disable/panic button22, a radio frequency transceiver23, a microphone27, an alarm-speaker24, an antenna25, a GPS satellite receiver26, and a standard interface28for providing wired or wireless communication with the pocket PC12, emergency room diagnostic system16, or physician's programmer18. A long distance voice/data communications interface29provides connectivity to the remote diagnostic center equipment14through voice and data telecommunications networks. For example, the microphone27and speaker24could be used for wired or wireless telephone calls to and from a medical practitioner at the remote diagnostic center. A built-in modem as part of the interface29would allow data to be transmitted to and from the remote diagnostic center equipment14over a voice connection. Alternately, a data communications capability of the interface29could allow data to be sent or received through a wired or wireless data network. The external alarm transceiver20may be a separate unit that can be carried by the patient and used by the patient's physician as the data interface to the cardiosaver system5or it may also be built into the pocket PC12, physician's programmer18or emergency room diagnostic system16

The pocket PC also described by Fischell et al. in U.S. Pat. No. 6,609,023 can provide the patient or physician the ability to check the status of the cardiosaver11and display a limited set of electrogram data uploaded from the cardiosaver11.

The emergency room diagnostic system16is a more sophisticated system that can upload and display any of the data stored within the cardiosaver11and would, in its preferred embodiment, use a touch screen display to facilitate triage of patients arriving in an emergency room who have the cardiosaver system5. This should greatly reduce the time from arrival at the emergency room until treatment for cardiosaver system patients having a cardiac event.

The purpose of the physician's programmer18shown inFIG. 1is to set and/or change the operating parameters of the implanted cardiosaver system5and to read out data stored in the memory of the cardiosaver11such as stored electrogram segments as described by Fischell et al. in U.S. Pat. No. 6,609,023.

The external alarm transceiver20would typically be a pager-sized device that the patient would carry on his person or keep in close proximity. If a cardiac event is detected by the cardiosaver system5, an alarm message is sent by a wireless signal3to the alarm transceiver20via the antennas6and25. When the alarm is received by the alarm transceiver20, a patient alerting sound is played through the loudspeaker24to warn the patient that a cardiac event has occurred. Examples of such sounds include a periodic buzzing, a sequence of tones and/or a speech message that instructs the patient as to what actions should be taken. Furthermore, the alarm transceiver20can, depending upon the nature of the signal3, send an outgoing message to the remote diagnostic center equipment14to alert medical practitioners that a cardiosaver system alarm has occurred. The medical practitioners can then utilize the voice communications capabilities of the remote diagnostic center equipment14to call back the patient similar to the call that occurs to car drivers through the ONSTAR service when their car's air bags deploy in an accident. The optional GPS receiver26would allow the data sent to the remote diagnostic center equipment14to include patient location to facilitate the summoning of emergency medical services.

The alarm disable/panic button22will turn off both the internal alarm of the implant5and the sound being emitted from the loudspeaker24. If no alarm is occurring, then pressing the alarm disable/panic button22will place a voice and/or data call to the remote diagnostic center similar to the call that is placed when the ONSTAR button is pressed in a car equipped to access the ONSTAR service. GPS information and a subset of patient electrogram data may be sent as well to the medical practitioners at the remote diagnostic center. The remotely located medical practitioner could then analyze the electrogram data and call the patient back to offer advice as to whether there is an emergency situation or the situation could be routinely handled by the patient's personal physician at some later time.

FIG. 2is a block diagram of the cardiosaver system5. The lead2includes the electrode4and the wire12. The wire12connects the electrode4to the amplifier circuit36that is also connected by the wire15to the cardiosaver case8acting as an indifferent electrode. The amplified electrogram signals37from the amplifier circuit36are converted to digital signals38by the analog-to-digital converter41. The digital electrogram signals38are then sent to the electrical signal processor44. The processor44in conjunction with the memory47can process the digital signals38according to the programming instructions stored in the program memory45. This programming (i.e. software) enables the cardiosaver system5to detect the occurrence of a cardiac event such as an ST segment elevation that is indicative of an acute myocardial infarction.

A clock/timing sub-system49provides the means for timing specific activities of the cardiosaver system5including the absolute or relative time stamping of detected cardiac events. The clock/timing sub-system49can also facilitate power savings by causing components of the cardiosaver system5to go into a low power stand-by mode in between times for electrogram signal collection and processing. Such cycled power savings techniques are often used in implantable pacemakers and defibrillators. In an alternative embodiment, the clock/timing sub-system can be provided by a program subroutine run by the central processing unit44. It is also envisioned that the processor44may include an integral or external First-In-First-Out (FIFO) buffer memory to allow saving of data from before the detection of a cardiac event.

Techniques for detecting cardiac events by the processor44are described by Fischell et al. in U.S. Pat. No. 6,609,023.

An important aspect of the present invention is the filtering of the electrical signals sensed by the electrodes4and8. The preferred embodiment of the present invention cardiosaver11(FIG. 1) will include high pass and/or low pass filtering of the electrical signals in the amplifier circuit36. An alternative embodiment would introduce filtering in any one, two or all of the following locations:1. a separate analog filter between the amplifier circuit36and analog-to-digital converter41,2. a separate digital filter circuit placed between the analog-to-digital converter41and the processor44, and/or3. digital filtering performed by the processor44on the digital signals38.

The memory47includes specific memory locations for patient data, electrogram segment data and any other relevant data.

It is envisioned that the cardiosaver system5could also contain pacemaker circuitry170and/or defibrillator circuitry180similar to the cardiosaver system described by Fischell, et al. et al. in U.S. Pat. No. 6,230,049.

The alarm sub-system48contains the circuitry and transducers to produce the internal alarm signals for the cardiosaver11(FIG. 1). The internal alarm signal can be a mechanical vibration, a sound or a subcutaneous electrical tickle or shock.

The telemetry sub-system46with antenna6provides the cardiosaver system5with the means for two-way wireless communication to and from the external equipment7ofFIG. 1. It is also envisioned that short-range telemetry such as that typically used in pacemakers and defibrillators could also be applied to the cardiosaver system5. It is also envisioned that standard wireless protocols such as Bluetooth and 802.11a or 802.11b might be used to provide communication with a wider group of peripheral devices.

A magnet sensor190may be incorporated into the cardiosaver system5. The primary purpose for a magnet sensor190is to keep the cardiosaver system5in an off condition until it is checked out just before it is implanted into a patient. This can prevent depletion of the battery life in the period between the time that the cardiosaver system5is packaged at the factory and the day it is implanted.

The preferred embodiment of the present invention associated with a pacemaker/ICD or combined pacemaker/ICD would have the event detection and alerting function integrated within the pacemaker, ICD or combined pacemaker/ICD. It is also envisioned that the lead might connect both to a standard pacemaker, ICD or combined pacemaker/ICD and a cardiosaver having an electrical signal processor for cardiac event detection and the ability to generate an escalating patient alert.

FIG. 3is an example of use of increasing the amplitude of an alarm signal to provide an escalating patient alert.FIG. 3shows the progression over time of the three successive sets of alerting signals31,32and33of the alarm signal30. The pattern displayed inFIG. 3can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set31has alerting signals31A,31B and31C, each alerting signal within the set31having an amplitude315, a duration316, and a time interval between the alerting signals31A and31B and the alerting signals31B and31C of311. The set32has alerting signals32A,32B and32C, each alerting signal within the set32having an amplitude325, a duration326and a time interval between the alerting signals32A and32B and the alerting signals32B and32C of321. The set33has alerting signals33A,33B and33C, each alerting signal within the set33having an amplitude335, a duration336and a time interval between the alerting signals33A and33B and the alerting signals33B and33C of331. The time interval between the sets31and32is312and the time interval between the sets32and33is323. It can be seen that the alarm signal30provides an escalating patient alert by progressively increasing the amplitude over time as the amplitude335is greater than the amplitude325which is greater than the amplitude315. Ideally, such an escalating amplitude alert would start at level barely detectable by the patient and increase to a level that cannot be ignored. The physician's programmer18ofFIG. 1would typically provide the capability to test different patterns and intensities of both internal and external alarm signals with the patient to set a patient alert that cannot be missed while also reducing the potential to startle the patient. It is also envisioned that the amplitude might also increase for successive alerting signals within a set. The present invention includes any increase in amplitude over time in any type of internal or external alarm signal. It is also envisioned that after a preset escalation period, the amplitude would reach a pre-set level and no longer increase. An important feature of the programmer18would be to set the initial alerting signal amplitude so that it is just barely perceptible and to set the highest alerting signal amplitude at a level that cannot be missed. AlthoughFIG. 3shows a constant duration of the alerting signals (316,326and336), a constant time between sets (312and323) and constant times between alerting signals within a set (311,321and331) they need not be constant. The times between alerting signals311,321and322are typically less than one second while the times between sets312and323are typically greater than one second.

FIG. 4is an example of use of increasing number of alerting signals within each set of alerting signals of an alarm signal to provide an escalating patient alert.FIG. 4shows the progression over time of the four successive sets of alerting signals41,42,43and44of the alarm signal40. The pattern displayed inFIG. 4can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set41has one alerting signal41A, the alerting signal41A having an amplitude45and a duration46. The set42has two alerting signals42A and42B, each alerting signal within the set42having an amplitude45, a duration46and a time interval between the alerting signals42A and42B of421. The set43has three alerting signals43A,43B and43C, each alerting signal within the set43having an amplitude45, a duration46and a time interval between the alerting signals43A and43B and the alerting signals43B and43C of431. The set44has four alerting signals44A,44B,44C and44D, each alerting signal within the set44having an amplitude45, a duration46, and a time interval between the alerting signals44A and44B, the alerting signals44B and44C, and the alerting signals44C and44D of44. The time interval between the sets41and42is412, the time interval between the sets42and43is423, the time interval between the sets43and44is434. It can be seen that the alarm signal40provides an escalating patient alert by progressively increasing the number of alerting signals per set over time.

Although the pattern shown inFIG. 4shows an increase by one of the number of alerting signals in successive sets, it is envisioned that an increase in the number of alerting signals per set could occur faster, e.g. an increase by two from one set to the next. It is also envisioned that the increase in the number of alerting signals per set could occur more slowly, e.g. an increase by one after every two sets. Ideally, such an escalating alert would start with a single alerting signal in a set such as the set41and increase to a preset number of alerting signals per set. The present invention includes any progressive increase in the number of alerting signals per set in an internal or external alarm signal. It is also envisioned that after a preset escalation period, the number of alerting signals per set would reach a pre-set level and no longer increase. AlthoughFIG. 4shows a constant amplitude45, a constant duration of the alerting signals46, a constant time between sets (412,423and434) and constant times between alerting signals within a set (421,431and441), they need not be constant. The times between alerting signals421,431and441are typically less than one second while the times between sets412,423and434are typically greater than one second. It is also envisioned that as the number of alerting signals within a set increases, the duration46of the alerting signals might decrease. This will subsequently reduce the total time for sets of alerting signals as the number of alerting signals increases.

FIG. 5is an example of use of decreasing time between alerting signals within a set of alerting signals of an alarm signal to provide an escalating patient alert.FIG. 5shows the progression over time of the three successive sets of alerting signals51,52and53of the alarm signal50. The pattern displayed inFIG. 5can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set51has alerting signals51A,51B and51C, each alerting signal within the set51having an amplitude55, a duration516and a time interval between the alerting signals51A and51B and the alerting signals51B and51C of511. The set52has alerting signals52A,52B and52C, each alerting signal within the set52having an amplitude55, a duration526and a time interval between the alerting signals52A and52B and the alerting signals52B and52C of521. The set53has alerting signals53A,53B and53C, each alerting signal within the set53having an amplitude55, a duration536and a time interval between the alerting signals53A and53B and the alerting signals53B and53C of531. The time interval between the sets51and52is512and, the time interval between the sets52and53is523. It can be seen that the alarm signal50provides an escalating patient alert by progressively decreasing the time between alerting signals within successive sets over time as the time511is greater than the time521which is greater than the time531. It is also envisioned that the time between alerting signals might decrease for successive alerting signals within a set. The present invention includes any progressive decrease in the time between successive alerting signals in an internal or external alarm signal. It is also envisioned that after a preset escalation period, the time between alerting signals would reach a pre-set level and no longer decrease. AlthoughFIG. 5shows a constant amplitude55, a constant duration of the alerting signals (516,526and536) and a constant time between sets (512and523) they need not be constant. The times between alerting signals511,521and531are typically less than the times between sets512and523.

FIG. 6is an example of use of decreasing time between sets of alerting signals of an alarm signal to provide an escalating patient alert.FIG. 6shows the progression over time of the four successive sets of alerting signals61,62,63and64of the alarm signal60. The pattern displayed inFIG. 6can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set61has alerting signals61A and61B, each alerting signal within the set61having an amplitude65, a duration616and a time interval between the alerting signals61A and61B of611. The set62has alerting signals62A and62B, each alerting signal within the set62having an amplitude65, a duration626and a time interval between the alerting signals62A and62B of621. The set63has alerting signals63A and63B, each alerting signal within the set63having an amplitude65, a duration636and a time interval between the alerting signals63A and63B of631. The set64has alerting signals64A and64B, each alerting signal within the set64having an amplitude65, a duration646and a time interval between the alerting signals64A and64B of641. The time interval between the sets61and62is612, the time interval between the sets62and63is623and the time interval between the sets63and64is634. It can be seen that the alarm signal60provides an escalating patient alert by progressively decreasing the time between sets of alerting signals over time as the time612is greater than the time623which is greater than the time634. The present invention includes any progressive decrease in the time between successive sets of alerting signals in an internal or external alarm signal. It is also envisioned that after a preset escalation period, the time between sets of alerting signals would reach a pre-set level and no longer decrease. AlthoughFIG. 6shows a constant amplitude65, a constant duration of the alerting signals (616,626,636and646) and a constant time between alerting signals within each set (611,621,631and641), they need not be constant. The times between alerting signals611,621,631and641are typically less than the times between sets612,623and634.

FIG. 7is an example of use of increasing frequency (decrease in wavelength) for successive sets of alerting signals of an alarm signal to provide an escalating patient alert.FIG. 7shows the progression over time of the three successive sets of alerting signals71,72and73of the alarm signal70. The pattern displayed inFIG. 7can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. For a visual display a change in frequency would typically entail a change in color. The set71has alerting signals71A and71B, each alerting signal within the set71having a wavelength717, an amplitude75, a duration716and a time interval between the alerting signals71A and71B of711. The set72has alerting signals72A and72B, each alerting signal within the set72having a wavelength727, an amplitude75, a duration726and a time interval between the alerting signals72A and72B of721. The set73has alerting signals73A and73B, each alerting signal within the set73having a wavelength737, an amplitude75, a duration736and a time interval between the signals73A and73B of731. The time interval between the sets71and72is712and the time interval between the sets72and73is723. It can be seen that the alarm signal70provides an escalating patient alert by progressively decreasing the wavelength (increasing the frequency) of the alerting signals within successive sets over time as the wavelength717is greater than the wavelength727which is greater than the wavelength737. It is also envisioned that the wavelength of the alerting signals might progressively decrease for successive alerting signals within a set. The present invention includes any use of a progressive decrease in the wavelength (which is equivalent to an increase in frequency) of alerting signals in an internal or external alarm signal. It is also envisioned that after a preset escalation period, the frequency of the alerting signals would reach a pre-set level and no longer change. AlthoughFIG. 7shows a constant amplitude75, a constant duration of the alerting signals (716,726and736), a constant time between alerting signals within each set (711,721, and731) and a constant time between sets (712and723), they need not be constant. The times between alerting signals711,721and731are typically less than the times between sets712and723. Although the alerting signals71A,71B,72A,72B,73A and73B as well as all of the alerting signals forFIGS. 2 through 6are shown as square waves, it is envisioned that any wave structure including sine waves and triangular waves could be used by the cardiosaver system5ofFIG. 1.

FIG. 8is an example of use of progressively increasing the duration of the alerting signals for successive sets of alerting signals of an alarm signal to provide an escalating patient alert.FIG. 8shows the progression over time of the three successive sets of alerting signals81,82and83of the alarm signal80. The pattern displayed inFIG. 8can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set81has alerting signals81A and81B, each alerting signal within the set81having an amplitude85, a duration816and a time interval between the alerting signals81A and81B of811. The set82has alerting signals82A and82B, each alerting signal within the set82having an amplitude85, a duration826and a time interval between the alerting signals82A and82B of821. The set83has alerting signals83A and83B each alerting signal within the set83having an amplitude85, a duration836and a time interval between the alerting signals83A and83B of831. The time interval between the sets81and82is812and the time interval between the sets82and83is823. It can be seen that the alarm signal80provides an escalating patient alert by progressively increasing the duration of the alerting signals for successive sets over time as the duration836is greater than the duration826which is greater than the duration816. It is also envisioned that the duration of alerting signals might increase for successive alerting signals within a set. The present invention includes any progressive increase in the duration of alerting signals in an internal or external alarm signal. It is also envisioned that after a preset escalation period, the duration of the alerting signals would reach a pre-set level and no longer increase. AlthoughFIG. 8shows a constant amplitude85, a constant time between alerting signals within each set (811,821and831) and a constant time between sets (812and823) they need not be constant. The times between alerting signals811,821and831are typically less than the times between sets812and823.

FIG. 9is an alternative to the alarm signal30ofFIG. 3as an example of use of increasing amplitude of an alarm signal to provide an escalating patient alert.FIG. 9shows the progression over time of the three successive sets of alerting signals91,92and93of the alarm signal90. The pattern displayed inFIG. 9can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set91has alerting signals91A,91B and91C with amplitudes915A,915B and915C respectively. Each alerting signal within the set91has a duration916and a time interval between the alerting signals91A and91B and the alerting signals91B and91C of911. The set92has alerting signals92A,92B and92C with amplitudes925A,925B and925C respectively. Each alerting signal within the set92has a duration926and a time interval between the alerting signals92A and92B and the alerting signals92B and92C of921. The set93has alerting signals93A,93B and93C with amplitudes935A,935B and935C respectively. Each alerting signal within the set93has a duration936and a time interval between the alerting signals93A and93B and the alerting signals93B and93C of931. The time interval between the sets91and92is912and the time interval between the sets92and93is923. It can be seen that the alarm signal90provides an escalating patient alert by progressively increasing the amplitude over time as the amplitude increases with each successive alerting signal within each set, e.g.915C is greater than the amplitude915B which is greater than the amplitude915A. There is also shown a progressive increase in amplitude between sets91,92and93. Ideally, such an escalating amplitude alert would start at level barely detectable by the patient and increase to a level that cannot be ignored. The physician's programmer18ofFIG. 1would typically provide the capability to test different patterns and intensities of both internal and external alarm signals with the patient to set a patient alert that cannot be missed while also reducing the potential to startle the patient. It is also envisioned that after a pre-set escalation period, the amplitude would reach a pre-set level and no longer increase. AlthoughFIG. 9shows a constant duration of the alerting signals (916,926and936), a constant time between sets (912and923) and constant times between alerting signals within a set (911,921and931) they need not be constant. The times between alerting signals911,921and931are typically less than one second while the times between sets912and923are typically greater than one second.

FIG. 10is an example of use of a combination of progressive escalating features of an alarm signal to provide an escalating patient alert.FIG. 10shows the progression over time of the three successive sets of alerting signals101,102and103of the alarm signal100. The pattern displayed inFIG. 10can be applied to internal and/or external alarm signals using vibration, sound, electrical stimulation (tickle) or a visual display. The set101has two alerting signals101A and101B, each alerting signal within the set101having an amplitude1015, a duration1016and a time interval between the alerting signals101A and1011B of1011. The set102has three alerting signals102A,102B and102C, each alerting signal within the set102having an amplitude1025, a duration1026and a time interval between the alerting signals102A and102B and the alerting signals102B and102C of1021. The set103has four alerting signals103A,103B,103C and103D, each alerting signal within the set103having an amplitude1035, a duration1036and a time interval between the alerting signals103A and103B, the alerting signals103B and103C and the alerting signals103C and103D of1031. The time interval between the sets101and102is1012and the time interval between the sets102and103is1023. It can be seen that the alarm signal100provides an escalating patient alert by combining several of the escalating features seen inFIGS. 3though7including:a) progressively increasing the amplitude of the alerting signals over time as the amplitude1035is greater than the amplitude1025which is greater than the amplitude1015;b) progressively increasing the number of alerting signals in each set as the set101contains two alerting signals, the set102contains 3 alerting signals and the set103contains 4 alerting signals;c) progressively decreasing the time interval between alerting signals within each set as the time interval1011is greater than the time interval1021which is greater than the time interval1031; and,d) progressively decreasing the time interval between sets of alerting signals as the time interval1012is greater than the time interval1023,

Although the alarm signal100shows a combination of four different escalation features of the alarm signals30,40,50and60, it is envisioned that an escalating signal could include any combination of two, three or more of the escalation techniques shown in the examples ofFIGS. 3 through 10. It is also envisioned that the present invention would also include any escalating alerting pattern that would over time become more and more perceptible to a patient.

Although the techniques for escalating patient alerting has been discussed with respect to an implanted system for the detection of cardiac events, it is also envisioned that these techniques are equally applicable to systems for the detection of cardiac events that are entirely external to the patient. For clarity, the time interval between alerting signals within a set is hereby termed as the intra-set time interval and the time interval between sets of alerting signals is hereby termed the inter-set time interval.

Various other modifications, adaptations, and alternative designs are of course possible in light of the above teachings. Therefore, it should be understood at this time that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically described herein.