Identifying a lead related condition based on detecting noise subsequent to signal delivery

In general, the disclosure describes techniques for detecting lead related conditions, such as lead fractures or other lead integrity issues. As described herein, delivering an electrical signal through selected electrodes may result in, reveal, or amplify noise if a lead related condition is present. A processor may detect electrical noise indicative of the lead related condition subsequent to the delivery of the electrical signal, and identify a lead related condition in response to detecting the noise.

This application claims the benefit of U.S. Provisional Application Nos. 61/237,154, filed on Aug. 26, 2009, and 61/285,459, filed on Dec. 10, 2009, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to medical devices and, more particularly, medical devices that are coupled to leads to sense electrical signals within a patient and/or deliver electrical signals to a patient.

BACKGROUND

A variety of medical devices for delivering a therapy and/or monitoring a physiological condition have been used clinically or proposed for clinical use in patients. Examples include medical devices that deliver therapy to and/or monitor conditions associated with the heart, muscle, nerve, brain, stomach or other organs or tissue. Some therapies include the delivery of electrical signals, e.g., stimulation, to such organs or tissues. Some medical devices may employ one or more elongated electrical leads carrying electrodes for the delivery of therapeutic electrical signals to such organs or tissues, electrodes for sensing intrinsic electrical signals within the patient, which may be generated by such organs or tissue, and/or other sensors for sensing physiological parameters of a patient.

Medical leads may be configured to allow electrodes or other sensors to be positioned at desired locations for delivery of therapeutic electrical signals or sensing. For example, electrodes or sensors may be carried at a distal portion of a lead. A proximal portion of the lead may be coupled to a medical device housing, which may contain circuitry such as signal generation and/or sensing circuitry. In some cases, the medical leads and the medical device housing are implantable within the patient. Medical devices with a housing configured for implantation within the patient may be referred to as implantable medical devices.

Implantable cardiac pacemakers or cardioverter-defibrillators, for example, provide therapeutic electrical signals to the heart via electrodes carried by one or more implantable medical leads. The therapeutic electrical signals may include pulses or shocks for pacing, cardioversion, or defibrillation. In some cases, a medical device may sense intrinsic depolarizations of the heart, and control delivery of therapeutic signals to the heart based on the sensed depolarizations. Upon detection of an abnormal rhythm, such as bradycardia, tachycardia or fibrillation, an appropriate therapeutic electrical signal or signals may be delivered to restore or maintain a more normal rhythm. For example, in some cases, an implantable medical device may deliver pacing stimulation to the heart of the patient upon detecting tachycardia or bradycardia, and deliver cardioversion or defibrillation shocks to the heart upon detecting fibrillation.

Implantable medical leads typically include a lead body containing one or more elongated electrical conductors that extend through the lead body from a connector assembly provided at a proximal lead end to one or more electrodes located at the distal lead end or elsewhere along the length of the lead body. The conductors connect signal generation and/or sensing circuitry within an associated implantable medical device housing to respective electrodes or sensors. Some electrodes may be used for both delivery of therapeutic signals and sensing. Each electrical conductor is typically electrically isolated from other electrical conductors and is encased within an outer sheath that electrically insulates the lead conductors from body tissue and fluids.

Medical lead bodies implanted for cardiac applications tend to be continuously flexed by the beating of the heart. Other stresses may be applied to the lead body, including the conductors therein, during implantation or lead repositioning. Patient movement can cause the route traversed by the lead body to be constricted or otherwise altered, causing stresses on the lead body and conductors. In rare instances, such stresses may fracture a conductor within the lead body. The fracture may be continuously present, or may intermittently manifest as the lead flexes and moves.

Additionally, the electrical connection between medical device connector elements and the lead connector elements can be intermittently or continuously disrupted. For example, connection mechanisms, such as set screws, may be insufficiently tightened at the time of implantation, followed by a gradual loosening of the connection. Also, lead pins may not be completely inserted.

Lead fracture, disrupted connections, or other causes of short circuits or open circuits may be referred to, in general, as lead related conditions. In the case of cardiac leads, sensing of an intrinsic heart rhythm through a lead can be altered by lead related conditions. Identifying lead related conditions may be challenging, particularly in a clinic, hospital or operating room setting, due to the often intermittent nature of lead related conditions. Identification of lead related conditions may allow modifications of the therapy or sensing, or lead replacement.

SUMMARY

In general, the disclosure describes techniques for identifying lead related conditions, such as lead fractures, or insufficient or intermittent coupling of a lead with a medical device. As described herein, the delivery of an electrical signal through a lead may result in, reveal, or amplify, noise indicative of a lead related condition if a lead related condition is present. Such noise may be detectable for a limited time after the delivery of the signal. Some example techniques for identifying lead related conditions include monitoring for such noise during a period that begins after the delivery of the signal and has a predetermined length. The example techniques include identifying a lead related condition utilizing a processor based on detecting such noise, e.g., detecting such noise due to, or based on, the amplification of such noise, subsequent to the delivery of the signal. The processor of the medical device may automatically identify the lead related condition based on noise detected subsequent to the delivery of the signal. In some examples, each of a plurality of electrical paths provided by one or more leads implanted in a patient are evaluated, e.g., by delivery of a signal via the path, and monitoring the path for subsequent noise indicative of a lead related condition.

In one example, a method comprises delivering an electrical signal via an electrical path that includes a medical lead, detecting noise indicative of a lead related condition on the electrical path within a period having a predetermined length subsequent to the delivery of the electrical signal, and identifying, by a processor, a lead related condition in response to detecting the noise indicative of the lead related condition.

In another example, a system comprises a signal generator that delivers an electrical signal via an electrical path that includes a medical lead, a sensing module that detects noise indicative of a lead related condition on the electrical path within a period having a predetermined length subsequent to the delivery of the electrical signal, and a processor that identifies a lead related condition in response to detecting the noise indicative of the lead related condition.

In another example, a system comprises means for delivering an electrical signal via an electrical path that includes a medical lead, means for detecting noise indicative of a lead related condition on the electrical path within a period having a predetermined length subsequent to the delivery of the electrical signal, and means for automatically identifying a lead related condition in response to detecting the noise indicative of the lead related condition.

In another example, a computer-readable medium comprises instructions for causing a programmable processor to deliver an electrical signal via an electrical path that includes a medical lead, detect noise indicative of a lead related condition on the electrical path within a period having a predetermined length subsequent to the delivery of the electrical signal, and identify a lead related condition in response to detecting the noise indicative of the lead related condition.

DETAILED DESCRIPTION

FIG. 1is a conceptual diagram illustrating an example system10that may be used for sensing of physiological parameters of patient14and/or to provide therapy to heart12of patient14. System10includes IMD16, which is coupled to leads18,20, and22, and programmer24. IMD16may be, for example, an implantable pacemaker, cardioverter, and/or defibrillator that provides electrical signals to heart12via electrodes coupled to one or more of leads18,20, and22. Patient12is ordinarily, but not necessarily a human patient.

Although an implantable medical device and delivery of electrical signals to heart12are described herein as examples, the techniques for detecting lead related conditions of this disclosure may be applicable to other medical devices and/or other therapies. In general, the techniques described in this disclosure may be implemented by any medical device, e.g., implantable or external, that includes leads to sense electrical signals or other physiological parameters from a patient, and/or deliver electrical signals to a patient, or any one or more components of a system including such a medical device. As one alternative example, IMD16may be a neurostimulator that delivers electrical stimulation to and/or monitor conditions associated with the brain, spinal cord, or neural tissue of patient16.

In the example ofFIG. 1, leads18,20,22extend into the heart12of patient16to sense electrical activity of heart12and/or deliver electrical signals to heart12. In the example shown inFIG. 1, right ventricular (RV) lead18extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium26, and into right ventricle28. Left ventricular (LV) coronary sinus lead20extends through one or more veins, the vena cava, right atrium26, and into the coronary sinus30to a region adjacent to the free wall of left ventricle32of heart12. Right atrial (RA) lead22extends through one or more veins and the vena cava, and into the right atrium26of heart12.

In some examples, system10may additionally or alternatively include one or more leads or lead segments (not shown inFIG. 1) that deploy one or more electrodes within the vena cava or other vein. These electrodes may allow alternative electrical sensing configurations that may provide improved or supplemental sensing in some patients. Furthermore, in some examples, system10may additionally or alternatively include temporary or permanent epicardial or subcutaneous leads, instead of or in addition to transvenous, intracardiac leads18,20and22. Such leads may be used for one or more of cardiac sensing, pacing, or cardioversion/defibrillation.

IMD16may sense electrical signals attendant to the depolarization and repolarization of heart12via electrodes (not shown inFIG. 1) coupled to at least one of the leads18,20,22. In some examples, IMD16provides pacing stimulation to heart12based on the electrical signals sensed within heart12. The configurations of electrodes used by IMD16for sensing and pacing may be unipolar or bipolar. IMD16may detect arrhythmia of heart12, such as tachycardia or fibrillation of ventricles28and32, and may also provide defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of the leads18,20,22. In some examples, IMD16may be programmed to deliver a progression of therapies, e.g., shocks with increasing energy levels, until a fibrillation of heart12is stopped. IMD16may detect fibrillation employing one or more fibrillation detection techniques known in the art.

In some examples, programmer24comprises a handheld computing device, computer workstation, or networked computing device. Programmer24may include a user interface that receives input from a user. It should be noted that the user may also interact with programmer24remotely via a networked computing device.

A user, such as a physician, technician, surgeon, electrophysiologist, or other clinician, may interact with programmer24to communicate with IMD16. For example, the user may interact with programmer24to retrieve physiological or diagnostic information from IMD16. A user may also interact with programmer24to program IMD16, e.g., select values for operational parameters of the IMD.

For example, the user may use programmer24to retrieve information from IMD16regarding the rhythm of heart12, trends therein over time, or arrhythmic episodes. As another example, the user may use programmer24to retrieve information from IMD16regarding other sensed physiological parameters of patient14, such as intracardiac or intravascular pressure, activity, posture, respiration, or thoracic impedance. As another example, the user may use programmer24to retrieve information from IMD16regarding the performance or integrity of IMD16or other components of system10, such as leads18,20and22, or a power source of IMD16. In some examples, this information may be presented to the user as an alert. For example, a lead related condition identified based on noise sensed subsequent to delivery of an electrical signal may trigger IMD16to transmit an alert to the user via programmer24.

IMD16and programmer24may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, programmer24may include a programming head that may be placed proximate to the patient's body near the IMD16implant site in order to improve the quality or security of communication between IMD16and programmer24.

FIG. 2is a conceptual diagram illustrating IMD16and leads18,20and22of system10in greater detail. Leads18,20,22may be electrically coupled to a signal generator, e.g., stimulation generator, and a sensing module of IMD16via connector block34. In some examples, proximal ends of leads18,20,22may include electrical contacts that electrically couple to respective electrical contacts within connector block34of IMD16. In addition, in some examples, leads18,20,22may be mechanically coupled to connector block34with the aid of set screws, connection pins, snap connectors, or another suitable mechanical coupling mechanism.

Each of the leads18,20,22includes an elongated insulative lead body, which may carry a number of concentric coiled conductors separated from one another by tubular insulative sheaths. Bipolar electrodes40and42are located adjacent to a distal end of lead18in right ventricle28. In addition, bipolar electrodes44and46are located adjacent to a distal end of lead20in coronary sinus30and bipolar electrodes48and50are located adjacent to a distal end of lead22in right atrium26. In the illustrated example, there are no electrodes located in left atrium36. However, other examples may include electrodes in left atrium36.

Electrodes40,44and48may take the form of ring electrodes, and electrodes42,46and50may take the form of extendable helix tip electrodes mounted retractably within insulative electrode heads52,54and56, respectively. In other examples, one or more of electrodes42,46and50may take the form of small circular electrodes at the tip of a tined lead or other fixation element. Leads18,20,22also include elongated electrodes62,64,66, respectively, which may take the form of a coil. Each of the electrodes40,42,44,46,48,50,62,64and66may be electrically coupled to a respective one of the coiled conductors within the lead body of its associated lead18,20,22, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads18,20and22.

In some examples, as illustrated inFIG. 2, IMD16includes one or more housing electrodes, such as housing electrode58, which may be formed integrally with an outer surface of hermetically-sealed housing60of IMD16or otherwise coupled to housing60. In some examples, housing electrode58is defined by an uninsulated portion of an outward facing portion of housing60of IMD16. Other division between insulated and uninsulated portions of housing60may be employed to define two or more housing electrodes. In some examples, housing electrode58comprises substantially all of housing60. As described in further detail with reference toFIG. 4, housing60may enclose a signal generator that generates therapeutic signals, such as cardiac pacing pulses and defibrillation shocks, as well as a sensing module for monitoring the rhythm of heart12.

IMD16may sense electrical signals attendant to the depolarization and repolarization of heart12via electrodes40,42,44,46,48,50,62,64and66. The electrical signals are conducted to IMD16from the electrodes via the respective leads18,20,22. IMD16may sense such electrical signals via any bipolar combination of electrodes40,42,44,46,48,50,62,64and66. Furthermore, any of the electrodes40,42,44,46,48,50,62,64and66may be used for unipolar sensing in combination with housing electrode58. The combination of electrodes used for sensing may be referred to as a sensing configuration.

In some examples, IMD16delivers pacing stimulation via bipolar combinations of electrodes40,42,44,46,48and50to produce depolarization of cardiac tissue of heart12. In some examples, IMD16delivers pacing stimulation via any of electrodes40,42,44,46,48and50in combination with housing electrode58in a unipolar configuration. Furthermore, IMD16may deliver defibrillation shocks to heart12via any combination of elongated electrodes62,64,66, and housing electrode58. Electrodes58,62,64,66may also be used to deliver cardioversion shocks to heart12. Electrodes62,64,66may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes. The combination of electrodes used for delivery of electrical signals or sensing, their associated conductors and connectors, and any tissue or fluid between the electrodes, may define an electrical path.

The configuration of system10illustrated inFIGS. 1 and 2is merely one example. In other examples, a system may include epicardial leads and/or patch electrodes instead of or in addition to the transvenous leads18,20,22illustrated inFIG. 1. Further, IMD16need not be implanted within patient14. In examples in which IMD16is not implanted in patient14, IMD16may deliver defibrillation shocks and other therapies to heart12via percutaneous leads that extend through the skin of patient14to a variety of positions within or outside of heart12.

In addition, in other examples, a system may include any suitable number of leads coupled to IMD16, and each of the leads may extend to any location within or proximate to heart12. For example, other examples of systems may include three transvenous leads located as illustrated inFIGS. 1 and 2, and an additional lead located within or proximate to left atrium36. As another example, other examples of systems may include a single lead that extends from IMD16into right atrium26or right ventricle28, or two leads that extend into a respective one of the right ventricle26and right atrium26. An example of this type of system is shown inFIG. 3. Any electrodes located on these additional leads may be used in sensing and/or signal delivery configurations.

Additionally, as previously mentioned, IMD16need not deliver therapy to heart12. In general, this disclosure may be applicable to any medical device, e.g., implantable or external, that includes leads to sense electrical signals or other physiological parameters from a patient, and/or deliver electrical signals to a patient.

FIG. 3is a conceptual diagram illustrating another example of system70, which is similar to system10ofFIGS. 1 and 2, but includes two leads18,22, rather than three leads. Leads18,22are implanted within right ventricle28and right atrium26, respectively. System70shown inFIG. 3may be useful for providing defibrillation shocks and pacing stimulation to heart12. Detection of lead related conditions according to this disclosure may be performed in two lead systems in the manner described herein with respect to three lead systems.

FIG. 4is a functional block diagram illustrating an example configuration of IMD16. In the illustrated example, IMD16includes a processor80, memory82, signal generator84, sensing module86, telemetry module88, and power source90. Memory82includes computer-readable instructions that, when executed by processor80, cause IMD16and processor80to perform various functions attributed to IMD16and processor80herein. Memory82may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processor80controls signal generator84to deliver therapy to heart12according to a selected one or more of therapy programs, which may be stored in memory82. For example, processor80may control stimulation generator84to deliver electrical pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the selected one or more therapy programs.

Signal generator84is electrically coupled to electrodes40,42,44,46,48,50,58,62,64, and66, e.g., via conductors of the respective lead18,20,22, or, in the case of housing electrode58, via an electrical conductor disposed within housing60of IMD16. In the illustrated example, signal generator84is configured to generate and deliver therapeutic electrical signals to heart12. For example, signal generator84may deliver defibrillation shocks to heart12via at least two electrodes58,62,64,66. Signal generator84may deliver pacing stimulation via ring electrodes40,44,48coupled to leads18,20, and22, respectively, and/or helical electrodes42,46, and50of leads18,20, and22, respectively. In some examples, signal generator84delivers pacing, cardioversion, or defibrillation signals in the form of electrical pulses. In other examples, signal generator may deliver one or more of these types of therapeutic electrical signals, such as sine waves, square waves, or other substantially continuous time signals.

Signal generator84may include a switch module and processor80may use the switch module to select, e.g., via a data/address bus, which of the available electrodes are used to deliver defibrillation shocks or pacing stimulation. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple the therapeutic electrical signal to selected electrodes.

Electrical sensing module86monitors signals from at least one of electrodes40,42,44,46,48,50,58,62,64or66in order to monitor electrical activity of heart12. Sensing module86may also include a switch module to select which of the available electrodes are used to sense the heart activity, depending upon which electrode combination is used in the current sensing configuration. In some examples, processor80may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing module86. Processor80may control the functionality of sensing module86by providing signals via a data/address bus.

Sensing module86may include one or more detection channels, each of which may comprise an amplifier. The detection channels may be used to sense the cardiac signals. Some detection channels may detect events, such as R- or P-waves, and provide indications of the occurrences of such events to processor80. One or more other detection channels may provide the signals to an analog-to-digital converter, for processing or analysis by processor80. In response to the signals from processor80, the switch module within sensing module86may couple selected electrodes to selected detection channels.

For example, sensing module86may comprise one or more narrow band channels, each of which may include a narrow band filtered sense-amplifier that compares the detected signal to a threshold. If the filtered and amplified signal is greater than the threshold, the narrow band channel indicates that a certain electrical cardiac event, e.g., depolarization, has occurred. Processor80then uses that detection in measuring frequencies of the sensed events. Different narrow band channels of sensing module86may have distinct functions. For example, various narrow band channels may be used to sense either atrial or ventricular events.

In one example, at least one narrow band channel may include an R-wave amplifier that receives signals from the sensing configuration of electrodes40and42, which are used for sensing and/or pacing in right ventricle28of heart12. Another narrow band channel may include another R-wave amplifier that receives signals from the sensing configuration of electrodes44and46, which are used for sensing and/or pacing proximate to left ventricle32of heart12. In some examples, the R-wave amplifiers may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm.

In addition, in some examples, a narrow band channel may include a P-wave amplifier that receives signals from electrodes48and50, which are used for pacing and sensing in right atrium26of heart12. In some examples, the P-wave amplifier may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in U.S. Pat. No. 5,117,824 to Keimel et al., which issued on Jun. 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of sensing module86may be selectively coupled to housing electrode58, or elongated electrodes62,64, or66, with or instead of one or more of electrodes40,42,44,46,48or50, e.g., for unipolar sensing of R-waves or P-waves in any of chambers26,28, or32of heart12.

In some examples, sensing module86includes a wide band channel which may comprise an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers. Signals from the selected sensing electrodes that are selected for coupling to this wide-band amplifier may be converted to multi-bit digital signals by an analog-to-digital converter (ADC) provided by, for example, sensing module86or processor80. In some examples, processor80may store the digitized versions of signals from the wide band channel in memory82as electrograms (EGMs).

In some examples, processor80may employ digital signal analysis techniques to characterize the digitized signals from the wide band channel to, for example detect and classify the patient's heart rhythm. Processor80may detect and classify the patient's heart rhythm by employing any of the numerous signal processing methodologies known in the art.

Processor80may maintain programmable interval counters. For example, if IMD16is configured to generate and deliver pacing stimulation to heart12, processor80may maintain programmable counters which control the basic time intervals associated with various modes of pacing, including anti-tachycardia pacing (ATP) and pacing associated with cardiac resynchronization therapy (CRT). Intervals maintained by processor80for pacing may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and, in examples in which pacing stimulation comprises pulses, the pulse widths of the pacing pulses. As another example, processor80may define a blanking period, and provide signals to sensing module86to blank one or more channels, e.g., amplifiers, for a period during and after delivery of a therapeutic electrical signal to heart12. The durations of these intervals may be determined by processor80in response to stored data in memory82. Processor80may also determine the amplitude of the cardiac pacing stimulation.

In some examples, processor80resets interval counters upon sensing of R-waves and P-waves with detection channels of sensing module86. Signal generator84may include pacer output circuits that are coupled, e.g., selectively by a switching module, to any combination of electrodes40,42,44,46,48,50,58,62, or66appropriate for delivery of a bipolar or unipolar pacing stimulation to one of the chambers of heart12. Processor80may reset the interval counters upon the generation of pacing stimulation by signal generator84, and thereby control the basic timing of cardiac pacing functions, including anti-tachyarrhythmia pacing.

The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processor80to measure the durations of R-R intervals, P-P intervals, PR intervals and R-P intervals, which are measurements that may be stored in memory82. Processor80may use the count in the interval counters to detect a suspected tachyarrhythmia event, such as ventricular fibrillation or ventricular tachycardia. In some examples, a portion of memory82may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by processor80to determine whether the patient's heart12is presently exhibiting atrial or ventricular tachyarrhythmia.

In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms. In one example, processor80may utilize all or a subset of the rule-based detection methods described in U.S. Pat. No. 5,545,186 to Olson et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on Aug. 13, 1996, or in U.S. Pat. No. 5,755,736 to Gillberg et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on May 26, 1998. U.S. Pat. No. 5,545,186 to Olson et al. U.S. Pat. No. 5,755,736 to Gillberg et al. is incorporated herein by reference in their entireties. However, other arrhythmia detection methodologies may also be employed by processor80in other examples.

In some examples, processor80may determine that tachyarrhythmia has occurred by identification of shortened R-R (or P-P) interval lengths. Generally, processor80detects tachycardia when the interval length falls below 220 milliseconds (ms) and fibrillation when the interval length falls below 180 ms. These interval lengths are merely examples, and a user may define the interval lengths as desired, which may then be stored within memory82. This interval length may need to be detected for a certain number of consecutive cycles, for a certain percentage of cycles within a running window, or a running average for a certain number of cardiac cycles, as examples.

Processor80may also control signal generator84and sensing module86to identify lead related conditions. Detection of lead related conditions may prevent or end inappropriate detection of cardiac events. Rapid, intermittent fracture of one or more of leads18,20,22or disconnection of the lead from IMD16may be interpreted by the IMD16as a plurality of sensed cardiac events, e.g., R-waves, and result in inappropriate detection of a cardiac arrhythmia by IMD16. More particularly, “make/break” events resulting from intermittent fracture or disconnection of a conductor within a lead that is electrically connected to an electrode used in an electrode combination for a current sensing configuration may introduce noise into the signal received by a sensing channel of sensing module86that is electrically coupled to the electrode combination, e.g., the signal that represents depolarization of heart12. An amplifier of the sensing channel may interpret such noise as events, e.g., R-waves, and provide indications of the events to processor80. The rate of sensed events when such noise is present may be similar to or greater than that for detection of a tachyarrhythmia, and processor80may detect a tachyarrhythmia based on the noise.

To identify lead related conditions, processor80may control signal generator84to deliver an electrical signal, e.g., a pacing stimulation, which may be in the form of one or more pulses, via an electrical path that includes a combination of one or more of the electrodes on one or more of leads18,20,22. The electrical signal is configured to result in, reveal, or amplify electrical noise if a lead related condition, e.g., conductor or connector failure, or insulation breach, is present. If a lead related condition is present, the electrical signal may cause a build-up of capacitive charge, e.g., at the lead-tissue interface and/or at the location of the fracture point. In addition, the lead related condition may be intermittent. As one example, an intermittent lead fracture or disconnection may fluctuate between a completed connection and a broken connection. The intermittent nature of the lead integrity issue may be detectable as noise indicative of a lead related condition on electrical path when the capacitive charge is present on the electrical path.

Processor80may control sensing module86to sense for electrical noise indicative of a lead related condition subsequent to the delivery of the electrical signal. For example, sensing module86may sense an EGM signal using the electrode configuration used to deliver the electrical signal. As described in further detail below, processor80may identify a lead related condition based on the sensed signal, e.g., based on whether electrical noise indicative of a lead related condition is sensed. If processor80senses electrical noise indicative of a lead related condition, processor80may automatically identify a lead related condition.

In some examples, processor80may control signal generator84to produce an electrical signal specifically for integrity testing. In other examples, processor80prompts sensing module86to sense for electrical noise indicative of a lead related condition subsequent to the delivery of a pacing stimulus delivered for therapeutic purposes, e.g., a pacing pulse to treat bradycardia or an antitachycardia pacing pulse. In this case, the integrity testing is performed using the pacing stimulation, e.g., pulse or pulses, delivered for therapeutic purposes, thus eliminating the need to provide separate electrical signals to the heart of the patient specifically for integrity testing.

In either case, processor80may select the signal parameter values used by signal generator84to test lead integrity. In some examples, processor80selects the signal parameter values for lead integrity testing based on the electrode configuration that signal generator84will be using to deliver the electrical signal. The stimulation parameter values may be based on the therapy typically delivered using the selected channel. For example, if signal generator84typically delivers pacing therapy via the electrode configuration selected for integrity testing, signal generator84may perform the integrity test using one or more electrical signals with the stimulation parameter values typical of pacing, whether or not the electrical signal is delivered to provide therapy.

As an alternative, signal generator84may deliver a non-therapeutic electrical signal to test lead integrity. For example, signal generator84may deliver signals that do not necessarily deliver stimulation therapy to heart12, due to, for example, the amplitudes of such signals and/or the timing of delivery of such signals. For example, these signals may comprise sub-threshold amplitude signals, e.g., below a threshold necessary to capture or otherwise activate tissue, such as cardiac tissue. In some cases, electrical signals may be delivered during a refractory period, in which case they also may not stimulate heart12. Signal generator84may deliver non-therapeutic electrical signals if the electrode configuration selected for integrity testing is not typically used for therapy delivery, e.g., is only used for sensing electrical signals of heart12. Examples of non-therapeutic electrical signals include sub-threshold, refractory, post sensed depolarization and pre T-wave, and fusion beat signals.

In some examples, regardless of whether the electrical signal for lead integrity testing provides a therapeutic effect, the selected signal parameters may be configured to increase electrical noise due to lead related conditions. An increase in the capacitive charge built up at the lead-tissue interface and/or the location of the lead integrity issue may result in an increase in the amplitude of the electrical noise due to the lead related condition. Therefore, increasing the signal amplitude and/or duration, e.g., pulse width, may increase electrical noise if a lead related condition is present. In some examples, electrical signals delivered for lead integrity testing may be at a maximum amplitude and/or a maximum duration, e.g., pulse width, available from signal generator84. Additionally, a biphasic electrical signal that includes two portions of opposite polarity may allow the capacitive charge built up due to a lead related condition to dissipate during the second phase. Therefore, suppressing the second phase of a biphasic signal may increase electrical noise if a lead related condition is present.

During lead integrity testing, processor80may modify one or more signal parameter values of a therapeutic electrical signal delivered by signal generator84to increase electrical noise due to lead related conditions. Processor80may also select stimulation parameter values for non-therapeutic signals delivered by signal generator84for lead integrity testing that maximize electrical noise due to lead related conditions while avoiding tissue capture. In some examples, memory82stores sets of parameter values associated with specified electrode combinations for electrical signals used for lead integrity testing for selection by processor80.

As another example, processor80may control delivery of additional electrical signals during lead integrity testing. For example, processor80may control delivery of pacing stimulation using signal parameter values typically used for pacing and one or more non-therapeutic electrical signals, e.g., during the refractory period of heart12. The one or more non-therapeutic electrical signals may be configured to amplify noise due to lead related conditions, e.g., using an increased amplitude, increased duration or pulse width, and/or a signal with a single polarity. A signal with a single polarity may be achieved by use of a DC bias or suppression of a second phase of a biphasic pulse, as examples.

In some examples, the one or more additional signals delivered during the refractory period are additional pacing stimuli, e.g., pulses, with parameters values typically used for pacing, and may further be pacing stimuli having the same parameters as the therapeutic pacing stimulus. Thus, in some examples, a pacing pulse delivered for therapeutic purposes may be followed by delivery of one or more additional pacing pulses during the refractory period after the pacing pulse to amplify the noise indicative of a lead related condition. In some examples, signals such as pacing pulses are similarly delivered during the refractory period after an intrinsic depolarization of heart12.

Processor80may perform lead integrity testing automatically, e.g., periodically according to a schedule, or in response to a command received via programmer24. Processor80may test a variety of electrical paths that include two or more of electrodes40,42,44,46,48,50,58,62,64and66. If an integrity issue is detected along one electrical path, processor80may test alternate electrode configurations to identify which conductor or connector of the path is experiencing an integrity issue. For example, if an integrity issue is detected when electrodes40and42are activated, processor80may test electrodes40and42independently, e.g., by separately testing each of40and42in combination with housing electrode58, to determine which of electrodes40and42, or its associated conductor(s) or connection(s), is causing the issue.

Processor80may control sensing module86to sense electrical noise subsequent to the delivery of an electrical signal for lead integrity testing. Sensing module86may sense electrical signals using each electrode configuration tested. Processor80may control detection or detect electrical noise using thresholds and/or digital signal processing. In some examples, processor80uses a shortened blanking period for sensing lead related noise. The blanking period may be configured to be long enough so that the electrical signal delivered for lead integrity testing is not sensed as a lead related condition. However, the blanking period used during lead integrity testing may not need to be long enough to prevent double counting of the R-wave of the cardiac cycle, as may be the case for a blanking period following delivery of a therapeutic electrical signal during periods in which lead integrity is not tested.

In some examples, processor80may identify each time the sensed signal exceeds a threshold value within a specified time interval or period having a predetermined length, e.g., of approximately 2 seconds, following the delivery of the electrical signal via signal generator84. The interval or period may begin after a blanking period, which may be shortened, as discussed above. Processor80may count the number of times the sensed signal exceeds the threshold value.

In some examples, the threshold value may correspond to an intrinsic depolarization threshold, e.g., used to detect P-waves or R-waves. In some examples, processor80may determine the intervals between depolarizations sensed within the period subsequent to delivery of the electrical signal, during which sensed depolarizations may be the result of noise indicative of a lead related condition. Processor80may further determine the number of times the interval between these sensed depolarizations is less than a threshold time interval, e.g., a tachyarrhythmia time interval. The threshold time interval may be, as one example, approximately 200 milliseconds. Processor80may determine whether a lead related condition is present based on the number of times the sensed signal exceeds the threshold value and/or the number of tachyarrhythmia events detected within the specified time interval.

In some examples, IMD16may compare a signal detected after delivery of an electrical signal with a threshold value or baseline signal to detect noise indicative of a lead related condition. The comparison may be an analog comparison by a detection channel of sensing module86under the control of processor80, or a digital comparison of a digitized EGM by processor80. In the case of an analog comparison, sensing module86may include a channel that comprises an amplifier that provides a sensing threshold for sensing noise after delivery of an electrical signal. As discussed above, some channels provided by sensing module86may use automatically-adjusting sensitivity to detect heartbeats from sensed signals and avoid oversensing due to the T-wave of the cardiac cycle. However, in some examples, IMD16may use a fixed, high sensitivity channel or algorithm to detect lead related conditions. IMD16may detect low amplitude noise due to lead related conditions better using a fixed sensitivity instead of an automatically-adjusting sensitivity. In some examples, the signal is passed through a high pass filter prior to analysis by sensing module86or processor80to help prevent the sensing module or processor from interpreting T-waves as noise due to lead related conditions.

As another example, processor80may use digital signal processing techniques to determine whether a lead related condition is present. As one example, processor80may compare an EGM of an electrode combination being tested to a baseline EGM, which may correspond to a far-field EGM sensed at the same time as the EGM corresponding to the electrode configuration being tested. As another example, memory82may store a template EGM signal, and processor80may compare the sensed EGM signal to the template to determine whether electrical noise indicative of a lead related condition is present. For example, processor80may detect one or more wavelets in the sensed EGM corresponding to the electrode combination being tested that are not present in the far-field or template EGM signal and identify a lead related condition based on the detected wavelets. Processor80may perform the comparison during a specified time interval, e.g., of approximately 2 seconds, following the electrical signal delivered via signal generator84for integrity testing.

Sensing module86may include a detection channel configured to detect electrical noise due to lead related conditions. For example, sensing module86may include a channel without a low pass filter. A low pass filter may filter some of the electrical noise due to lead related conditions, so a detection channel without a low pass filter may improve the detection of lead related conditions. Additionally or alternatively, sensing module86may include a high pass filter. A high pas filter may filter T-waves of the cardiac cycle to help prevent processor80from interpreting the T-waves as noise due to lead related conditions. In examples in which sensing module86includes digital circuitry, the low pass filter may be switched off when sensing during lead integrity testing and/or the high pass filter may be switched on when sensing during lead integrity testing.

Processor80may automatically identify a lead related condition by determining whether a signal sensed subsequent to delivery of an electrical signal is indicative of a lead related condition, e.g., using any of the techniques described above. In addition, processor80may take one or more actions in response to detecting a lead related condition. For example, processor80may reconfigure sensing and/or therapy delivery to avoid use of channels with integrity issues. Additionally or alternatively, processor80may reconfigure sensing and/or therapy delivery parameters for channels with integrity issues. As one example, processor80may extend the blanking period of one or more sensing channels, e.g., amplifiers, of sensing module86. As another example, processor80may increase a sensing threshold, e.g., a threshold used to detect cardiac events, such as depolarizations, following delivery of a therapeutic electrical signal, e.g., an ATP pulse. Extending a blanking period and/or increasing a threshold value may help prevent inappropriate detection of arrhythmias and/or other cardiac events.

As yet another example, in a channel used for pacing, processor80may extend the second phase of a biphasic pacing pulse, e.g., to greater than 16 milliseconds, in response to detecting a lead related condition in that channel. In some examples, processor80may extend the second phase of a biphasic pacing pulse to approximately 30 or more milliseconds. As yet another example, processor80may extend the second phase of a biphasic pacing pulse up to approximately 50 milliseconds. In this manner, the duration of the second phase of the pacing pulse may be increased relative to the duration of the second phase of biphasic pacing pulses delivered prior to detection of the lead related condition. Extending the second phase of the pacing pulse may allow the capacitive charge built up during the first phase of the pacing pulse to more fully dissipate. As an alternative, processor80may short the electrodes used to deliver a pacing pulse after delivering the pacing pulse to allow the charge to dissipate. Signal generator84and/or leads18,20,22may include one or more switches and/or multiplexers to facilitate shorting across the electrodes. If the pacing channel is also used to detect cardiac events, dissipating the charge may result in less noise and more accurate detection.

In some examples, processor80may provide an alert to a user, e.g., of programmer24, regarding any detected lead related conditions via telemetry module88. For example, programmer24may report the alert provided by processor80via user interface104. Additionally or alternatively, IMD16may suggest a response to a lead related condition and/or receive user approval of a response via telemetry module88. Alternatively, IMD16may provide an EGM or other sensed signal to an external device, e.g., programmer24, via telemetry module88for identification of lead related conditions, and processor100of programmer24may automatically identify a lead related condition based on the sensed signal received from IMD16.

Telemetry module88includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer24(FIG. 1). Under the control of processor80, telemetry module88may receive downlink telemetry from and send uplink telemetry to programmer24with the aid of an antenna, which may be internal and/or external. Processor80may provide the data to be uplinked to programmer24and the control signals for the telemetry circuit within telemetry module88, e.g., via an address/data bus. In some examples, telemetry module88may provide received data to processor80via a multiplexer.

In some examples, processor80may transmit atrial and ventricular heart signals (e.g., electrocardiogram signals) produced by atrial and ventricular sense amp circuits within sensing module86to programmer24. Programmer24may interrogate IMD16to receive the heart signals. Processor80may store heart signals within memory82, and retrieve stored heart signals from memory82. Processor80may also generate and store marker codes indicative of different cardiac events that sensing module86detects, and transmit the marker codes to programmer24. An example pacemaker with marker-channel capability is described in U.S. Pat. No. 4,374,382 to Markowitz, entitled, “MARKER CHANNEL TELEMETRY SYSTEM FOR A MEDICAL DEVICE,” which issued on Feb. 15, 1983 and is incorporated herein by reference in its entirety.

In addition, processor80may transmit information regarding lead related conditions to programmer24via telemetry module88. For example, processor80may provide an alert regarding any detected lead related conditions, suggest a response to a lead related condition, or provide an EGM or other sensed signal for identification of lead related conditions to programmer24via telemetry module88. In some examples, processor100of programmer24may automatically identify a lead related condition based on the sensed signal received from IMD16. For example, processor100may use any of the identification techniques described previously with respect to processor80of IMD16. Processor80may also receive information regarding lead related conditions or responses to such conditions from programmer24via telemetry module88.

In some examples, IMD16may signal programmer24to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic, Inc., of Minneapolis, Minn., or some other network linking patient14to a clinician.

FIG. 5is functional block diagram illustrating an example configuration of programmer24. As shown inFIG. 5, programmer24may include a processor100, memory102, user interface104, telemetry module106, and power source108. Programmer24may be a dedicated hardware device with dedicated software for programming of IMD16. Alternatively, programmer24may be an off-the-shelf computing device running an application that enables programmer24to program IMD16.

A user may use programmer24to select therapy programs (e.g., sets of stimulation parameters), generate new therapy programs, modify therapy programs through individual or global adjustments or transmit the new programs to a medical device, such as IMD16(FIG.1). The clinician may interact with programmer24via user interface104, which may include display to present graphical user interface to a user, and a keypad or another mechanism for receiving input from a user.

The user may also use programmer24to adjust or control the detection of lead related conditions performed by IMD16. For example, the user may use programmer24to program the timing of electrical signals, the parameters of each electrical signal, or any other aspects of the integrity test. In this manner, the user may be able to finely tune the integrity test to the specific condition of patient14. In some examples, the user uses programmer24to control the performance of an integrity test for detecting lead related conditions, e.g., in a clinic, hospital, or operating room setting, at the time of implant or during a follow-up visit.

In addition, the user may receive an alert from IMD16indicating a potential lead related condition via programmer24. Programmer24may report the alert provided by IMD16via user interface104. The user may respond to IMD16by suggesting a response to a detected lead related condition. Alternatively, IMD16may automatically suggest a response to a lead related condition. Such a response may also be displayed on user interface104of programmer24. Programmer24may prompt the user to confirm the response.

Processor100can take the form one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed to processor100herein may be embodied as hardware, firmware, software or any combination thereof. Memory102may store instructions that cause processor100to provide the functionality ascribed to programmer24herein, and information used by processor100to provide the functionality ascribed to programmer24herein. Memory102may include any fixed or removable magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like. Memory102may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow patient data to be easily transferred to another computing device, or to be removed before programmer24is used to program therapy for another patient.

Programmer24may communicate wirelessly with IMD16, such as using RF communication or proximal inductive interaction. This wireless communication is possible through the use of telemetry module106, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled to programmer24may correspond to the programming head that may be placed over heart12, as described above with reference toFIG. 1. Telemetry module106may be similar to telemetry module88of IMD16(FIG. 4).

Telemetry module106may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. Examples of local wireless communication techniques that may be employed to facilitate communication between programmer24and another computing device include RF communication according to the 802.11 or Bluetooth specification sets, infrared communication, e.g., according to the IrDA standard, or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating with programmer24without needing to establish a secure wireless connection. An additional computing device in communication with programmer24may be a networked device such as a server capable of processing information retrieved from IMD16.

In some examples, processor100of programmer24and/or one or more processors of one or more networked computers may perform all or a portion of the techniques described herein with respect to processor80and IMD16. For example, processor100or another processor may receive an EGM or other sensed signal for identification of lead related conditions.

FIG. 6is a block diagram illustrating an example system that includes an external device, such as a server204, and one or more computing devices210A-210N, that are coupled to the IMD16and programmer24shown inFIG. 1via a network202. In this example, IMD16may use its telemetry module88to communicate with programmer24via a first wireless connection, and to communication with an access point200via a second wireless connection. In the example ofFIG. 6, access point200, programmer24, server204, and computing devices210A-210N are interconnected, and able to communicate with each other, through network202. In some cases, one or more of access point200, programmer24, server204, and computing devices210A-210N may be coupled to network202through one or more wireless connections. IMD16, programmer24, server204, and computing devices210A-210N may each comprise one or more processors, such as one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, that may perform various functions and operations, such as those described herein.

Access point200may comprise a device that connects to network202via any of a variety of connections, such as telephone dial-up, digital subscriber line (DSL), or cable modem connections. In other embodiments, access point200may be coupled to network202through different forms of connections, including wired or wireless connections. In some embodiments, access point200may be co-located with patient14and may comprise one or more programming units and/or computing devices (e.g., one or more monitoring units) that may perform various functions and operations described herein. For example, access point200may include a home-monitoring unit that is co-located with patient14and that may monitor the activity of IMD16. In some embodiments, server204or computing devices210may control or perform any of the various functions or operations described herein, e.g., control performance of integrity tests by IMD16.

In some cases, server204may be configured to provide a secure storage site for archival of sensing integrity information that has been collected from IMD16and/or programmer24. Network202may comprise a local area network, wide area network, or global network, such as the Internet. In some cases, programmer24or server204may assemble sensing integrity information in web pages or other documents for viewing by and trained professionals, such as clinicians, via viewing terminals associated with computing devices210. The system ofFIG. 6may be implemented, in some aspects, with general network technology and functionality similar to that provided by the Medtronic CareLink® Network developed by Medtronic, Inc., of Minneapolis, Minn.

FIGS. 7-10illustrate example EGM signals that may indicate lead related conditions.FIG. 7illustrates an example normal EGM signal before any electrical signals are delivered. A-A intervals110and V-V intervals112are of consistent duration, and no atrial or ventricular contractions are inappropriately detected.FIG. 8illustrates an example EGM signal after a sub-threshold electrical signal is delivered at time120. Subsequent to the sub-threshold electrical signal, ventricular contractions are improperly detected due to signal noise resulting from a lead related condition. Consequently, detected V-V intervals112are of inconsistent duration.

FIG. 9illustrates an example EGM signal following a bradycardia pacing pulse at time130. Similarly,FIG. 10illustrates an example EGM signal following bradycardia pacing pulses at times132and134. Subsequent to the bradycardia pacing pulses, ventricular contractions are improperly detected due to signal noise resulting from a lead related condition. Consequently, detected V-V intervals112are of inconsistent duration.

FIG. 11is a flow diagram of an example method of identifying a lead related condition. The functionality described with respect toFIG. 11as being provided a particular processor or device may, in other examples, be provided by any one or more of the processors or devices described herein.

Processor80may control signal generator84to deliver an electrical signal via an electrical path that includes a combination of the electrodes on one or more of leads18,20,22. The electrical signal is configured to result in, reveal, or amplify electrical noise if a lead related condition, e.g., conductor or connector failure, or insulation breach, is present (160). If a lead related condition is present, the electrical signal may cause a build-up of capacitive charge, e.g., at the lead-tissue interface, at the location of the fracture point, and/or at another location along the electrical path. In addition, the lead related condition may be intermittent. As one example, an intermittent lead fracture or disconnection may fluctuate between a completed connection and a broken connection. The intermittent nature of the lead integrity issue may be detectable as noise indicative of a lead related condition on electrical path when the capacitive charge is present on the electrical path.

Processor80may control sensing module86to sense for electrical noise indicative of a lead related condition subsequent to the electrical signal (162). For example, sensing module86may sense an electrogram (EGM) signal using the electrode configuration used to deliver the electrical signal. Sensing module86may sense the EGM during a period having a predetermined length subsequent to the delivery of the electrical signal.

If processor80and/or sensing module86do not detect noise indicative of a lead related condition, processor80may determine whether to test the integrity of a different electrical path (168). If processor80and/or sensing module86detect noise indicative of a lead related condition, processor80may identify a lead related condition based on the sensed signal (164). For example, processor80may identify a lead related condition using thresholds and/or digital signal processing. In this manner, processor80may automatically identify a lead related condition based on the sensed signal.

Processor80may take one or more actions in response to detecting a lead related condition (166). For example, processor80may reconfigure sensing and/or therapy delivery to avoid use of channels with integrity issues. As another example, in a channel used for pacing, processor80may extend the second phase of a biphasic pacing pulse, e.g., to greater than 16 milliseconds. In some examples, processor80may extend the second phase of a biphasic pacing pulse to approximately 30 or more milliseconds. As yet another example, processor80may extend the second phase of a biphasic pacing pulse up to approximately 50 milliseconds. Extending the second phase of the pacing pulse may allow the capacitive charge built up during the first phase of the pacing pulse to more fully dissipate. As an alternative, processor80may short across the electrode after delivering a pacing pulse to allow the charge to dissipate. Signal generator84and/or leads18,20,22may include one or more switches and/or multiplexers to facilitate shorting across the electrode. If the pacing channel is also used to detect cardiac events, dissipating the charge may result in less noise and more accurate detection.

Processor80may determine whether to test the integrity of an additional electrical path (168). For example, signal generator84may deliver an electrical signal to a different combination of the electrodes on one or more of leads18,20,22to test the integrity of another electrical path. As one example, processor80may test a plurality of electrical paths according to a schedule stored within memory82. The schedule may include a plurality of electrical paths that IMD16uses for sensing and/or therapy delivery. As another example, if an integrity issue is detected along one electrical path, processor80may test alternate electrode configurations to identify which conductor is experiencing an integrity issue. For example, if an integrity issue is detected when electrodes40and42are activated, processor80may test electrodes40and42independently, e.g., by separately testing each of40and42in combination with housing electrode58, to determine which one of electrodes40and42is causing the issue. In some examples, processor80may not may take one or more actions in response to detecting a lead related condition (166) until processor80identifies which conductor is experiencing an integrity issue, e.g., by testing the electrodes of an electrical path with an identified lead related condition independently.

FIGS. 12A-15Billustrate example EGM signals collected from patients that experienced lead fractures. EGM signals indicating noise related to lead fractures from 44 patients were collected and analyzed. All of the lead fractures were confirmed by analysis of returned, explanted leads.

EGMs were collected and analyzed if a true-bipolar, i.e., tip-ring, EGM was recorded and included at least three sensed and at least three paced true ventricular beats. EGMs were censored at the first shock. Up to five EGMs were analyzed per patient.

Various patterns of noise and oversensing indicative of lead related conditions were observed. Pacing-induced oversensing was defined as oversensing caused by high-frequency, nonphysiological signals that either occurred transiently after a ventricular paced beat (e.g., VP) but not after ventricular sensed beats (e.g., VS), or was absent after ventricular sensed beats (e.g., VS) but persisted longer than one cardiac cycle after a ventricular paced beat (e.g., VP). Noise and oversensing that occurred only after ventricular sensed beats fulfilled the reverse criteria.

An example of persistent noise following delivery of anti-tachycardia pacing pulses (TP) at time170is illustrated inFIGS. 12A and 12B. In particular,FIG. 12Aillustrates an absence of oversensing during a series of ventricular sensed beats that met a ventricular tachycardia criterion (TS). Noise is evident following delivery of ventricular anti-tachycardia pacing pulses (TP) during time170, as illustrated inFIG. 12B. Persistent oversensing following the anti-tachycardia pacing pulses (TP) is illustrated by the ventricular sensed beats meeting the tachycardia (TS) and fibrillation (FS) criteria during the cardiac cycle following the anti-tachycardia pacing pulses (TP).

FIGS. 13A and 13Billustrate an example of transient oversensing.FIG. 13Aillustrates an absence of noise during a series of ventricular sensed beats that met a ventricular tachycardia criterion (TS). Noise is evident following delivery of ventricular anti-tachycardia pacing during time180, as illustrated inFIG. 13B. Transient oversensing following the anti-tachycardia pacing pulses (TP) is illustrated by the ventricular sensed beats meeting the tachycardia (TS) and fibrillation (FS) criteria during the cardiac cycle following the anti-tachycardia pacing pulses (TP).

Another example of transient noise is illustrated inFIG. 14following delivery of a ventricular bradycardia pacing pulse (VP) at time190. Transient oversensing following the pacing pulse is evidenced by the ventricular sensed beats meeting the fibrillation (FS) criterion during the cardiac cycle following the ventricular bradycardia pacing pulse (VP).

FIGS. 15A and 15Billustrate another example of persistent noise following delivery of biventricular pacing pulses (BV) at time192. Persistent oversensing lasting greater than one cardiac cycle after the pacing pulses is evidenced by the sensed ventricular beats meeting the fibrillation criterion (FS) following the pacing pulses and more than one cardiac cycle after the pacing pulses.

Overall 153 EGMs in 44 patients included at least three ventricular pace beats and at least three ventricular sensed beats. Oversensing was not related to ventricular pacing or ventricular sensing in 35 pts (80%). No patient had oversensing only after ventricular sensing. Pacing-induced oversensing occurred in 9 patients (20%, P<0.001). 2 of the 9 patients that experienced pacing-induced oversensing did not receive bradycardia pacing therapy. In these 2 patients, pacing-induced oversensing occurred only after antitachycardia pacing. Pacing-induced oversensing occurred in 14% of all EGMs analyzed (22/153). Of the 44 patients studied fractures occurred in the cable conductor to the ring electrode in 22 patients and in the coil conductor to the tip electrode in 22 patients. Pacing-induced oversensing occurred in 36% of cable fractures (8/22) versus 5% of coil fractures (1/22), p=0.02.

Detecting noise indicative of a lead related condition subsequent to the delivery of an electrical signal may provide insight into the origin of lead-noise signals. Since many patients with implantable cardiac devices, such as implantable cardioverter defibrillators, do not receive ventricular pacing or other electrical signals that may result in, reveal, or amplify, noise indicative of a lead related condition for therapeutic reasons, delivery of such signals may be performed to provoke noise indicative of lead related conditions in these patients, e.g., patient who are in ventricular sinus rhythm.

FIGS. 16A and 16Billustrate example electrogram (EGM) signals that may indicate lead related conditions. In particular,FIGS. 16A and 16Billustrate pacing-exacerbated oversensing. Pacing-exacerbated oversensing results in a marked increase in amplitude and duration of noise resulting in a marked increase in oversensing after ventricular pacing. Examples of pacing exacerbated noise are illustrated inFIGS. 16A and 16B, in which the amplitude and/or duration of noise increases subsequent to delivery of biventricular pacing pulses, e.g., at times200A,200B, and200C, as examples. Oversensing evidenced by fibrillation senses (FS) is present after ventricular sensed beats (VS), but increases following the delivery of the pacing pulses.

Various examples have been described. These and other examples are within the scope of the following claims. For example, although detection of lead related conditions is directed herein toward cardiac therapy, this disclosure may also be applicable to other therapies in which detection of lead related conditions may be appropriate. These therapies may include spinal cord stimulation, deep brain stimulation, pelvic floor stimulation, gastric stimulation, occipital stimulation, functional electrical stimulation, and any other stimulation therapy utilizing electrode sensing and/or stimulation methods. Furthermore, although described herein as implemented by an IMD and system including an IMD, in other examples, the techniques described herein may be implemented in an external medical device. An external medical device may be coupled to leads during implant, and may perform a lead integrity test as described herein to detect any lead related conditions of the recently implanted leads.

In addition, it should be noted that therapy system10may not be limited to treatment of a human patient. In alternative examples, therapy system10may be implemented in non-human patients, e.g., primates, canines, equines, pigs, and felines. These other animals may undergo clinical or research therapies that my benefit from the subject matter of this disclosure.

The techniques described in this disclosure, including those attributed to IMD16, programmer24, or various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, image processing devices or other devices. The term “processor” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

When implemented in software, the functionality ascribed to the systems, devices and techniques described in this disclosure may be embodied as instructions on a computer-readable medium such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.