Apparatus for selecting a sensing vector configuration in a medical device

0001The present disclosure relates generally to implantable medical devices, and more precisely to devices and methods for selecting sensing vectors in medical devices.

0002Implantable medical devices are available to prevent and treat cardiac arrhythmias by delivering anti-tachycardia pacing therapy and electroconvulsive therapy to perform cardioversion or defibrillation of the heart. Implantable cardioverter defibrillators or such devices, commonly known as "ICDs," sense the patient's ventricular rhythm to detect episodes of tachycardia or fibrillation and perform the rhythm in multiple beats. Classify according to zone.

0003As soon as the abnormal rhythm is detected, the ICD will deliver the appropriate therapy. Pathological forms of ventricular tachycardia can usually be terminated by anti-tachycardia pacing therapy. Anti-tachycardia pacing therapy is followed by high-energy shock therapy when needed. The termination of tachycardia by shock therapy is commonly referred to as the "cardio version." Ventricular fibrillation (VF) is a form of tachycardia that is a seriously life-threatening condition and is usually treated by immediate delivery of high-energy shock therapy. The termination of VF is commonly referred to as "defibrillation." Accurate in choosing the right therapy to effectively treat arrhythmias and in avoiding the delivery of unwanted cardioversion / defibrillation (CV / DF) shocks that can be distressing to the patient. Arrhythmia detection and arrhythmia differentiation are essential.

0004In past practice, ICD systems have employed intracardiac electrodes carried by intravenous leads to sense electrical signals in the heart and to deliver electrotherapy. Newly emerging ICD systems are adapted for subcutaneous or submuscular implantation and employ electrodes that are integrated onto the ICD housing and / or are supported on subcutaneous or submuscular leads. These systems, commonly referred to herein as "subcutaneous ICD" or "SubQ ICD" systems, do not rely on electrodes that are implanted in direct contact with the heart. SubQ ICD systems are less invasive and are therefore easier and faster to implant than ICD systems that employ intracardiac electrodes. However, the reliable detection of cardiac arrhythmias using a subcutaneous system poses a greater challenge. The amplitude of the R wave on the SubQ ECG signal may be about 1/10 to 1/100 of the amplitude of the R wave perceived in the ventricle. Furthermore, the signal quality of the subcutaneously sensed ECG signal is more likely to be influenced by myoelectric potential noise, environmental noise, patient posture, and patient activity than the intracardiac myocardial electrocardiogram (EGM) signal.

0005The ability of a subcutaneous ICD to detect tachyarrhythmias and eliminate noise depends on its ECG signaling characteristics. For higher amplitude R waves, higher frequency (higher through rate) R waves, higher R wave / T wave ratios, lower frequency signals around R waves (eg P and T waves), skeletal myoelectric potential ECG vectors with lower sensitivity and greater R-wave consistency between periods are preferred over ECG vectors without these attributes. Subcutaneous ICDs with a minimum of 2 ECG leads or vectors in a plane (using a minimum of 3 electrodes) use these physical vectors to generate a virtual ECG vector using a linear combination of the physical vector ECGs. can do. However, given the changing environment of the subcutaneous system, choosing the optimal vector can sometimes be a challenge. Thus, there is a need for systems and methods that advance reliable and accurate sensing arrhythmia detection using optimally available sensing vectors when sensing ECG signals via subcutaneous electrodes.

<p num="0006"><patcit num="1"><text>U.S. Pat. No. 5,163,427</text></patcit><patcit num="2"><text>U.S. Pat. No. 5,188,105</text></patcit><patcit num="3"><text>U.S. Pat. No. 6,505,067</text></patcit><patcit num="4"><text>U.S. Pat. No. 6,236,882</text></patcit><patcit num="5"><text>U.S. Pat. No. 5,464,434</text></patcit><patcit num="6"><text>U.S. Pat. No. 5,593,431</text></patcit><patcit num="7"><text>U.S. Pat. No. 4,567,892</text></patcit><patcit num="8"><text>U.S. Pat. No. 5,176,137</text></patcit><patcit num="9"><text>U.S. Pat. No. 4,548,209</text></patcit><patcit num="10"><text>U.S. Pat. No. 5,127,404</text></patcit><patcit num="11"><text>U.S. Pat. No. 4,374,382</text></patcit><patcit num="12"><text>U.S. Pat. No. 4,556,063</text></patcit><patcit num="13"><text>U.S. Patent Application No. 14 / 250,040</text></patcit><patcit num="14"><text>U.S. Patent Application No. 13 / 826,097</text></patcit><patcit num="15"><text>U.S. Patent Application No. 14 / 255,158</text></patcit></p>

<p num="0007"> An object of the present invention is to provide a system and a method for advancing highly reliable and accurate sensing arrhythmia detection using an optimally available sensing vector when sensing an ECG signal via a subcutaneous electrode.</p>

<p num="0008"> A method for determining a sensing vector and a step in which a medical device senses a cardiac signal from a plurality of electrodes forming a plurality of sensing vectors and a step in determining a sensing vector metric in response to the sensed cardiac signal. And the stage of determining the morphological metric associated with the morphology of the sensed cardiac signal, the stage of determining the confirmed sensing vector metric and the vector selection metric in response to the confirmed morphology setting, and the confirmed vector selection metric. It includes a step of selecting a certain sensing vector from a plurality of sensing vectors in response to.</p>

0009<figref num="1">It is a conceptual diagram of a patient who is implanted with an extravascular cardiac fibrillation system as an example.</figref><figref num="2">FIG. 6 is a wiring diagram as an example of an electronic circuit mechanism in a sealed housing of a subcutaneous device according to an embodiment of the present invention.</figref><figref num="3">FIG. 5 is a flow chart of a method for selecting a sensing vector in a medical device according to one embodiment.</figref><figref num="4">One embodiment is a graph representation of a cardiac signal sensed along a plurality of sensing vectors during selection of sensing vectors in a medical device.</figref><figref num="5">FIG. 6 is a flow diagram of a method for determining a morphological metric to select a sensing vector according to one embodiment.</figref><figref num="6">FIG. 5 is a chart depicting a method of utilizing a fixed selection metric to select a sensing vector, according to an exemplary embodiment.</figref><figref num="7">FIG. 5 is a flow diagram of a method for selecting a fixed vector selection metric and a sensing vector using a morphology selection metric according to an embodiment.</figref>

0010FIG. 1 is a conceptual diagram of a patient 12 implanted with an extravascular cardiac fibrillation system 10 as an example. In the embodiment depicted in FIG. 1, the extravascular cardiac defibrillation system 10 is an implantable subcutaneous ICD system. On the other hand, the techniques of the present disclosure include other extravascular implantable cardiac fibrillation systems, such as cardiac fibrillation systems with leads that are implanted at least partially substernally or submuscularly. It can also be used with. In addition, the techniques of the present disclosure are like implantable pacing systems, implantable neurostimulation systems, drug delivery systems, or other systems in which leads, catheters or other components are implanted extravascularly within patient 12. It can also be used with other implantable systems. The present disclosure, however, is described in the context of an implantable extravascular cardiac fibrillation system for purposes of illustration.

0011The extravascular cardiac defibrillation system 10 includes an implantable cardioverter defibrillator (ICD) 14 connected to at least one implantable cardioverter-defibrillator lead 16. ICD14 in FIG. 1 is subcutaneously implanted on the left side of patient 12. The defibrillation lead 16 connected to the ICD 14 extends inward from the ICD 14 towards the patient 12's sternum 28 and xiphoid process 24. Near the xiphoid process 24, the defibrillation lead 16 bends or turns and extends subcutaneously upwards, substantially parallel to the sternum 28. In the embodiment depicted in FIG. 1, the defibrillation lead 16 is implanted with the lead 16 offset outward to the left side of the sternum 28 (eg, towards the left side of patient 12). There is.

0012The defibrillation lead 16 has a therapy vector between the defibrillation electrode 18 and the second electrode (eg, the housing of the ICD14 or the electrode located on the can 25 or the second lead) that is substantially the heart 26. It is placed along the sternum 28 across the ventricles of the heart. The therapy vector, in one embodiment, is viewed as a line extending from a point on the defibrillation electrode 18 to a point on the housing or can 25 of the ICD14. In another embodiment, the defibrillation lead 16 has a sternum such that the therapy vector between the defibrillation electrode 18 and the housing or can 25 (or other electrode) of the ICD 14 substantially crosses the atrium of the heart 26. It may be installed along 28. In this case, the extravascular ICD system 10 is used to provide atrial therapy, such as therapy to treat atrial fibrillation.

0013The embodiment depicted in FIG. 1 is an example configuration of an extravascular ICD system 10 and should not be considered to limit the techniques described herein. For example, the defibrillation lead 16 is depicted in the embodiment of FIG. 1 as being offset outward from the midline of the sternum 28, but the lead 16 is offset to the right of the sternum 28 or the sternum 28. It may be planted so as to be more centrally located. In addition, the defibrillation lead 16 is not substantially parallel to the sternum 28, but instead offsets at an angle from the sternum 28 (eg, the sternum 28 at either the proximal or distal end). It may be implanted so that it can be angled outward from. As another embodiment, the distal end of the defibrillation lead 16 may be positioned near the second or third rib of patient 12. On the other hand, the distal end of the defibrillation lead 16 may be positioned further up or down, depending on the location of the ICD 14, the locations of the electrodes 18, 20, and 22, or other factors. Good.

0014ICD14 is depicted as being implanted near the mid-axillary line of patient 12, while ICD14 is also depicted at other subcutaneous locations in patient 12, eg, further posterior to the posterior axillary line on the trunk. It may be implanted further anterior to the anterior axillary line on the trunk, within the pectoral muscle area, or elsewhere in patient 12. In the case of ICD14 being implanted in the pectoralis major, the lead 16 would follow a different path, for example across the upper thoracic area and downward along the sternum 28. When the ICD14 is implanted in the thoracic muscle region, the extravasation ICD system includes a second lead containing a defibrillation electrode that extends along the patient's left side and defibrillates the second lead. The moving electrode is positioned along the left side of the patient to act as the anode or cathode of the therapy vector of such an ICD system.

0015The ICD14 includes a housing or can 25 that forms a sealing seal to protect the components within the ICD14. The housing 25 of the ICD14 can be formed of a conductive material such as titanium or other biocompatible conductive material or a combination of a conductive material and a non-conductive material. In some cases, the housing 25 of the ICD 14 is used in combination with one of the electrodes 18, 20, or 22 to deliver therapy to the heart 26 or to sense the electrical activity of the heart 26 (housing electrode). Or it is called a can electrode). The ICD14 may further include a connector assembly (sometimes also referred to as a connector block or header) that includes an electrical feedthrough, through which the electrical connection is within the defibrillation lead 16. It is made between the conductor and the electronic components contained within the housing. The housing contains one or more of the processor, memory, transmitter, receiver, sensor, sensing circuit mechanism, therapy circuit mechanism, and other suitable components (often referred to here as modules). The components may be enclosed.

0016The defibrillation lead 16 has a lead body having a proximal end including a connector configured to connect to the ICD 14 and a distal end containing one or more electrodes 18, 20, and 22. Includes. The lead body of the defibrillation lead 16 can be formed from non-conductive materials, including silicones, polyurethanes, fluoropolymers, mixtures thereof, and other suitable materials, and one or more conductors. It can be molded to form one or more lumens extending therein. However, the technique is not limited to such construction. Although the defibrillation lead 16 is depicted as containing three electrodes 18, 20, and 22, the defibrillation lead 16 may contain more or fewer electrodes.

0017The defibrillation lead 16 is an elongated electrical conductor (not depicted) that extends within the lead body from the connector on the proximal end side of the defibrillation lead 16 to electrodes 18, 20, and 22. ) Is included. In other words, each of one or more elongated electrical conductors housed within the lead body of the defibrillation lead 16 can engage the electrodes 18, 20, or 22, respectively. When the connectors at the proximal end of the defibrillation lead 16 are connected to the ICD14, each conductor connects to a connector assembly containing a feedthrough associated with a circuit mechanism such as the therapy module or sensing module of the ICD14. Will be electrically connected via. The electrical conductor transmits therapy from the therapy module within ICD14 to one or more of electrodes 18, 20, and 22, and sensed electricity from one or more of electrodes 18, 20, and 22. The signal is transmitted to the sensing module in ICD14.

0018The ICD14 can sense the electrical activity of the heart 26 via one or more sensing vectors that include a combination of electrodes 20 and 22 with the housing or can 25 of the ICD14. For example, the ICD 14 is sensed using the sensing vector between the electrode 20 and the conductive housing of the ICD 14 or the can 25, which obtains the sensed electrical signal using the sensing vector between the electrodes 20 and 22. Obtaining an electrical signal, using the sensing vector between the electrode 22 and the conductive housing of the ICD 14 or the can 25 to obtain the sensing electrical signal, or using a combination thereof to obtain the sensing electrical signal. Can be done. In some cases, the ICD14 is like a sensing vector between the defibrillation electrode 18 and one of the electrodes 20 or 22 or between the defibrillation electrode 18 and the housing or can 25 of the ICD14. A sensing vector containing a defibrillation electrode 18 is used to sense the electrical signal of the heart.

0019The ICD can analyze the sensed electrical signals to detect tachycardia such as ventricular tachycardia or ventricular fibrillation and generate electrotherapy in response to the detection of tachycardia to the heart 26. Can be delivered. For example, the ICD 14 can deliver one or more defibrillation shocks via a therapy vector that includes a defibrillation electrode 18 of the defibrillation lead 16 and a housing or can 25. The defibrillation electrode 18 may be, for example, an elongated coil electrode or another type of electrode. In some cases, ICD14 may be given one or more pacing therapies, such as anti-tachycardia pacing (ATP) or post-shock pacing, prior to or after delivery of defibrillation shock. It may be delivered. In these cases, ICD14 generates and delivers pacing pulses via a therapy vector that includes one or both of electrodes 20 and 22 and / or housing or can 25. Electrodes 20 and 22 may include ring electrodes, hemispherical electrodes, coil electrodes, spiral electrodes, split electrodes, directional electrodes, or other types of electrodes, or a combination thereof. The electrode 20 and the electrode 22 may be of the same type or different types of electrodes, but in the embodiment of FIG. 1, both the electrode 20 and the electrode 22 are drawn as ring electrodes.

0020The defibrillation lead 16 may further include an attachment form 29 at or near the distal end of the lead 16. The attachment form 29 may be a loop, link, or other attachment form. For example, the attachment form 29 may be a loop formed by sutures. As another embodiment, the attachment feature 29 may be a metal, coated metal, or polymer loop, link, or ring. The attachment feature 29 may be formed in any of a number of shapes having uniform or varying thicknesses and varying dimensions. The attachment feature 29 may be integrated into the reed or may be added by the user prior to implantation. The attachment form 29 may be useful to assist in implanting the lead 16 and / or to secure the lead 16 to the desired implantation site. In some cases, the defibrillation lead 16 may include a anchoring mechanism in addition to or in place of the adherent feature. The defibrillation lead 16 is depicted with the attachment form 29, but in other embodiments the lead 16 may not include the attachment form 29.

0021The lead 16 may further include a connector, such as a DF4 connector, a bifurcated connector (eg, a DF-1 / IS-1 connector), or other type of connector, at the proximal end of the lead 16. The connector at the proximal end of the lead 16 may include a terminal pin that connects to a port in the connector assembly of the ICD14. In some cases, the lead 16 may include an attachment feature at the proximal end of the lead 16 that can be connected to an implantation tool that assists in implanting the lead 16. The attachment form at the proximal end of the reed may either be separated from the connector and integrated into the reed or added by the user prior to implantation.

0022The defibrillation lead 16 further has a suture sleeve or other anchoring mechanism (not shown) configured to anchor the lead 16 near the xiphoid process or lower sternum location close to the electrode 22. May be included. The anchoring mechanism (eg, suture sleeve or other mechanism) may be integrated into the lead or may be added by the user prior to implantation.

0023The examples depicted in FIG. 1 are illustrative in nature and should not be considered limiting the techniques described in this disclosure. For example, the extravascular cardiac fibrillation system 10 may contain more than one lead. In one embodiment, the extravascular cardiac defibrillation system 10 may include a pacing lead in addition to the defibrillation lead 16.

0024In the embodiment depicted in FIG. 1, the defibrillation lead 16 is implanted subcutaneously, eg, between the skin and the ribs or sternum. In other cases, defibrillation leads 16 (and / or voluntary pacing leads) may be implanted at other extravascular sites. In one embodiment, the defibrillation lead 16 may be implanted at least partially below the sternum. In such a configuration, at least a portion of the defibrillation lead 16 may be located in the mediastinum just below or behind the sternum, or more precisely in the anterior mediastinum. The anterior mediastinum is bordered laterally by the pleura, posteriorly by the pericardium, and anteriorly by the sternum 28. The defibrillation lead 16 is implanted, at least in part, in another extrapericardial location, i.e., within the region around the outer surface of the heart 26, but without direct contact with the outer surface of the heart 26. You may be. These other extrapericardial locations are within the mediastinum, but offset from the sternum 28, within the superior mediastinum, within the mediastinum, within the posterior mediastinum, below the xiphoid process or within the xiphoid process area, and the apex of the heart. It can include the vicinity, or other places that are not in direct contact with the heart 26 and are not subcutaneous. In yet another embodiment, the reed may be implanted in the pericardium or epicardial location outside the heart 26.

0025FIG. 2 is a wiring diagram as an example of an electronic circuit mechanism in a sealed housing of a subcutaneous device according to an embodiment of the present invention. As depicted in FIG. 2, the subcutaneous device 14 is a power supply unit that supplies power to the circuit mechanism of the subcutaneous device 14 and a pacing output capacitor that supplies pacing energy by a method well known in the art. Includes a low voltage battery 153 connected to (not shown). The low voltage battery 153 may be, for example, one or two conventional LiCFs._XCell, LiMnO₂Cell or Lil₂It can be formed in cells. The subcutaneous device 14 further comprises one or two conventional LiSVO cells or LiMnO.₂It includes a high voltage battery 112, which may be formed of cells. According to an embodiment of the present invention, FIG. 2 shows both a low voltage battery and a high voltage battery, but the device 14 uses a single battery for both high voltage use and low voltage use. It is possible that you are doing it.

0026Further referring to FIG. 2, the functions of the subcutaneous device 14 are controlled using software, firmware, and hardware, which collaboratively monitor the ECG signal, and the cardio version-defibrillation shock. Alternatively, determine if pacing is required and deliver the prescribed cardioversion-defibrillation therapy and pacing therapy. Subcutaneous device 14 is US Pat. No. 5,163,427 to Keimel, "A device for delivering single and multiple cardioversions and defibrillation pulses" and US Pat. No. 4,037, to Keimel, which was transferred to the transferee of the present application. Devices and Methods for Treating Tachyarrhythmias, Nos. 5,188,105, Monophasic, Simultaneous Biphasic, and Sequential Biphasic Cardioversions-Circuit for Selective Defibrillation Shock Delivery A mechanism, typically to the ICD IPG housing electrode 28 connected to the common output 123 of the high voltage output circuit 140 and to the HVI output 113 of the high voltage output circuit 140 located subcutaneously behind. A connected cardiover version-a defibrillation electrode 24 and a circuit mechanism that employs it may be incorporated.

0027Cardioversion-Defibrillation shock energy and capacitor charging voltage is at least one cardioversion in contact with the heart-ICD with defibrillation electrodes and cardioversion in contact with skin-Most AEDs with defibrillation electrodes Can be intermediate to the voltage supplied by. The typical maximum voltage required for an ICD using most biphasic waveforms is approximately 750 volt, with an associated maximum energy of approximately 40 joules. The typical maximum voltage required for an AED is approximately 2000-5000 Volts and the associated maximum energy is approximately 200-360 joules, depending on the model and waveform used. The subcutaneous device 14 of the present invention uses a maximum voltage in the range of about 300 to about 1500 volts and is associated with an energy of about 25 to 150 joules or more. The total high voltage capacitance can range from about 50 to about 300 microfarads. Such cardioversion-defibrillation shocks occur only during malignant tachyarrhythmias, eg, through the processing of the Farfield cardiac ECG, where ventricular fibrillation employs the detection algorithms described below. Delivered only when detected.

0028In FIG. 2, the sensing amplifier 190, in combination with the pacer / device timing circuit 178, traverses a particular ECG sensing vector defined by a selected pair of subcutaneous electrodes 18, 20, 22 and a can or housing 25 of the device 14. The Farfield ECG sensed signal expressed in the above, or optionally, a virtual signal (ie, a mathematical combination of the two vectors) is processed. For example, the device may be adapted to generate the virtual vector signal described in US Pat. No. 6,505,067 to Lee et al., "Systems and Methods for Deriving Virtual ECG or EGM Signals." , Both patents are used here as references in their entirety. In addition, vector selection may be selected by the patient's physician and programmed by the programmer via telemetry links.

0029The selection of sensing electrode pairs is made in a manner that provides the most reliable sensing of the ECG signal of interest through the switch matrix / MUX191, and the ECG signal of interest is at risk of ventricular fibrillation leading to sudden death. For a convinced patient, it is an R wave. The Farfield ECG signal is passed to the input of the sensing amplifier 190 through the switch matrix / MUX191, which, in combination with the pacer / device timing circuit 178, evaluates the perceived EGM. Asystole, or asystole, is typically determined by a replenishment contraction interval timer in the pacer timing circuit 178 and / or control circuit 144. If the interval between successive R waves exceeds the replenishment contraction interval, a pace trigger signal is applied to the pacing pulse generator 192 to generate the pacing stimulus. Defibrillation pacing is usually provided temporarily to maintain cardiac output after delivery of cardioversion-defibrillation shock, slowly slowing the heart as it recovers to normal function. Can be beaten. Sensing of subcutaneous farfield signals in the presence of noise is by using the appropriate denial and expandable adaptation period described in US Pat. No. 6,236,882, "Noise Removal for Monitoring ECGs" to Lee et al. It may be supported, and the patent is used here as a reference in its entirety.

0030The detection of malignant tachyarrhythmia is determined in the control circuit 144 as a function of the interval between the pacer / device timing circuit 178 and the sensing amplifier circuit 190 to the timing and the R wave sensing event signal output to the control circuit 144. To. It should be noted that the present invention utilizes not only interval-based signal analysis methods, but also auxiliary sensors and morphological processing methods and equipment as described herein below.

0031Auxiliary sensors such as tissue color, tissue oxygenation, respiration, patient activity, and the like can be used to help determine whether to apply or withhold defibrillation therapy. This is described in its entirety in US Pat. No. 5,464,434, "Medical Intervention Device Responsive to Sudden Hemodynamic Changes," to Alt, which is incorporated herein by reference in its entirety. To do. The sensor processing block 194 provides sensor data to the microprocessor 142 via the data bus 146. Specifically, patient activity and / or posture is described in US Pat. No. 5,593,431 to Sheldon, "Medical Services and Methods Adopting Multiple DC Accelerometers for Patient Activity and Posture Sensing." It can be determined by the equipment and methods described in, and the patent is incorporated herein by reference in its entirety. Patient respiration can be determined by the equipment and methods described in US Pat. No. 4,567,892, "Implantable Cardiac Pacemaker" to Plicchi et al., Which patent is hereby incorporated by reference in its entirety. Patient tissue oxygenation or tissue color can be determined by the sensor devices and methods described in US Pat. No. 5,176,137 to Erickson et al., Which patent is hereby incorporated by reference in its entirety. To do. The '137 patented oxygen sensor may be located in the subcutaneous device pocket or instead located on the lead 18 to allow oxygenation or color sensing of the tissue in contact or near contact. You may be.

0032Specific steps in the performance of the detection algorithm criteria are programmed into the microprocessor, RAM and ROM, associated circuit mechanisms, and RAM via the prior art telemetry interface (not shown). It is performed collaboratively within a microcontroller 142 that includes a stored detection criterion that may be acceptable. Data and commands are exchanged between the microcomputer 142 and the timing and control circuit 144, the pacer timing / amplifier circuit 178, and the high voltage output circuit 140 via the bidirectional data / control bus 146. The pacer timing / amplifier circuit 178 and control circuit 144 are clocked at a slower clock speed. The microcomputer 142 is normally in a sleep state, but an interrupt generated by each R wave sensing event, an interrupt generated when a downlink telemetry programming instruction is received, or an interrupt generated as soon as a cardiac pacing pulse is delivered. Awakened by, operated by a fast clock, to perform any necessary mathematical calculation, to perform tachycardia and fibrillation detection procedures, and to be monitored and controlled by a timer in the pacer / device timing circuit mechanism 178. Update the time interval to be done.

0033When malignant tachycardia is detected, the high voltage capacitors 156, 158, 160, and 162 are charged to voltage levels pre-programmed by the high voltage charging circuit 164. It is generally considered inefficient to maintain a constant charge on the high voltage output capacitors 156, 158, 160, 162. Instead, charging is initiated by the control circuit 144 issuing a high voltage charging command HVCHG delivered over line 145 to the high voltage charging circuit 164, charging from the bidirectional control / data bus 166 and HV output circuit 140. It is controlled by using the feedback signal VCAP of. The high voltage output capacitors 156, 158, 160, and 162 may be constructed of film, aluminum electrolysis, or wet tantalum.

0034The negative terminal of the high voltage battery 112 is directly connected to the system ground. Since the switch circuit 114 is normally open, the positive terminal of the high voltage battery 112 is disconnected from the positive power input of the high voltage charging circuit 164. The high voltage charging command HVCHG is further conducted through the conductor 149 to the control input of the switch circuit 114, which in response closes and closes the positive high voltage battery voltage EXT B + to the positive of the high voltage charging circuit 164. Connect to the power input. The switch circuit 114 may be, for example, a field effect transistor (FET) whose source-drain path interrupts the EXT B + conductor 118 and whose gate is receiving the HVCHG signal on the conductor 145. The high voltage charging circuit 164 is thereby ready to begin the stage of charging the high voltage output capacitors 156, 158, 160, and 162 with the charging current from the high voltage battery 112.

0035High voltage output capacitors 156, 158, 160, and 162 are charged to very high voltages, such as 300-1500V, and discharged through the body and heart between the electrode pairs of subcutaneous cardioversion-defibrillation electrodes 113 and 123. It may be. The details of the voltage charging circuit mechanism are also not considered definitive with respect to the practice of the present invention, but one high voltage charging circuit that is believed to be suitable for the purposes of the invention is disclosed. The high voltage capacitors 156, 158, 160, and 162 are described in detail in, for example, US Pat. No. 4,548,209 "Energy transducers for implantable cardioverters" to Wileders et al., Transferred to the assignee of the present application. It can be charged by the high voltage charging circuit 164 and the high frequency high voltage transformer 168 described. Proper charging polarity is maintained by diodes 170, 172, 174, and 176 that interconnect the output windings of the high voltage transformer 168 with the capacitors 156, 158, 160, and 162. As pointed out above, the state of capacitor charging is monitored by a circuit mechanism within the high voltage output circuit 140, which provides the timing and control circuit 144 with VCAP, which is a feedback signal indicating the voltage. To do. The timing and control circuit 144 terminates the high voltage charging command HVCHG when the VCAP signal matches the programmed capacitor output voltage, i.e. cardioversion-defibrillation peak shock voltage.

0036The control circuit 144 then expresses NPULSE1 and NPULSE2, respectively, which are the first and second control signals applied to the high voltage output circuit 140 to trigger the delivery of the shock for cardioversion or defibrillation. In particular, the NPULSE1 signal triggers the discharge of the first capacitor bank with capacitors 156 and 158. The NPULSE2 signal triggers the discharge of the first capacitor bank and the second capacitor bank with capacitors 160 and 162. Selection between multiple output pulse regimes is feasible by simply modifying the number and chronological order of assertions for the NPULSE1 and NPULSE2 signals. The NPULSE1 signal and the NPULSE2 signal can be provided sequentially, simultaneously or individually. In this way, the control circuit mechanism 144 has a pair of cardioversion-defibrillation electrodes that connect a high-energy cardioversion-defibrillation shock to the HV-1 and COMMON outputs, as shown in FIG. It serves to control the operation of the high voltage output stage 140 delivered between 18 and 25.

0037Thus, the subcutaneous device 14 monitors the patient's heart condition and requires cardioversion-in response to the detection of defibrillation tachyarrhythmia, cardioversion-cardioversion through defibrillation electrodes 18 and 25- Initiate delivery of defibrillation shock. The high HVCHG signal connects the high voltage battery 112 to the high voltage charging circuit 164 through the switch circuit 114 to initiate charging of the output capacitors 156, 158, 160, and 162. Charging continues until the programmed charging voltage is reflected by the VCAP signal, at which point the control and timing circuit 144 sets the HVCHG signal low to terminate charging and open the switch circuit 114. The subcutaneous device 14 can also be programmed to attempt to deliver a cardioversion shock to the heart in the manner described above in time with the detected R wave, or described above. Cardioversion shocks to the heart in the manner in which it is used can also be programmed or made to deliver without attempting to synchronize delivery to the detected R wave. Detection of Tachyarrhythmias and Cardioversion-Episode data associated with the delivery of defibrillation shocks is uploaded to external programmers well known in the art to facilitate the diagnosis of the patient's cardiac condition. It can be stored in RAM in preparation for link telemetry transmission. Patients accepting device 14 for prophylactic reasons should report each such episode to their physician for further assessment of the patient's condition and assessment of the need for more advanced ICD implantation. Will be instructed by.

0038The subcutaneous device 14 preferably includes a telemetry circuit (not shown) so that the device is programmed by an external programmer 20 via a two-way telemetry link (not shown). Is possible. Uplink telemetry allows device status and diagnostic / event data to be sent to an external programmer 20 for review by the patient's physician. Downlink telemetry allows external programmers to program device functions and optimize detection and therapy for specific patients under the control of a physician. Programmers and telemetry systems suitable for use in the practice of the present invention have been well known for many years. So that the programmer can send control commands and operating parameter values that should be received by the implanted device, and that the implanted device can communicate diagnostic and operational data to the programmer. Known programmers typically communicate with the implanted device partner via a bidirectional radio frequency telemetry link. Programmers believed to be suitable for the purposes of practicing the present invention include programmers of Model 9790 and CareLink® commercially available from Medtronic, Inc., Minneapolis, Minnesota. ..

0039Various telemetry systems have been developed to provide the required communication channels between the external programming unit and the implanted device and are well known in the art. A telemetry system believed to be suitable for the purposes of practicing the present invention is, for example, entitled "Telemetry Format for Implanted Medical Devices" to the following US patent, Wyborny et al. US Pat. No. 5,127,404, US Pat. No. 4,374,382 entitled "Markowitz Markowitz," US Pat. No. 4,374,382, "Telemetry for Medical Devices," to Thompson et al. It is disclosed in US Pat. No. 4,556,063, entitled "System." Wibonnie et al. '404, Markovitz's '382, and Thompson et al. '063 have been assigned to the assignees of the present invention, each of which is incorporated herein by reference in its entirety.

0040According to certain embodiments of the present invention, in order to automatically select a suitable ECG vector set, it is necessary to have an index of merit on which to rate the quality of the signal. "Quality" is defined as the ability of the signal to provide accurate heart rate estimation and accurate morphological waveform separation between the patient's normal sinus rhythm and the patient's ventricular tachyarrhythmia.

0041Appropriate indicators are R-wave amplitude, R-wave peak amplitude vs. R-wave waveform amplitude (ie signal-to-noise ratio), low slope content, relative high-to-low frequency power, average frequency estimation, probability density. It may include a function, or any combination of these metrics.

0042The automatic vector selection may be performed at the time of implantation, regularly (daily, weekly, monthly), or both. At the time of implantation, automatic vector selection may be initiated as part of an automated device turn-on procedure that performs activities such as measuring lead impedance and battery voltage. The device turn-on procedure may be initiated by the implant physician (eg, by pressing the programmer button) or instead, it will be initiated automatically as soon as there is automatic detection of the device / lead implant. You may be. The device of the subcutaneous device 14 is sewn in place and prior to closing the incision, the turn-on procedure also uses automatic vector selection confirmation criteria, and the quality of the ECG vector is for the current patient and for the device and lead position. , May be to determine if it is appropriate. Such an ECG quality label should allow the implant physician to steer the device to a new location or direction to improve the quality of the ECG signal as needed. In addition, a suitable singular or plural ECG vector may be selected at the time of implantation as part of the device turn-on procedure. A suitable vector may be a vector having an index that maximizes rating estimation and detection accuracy. Moreover, as long as there is a deductive set of vectors preferred by the physician, and those vectors exceed a minimum threshold, or they are negligible than some other more desirable vectors. As long as it is not bad, a vector suitable for deduction may be selected. Certain vectors may be considered nearly identical and they will not be tested unless the deductively selected vector index falls below a predetermined threshold.

0043Instrument Metrics Depending on power consumption and power requirements, ECG signal quality metrics may be measured as often as desired based on a range of vectors (or a subset instead). Data may be collected, for example, on a minute, hourly, daily, weekly, or monthly basis. More frequent (eg, minutely) measurements are averaged over time and used, for example, based on the susceptibility of the vector to transient noise, motion noise, or EMI. You may choose a vector.

0044Instead, the subcutaneous device 14 has a patient activity indicator / sensor (piezoresistive, accelerometer, impedance, or similar) with minimal or no automatic vector measurements during medium or high patient activity periods. It may be delayed for automatic vector measurements during the activity period. One typical scenario is that the ECG vector was determined to be asleep (using an internal clock (eg 2:00 am)) once daily or once weekly, or (axis 2 or 3). It may include testing / assessing while inferred to be asleep by determining the patient's position and lack of activity (via accelerometer). In another possible scenario, the step of testing / evaluating the ECG vector may be performed once daily or once weekly while the patient is known to be doing gymnastics.

0045Even if infrequent, automatic, and regular measurements are taken, the noise in the signal (eg muscle, exercise, EMI, etc.) is still measured and vector selection measurements are performed until the noise subsides. It is desirable to postpone it.

0046The subcutaneous device 14 may optionally have an indication of the patient's posture (via a 2-axis or 3-axis accelerometer). This sensor can be used to ensure that ECG quality differences are not simply the result of attitude / position changes. Sensors may be used to collect data in multiple postures so that ECG quality can be averaged over these postures, or otherwise combined, or instead a preferred posture. May be selected for.

0047In one embodiment, vector quality metric calculations are performed by the clinician using the programmer either at the time of implantation or during subsequent visits, or a remote link with the device and programmer. It is designed to be carried out remotely via. According to another embodiment, the vector quality metric calculation is automatically performed by the device a predetermined number of times, such as multiple times daily, once daily, once weekly, or monthly, for each available sensing vector. It is supposed to be carried out. In addition, those values may be averaged for each vector, for example over the course of a week. The averaging may consist of moving averages or iterative averaging, depending on time weighting and memory considerations.

0048FIG. 3 is a flow chart of a method for selecting a sensing vector in a medical device according to one embodiment. As shown in FIG. 3, according to one embodiment of the present disclosure, the device incorporates a cardiac signal for each of the available sensing vectors 102-106, eg, in its entirety here as a reference. Sensing using known sensing techniques in the art as described in US Patent Application No. 14 / 250,040. The device obtains the perceived R-wave of the cardiac signal for each available sensing vector 102-106, and is perceived for block 124, and for that sensing vector 102-106, as described below. Block 126, which determines the vector quality metric for determining the quality of vector perception associated with the R wave, and block 128, which determines the morphological quality metric for determining the quality of morphological analysis. Once the vector quality metric at block 126 and the morphological metric at block 128 associated with the perceived R wave have been determined for each sensing vector 102-106, the device has the vector quality metric and morphological metric the sensing vector. Determine if each of 102-106 has been established for a predetermined threshold number of cardiac cycles, block 130. If the vector quality and morphological metrics are not established for a predetermined threshold number of cardiac cycles for each sensing vector 102-106, ie No in block 130, then the device has the next R wave for each sensing vector 102-106. 124 is obtained and the process is repeated for the next sensed cardiac cycle for each of the sense vectors 102-106. According to one embodiment, vector quality and morphological metrics are established for, for example, 15 cardiac cycles.

0049If the vector and morphological metrics were established for a predetermined threshold number of cardiac cycles for each sensing vector 102-106, ie Yes at block 130, the device was determined as described below. The vector quality and morphological metrics are used to determine the selection metric, and one or more vectors to be utilized during block 132, subsequent sensing and device arrhythmia detection are selected based on the determined selection metric. Block 134. Depending on the amount of time programmed to occur between updates of the sensing vectors 102-106, i.e. hours, days, weeks, or months as an example, the device confirms the next scheduled vector selection. Wait until block 136, at which point the vector selection process is repeated.

0050FIG. 4 is a graph representation of a cardiac signal sensed along a plurality of sensing vectors during selection of sensing vectors in a medical device according to one embodiment. As depicted in FIG. 4, during the vector selection process, the device references 100 cardiac signals for each of the available sensing vectors 102-106, eg, here as a reference in its entirety, a U.S. patent application. Sensing using known sensing techniques in the art, such as No. 14 / 250,040. For example, according to one embodiment as depicted in FIG. 4, the device has a horizontal sensing vector 102 extending between the housing or can 25 and electrode 22, and an oblique extending between the housing or can 25 and electrode 20. The ECG signal 100 is sensed from each of the available sensing vectors 104, including the sensing vector 104, and the vertical sensing vector 106 extending between the electrodes 20 and 22. For each sensing vector 102-106, the device determines that the sensed R wave 108 is occurring when the sensed signal exceeds the time-dependent autonomously controlled sensing threshold 110.

0051When the R wave 108 is sensed, the device determines the vector quality and morphological metrics for the sensed R wave, blocks 126 and 128 in FIG. To determine the vector quality metric in block 126 of FIG. 3, as depicted in FIG. 4, for example, the device has a vector quality metric detection window 112 for vector quality metric determination associated with the sensing vector 102-106. Is set based on the perceived R wave 108 for each of the sensing vectors 102-106. According to one embodiment, the device associates a quality metric detection window 112 starting at a starting point 114 located at a predetermined distance 116 from the R wave 108 with a QRS signal associated with the R wave 108 being sensed for analysis of signal 100. A detection window width of 118 is set to allow the T-wave to be carried out within the expected range of the signal 100 in which it may occur. For example, the device has a quality metric detection window 112 with a width of approximately 200 ms and is positioned between the R wave 108 where the start point 114 of the quality metric detection window 112 is detected and approximately 150-180 ms. The width 118 is set to extend 200 ms from the detection window start point 114 to the detection window end point 120, that is, from the detected R wave 108 to the end point 120 at a distance of approximately 350-380 ms. Once the quality metric detection window 112 is set, the device sets the minimum signal difference 122 between the perceived signal 100 and the perceived threshold 110 in the quality metric detection window 112, i.e. between the perceived signal 100 and the perceived threshold 110. Determine the minimum distance to extend. This fixed minimum signal difference 122 for each of the three sensing vectors 102-106 is then set as a vector quality metric for the simultaneously sensed R waves 108 at those sensing vectors, block 126.

0052FIG. 5 is a flow diagram of a method for determining morphological metrics to select a sensing vector, according to one embodiment. To determine the morphological metric at block 126 in FIG. 3, the device determines the narrow pulse count or pulse count for the R wave 108. For example, in order to determine the narrow pulse count for each R wave 108 associated with the sensing vector 102-106, the device has transferred the individual pulse associated with the R wave, eg, to the assignee of the present application, here. It is established using known techniques such as those described in US Patent Application Nos. 13 / 826,097 and 14 / 255,158, which are incorporated in their entirety. For each of the identified pulses, the device determines if the pulse width is less than the default threshold. Specifically, as shown in FIG. 5, the device obtains a single pulse of the identified pulse associated with the R wave and determines the block 200, the pulse width associated with that pulse. Block 202, and block 204, which determines if the pulse width is less than or equal to the pulse width threshold.

0053In addition to Yes in block 204, which is the step of determining whether the pulse width of an individual pulse is less than or equal to the pulse width threshold, the device further determines whether the absolute amplitude of the pulse is greater than the amplitude threshold. Block 206, which may be to determine. According to certain embodiments, the pulse width threshold may be set, for example, as 23 ms, and the amplitude threshold has been transferred to the assignee of the present application, the United States of which the whole is incorporated herein by reference. A percentage of the maximum gradient used to determine if the beat and template alignment gradient thresholds described in patent applications 13 / 826,097 and 14 / 255,158 were met, eg 8 minutes. It is set as 1 etc.

0054Although the block 204, which is the pulse width determination, is depicted as occurring before the block 206, which is the amplitude threshold determination, it is understood that the determinations of the block 204 and the block 206 may be performed in any order. Therefore, either the pulse width of the individual pulse is neither less than the pulse width threshold nor equal to the pulse width threshold, ie No at block 204, or the absolute amplitude of the pulse is not greater than the amplitude threshold, ie No at block 206. If so, it is determined that the pulse should not be included in the narrow pulse count. The device proceeds to determine if the number of pulses meets the narrow pulse counting parameter for all identified pulses of the R wave beat, block 210. If the determination is not made for all identified pulses, ie No at block 210, the device identifies the next pulse associated with the R wave and counts narrow pulses for block 200, and beats. The determining process, block 202-block 208, is repeated for the next pulse.

0055If the pulse width of the individual pulse is less than or equal to the pulse width threshold, ie yes at block 204 and the absolute amplitude of the pulse is greater than the amplitude threshold, ie yes at block 206, then the number of pulses is the width for the individual R wave. It means that the threshold and the amplitude threshold are met, and the narrow pulse count is incremented by 1, block 208.

0056If the determination has been made for all identified pulses associated with the R wave, i.e. yes at block 210, the device has updated the narrow pulse count for the R wave as a result at block 208. Set equal to, block 212. In this way, the narrow pulse count for the R wave has a total number of identified pulses for the R wave that meet both the width and amplitude thresholds, that is, a pulse width less than 23 milliseconds. Moreover, for example, it is the total number of pulses having an absolute amplitude larger than 1/8 of the maximum gradient used when aligning the beat with the template. The final narrow pulse count from block 212 is then stored as a morphological metric for each R wave.

0057In this way, the process is repeated for multiple R waves perceived along each of the sensing vectors 102-106, resulting in both the vector quality metric and the morphological metric having a predetermined threshold number for each sensing vector 102-106. Cardiac Cycles For example, once determined for 15 cardiac cycles, i.e. after block 130, the device establishes a selection metric or vector selection metric and a morphology selection metric, block 132 of FIG. As shown in FIGS. 3 and 4, if the minimum signal difference 122 has been determined for all of the predetermined threshold number of cardiac cycles, i.e. yes at block 130, the device is for each vector 102-106. The vector selection metric is determined based on the 15 minimum signal differences 122 determined for the sensing vector. For example, according to one embodiment, the device determines the median of 15 minimum signal differences 122 for each sensing vector and the minimum signal difference 122 associated with the vector selection metric for that sensing vector. Set equal to the median. Once the vector selection metrics have been determined, one for each of the sensing vectors 102-106, the device ranks those vector selection metrics for the sensing vectors 102-106. For example, the device ranks the determined vector selection metrics from top to bottom, so that in the embodiment of FIG. 4, the oblique sensing vector 104 has a median minimum signal difference of 0.84 for that vector. The horizontal sensing vector 102 is ranked first because it was millivolts, the horizontal sensing vector 102 is ranked second because the median minimum signal difference for that vector is 0.82 millivolts, and the vertical sensing vector 106 is relevant. Since the median minimum signal difference for the sensing vector is 0.55 millivolts, it will be ranked at the bottom.

0058Similarly, to determine the morphology selection metric at block 132 of FIG. 3, the device calculates the mean, median, or maximum pulse count of 15 fixed narrow pulse counts for each of the sensing vectors 102-106. Can be confirmed. Based on the determined mean, median, or maximum narrow pulse counts for the R waves simultaneously sensed along the sensing vectors 102-106, the device sets those vectors to low pulses based on the determined morphological selection metrics. Rank as one of counting, medium pulse counting, and high pulse counting. For example, according to one embodiment, if the mean, median, or maximum pulse count associated with the sensing vector is greater than 5, the final pulse count or form selection metric for that vector is "high." Is determined. If the mean, median, or maximum pulse count associated with the sensing vector is 5 or less, but 2 or more, the final pulse count or morphology selection metric for the vector is determined to be "medium". Otherwise, if the mean, median, or maximum pulse count associated with the sensing vector is less than or equal to 1, the final pulse count or morphology selection metric for that vector is determined to be "low". Will be done.

0059According to another embodiment, the sensing vectors 102-106 may be ranked relative to each other based on the morphology selection metric, so that the sensing vector with the highest pulse count is "high", the second largest. The sensing vector with the pulse count will be identified as "medium" and the sensing vector with the lowest pulse count will be identified as "low".

0060FIG. 6 is a chart illustrating a method of utilizing a fixed selection metric to select a sensing vector, according to an exemplary embodiment. As depicted in FIG. 6, the result of determining the vector selection metric described above ranks the sensing vector 102 in the 1st place, the sensing vector 104 in the 2nd place, and the sensing vector 106 in the 3rd place. If we assume that the sensing vectors 102-106 are ranked relative to each other based on the morphology selection metric, then six feasible scenarios are shown and the result of the morphology selection metric is six feasible scenarios. It may be indicated according to any one of. In the first morphological selection scenario 300, the sensing vector 102 has a low relative narrow pulse count (ie, as opposed to the sensing vectors 104 and 106) over 15 cardiac cycles, and the sensing vector 104 has a medium relative narrow pulse counting (ie, contrasted with the sensing vectors 104 and 106). It is determined that the sensing vector 106 has a high relative narrow pulse count (ie, contrasted with the sensing vectors 102 and 104). In the second morphology selection scenario 302, the sensing vector 102 has a low relative narrow pulse count over 15 cardiac cycles, the sensing vector 104 has a high relative narrow pulse count, and the sensing vector 106 has a medium relative narrow pulse count. It is determined to have a count.

0061In the third form selection scenario 304, the sensing vector 102 has a medium relative narrow pulse count over 15 cardiac cycles, the sensing vector 104 has a high relative narrow pulse count, and the sensing vector 106 has a low relative narrow pulse count. It is determined to have a count. In the fourth form selection scenario 306, the sensing vector 102 has a medium relative narrow pulse count over 15 cardiac cycles, the sensing vector 104 has a low relative narrow pulse count, and the sensing vector 106 has a high relative narrow pulse count. It is determined to have a count. In the fifth form selection scenario 308, the sensing vector 102 has a high relative narrow pulse count over 15 cardiac cycles, the sensing vector 104 has a low relative narrow pulse count, and the sensing vector 106 has a medium relative narrow pulse count. It is determined to have a count. Finally, in the sixth morphology selection scenario 310, the sensing vector 102 has a high relative narrow pulse count over 15 cardiac cycles, the sensing vector 104 has a medium relative narrow pulse count, and the sensing vector 106 has a low relative narrow pulse count. It has been determined to have a narrow pulse count.

0062FIG. 7 is a flow diagram of a method for selecting a fixed vector selection metric and a sensing vector using the morphology selection metric according to an embodiment. Once the vector selection and morphology selection metrics have been determined for the sensing vectors 102-106, as depicted in FIGS. 6 and 7, the device results in the sensing vectors 102 and 104 in the embodiment of FIG. Identify the vectors ranked first and second as, block 320, does one of the corresponding confirmed form selection metrics have a "high" pulse count? Determine if, block 322. In the embodiment of FIG. 6, this happens in form selection scenarios 302, 304, 308, and 310, that is, yes in block 322, and does not occur in form selection scenarios 300 and 306, that is, no in block 322. If none of the confirmed morphological selection metrics associated with the 1st and 2nd ranked vectors are "high" morphological selection metrics, i.e. No in block 322, then 1st and 2nd place Block 324, where the attached vector is selected as the sensing vector.

0063If either the first-ranked vector or the second-ranked vector form selection metric is a "high" form selection metric, i.e. Yes in block 322, the device is the other. Block 326, which sets the vector as a vector that can be ranked first. For example, in the morphological selection metric scenarios 308 and 310, the vector ranked second, that is, the sensing vector 104, is set as the vector ranked first, and the sensing vector 102 is set as the vector ranked second after the update. In the set and morphological selection metric scenarios 302 and 304, the first-ranked sensing vector, ie, the first-ranked sensing vector 102, is set (maintained) as the first-ranking vector.

0064To determine which of the remaining two sensing vectors is selected as the vector to be ranked second, the device then determines the difference in morphological metric between the updated second and updated vector. Determine if the morphological metric difference threshold is less than block 328, and determine if the vector metric difference between the updated second and updated vector is greater than the vector metric difference threshold, block 330. For example, according to one embodiment, the device is determined in block 328 between the vector identified as having the "high" morphology selection metric and the vector ranked in the third place as described above. It may be designed to determine whether the difference between the narrow pulse counts is greater than or equal to 3.

0065By way of example, in morphological selection metric scenarios 308 and 310, the device is more than about the sensing vector ranked third, whether the difference between the sensing vector 102 and the sensing vector 106 is greater than the morphological metric difference threshold. Determined by subtracting the determined morphological metric or narrow pulse count from the determined morphological metric for the vector identified as having the "high" morphological selection metric or sensing vector 102. Similarly, in morphological selection metric scenarios 302 and 304, the device determines whether the difference between the sensing vector 104 and the sensing vector 106 is greater than the morphological metric difference threshold for the sensing vector ranked third. Determined by subtracting the determined morphological metric or narrow pulse count from the determined morphological metric for the vector identified as having the "high" morphological selection metric or sensing vector 104.

0066If the difference in morphological metric between the updated second-place vector and the updated third-place vector is not greater than the morphological metric difference threshold, that is, No in block 328, the vectors ranked first and second are detected. Block 324 selected as a vector.

0067Similarly, according to one embodiment, the device is used to determine if the vector metric difference between the updated second place vector and the updated third place vector in block 330 is less than the vector metric difference threshold. , The difference in the minimum signal difference determined above between the vector identified as having the "high" morphology selection metric and the vector ranked in the third place is the nominal minimum, for example 0.10 millivolts. It is also possible to determine whether it is smaller than the threshold value.

0068By way of example, in morphological selection metric scenarios 308 and 310, the device is more than about the sensing vector ranked third to see if the difference between the sensing vector 102 and the sensing vector 106 is greater than the vector metric difference threshold. Determined by subtracting the determined vector metric or minimum signal difference from the determined vector metric for the vector identified as having the "high" morphology selection metric, i.e. the sense vector 102. Similarly, in morphological selection metric scenarios 302 and 304, the device determines whether the difference between the sensing vector 104 and the sensing vector 106 is less than the vector metric difference threshold for the sensing vector ranked third. Determined by subtracting the determined vector metric or minimum signal difference from the determined vector metric for the vector identified as having the "high" morphology selection metric, i.e. the sensing vector 104.

0069If the difference in vector metric between the updated second place vector and the updated third place vector is not less than the vector metric difference threshold, that is, No in block 330, the vectors ranked in the first and second places are detected. Block 324 selected as a vector. The difference in the morphological metric between the updated 2-position vector and the updated 3-position vector is larger than the morphological metric difference threshold, that is, Yes in block 328, and the vector metric between the updated 2-position vector and the updated 3-position vector. If the difference is less than the vector metric difference threshold, i.e. Yes at block 330, then the updated 1st and 3rd place vectors are selected as sensing vectors, block 332. For example, assuming that both the morphological metric difference threshold and the vector metric difference threshold are satisfied, that is, both blocks 328 and 330 are Yes, then in the morphological selection metric scenarios 308 and 310 vector 104 and vector 106 are selected as sensing vectors. Then, in the morphological selection metric scenarios 302 and 304, the vector 102 and the vector 106 are selected as the sensing vectors.

0070In some cases, the morphological selection metrics may have the same ranking for two or more of the sensing vectors 102-106. Therefore, according to one embodiment, if the two sensing vectors have the same morphological selection metric, then the device is a vector ranked first and second from the vector selection metric, ie FIG. 7. In the embodiment shown in, vector 102 and vector 104 may be selected as sensing vectors to be utilized. Alternatively, according to another embodiment, if the morphological selection metric for two or more of the sensing vectors 102-106 is "high", then the device ranks first and second from the vector selection metric. The attached vector, i.e., in the embodiment shown in FIG. 7, may be configured to select the vector 102 and the vector 104 as the sensing vectors to be utilized. In both situations, the vectors 102 and 104 were selected based solely on the fixed minimum signal difference for the sense vectors 102-106, so the update of the sense vectors ranked first and second occurred. There will be no.

0071In addition to the three sensing vectors 102-16 described above, an optional virtual signal (ie, a mathematical combination of the two vectors) can be used in addition to the aforementioned sensing vectors, resulting in more than three. It is understood that the sensing vector of the above may be used, or the virtual signal may be used instead of the sensing vector described above. For example, the device may be adapted to generate the virtual vector signal described in US Pat. No. 6,505,067 to Lee et al., "Systems and Methods for Deriving Virtual ECG or EGM Signals," both patents. Is used here as a reference in its entirety. In addition, vector selection may be selected by the patient's physician and programmed by the programmer via telemetry links.

0072In addition, although the use of minimum signal differences is described, the device can also utilize other selection criteria for vector ranking. For example, according to one embodiment, the device determines the maximum signal amplitude in the detection window for each R wave for each vector and determines the difference between the maximum amplitude and the sensing threshold for each of the maximum amplitudes. The median maximum amplitude difference for each sensing vector over 15 cardiac cycles may be determined. The device then selects the vector with the largest median maximum amplitude difference as the (s) sensing vector to be utilized during subsequent sensing and arrhythmia detection by the device.

0073As described above, the methods and devices for selecting the sensing vector configuration in the medical device have been presented with reference to the specific embodiments in the above description. It is understood that various modifications to the referenced embodiments may be made without departing from the scope of the present disclosure set forth in the accompanying claims.

007410 Extravascular cardiac fibrillation system 12 patients 14 Implantable Cardioverter Defibrillator (ICD) 16 Implantable Cardiac Defibrillation Lead 18 Defibrillation electrode 20, 22 electrodes 24 xiphoid process 25 housing or can 26 Heart 28 Sternum 29 Adhesive body part 100 ECG signal (heart signal) 102 horizontal sensing vector 104 Diagonal sensing vector 106 vertical sensing vector 108 R wave 110 Sensing threshold 112 High voltage battery (Fig. 2) 112 Quality Metric Detection Window (Figure 3) 114 Switch circuit (Fig. 2) 114 Window starting point (Fig. 3) 116 Default distance from R wave 118 Positive high voltage battery voltage EXT B + conductor (Figure 2) 118 Window width (Fig. 3) 120 window end point 122 Minimum signal difference 140 High voltage output circuit 142 microprocessor (microcomputer) 144 Timing and control circuit 145 line (conductor) 146 Bidirectional data / control bus (data bus) 149 conductor 153 Low voltage battery 156, 158, 160, 162 High voltage output capacitors 164 High voltage charging circuit 166 Bidirectional control / data bus 168 High frequency high voltage transformer 170, 172, 174, 176 diodes 178 Pacer / Equipment Timing Circuit 190 Sensing amplifier 191 Switch Matrix / MUX 192 Pacing pulse generator 194 Sensor processing block