A system and method for identifying cardiac arrhythmia events after myocardial infarction.

Abstract

A system for identifying cardiac arrhythmia events (AEs) in a patient (P) comprises an implantable medical device (1) for sensing electrocardiogram signals, the implantable medical device (1) comprising an arrangement of poles (12, 13) configured to sense electrocardiogram signals. The processing arrangement is configured to use a first setting of at least one detection parameter for detecting cardiac arrhythmia events (AEs) based on the electrocardiogram signals, to acquire information indicating a myocardial infarction event (MI), and in response to acquiring said information, to adapt the at least one detection parameter to a second setting different from the first setting for detecting cardiac arrhythmia events (AEs) during a period (SP) after acquiring said information indicating a myocardial infarction event (MI).

Description

Technical Field

[0001] The present invention generally relates to a system for identifying a patient's cardiac arrhythmia events and a method for operating such a system.

[0002] Systems of the type relevant to this specification include an implantable medical device for sensing an electrocardiogram signal, the implantable medical device comprising an arrangement of electrodes configured to sense the electrocardiogram signal. A processing arrangement is configured to process the electrocardiogram signal obtained by the implantable medical device.

[0003] This type of implantable medical device can be, for example, a pacemaker, an implantable defibrillator, a sensor device such as a biosensor, or a monitoring device. The implantable medical device of this specification is configured to sense an electrocardiogram signal.

[0004] For example, the implantable medical device can be a monitoring device configured to record an electrocardiogram signal and transmit the recorded electrocardiogram signal or information derived from the recorded electrocardiogram signal to an external device in the context of a home monitoring system.

[0005] An implantable medical device, such as that described in European Patent No. 3278836, for example, may comprise, for example, a housing and an arrangement of electrodes disposed on the housing. The electrodes of the device are disposed on the housing of the implantable medical device such that the electrodes are aligned along the longitudinal axis along which the implantable medical device extends. The electrodes can be made of a conductive material, such as a metallic material, and can be formed by a housing segment that is externally exposed so as to be able to make electrical contact with the surrounding tissue to establish an electrical coupling with the tissue in the implanted state of the implantable medical device.

[0006] For example, implantable medical devices used in home monitoring systems enable reliable monitoring of a patient's physiological state. In particular, implantable medical devices make it possible to reliably detect abnormal cardiac conditions based on recorded electrocardiogram signals. If an abnormality is detected in the electrocardiogram signal, the implantable medical device can communicate with an external device in the home monitoring system, for example, to trigger a message to a service center to warn healthcare professionals that attention may be required.

[0007] The types of systems and methods relating to this specification shall, in particular, be configured to identify cardiac arrhythmia events in patients. Generally, within a system, cardiac arrhythmia events such as ventricular tachycardia, ventricular fibrillation, or ventricular premature contractions are identified by processing the electrocardiogram signal according to the amplitude and frequency content of the processed signal. In detection schemes for identifying cardiac arrhythmia events, which present the inherent problem of distinguishing the relevant signal portion from noise contributions, the detection settings are generally prone to a conflict between enabling high-sensitivity identification of cardiac arrhythmia events on the one hand and avoiding a large number of false-positive classifications on the other hand, which can increase the review burden and alarm fatigue of clinical professionals.

[0008] In particular, when cardiac arrhythmia events are detected with high sensitivity based on electrocardiogram signals, this is usually done at the expense of an increased number of false positive classifications. However, reducing sensitivity to decrease the number of false positive classifications comes at the cost of potentially reducing the reliability of detecting cardiac arrhythmia events.

[0009] A patient's risk of cardiac arrhythmias can depend on their physical condition, particularly their cardiac condition. Especially during the acute phase following a myocardial infarction, patients may have an increased risk of ventricular tachycardia and ventricular premature contractions. When a patient has experienced a myocardial infarction, cardiac arrhythmias are more likely to occur and may have a more serious impact on them compared to a patient with a healthy heart.

[0010] The objective is to provide a system for identifying cardiac arrhythmia events in a patient, and a method for operating such a system, which ensures reliable identification of cardiac arrhythmia events based on electrocardiogram signals by taking into account the patient's physical condition.

[0011] In one embodiment, a system for identifying cardiac arrhythmia events in a patient comprises an implantable medical device for sensing electrocardiogram signals, the implantable medical device comprising an arrangement of (preferably two) poles configured to sense electrocardiogram signals. The system further comprises a processing arrangement for processing the electrocardiogram signals acquired by the implantable medical device. The processing arrangement is configured to use a first setting of at least one detection parameter for detecting cardiac arrhythmia events based on the electrocardiogram signals, acquire information indicating a myocardial infarction event, and in response to acquiring said information, to adapt the at least one detection parameter to a second setting different from the first setting for detecting cardiac arrhythmia events during the period after acquiring said information indicating a myocardial infarction event.

[0012] Generally, the system is configured to identify cardiac arrhythmia events based on electrocardiogram signals sensed by an implanted medical device. In this specification, the electrocardiogram signals are processed, and based on the processing, cardiac arrhythmia events such as ventricular tachycardia (VT), ventricular fibrillation (VF), or ventricular premature contractions (PVCs) are identified. Other arrhythmias include, but are not limited to, supraventricular tachycardia (SVT), bradycardia, asystole, sudden velocity changes, ectopic events, and other morphological changes to the ECG, such as ST segment elevation or depression, changes in timing between ECG components, and other diagnostic characteristics. These arrhythmias may be considered cardiac arrhythmia events (in all embodiments described).

[0013] Identification in this specification is performed by evaluating the electrocardiogram signal according to one or more detection parameters, for example by using specific filter settings, automatic sensing parameter settings, timer settings, or refractory period settings, each of which represents a detection parameter used to identify cardiac arrhythmia events.

[0014] For example, cardiac arrhythmia events such as ventricular premature contractions may be detected based on timing by evaluating the timing distance of at least one ventricular contraction to a previous and subsequent ventricular contraction. Setting a timing threshold for the timing distance to a previous and / or subsequent ventricular contraction determines the sensitivity to which ventricular premature contractions are identified based on the processing of the electrocardiogram signal.

[0015] In another example, a ventricular tachycardia event may be identified based on the timing of a series of heartbeats. In this specification, a ventricular tachycardia event may be identified, for example, when the heart rate exceeds a predetermined heart rate threshold for a given number of heartbeats. In this specification, the given number of heartbeats and the predetermined heart rate threshold represent detection parameters.

[0016] In the patient's default state, i.e., a state in which no actual or potential myocardial infarction event has been identified in the patient, a setting of one or more detection parameters may be employed that enables the detection of cardiac arrhythmia events with appropriate sensitivity and a low risk of false-positive classification. Therefore, in the patient's default state, the system's processing configuration is configured to use a first setting of at least one detection parameter for detecting cardiac arrhythmia events based on the sensed electrocardiogram signal.

[0017] However, if information regarding a myocardial infarction event is obtained, that is, if the information indicates that a myocardial infarction event has already occurred or is very likely to occur in the very near future, the processing configuration is configured to adapt at least one detection parameter to a second setting different from the first setting for detecting cardiac arrhythmia events during the period following the acquisition of information regarding the myocardial infarction event. If a myocardial infarction event is identified (automatically by the system or by user input), then the settings for detecting cardiac arrhythmia events are adapted so that, during the period following the detection of the myocardial infarction event, cardiac arrhythmia events can be detected, for example, with increased sensitivity, at the cost of a potentially increased number of false-positive classifications during that period.

[0018] In the acute phase following a myocardial infarction event, patients may exhibit an increased risk of cardiac arrhythmias, particularly ventricular tachycardia, ventricular fibrillation, or ventricular premature contractions, within the period following the identification of the myocardial infarction event. It may be desirable to increase the sensitivity for detecting cardiac arrhythmias, and an increase in the number of false-positive classifications may be acceptable during the high-alert period following a myocardial infarction event.

[0019] For example, in order to detect ventricular premature contractions during the period following the identification of a myocardial infarction event, one or more timing thresholds may be set to evaluate the timing distance of at least one ventricular contraction event to previous and subsequent ventricular contractions, thereby increasing the sensitivity with which the at least one ventricular contraction event is classified as a ventricular premature contraction event.

[0020] In another example, to detect ventricular tachycardia, the settings for the heart rate or heart rate threshold may be adapted. For example, in the default state, a set of heartbeats may be classified as ventricular tachycardia if, for example, a predetermined heart rate threshold (e.g., in the range of 150 bpm to 220 bpm, e.g., 200 bpm) is exceeded for a predetermined heart rate (e.g., in the range of 150 bpm to 220 bpm, e.g., 200 bpm) or a predetermined heart rate threshold (e.g., a value of 80 bpm to 140 bpm). Following the identification of a myocardial infarction event, the settings may be adapted by, for example, decreasing the predetermined heart rate (e.g., in the range of 2 to 10 beats, e.g., 4 beats) and / or the heart rate threshold (e.g., a value of 80 bpm to 140 bpm). For example, in the default state, a series of heartbeats may be classified as ventricular tachycardia if, for example, eight beats exceed a predetermined heart rate threshold of 200 bpm. However, the settings may be adapted after the identification of a myocardial infarction event, such that a series of heartbeats is already classified as ventricular tachycardia if, for example, four beats exceed a predetermined heart rate threshold of, for example, 120 bpm. Thus, sensitivity for detecting ventricular tachycardia is increased by reducing the value of the number of heartbeats and / or the heart rate threshold.

[0021] In one embodiment, the implantable medical device comprises a processing module that forms at least a portion of the processing arrangement. In particular, in one embodiment, the processing module may be configured to perform the steps of: using a first setting of at least one detection parameter for detecting cardiac arrhythmia events based on the electrocardiogram signal; acquiring information indicating a myocardial infarction event; and, in response to acquiring the information, adapting the at least one detection parameter to a second setting different from the first setting for detecting cardiac arrhythmia events during a period after acquiring the information regarding the myocardial infarction event. In another embodiment, the processing module may be configured to perform only a portion, and not all, of the processing. For example, the processing module of the implantable medical device may be configured to identify ventricular contraction events and record waveforms associated with ventricular contraction events, while the actual processing for identifying cardiac arrhythmia events is performed by another processing entity, such as an external device communicating with the implantable medical device, for example, within the context of a home monitoring system. In yet another embodiment, the implantable medical device may be used only to record the electrocardiogram signal, while the entire processing for identifying cardiac arrhythmia events is performed outside the implantable medical device, for example, by an external device within the context of a home monitoring system.

[0022] In one embodiment, the processing configuration is configured to detect myocardial infarction events based on sensed electrocardiogram signals in order to acquire information indicating myocardial infarction events. Thus, the detection of myocardial infarction events is performed by the processing configuration, for example, the processing module of an implantable medical device. Consequently, myocardial infarction events are automatically detected by processing the sensed electrocardiogram signals, for example, by evaluating the so-called ST segment elevation in the QRS complex of the electrocardiogram signals.

[0023] In another embodiment, information related to a myocardial infarction event may be entered into the system by manual user input, for example, so that information related to the occurrence of a myocardial infarction event is manually entered by a clinic user into an external device that communicates with the system's implantable medical device.

[0024] In one embodiment, the processing configuration is configured to detect cardiac arrhythmia events with increased sensitivity during the period after information indicating a myocardial infarction event has been acquired, by fitting at least one detection parameter in response to a myocardial infarction event. For example, the setting of one or more detection parameters related to a timing threshold for detecting ventricular premature contraction events, or, for example, a filter setting for detecting ventricular fibrillation or ventricular tachycardia events, is fitted in response to the acquisition of information regarding the occurrence of a myocardial infarction event so that cardiac arrhythmia events are detected with increased sensitivity.

[0025] In one embodiment, the processing configuration is configured to slowly return at least one detection parameter to its default state (before a myocardial infarction event). In other words, at least one detection parameter is slowly returned to its default state after the end of a period of heightened sensitivity (as opposed to a sudden, abrupt change). This includes three options: 1) automatically return after a programmable period, 2) return when some signal condition is reached, such as the disappearance of ST segment elevation, and 3) return to the original / default state in accordance with some criteria (e.g., no subsequent increase in arrhythmia).

[0026] In one embodiment, the processing configuration is configured to detect cardiac arrhythmia events, including at least one of ventricular tachycardia (VT) events, ventricular fibrillation (VF) events, and asystole events, bradycardia events, and / or ventricular premature contraction (PVC) events. For example, at least one detection parameter includes at least one of a heart rate value threshold, a number of heartbeats to determine the heart rate value, a timing threshold indicating the timing between consecutive beats, or an amplitude threshold. In one embodiment, at least one detection parameter may include at least one of a filter setting, an autosensing parameter setting, a timer setting, or a refractory period setting.

[0027] In one embodiment, the processing arrangement is configured to adapt at least one detection parameter back to a first setting in order to detect an arrhythmia event upon the passage of a period. During a period after a myocardial infarction event, a second setting for at least one detection parameter is used. When the period has elapsed, the system automatically returns to the default state, and when the period has elapsed, the first setting for at least one detection parameter is used to identify an arrhythmia event. Thus, when the period has elapsed, the previous default setting for one or more detection parameters is automatically restored, whereby an arrhythmia event is detected with a reduced risk of false positive classification (and a slightly reduced sensitivity).

[0028] The period can be, for example, in the range of 10 minutes to 30 days, preferably 1 hour to 30 days, particularly preferably 1 hour to 24 hours. This period particularly encompasses the acute phase after a myocardial infarction event and is obtained within the time range.

[0029] In one embodiment, the processing arrangement is configured to identify at least one ventricular contraction event (or a series of ventricular contraction events) based on an electrocardiogram signal and classify a ventricular contraction event (or at least a part of a series of ventricular contraction events) as an arrhythmia event (or a series including at least one arrhythmia event) based on at least one detection parameter. Thus, based on the sensed electrocardiogram signal, in particular ventricular contraction events represented by QRS waveforms in the electrocardiogram signal are identified and evaluated to classify a particular ventricular contraction event or a series of ventricular contraction events as an arrhythmia event such as ventricular tachycardia, ventricular fibrillation, or ventricular premature contraction events.

[0030] In one embodiment, the processing arrangement is configured to classify at least one ventricular contraction event as a premature ventricular contraction event based on a first timing distance between a ventricular contraction event and the immediately preceding ventricular contraction event and / or a second timing distance between a ventricular contraction event and the immediately following ventricular contraction event. Generally, for a premature ventricular contraction event, it is characteristic that the contraction event occurs at a relatively short timing distance after a previous ventricular contraction event and a long pause continues before another regular ventricular contraction event occurs. Thus, it may be possible to evaluate the timing of the currently evaluated ventricular contraction event in order to define additional necessary conditions that must be met to classify the currently evaluated ventricular contraction event as a premature ventricular contraction event. For example, if the first timing distance between a ventricular contraction event and the immediately preceding ventricular contraction event is less than a first timing threshold and / or the second timing distance between a ventricular contraction event and the immediately following ventricular contraction event is greater than a second timing threshold, and further, if the evaluation of at least one discrimination metric value calculated based on the currently evaluated ventricular contraction event results in an abnormality, the currently evaluated ventricular contraction event may be classified as a premature ventricular contraction event.

[0031] In one embodiment, the first timing threshold represents a first detection parameter and / or the second timing threshold represents a second detection parameter. For at least one of the detection parameters in the default state, a first setting of the detection parameter, for example, a first setting of the first timing threshold, is used. When a myocardial infarction event occurs, the processing arrangement is configured to adapt a specific detection parameter such that a second setting of the specific detection parameter is used during a period after the myocardial infarction event. Thus, the setting of the first timing threshold and / or the second timing threshold may be adapted after detection of a myocardial infarction event.

[0032] In one embodiment, in addition to classifying at least one ventricular contraction event as a ventricular premature contraction event based on timing distance, the processing configuration may be configured to identify ventricular premature contractions based on the waveform morphology associated with the ventricular contraction event. In particular, in one embodiment, the processing configuration may be configured to calculate at least one discrimination metric value for a ventricular contraction event, compare the at least one discrimination metric value with at least one of a first criterion value calculated based on a first number of previous ventricular contraction events and a second criterion value calculated based on a second number of subsequent ventricular contraction events, and classify the ventricular contraction event as a ventricular premature contraction event based on the comparison.

[0033] To identify ventricular premature contractions (VTTs), which represent potentially dangerous cardiac arrhythmia events, it is possible to utilize the fact that, in particular, the waveform associated with VTTs can be assumed to contain an abnormal shape compared to other regular ventricular contractions. Therefore, within the system, VTTs can be identified by evaluating the waveform morphology associated with a particular ventricular contraction. If an abnormality is found in a particular ventricular contraction that indicates a VTT, that particular ventricular contraction can be classified as a VTT.

[0034] Within the system, one or more discrimination metric values ​​can be calculated. These discrimination metric values ​​relate to the waveform morphology of the ventricular contraction event currently being evaluated. One or more discrimination metric values ​​are compared to a baseline value, and based on this comparison, it is identified (or not identified) whether the discrimination metric value exhibits an abnormal waveform that may indicate a ventricular premature contraction event.

[0035] In this specification, one or more discrimination metric values ​​are compared to one or more reference values ​​associated with a previous ventricular contraction event, which can generally be assumed to be a regular ventricular contraction event of a regular heartbeat, and / or a subsequent ventricular contraction event, which can also be assumed to be associated with a regular heartbeat. Thus, the reference values ​​are determined based on the previous ventricular contraction event and / or the subsequent ventricular contraction event.

[0036] Each reference value should represent the value of the discrimination metric that indicates a normal state, and therefore a normal ventricular contraction event with a regular heartbeat. By comparing the discrimination metric values ​​calculated for instantaneous ventricular contractions, if it is found that the discrimination metric value differs from the reference value by, for example, a certain margin, then an abnormal waveform exhibiting an abnormal form may be identified, and as a result, the ventricular contraction event may be classified as a ventricular premature contraction event.

[0037] Based on this, the first number of ventricular systolic events prior to the determination of the first reference value can be within the range of, for example, 2 to 50, 3 to 20, or 6 previous ventricular systolic events. The previous ventricular systolic events may be consecutive ventricular systolic events immediately preceding the ventricular systolic event evaluated instantaneously, or they may be discontinuous.

[0038] The second number of subsequent ventricular systolic events, for which a second reference value is determined based on this, can be within the range of, for example, 2 to 50, 3 to 20, or 6 subsequent ventricular systolic events. The subsequent ventricular systolic events may be consecutive ventricular systolic events immediately following the ventricular systolic event evaluated instantaneously, or they may be discontinuous.

[0039] The first number may be equal to the second number, or it may be different from the second number.

[0040] The classification of ventricular premature contraction events is generally performed when a second reference value, particularly one related to subsequent ventricular contractions, is considered, and involves a time delay that covers the period during which subsequent ventricular contractions are recorded.

[0041] In one embodiment, the processing configuration is configured to calculate at least one discrimination metric value with respect to a signal portion associated with a ventricular contraction event, based on at least one of the following: maximum positive amplitude, maximum negative amplitude, maximum rectified amplitude, peak-to-peak amplitude, maximum first derivative, maximum second derivative, area under the curve of the signal portion up to a first zero crossing, area under the curve of the signal portion between a first and a second zero crossing, area under the curve of the signal portion between a second and a third zero crossing, duration value up to a first zero crossing, duration value between a first and a second zero crossing, duration value between a second and a third zero crossing, and / or duration value between an upward crossing and a downward crossing of the ventricular detection threshold.

[0042] Therefore, one or more quantities may be calculated as one or more discrimination metric values. The discrimination metric values ​​may be calculated, for example, according to the maximum positive amplitude, maximum negative amplitude, maximum rectified amplitude, or peak-to-peak amplitude of the waveform associated with the ventricular contractile event currently being evaluated. Alternatively or additionally, the discrimination metric values ​​may be calculated according to the maximum value of the first or second derivative of the waveform associated with the ventricular contractile event currently being evaluated. Alternatively or additionally, the discrimination metric values ​​may be calculated according to an area value representing the area under the curve associated with the ventricular contractile event currently being evaluated, and the area value may be related to the area up to the first zero crossing, the area between the first zero crossing and the second zero crossing, or the area between the second zero crossing and the third zero crossing. Alternatively or additionally, the discrimination metric value may be calculated to indicate, for example, the duration between the initial detection of a ventricular contractile event and the first zero crossing, between the first zero crossing and the second zero crossing, or between the second zero crossing and the third zero crossing, or, based on that, the duration between the upward crossing of the ventricular detection threshold and the downward crossing of the ventricular detection threshold at which the ventricular detection event is first identified.

[0043] Generally, one or more discrimination metric values ​​can be calculated, and any combination of these discrimination metric values ​​can be used to identify ventricular premature contraction events. Each discrimination metric value in this specification is compared to at least one of a relevant first reference value and a relevant second reference value, where a particular reference value represents the normal value for that particular discrimination metric value.

[0044] Each reference value may be calculated by applying a statistical analysis of previous and / or subsequent ventricular systolic events. In particular, the first reference value may be calculated based on a first statistical scale related to the first number of previous ventricular systolic events. Then, the second reference value may be calculated based on a second statistical scale related to the second number of subsequent ventricular systolic events. Thus, the first reference value is determined by a statistical analysis of previous ventricular systolic events. In contrast, the second reference value is determined by a statistical analysis of subsequent ventricular systolic events.

[0045] In particular, specific reference values ​​may be calculated according to any standard statistic obtained by statistical analysis. For example, the first and / or second reference values ​​may be calculated according to the mean, standard deviation, coefficient of variation, Shannon entropy value, exponential moving mean value following a function with fluctuating beats / fluctuating weights related to the surrounding beats, median, percentile values ​​such as the 5th to 95th percentile, skew value, kurtosis value, and / or, for example, the root mean square of consecutive differences. For example, if the discrimination metric value is calculated according to the maximum amplitude of the waveform related to the current ventricular contraction event, the reference value is determined, for example, by the averaging of the maximum amplitude values ​​of previous and / or subsequent ventricular contraction events or by another statistical measure. If the discrimination metric value is an area value or duration value related to the waveform of the current ventricular contraction event, the reference value is determined by a statistical measure related to the area value or duration value related to previous and / or subsequent ventricular contraction events.

[0046] Certain reference values ​​may be calculated using the first setting, for example, according to the default statistical scale, under default conditions. In response to the occurrence of a myocardial infarction event, certain reference values ​​may be calculated according to a different setting, for example, according to a different statistical scale or a fitted statistical scale. Thus, after the detection of a myocardial infarction event, different settings may be used to calculate any of the reference values, each of which represents a detection parameter used to identify a ventricular premature contraction event.

[0047] In one embodiment, the processing configuration is configured to classify a currently evaluated ventricular systolic event as a ventricular premature contraction event if at least one discrimination metric value deviates beyond a first margin from a first criterion value and / or beyond a second margin from a second criterion value. To classify a currently evaluated ventricular systolic event as a ventricular premature contraction event, the processing configuration compares one or more calculated discrimination metric values ​​to one or more criterion values ​​associated with previous and / or subsequent ventricular systolic events. If one or more discrimination metric values ​​are found to differ from the associated criterion values, this is interpreted as indicating that the waveform of the currently evaluated ventricular systolic event is abnormal in that it differs from the waveform of a regular ventricular systolic event, and therefore the ventricular systolic event may be classified as a ventricular premature contraction event (potentially further conditions may be considered).

[0048] For example, the processing configuration is configured to determine a first margin based on a percentage value of a first reference value and / or a second margin based on a percentage value of a second reference value. The first and second reference values ​​are determined dynamically based on the number of previous ventricular contraction events and / or the number of subsequent ventricular contraction events. The first and / or second margins are set based on the current values ​​of the first and / or second reference values. The percentage values ​​herein may be fixed within a range, for example, 1% to 50%.

[0049] In one embodiment, the first margin represents a third detection parameter, and / or the second margin represents a fourth detection parameter. Thus, the first margin and / or the second margin represent (respectively) detection parameters that are adapted in response to the occurrence of a myocardial infarction event. For example, in the default state, the first value may be used for the first margin and the second margin, respectively, for example, specific respective percentage values. In response to the occurrence of a myocardial infarction event, each margin is adapted so that the second value for the detection parameter is used for a second percentage value different from the first value, for example.

[0050] In one embodiment, the system includes an external device configured to operate outside the patient. The implanted medical device is configured to communicate with the external device outside the patient, and is configured to transmit to the external device information relating to identified ventricular systolic events, myocardial infarction events, and / or identified cardiac arrhythmia events. Depending on the amount of processing performed by the implanted medical device, the information transmitted to the external device may vary. If the implanted medical device performs the entire processing for identifying cardiac arrhythmia events, it may transmit to the external device information relating to the identified cardiac arrhythmia events. If the implanted medical device performs only a portion of the processing, it may transmit to the external device information relating to the intermediate processing results. If the entire processing for identifying cardiac arrhythmia events is performed by a processing device outside the implanted medical device, the implanted medical device may transmit to the external device only information relating to, for example, recorded electrocardiogram signals, within the context of a home monitoring system.

[0051] In one embodiment, an implantable medical device may include multiple poles aligned, for example, along the longitudinal axis and thus positioned at different axial locations of the implantable medical device. The different poles establish electrical coupling to the surrounding tissue when the implantable medical device is implanted in the patient, and the different poles may be used to sense electrocardiogram signals.

[0052] In another embodiment, a method for operating a system for identifying cardiac arrhythmia events in a patient includes sensing an electrocardiogram signal using the arrangement of poles of an implantable medical device, and processing the electrocardiogram signal acquired by the implantable medical device, the processing of which includes using a first value of at least one detection parameter for detecting cardiac arrhythmia events based on the electrocardiogram signal, acquiring information indicating a myocardial infarction event, and in response to acquiring the information, fitting the at least one detection parameter to a second value different from the first value for detecting a cardiac arrhythmia event during a period after acquiring the information indicating a myocardial infarction event.

[0053] The advantages and favorable embodiments of the system described above also apply equally to the method, as mentioned above in this regard.

[0054] In general, an implantable medical device may include a processing circuit that can be configured to perform at least some of the processing steps of the method. However, this is not required. In one embodiment, the implantable medical device is configured to sense an electrocardiogram signal but is not configured to process the electrocardiogram signal by performing specific processing steps to identify a cardiac arrhythmia event. In one embodiment, some or all of the processing steps for identifying a cardiac arrhythmia event are performed by the processing circuit of the implantable medical device.

[0055] The various features and advantages of the present invention can be more readily understood by referring to the embodiments shown in the following detailed description and drawings. [Brief explanation of the drawing]

[0056] [Figure 1] This shows a schematic diagram of an implanted medical device embedded in a patient. [Figure 2] A schematic diagram of one embodiment of an implantable medical device, including the arrangement of pole columns, is shown. [Figure 3] A schematic diagram of another embodiment of the implantable medical device is shown. [Figure 4] This shows a ventricular contraction event that indicates a myocardial infarction event. [Figure 5] This diagram shows a schematic timeframe for identifying cardiac arrhythmia events following a myocardial infarction event. [Figure 6] This shows waveforms associated with ventricular premature contractions. [Figure 7] This shows a series of ventricular contractions. [Figure 8] This shows a ventricular premature contraction event within a series of ventricular contraction events.

[0057] Next, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, similar reference numerals indicate similar structural elements.

[0058] It should be noted that the embodiments are not intended to limit the present invention, but merely to represent illustrative examples.

[0059] Referring to Figure 1, in one embodiment, the system comprises an implantable medical device 1 implanted in a patient (e.g., subcutaneously) to perform therapeutic and / or diagnostic functions. The implantable medical device 1 may, for example, be implanted subcutaneously in patient P to monitor the activity of the patient's heart H. For this purpose, the implantable medical device 1 comprises an arrangement of poles that are bound to the surrounding tissue and used to sense electrocardiogram signals originating from the heart H.

[0060] The system is located outside of patient P and further includes an external device 2 that communicates with the implantable medical device 1.

[0061] Referring to Figure 2, in one embodiment, the implantable medical device 1 comprises a housing 10 formed by, for example, different housing segments, the housing 10 enclosing and enclosing a processing module 16 formed by an electronic circuit and a battery module 17. Specifically, the first housing segment receives and encloses the processing module 16, while the second housing segment receives and encloses the battery module 17. Another housing segment extends longitudinally from the first and second housing segments and forms a header portion 11 with a smaller cross-sectional dimension than the other housing segments.

[0062] In the embodiment shown in Figure 2, the first pole column 12 is formed by a housing segment surrounding the battery module 17, the second pole column 13 is located at the far end of the housing segment forming the header portion 11, and the (optional) third pole column 14 is formed by a housing segment surrounding the processing module 16. The implantable medical device 1 having the housing 10 generally extends along a longitudinal axis L, and the pole columns 12, 13, and 14 are aligned along the longitudinal axis L and displaced axially from each other along the longitudinal axis L. The pole columns 12, 13, and 14 in this specification are electrically isolated from each other, and an electrical isolation segment 15 is located between the pole columns 12 and 14 formed in the main housing portion and the header portion 11 formed by a housing segment separating pole column 13 from the other two pole columns 12 and 14.

[0063] In the embodiment shown in Figure 2, the pole posts 12, 13, and 14 may be formed from a portion of the housing 10 itself, which is made of, for example, a conductive material, particularly a metallic material. By exposing a portion of the housing 10 to the outside, the pole posts 12, 13, and 14 are formed and may be in electrical contact with the surrounding tissue to establish a bond between the pole posts 12, 13, and 14 and the surrounding tissue.

[0064] Referring now to Figure 3, in another embodiment, the first pole post 12 is formed at the end of the housing segment of the housing 10 enclosing the battery module 17, while the (optional) pole post 14 is formed by an electrode element electrically insulated from the rest of the housing 10 by an electrically insulating segment 15. For example, multilayer electrode elements may be used to form the pole post 14, as described in European Patent No. 3278836. The pole post 13 is again formed at the far end of the housing segment forming the header portion 11.

[0065] In both embodiments of Figures 2 and 3, the arrangement of poles 12, 13, and 14 allows the electrocardiogram signal to be received and processed by the processing module 16. Based on this processing, communication with an external device 2 may be established, for example, to send a warning message to the external device 2, within the context of a home monitoring system for monitoring the physiological state of patient P.

[0066] The different pole posts 12, 13, and 14 described herein define signal reception vectors A, B, and C that can receive electrocardiogram signals using the associated pairs of pole posts 12, 13, and 14. In particular, a first signal reception vector A is formed between the first pole post 12 and the second pole post 13, a second signal reception vector B is formed between the third pole post 14 and the second pole post 13, and a third signal reception vector C is formed between the first pole post 12 and the third pole post 14. Since the first pole post 12 and the second pole post 13 are located at opposite ends of the housing 10, the associated signal reception vector A is longer than the other two signal reception vectors B and C.

[0067] Different poles 12, 13, and 14 form different pairs of poles 12, 13, and 14 that span different signal reception vectors A, B, and C. Different electrocardiogram signals may be received by the different signal reception vectors A, B, and C, and may be processed in multi-channel processing.

[0068] It should be noted that in this specification, the implantable medical device 1 may be a monitoring device (as schematically shown in Figures 2 and 3), a pacemaker, a defibrillator, or any other implantable medical device configured for implantation in a patient P. This text is not limited in particular to monitoring devices configured for implantation outside the patient's heart H.

[0069] A system comprising an implantable medical device 1 and an external device 2 as described herein is generally configured to identify cardiac arrhythmia events such as ventricular tachycardia, ventricular fibrillation, and / or ventricular premature contractions.

[0070] In this specification, one or more detection parameters are employed according to a first default setting to identify cardiac arrhythmia events. In the case of myocardial infarction events, one or more settings of the detection parameters are adapted so that different settings are employed to detect cardiac arrhythmia events when myocardial infarction events occur.

[0071] In particular, during the acute phase following a myocardial infarction event, it can be assumed that patients face an increased risk of cardiac arrhythmias, which are potentially dangerous for post-myocardial infarction patients. Therefore, during the period following a myocardial infarction event, it is necessary to ensure that cardiac arrhythmia events are reliably detected, even at the cost of potentially increasing the number of false-positive classifications.

[0072] Referring here to Figure 4, in one embodiment, the system is configured to automatically detect myocardial infarction events (MI) based on the sensed electrocardiogram signal. In particular, the system's processing configuration, especially the processing module 16 of the implantable medical device 1 which potentially cooperates with the processing circuit of an external device 2, may be configured to process the sensed electrocardiogram signal to identify QRS waveforms associated with ventricular systolic events. According to such QRS waveforms, myocardial infarction events (MI) can be identified based on so-called ST segment elevations, which correspond to increased segment elevations above baseline in the so-called ST segment following the QRS complex and subsequent T waves. Based on the increased ST segment elevation, myocardial infarction events (MI) can be identified, and information related to myocardial infarction events (MI) can be output to the external device 2, which can then adapt the settings for further processing of the sensed electrocardiogram signal after the detection of myocardial infarction events (MI).

[0073] Alternatively or additionally, information related to a myocardial infarction event may be input into the system, for example, an external device 2, and the information may then be transmitted to, for example, an implantable medical device 1. In particular, a myocardial infarction event may be identified by a clinician using a diagnostic tool outside the system, and information related to the identified myocardial infarction event may be input into the system by the clinician.

[0074] In the default state where there is no myocardial infarction event (MI), the system (in particular, the processing module 16 of the implantable medical device 1) may adopt default settings for detecting cardiac arrhythmia events. However, such settings may be adapted after the identification of a myocardial infarction event (MI) so that different settings are adopted to detect cardiac arrhythmia events after the identification of a myocardial infarction event (MI).

[0075] Referring to Figure 5, at time t1, a myocardial infarction event (MI) is identified automatically by the system, particularly the implantable medical device 1, or by manual user input. Following the identification of the myocardial infarction event (MI) at time t1, the system is configured to adapt settings for detecting cardiac arrhythmia events (AE) within a (highly sensitive) period SP between time t1 and time t2 after the identification of the myocardial infarction event (MI), and as a result, different settings are employed to detect cardiac arrhythmias within period SP.

[0076] Following the SP period, the system can automatically revert to its original default settings, and as a result, the default settings for detection parameters for detecting cardiac arrhythmia events are re-adopted during the SP period.

[0077] The system, in particular the implantable medical device 1 having its processing module 16, may be configured to detect cardiac arrhythmia events such as ventricular tachycardia, ventricular fibrillation, and / or ventricular premature contractions.

[0078] For example, ventricular tachycardia may be detected by evaluating electrocardiogram signals, and is identified when a predetermined number of heartbeats in a given sequence exceeds a predetermined threshold.

[0079] In the default settings, a given heart rate can be in the range of, for example, 6 to 20 beats, or 8 beats. The heart rate threshold can be, for example, 200 bpm. That is, if the heart rate threshold is exceeded for a series of beats with a given heart rate—for example, if a heart rate exceeding 200 bpm is detected for 8 beats—a ventricular tachycardia event is concluded.

[0080] If a myocardial infarction event (MI) is detected, such settings may be adapted to detect ventricular tachycardia within the interval SP. For example, a setting for a given number of heartbeats may be adapted. Alternatively or additionally, a setting for a heart rate threshold may be adapted. For example, the setting for a given number of heartbeats may be adapted to a lower number, e.g., 2 to 10 heartbeats, e.g., 4 heartbeats. The heart rate threshold may be adapted to a lower heart rate value in the range of, for example, 80 bpm to 140 bpm, e.g., 90 bpm, 100 bpm, 110 bpm, or 120 bpm. Thus, after the detection of a myocardial infarction event (MI), ventricular tachycardia is identified with increased sensitivity. For example, if a given number of heartbeats is set to 4 and the heart rate threshold is set to 120 bpm, ventricular tachycardia will be detected after the myocardial infarction event (MI) if a heart rate exceeding 120 bpm has already been detected for 4 heartbeats.

[0081] In another example, ventricular premature contraction events may be detected based on the processing of electrocardiogram signals, for example, based on the processing of timing and / or morphological parameters of ventricular contraction events, and the setting of detection parameters may be adapted after the identification of myocardial infarction events (MI).

[0082] Generally, ventricular premature contractions (VCTs) are characterized by occurring shortly after a previous VCT, followed by a relatively long pause before another subsequent VCT. Furthermore, VCTs generally exhibit a waveform that is substantially different in form from that of regular VCTs.

[0083] Referring here to Figure 6, ventricular premature contractions (PVCs) include forms distinct from regular ventricular contractions of the regular sine rhythm of the patient's heart H. The forms described herein may be characterized by specific discrimination metrics such as the maximum positive amplitude X1, maximum negative amplitude X2, maximum peak-to-peak amplitude X3, maximum gradient value X4, maximum value of the second derivative X5, area under the positive R peak before the first zero crossing X6 X6, area under the curve between the first and second zero crossings X7, area under the curve between the second and third zero crossings X8, duration between the upward and downward crossings of the ventricular detection threshold TH X9, duration between the upward crossing of the ventricular detection threshold TH and the first zero crossing X10, duration between the upward crossing of the ventricular detection threshold TH and the second zero crossing X11, and / or duration between the upward crossing of the ventricular detection threshold TH and the third zero crossing X12.

[0084] For the specific ventricular contraction waveform, values ​​for all or part of the discrimination metrics may be calculated and evaluated to identify whether there is an abnormal pattern that potentially indicates a ventricular premature contraction event.

[0085] To classify at least one ventricular contraction event as a ventricular premature contraction event, at least one discrimination metric value X1...X12 is calculated. Then, at least one discrimination metric value is compared to at least one reference value, and based on the comparison, the ventricular contraction event is classified as a ventricular premature contraction waveform (or not a ventricular premature contraction waveform).

[0086] Referring here to Figure 7, the reference value may be determined in particular according to the number n of previous ventricular systolic events E(in)...E(i-1) and / or the number m of subsequent ventricular systolic events E(i+1)...E(i+m).

[0087] In particular, for specific discrimination metric values ​​such as the maximum positive amplitude X1 before the first zero crossing or the area under the positive R peak X6, the associated first reference value may be calculated based on the associated discrimination metric for the number n of previous ventricular systolic events E(in)...E(i-1). Alternatively or additionally, the second reference value may be calculated based on the associated discrimination metric for the number m of subsequent ventricular systolic events E(i+1)...E(i+m).

[0088] Specific reference values ​​may be calculated according to a statistical scale, in particular, by applying statistical analysis. For example, specific reference values ​​may correspond to the mean, standard deviation, coefficient of variation, Shannon entropy value, exponential moving mean, median, percentile, skew value, kurtosis value, or root mean square value associated with a specific discrimination metric X1...X12.

[0089] For example, if the maximum positive amplitude X1 is evaluated as the discrimination metric, the first criterion value may be determined by averaging the maximum positive amplitude values ​​of n previous ventricular contraction events E(in)...E(i-1), and the second criterion value may be determined by averaging the maximum positive amplitude values ​​of m subsequent ventricular contraction events E(i+1)...E(i+m).

[0090] In this specification, settings may be adapted for calculating specific reference values ​​following the identification of a myocardial infarction event (MI). In particular, a first setting may be adopted as the default for calculating specific reference values. Following the identification of a myocardial infarction event (MI), settings may be adapted so that specific reference values ​​are calculated according to different statistical scales or by using adapted processes for calculating statistical scales.

[0091] Using reference values, a particular ventricular systolic event may be classified as a ventricular premature contraction if, for example, a specific discrimination metric value calculated for the ventricular systolic event differs from its respective reference value by a certain margin. For example, if both a first reference value associated with a previous ventricular systolic event E(in)...E(i-1) and a second reference value associated with a subsequent ventricular systolic event E(i+1)...E(i+m) are considered, the ventricular systolic event may be classified as a ventricular premature contraction if the discrimination metric value differs from the first reference value by a first margin and from the second reference value by a second margin.

[0092] When multiple discrimination metric values ​​are calculated that relate to different discrimination metrics, multiple different first reference values ​​and / or multiple different second reference values ​​may be considered, where different reference values ​​relate to different discrimination metrics. In this specification, a ventricular systolic event may be classified as a ventricular premature contraction event if, for at least a subset of discrimination metric values, a set of relevant conditions is met. For example, a ventricular premature contraction event may be determined if, for two of three discrimination metric values, a particular discrimination metric value is found to differ from the associated reference value by a certain margin.

[0093] The margin may, in each case, be calculated, for example, based on a percentage of a specific baseline value, and the percentage may be fixed or dynamically adjusted during the operation of the system.

[0094] Each margin represents a detection parameter for detecting ventricular premature contractions. Settings for specific margins may be adapted after the identification of a myocardial infarction event (MI), and as a result, different settings for each margin, such as different percentage values, may be used after the identification of a myocardial infarction event (MI) compared to the default state.

[0095] In the example in Figure 7, for ventricular systolic event E(i), there was a substantial deviation in morphology compared to previous ventricular events E(in)...E(i-1) and / or subsequent ventricular events E(i+1)...E(i+m), for example, based on one or more discrimination metric values ​​for one or more different discrimination metrics, and as a result, ventricular systolic event E(i) was found to be classified as a ventricular premature contraction (PVC).

[0096] Generally, ventricular premature contractions (PVCs) differ substantially not only in the morphology of the associated waveform but also in their timing relative to regular contractions. Therefore, in addition to evaluating the morphology of the contraction, or instead, it may be evaluated whether the timing distance T1 of the ventricular contraction event E(i) is smaller than a first timing threshold, thus indicating that the ventricular contraction event E(i) occurs prematurely compared to the previous ventricular contraction event E(i-1), as shown in Figure 8. Furthermore, it may be evaluated whether the timing distance T2 of the ventricular contraction event E(i) is larger than a second timing threshold, thus indicating that a substantial pause longer than the length of a regular heartbeat occurs after the ventricular contraction event E(i), as seen in Figure 8.

[0097] The timing threshold represents a detection parameter. In this specification, after the identification of a myocardial infarction event (MI), different settings for a particular timing threshold may be adopted compared to the default state, thereby adapting the setting for the particular timing threshold after the identification of a myocardial infarction event (MI). [Explanation of Symbols]

[0098] 1. Implantable medical devices 10 Housing 11 Header section 12. The First Pillar 13. The Second Pillar 14. The Third Pillar 15 Electrical insulation segment 16 Processing Modules 17 Battery Modules 2 External device A, B, C signal reception vectors E(in)...E(i+m) Ventricular contraction event H Heart i. Current ventricular contraction event (pulse) L Longitudinal axis n Previous ventricular contraction events (pulses) m Subsequent ventricular contraction event (pulse) MI (Minor Infarction) P patient PVC (Premature Ventricular Contraction) QRS QRS group QQ wave RR wave SP (Sensitivity Increase) Period ST ST segment TT wave T1 Timing Distance T2 Timing Distance TH ventricular detection threshold X1…X12 Discrimination Metric Value

Claims

1. A system for identifying cardiac arrhythmia events (AEs) in a patient (P), An implantable medical device (1) for sensing electrocardiogram signals, comprising an arrangement of poles (12, 13) configured to sense electrocardiogram signals, The system includes a processing arrangement for processing electrocardiogram signals acquired by the implantable medical device (1), The aforementioned processing arrangement is Using a first setting of at least one detection parameter for detecting cardiac arrhythmia events (AEs) based on the electrocardiogram signal, We obtain information indicating a myocardial infarction event (MI). A system configured to, in response to the acquisition of the aforementioned information, adapt the at least one detection parameter to a second setting different from the first setting in order to detect a cardiac arrhythmia event (AE) during the period (SP) following the acquisition of the information indicating a myocardial infarction event (MI).

2. The system according to claim 1, wherein the implantable medical device (1) comprises a processing module (16) that forms at least a part of the processing arrangement.

3. The system according to claim 1 or 2, wherein the processing arrangement is configured to detect a myocardial infarction event (MI) based on the electrocardiogram signal in order to acquire the information indicating a myocardial infarction event (MI).

4. The system according to any one of claims 1 to 3, wherein the processing configuration is configured to adapt the at least one detection parameter in response to the myocardial infarction event (MI) to detect cardiac arrhythmia events (AE) with increased sensitivity during the period (SP) after acquiring the information indicating the myocardial infarction event (MI).

5. The system according to any one of claims 1 to 4, wherein the processing configuration is configured to detect at least one of the following as cardiac arrhythmia events (AEs): ventricular tachycardia, ventricular fibrillation, bradycardia, asystole, or ventricular premature contraction (PVC).

6. The system according to any one of claims 1 to 5, wherein the at least one detection parameter includes at least one of a heart rate value threshold, a number of heartbeats for determining the heart rate value, a timing threshold indicating the timing between consecutive heartbeats, or an amplitude threshold.

7. The system according to any one of claims 1 to 6, wherein the processing arrangement is configured to, at the end of the period (SP), return and adapt the at least one detection parameter to the first setting for detecting cardiac arrhythmia events (AEs).

8. The system according to any one of claims 1 to 7, wherein the aforementioned period (SP) is in the range of 1 hour to 30 days.

9. The system according to any one of claims 1 to 8, wherein the processing arrangement is configured to identify at least one ventricular contraction event (E(i)) based on the electrocardiogram signal and to classify the ventricular contraction event (E(i)) as an arrhythmia event (AE) based on at least one detection parameter.

10. The system according to any one of claims 1 to 9, wherein the processing arrangement is configured to classify at least one ventricular systolic event (E(i)) as a ventricular premature contraction (PVC) based on a first timing distance (T1) between the ventricular systolic event (E(i)) and the immediately preceding ventricular systolic event (E(i-1)) and / or a second timing distance (T2) between the ventricular systolic event (E(i)) and the immediately following ventricular systolic event (E(i+1)).

11. The system according to claim 10, wherein the processing configuration is configured to evaluate, for the purpose of classification, whether the first timing distance (T1) between the ventricular contraction event (E(i)) and the immediately preceding ventricular contraction event (E(i-1)) is less than a first timing threshold representing a first detection parameter, and / or whether the second timing distance (T2) between the ventricular contraction event (E(i)) and the immediately following ventricular contraction event (E(i+1)) is greater than a second timing threshold representing a second detection parameter.

12. The system according to any one of claims 1 to 11, wherein the processing configuration is configured to calculate at least one discrimination metric value (X1...X12) for at least one ventricular contractile event (E(i)), compare the at least one discrimination metric value (X1...X12) with at least one of a first reference value calculated based on a first number (n) of previous ventricular contractile events (E(i-n)...E(i-1)) and a second reference value calculated based on a second number (n) of subsequent ventricular contractile events (E(i-1)...E(i+m)), and classify the ventricular contractile event (E(i)) as a ventricular premature contraction (PVC) based on the comparison.

13. The system according to claim 12, wherein the processing configuration is configured to calculate the first reference value based on a first statistical scale relating to the first number (n) of previous ventricular contractile events (E(i-n)...E(i-1)), and / or calculate the second reference value based on a second statistical scale relating to the second number (n) of subsequent ventricular contractile events (E(i-1)...E(i+m)).

14. The system according to claim 12 or 13, wherein the processing configuration is configured to classify the ventricular contractile event (E(i)) as a ventricular premature contraction event (PVC) if the at least one discrimination metric value (X1...X12) deviates by a first margin from a first reference value and / or by a second margin from a second reference value, the first margin representing a third detection parameter and / or the second margin representing a fourth detection parameter.

15. A method for operating a system for identifying cardiac arrhythmia events (AEs) in a patient (P), wherein the method is The arrangement of poles (12, 13) of the implantable medical device (1) is used to detect the electrocardiogram signal, This includes processing the electrocardiogram signal acquired by the implantable medical device (1), The above process is performed Using a first setting of at least one detection parameter for detecting cardiac arrhythmia events (AEs) based on the electrocardiogram signal, To obtain information indicating a myocardial infarction event (MI), A method comprising, in response to obtaining the aforementioned information, adapting the at least one detection parameter to a second setting different from the first setting for detecting cardiac arrhythmia events (AE) during the period (SP) following the acquisition of the information indicating a myocardial infarction event (MI).

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