Source: https://patents.google.com/patent/US20040030256
Timestamp: 2018-03-17 22:54:03
Document Index: 595627916

Matched Legal Cases: ['art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104', 'art 104']

US20040030256A1 US10213364 US21336402A US20040030256A1 US 20040030256 A1 US20040030256 A1 US 20040030256A1 US 10213364 US10213364 US 10213364 US 21336402 A US21336402 A US 21336402A US 20040030256 A1 US20040030256 A1 US 20040030256A1
US10213364
US7215993B2 (en )
In a fourth example, this document discusses a method. The method includes detecting an intrinsic cardiac signal, detecting a depolarization on the intrinsic cardiac signal by comparing a level of the intrinsic cardiac signal to a level threshold value to yield a level-detected depolarization, sampling the intrinsic cardiac signal to produce a sampled cardiac signal, detecting a peak sample from the sampled cardiac signal, wherein the peak sample is associated with the level-detected depolarization, detecting a preceding sample to the peak sample from the sampled cardiac signal, detecting a subsequent sample to the peak sample from the sampled cardiac signal, and validating, using the peak sample, the preceding sample, and the subsequent sample, the leveldetected depolarization by computing a weighted average using the peak sample, the preceding sample, and the subsequent sample, and comparing the weighted average to a noise threshold. In one variation, the computing the weighted average is computed as NWA=[P(n−1)+2*P(n)+P(n+1)]/[4*P(n)].
[0018]FIG. 1 is a schematic diagram illustrating generally, by way of example, but not by way of limitation, portions of a cardiac rhythm management system.
[0019]FIG. 2 is a graph illustrating generally a relatively noise-free cardiac signal.
[0020]FIG. 3A is a graph illustrating generally a relatively noisy cardiac signal.
[0021]FIG. 3B is a graph illustrating in more detail a portion of a relatively noisy sampled cardiac signal.
[0022]FIG. 4 is a flow chart illustrating generally, by way of example, but not by way of limitation, using a weighted average to validate or invalidate a depolarization detected by level-detecting or other techniques.
[0023]FIG. 5 is a flow chart illustrating generally, by way of example, but not by way of limitation, using a weighted average to detect a depolarization.
[0024]FIG. 6 is a graph illustrating generally, by way of example, but not by way of limitation, experimental data in which detected depolarizations were validated using the technique described in the flow chart of FIG. 4.
[0025]FIG. 7 is a graph illustrating generally, by way of example, but not by way of limitation, experimental data in which detected depolarizations (during the onset of ventricular fibrillation) were validated using the technique described in the flow chart of FIG. 4.
[0029]FIG. 1 is a block diagram illustrating generally portions of a cardiac rhythm management system 100 and portions of an environment in which it is used. In this example, system 100 includes a cardiac rhythm management device 102 coupled to a heart 104 by one or more electrodes associated with heart 104, such as for sensing intrinsic cardiac signals and/or for delivering energy or other therapy to heart 104. System 100 also includes a programmer or other remote interface 106, which is wirelessly or otherwise communicatively coupled to a telemetry circuit 108 or other communication circuit in device 102. Device 102 includes a pacer, a defibrillator, a cardiac resynchronization therapy (CRT) device, a monitor, a device that combines more than one of these functions, or any other implantable or external device for diagnosing and/or treating the heart. In one example, device 102 is sized and shaped for being pectorally or abdominally implanted in a human patient. The electrode(s) coupling device 102 to heart 104 may include an intravascular electrode, an intracardiac electrode, an epicardial electrode, or a housing or a header electrode located on a housing of device 102 or a header attached thereto, or any combination of the above. In some configurations, such as where portion(s) of device 102 are external to the patient, the electrode(s) coupling device 102 to heart 104 may include a skin surface electrode external to the patient. The electrodes may be associated with the heart for bipolar (i.e., two electrodes that are relatively close together) or for unipolar (i.e., two electrodes that are farther apart) signal sensing or therapy energy delivery (e.g., pacing pulse or shocks). In one example, the electrodes include a tip electrode located at or near a right ventricular apex of heart 104 and a shock or coil electrode located slightly superior thereto within the right ventricle of heart 104.
[0032]FIG. 2 is a graph illustrating generally a relatively noise-free cardiac signal 200 obtained from electrodes associated with heart 104. FIG. 3A is a graph illustrating generally a relatively noisy cardiac signal 300 similarly obtained from electrodes associated with heart 104. In the example of FIG. 3A, the additional noise may make the underlying heart chamber depolarizations difficult to detect, since the noise may include frequencies within the passband of the depolarizations and may, therefore, erroneously be level-detected as an actual heart depolarization. FIG. 3B is a graph illustrating in more detail a portion of a relatively noisy sampled cardiac signal 305, which is similarly obtained from electrodes associated with heart 104. The example of FIG. 3B illustrates, among other things, noise peak amplitude samples 310 and a cardiac beat peak amplitude sample 315. As illustrated by the example of FIG. 3B, the morphology and slew rate about noise peak sample 310 is different from that about cardiac beat peak sample 315. As described below, such differences can be used to distinguish between a noise peak sample and a cardiac depolarization peak sample. This information, in turn, may be used to avoid the inappropriate withholding or delivery of therapy based on an erroneous detection of a noise peak sample as a cardiac beat.
[0038]FIG. 4 is a flow chart illustrating generally, by way of example, but not by way of limitation, using a weighted average to validate or invalidate a depolarization detected by level-detecting or other techniques. In the example of FIG. 4, at 400, a depolarization is detected, such as by depolarization detector 111 using level detecting and/or other techniques. At 405, a peak amplitude sample P(n) is located at the peak amplitude of the detected depolarization. At 410, an immediately preceding sample P(n−1) and an immediately subsequent sample P(n+1) are located. At 415, a weighted average is computed, such as described in the examples of Equations 1 or 2. At 420, if the weighted average exceeds a predetermined threshold, the depolarization detected at 400 is validated at 425 as an actual beat; otherwise the depolarization detected at 400 is invalidated at 430, i.e., deemed noise. At 435, an indication of whether the depolarization detected at 400 was validated or invalidated is provided to a therapy algorithm used by controller 114, such as for determining whether the heart rhythm indicates that responsive therapy should be delivered by device 102.
[0039]FIG. 5 is a flow chart illustrating generally, by way of example, but not by way of limitation, using a weighted average to detect a depolarization. In the example of FIG. 5, at 500, a peak amplitude sample P(n) is located on the sampled cardiac signal x(n), such as by using a digital peak detector. At 510, an immediately preceding sample P(n−1) and an immediately subsequent sample P(n+1) are located. At 515, a weighted average is computed, such as described in the example of Equations 1 or 2. At 520, if the weighted average exceeds a predetermined threshold, a detected depolarization is declared at 525; otherwise the peak amplitude sample is declared noise at 530. At 535, an indication of whether a depolarization was detected and declared at 525 is provided to a therapy algorithm used by controller 114, such as for determining whether the heart rhythm indicates that responsive therapy should be delivered by device 102.
[0040]FIG. 6 is a graph illustrating generally, by way of example, but not by way of limitation, experimental data in which detected depolarizations were validated using the technique described in the flow chart of FIG. 4. In the example of FIG. 6, heart signal 600 was obtained from (1) right ventricular apical tip and (2) right ventricular shock coil electrodes associated with a subject's heart 104. The amplitude peaks of heart signal 600 that are marked by circles (such as 605) represent level-detected depolarizations. The level-detected depolarizations marked by open circles (such as 610) were validated as actual cardiac beats. The level-detected depolarizations that are marked by circles having X's (such as 615) were invalidated as actual cardiac beats, i.e., deemed noise. In this example, a predetermined noise threshold 132 value of 0.62 was used. The average value of NWA for actual beats was 0.89, with a standard deviation of 0.08. The average value of NWA for noise peaks was 0.43, with a standard deviation of 0.08.
[0042]FIG. 7 is a graph illustrating generally, by way of example, but not by way of limitation, experimental data in which detected depolarizations (during the onset of an arrhythmia, such as ventricular fibrillation) were validated using the technique described in the flow chart of FIG. 4. Unlike the example of FIG. 6, for which depolarizations were validating during normal sinus rhythm (NSR), in FIG. 7, depolarizations were validated during the onset of a ventricular fibrillation (VF) episode. The morphologies (shapes) of NSR cardiac complexes may differ substantially from those of VF cardiac complexes. However, as illustrated by FIG. 7, the technique described in the flow chart of FIG. 4 is also effective at distinguishing cardiac complexes from noise even when such cardiac complexes are VF complexes instead of NSR complexes. In FIG. 7, the circles 705 represent level-detected cardiac depolarizations that were validated as actual cardiac beats during normal sinus rhythm. The circles 710 (e.g., the seventh and all subsequent beats illustrated in FIG. 7) represent level-detected cardiac depolarizations that were validated as actual cardiac beats during ventricular fibrillation, despite significant fluctuations in the cardiac signal due to the ventricular fibrillation. Heart signal 700 represents a period of time before and during the onset of a VF episode. Heart signal 700 was obtained from (1) right ventricular apical tip and (2) right ventricular shock coil electrodes associated with a subject's heart 104. In this example, a predetermined noise threshold 132 value of 0.62 was used.
US10213364 2002-08-06 2002-08-06 Cardiac rhythm management systems and methods for detecting or validating cardiac beats in the presence of noise Active 2024-02-17 US7215993B2 (en)
US11625432 Continuation-In-Part US8078272B2 (en) 2002-08-06 2007-01-22 Systems and methods for detecting or validating signals in the presence of noise
US20040030256A1 true true US20040030256A1 (en) 2004-02-12
US20070135722A1 (en) 2007-06-14 application