ASYSTOLE AND COMPLETE HEART BLOCK DETECTION
In one example, an apparatus of a wearable cardioverter defibrillator (WCD) system comprises a support structure wearable by a patient, a plurality of electrocardiogram (ECG) electrodes to obtain an ECG signal, a processor to receive and analyze the ECG signal of the patient, wherein the processor is configured to monitor four or more channels of the ECG signal, a high voltage subsystem coupled with defibrillation electrodes configured to be coupled with patient, wherein processor is configured to cause the high voltage subsystem to apply a therapeutic shock to the patient through the defibrillation electrodes in response to a shockable event detected by the processor from the ECG signal. The processor measures a peak-to-peak amplitude of QRS complexes of the ECG signal, and detects asystole in the patient when the peak-to-peak amplitude of one or more QRS complexes is less than an asystole threshold.
1 . An apparatus of a wearable cardioverter defibrillator (WCD) system, comprising:
a support structure wearable by a patient;
a plurality of electrocardiogram (ECG) electrodes capable of being applied to the skin of the patient to obtain an ECG signal;
a processor to receive and analyze the ECG signal of the patient, wherein the processor is configured to monitor four or more channels of the ECG signal;
a high voltage subsystem coupled with defibrillation electrodes configured to be coupled with patient, wherein the high voltage subsystem is configured to apply a therapeutic shock to the patient through the defibrillation electrodes in response to a shockable detected by the processor from the ECG signal;
wherein the processor is configured to:
measure a peak-to-peak amplitude of QRS complexes of the ECG signal; and
detecting asystole in the patient when the peak-to-peak amplitude of one or more QRS complexes is less than an asystole threshold.
2 . The apparatus of claim 1 , wherein the asystole threshold is set to a fixed value.
3 . The apparatus of claim 1 , wherein the fixed value ranges from about 100 microvolts to about 200 microvolts.
4 . The apparatus of claim 1 , wherein the asystole threshold is set to a percentage of a peak-to-peak amplitude of a normal QRS complex of the patient.
5 . The apparatus of claim 1 , wherein a unique asystole threshold is set for each of the plurality of channels.
6 . The apparatus of claim 1 , wherein the processor is further configured to:
detect respiration of the patient; and
determine that the patient is in asystole when the peak-to-peak amplitude of one or more of the QRS complexes is lower than a conditional threshold and higher than an absolute threshold, and no patient respiration is detected.
7 . The apparatus of claim 1 , wherein asystole is detected only when the peak-to-peak amplitudes of QRS complexes in all four channels falls below the asystole threshold.
8 . A method to detect complete heart block in a patient using a wearable cardioverter defibrillator (WCD), wherein the WCD includes a support structure wearable by the patient, a plurality of electrocardiogram (ECG) electrodes capable of being applied to the skin of the patient to obtain an ECG signal, a processor to receive and analyze the ECG signal of the patient, wherein the processor is configured to monitor four or more channels of the ECG signal, and a high voltage subsystem coupled with defibrillation electrodes configured to be coupled with patient, wherein the high voltage subsystem is configured to apply a therapeutic shock to the patient through the defibrillation electrodes in response to a shockable detected by the processor from the ECG signal, the method comprising:
measuring a peak-to-peak amplitude of QRS complexes of a monitored ECG signal;
determining whether the peak-to-peak amplitude of one or more of the QRS complexes has dropped in amplitude by an amount greater than a predetermined amount; and
detecting complete heart block in the patient when the peak-to-peak amplitude of one or more of the QRS complexes has dropped greater than the predetermined amount.
9 . The method of claim 8 , wherein the predetermined amount is greater than fifty percent of the peak-to-peak amplitude of a normal QRS complex.
10 . The method of claim 8 , further comprising detecting complete heart block when the peak-to-peak amplitude has dropped greater than the predetermined amount and the peak-to-peak amplitude is less than about 200 microvolts.
11 . The method of claim 8 , further comprising, responsive to the peak-to-peak amplitude of one or more of the QR complexes dropping greater than the predetermined amount:
comparing the monitored ECG signal with a QRS complex template; and
detecting complete heart block when there is a mismatch between the monitored QRS complex template.
12 . The method of claim 8 , further comprising, responsive to the peak-to-peak amplitude of one or more of the QR complexes dropping greater than the predetermined amount:
comparing the monitored ECG signal with a p-wave template; and
detecting complete heart block when there is a mismatch between the monitored p-wave template.
13 . A method to detect bradycardia in a patient using a wearable cardioverter defibrillator (WCD), wherein the WCD includes a support structure wearable by the patient, a plurality of electrocardiogram (ECG) electrodes capable of being applied to the skin of the patient to obtain an ECG signal, a processor to receive and analyze the ECG signal of the patient, wherein the processor is configured to monitor four or more channels of the ECG signal, and a high voltage subsystem coupled with defibrillation electrodes configured to be coupled with patient, wherein the high voltage subsystem is configured to apply a therapeutic shock to the patient through the defibrillation electrodes in response to a shockable detected by the processor from the ECG signal, the method comprising:
monitoring the ECG signal of the patient to determine a heart rate of the patient;
monitoring respiration of the patient;
determining whether the heart rate of the patient is in a conditional zone defined as being less than a conditional threshold for bradycardia and above an absolute threshold for bradycardia; and
detecting non-perfusing bradycardia in the patient when the heart rate is in the conditional zone and no respiration is detected.
14 . The method of claim 13 , further comprising:
detecting perfusing bradycardia when the heart rate is in the conditional zone and respiration is detected.
15 . The method of claim 13 , wherein monitoring respiration of the patient comprises measuring changes in impedance of the patient's skin between two or more of the plurality of ECG electrodes.
16 . The method of claim 13 , wherein the conditional threshold is about 40 beats per minute.
17 . The method of claim 13 , wherein the absolute threshold is about 20 beats per minute.
18 . The method of claim 13 , further comprising measuring a pulse of the patient via an external monitor, and confirming the heart rate of the patient based on the measured pulse.
19 . The method of claim 13 , further comprising measuring a blood pressure of the patient via an external monitor, and detecting non-perfusing bradycardia when the measured blood pressure is below a threshold value.