Wearable medical device with zoneless arrhythmia detection
Embodiments of a wearable monitoring device system can include a wearable monitoring device comprising one or more patient physiological sensors and a detector to zonelessly detect arrhythmias from physiological signals sensed by the one or more sensors, and optionally other signals. In embodiments the detector includes a processor configured with a sudden rate change onset (SRCO) algorithm, one or more arrythmia detection algorithms and, optionally, a noise detection algorithm. In embodiments, in response to detecting SRCO, the wearable monitoring device or a remote system that receives data from the wearable medical device determines whether the patient has an arrhythmia from physiological signals sensed by the one or more sensors.
1 . A wearable cardioverter defibrillator (WCD) system, comprising:
a support structure to be worn by a patient;
an energy storage module to store an electrical charge;
at least one therapy electrode coupled to the support structure;
at least one sensor, coupled to the support structure, configured to generate an electrocardiogram (ECG) of the patient when the patient is wearing the support structure; and
a processor, communicatively coupled to the at least one sensor, configured to:
receive the ECG of the patient from the at least one sensor;
determine, based on the received ECG, whether a heart rate and/or QRS width of the patient is within a predefined ventricular fibrillation (VF) zone, wherein the predefined VF zone corresponds to one or more ranges of the heart rate and/or the QRS width indicating VF;
in response to a determination that the heart rate and/or the QRS width of the patient is outside the predefined VF zone, perform a sudden rate change onset (SRCO) detection of the received ECG, wherein to perform the SRCO detection, the processor is configured to:
detect a first heart parameter value from the received ECG at a first time,
detect a second heart parameter value from the received ECG at a second time, wherein the first heart parameter value and the second heart parameter value comprise one of a heart rate (HR), R-R interval, average HR, or an average R-R interval,
determine a difference between the first heart parameter value and the second heart parameter value, and
detect the SRCO of the received ECG based, at least in part, on comparison of absolute value of the difference between the first heart parameter value and the second heart parameter value with a predetermined threshold;
responsive to the detected SRCO, perform a process to determine whether the received ECG is indicative of VF; and
cause the energy storage module to discharge at least a portion of the stored electrical charge to the patient using the at least one therapy electrode, at least in part, in response to a determination that VF is indicated.
2 . The WCD system of claim 1 , wherein the processor is further configured to determine whether the received ECG is indicative of one or more of pulseless ventricular tachycardia (PVT), monomorphic ventricular tachycardia (MVT), or noise in response to the detected SRCO.
3 . The WCD system of claim 1 , wherein responsive to the detected SRCO, the processor is configured to:
save the first heart parameter value, wherein the first heart parameter is detected before the SRCO;
determine whether the received ECG of the patient is indicative of supraventricular tachycardia (SVT);
responsive to a determination that the received ECG of the patient is indicative of SVT, determine whether a current heart parameter value determined from the received ECG of the patient is less than the saved value;
responsive to a determination that the current value is less than the saved value, detect whether the received ECG of the patient is indicative of a subsequent SRCO; and
responsive to a determination that the current value is not less than the saved value, determine whether the received ECG of the patient remains indicative of SVT.
4 . The WCD system of claim 3 , wherein:
responsive to the received ECG of the patient being not indicative of SVT, the process further includes:
determining whether the received ECG of the patient is indicative of monomorphic ventricular tachycardia (MVT),
wherein the process determines that the received ECG of the patient is determined to be indicative of VF when the received ECG of the patient is not indicative of MVT.
5 . The WCD system of claim 4 , wherein responsive to the received ECG being not indicative of MVT, the process further includes:
determining whether the received ECG of the patient is noisy.
6 . The WCD system of claim 5 , wherein the process determines that the received ECG of the patient is determined to be indicative of VF when the received ECG of the patient is determined to not be noisy.
7 . The WCD system of claim 5 , wherein the processor is further configured to:
determine whether a physiological parameter of the patient sensed by the at least one sensor is indicative of the patient being conscious; and
classify the received ECG of the patient as VF in response to the sensed physiological parameter being not indicative of the patient being conscious.
8 . The WCD system of claim 7 , wherein the sensed physiological parameter comprises a vital sign.
9 . The WCD system of claim 1 , wherein the processor is further configured to:
not perform the SRCO detection in response to the heart rate and/or the QRS width being within the predefined VF zone.
10 . The WCD system of claim 1 , wherein the first heart parameter value is determined by taking an average of a first group of heart parameter values.
11 . The WCD system of claim 10 , wherein the second heart parameter value is determined by taking an average of a second group of heart parameter values, the second group having the same number of heart parameter values as the first group.
12 . The WCD system of claim 1 , wherein the WCD system further comprises an outside monitoring device configured to monitor at least one local parameter.
13 . The WCD system of claim 12 , wherein the at least one local parameter includes at least one of a parameter of the patient, a parameter of the WCD system, or a parameter of the environment surrounding the patient.
14 . The WCD system of claim 1 , wherein the first heart parameter value and the second heart parameter value correspond to the HR, wherein the predetermined threshold is a change of eighty beats per minute over twelve HR samples, wherein the first time and the second time correspond to a first and a last of the twelve HR samples respectively, and wherein the HR samples are generated at intervals of 2.4 seconds.
15 . The WCD system of claim 1 , wherein the first heart parameter value and the second heart parameter value correspond to the R-R interval, wherein the predetermined threshold is 200 milliseconds over twelve R-R interval samples, and wherein the first time and the second time correspond to a first and a last of the twelve R-R interval samples respectively.
16 . The WCD system of claim 1 , wherein the first heart parameter value and the second heart parameter value correspond to the HR, wherein the predetermined threshold is a change in a range of 10 beats per minute to 50 beats per minute over a number of HR samples, wherein the number of HR samples ranges from 10 samples to 20 samples, and wherein the first time and the second time correspond to a first and a last of the number of HR samples respectively.
17 . The WCD system of claim 1 , wherein the comparison of the absolute value of the difference between the first heart parameter value and the second heart parameter value with the predetermined threshold comprises the absolute value of the difference between the first heart parameter value and the second heart parameter value exceeding the predetermined threshold.
18 . The WCD system of claim 1 , wherein the processor is configured to detect the SRCO of the received ECG based, at least in part, on the comparison of the absolute value of the difference between the first heart parameter value and the second heart parameter value over a timing value with the predetermined threshold, and wherein the timing value comprises a time duration, a number of samples, or a number of heart beats.
19 . The WCD system of claim 1 , wherein the predetermined threshold is based on a running average of HR or R-R interval measurements.
20 . The WCD system of claim 19 , wherein the predetermined threshold is a change in the running average of fifty-five beats per minute over twenty HR samples.