| CPC A61B 5/35 (2021.01) [A61B 5/25 (2021.01); A61B 5/256 (2021.01); A61B 5/28 (2021.01); A61B 5/361 (2021.01); A61B 5/363 (2021.01); A61B 5/366 (2021.01); A61B 5/6805 (2013.01); A61B 5/7221 (2013.01); A61B 5/7282 (2013.01); A61B 5/746 (2013.01)] | 20 Claims |

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1. A wearable medical device for determining whether a patient is experiencing a cardiac event, comprising:
a plurality of electrocardiogram (ECG) electrodes configured to sense an ECG signal of the patient; and
a medical device controller in communication with the plurality of ECG electrodes, the medical device controller comprising
a memory configured to store a plurality of ECG templates, the plurality of ECG templates comprising a first ECG template corresponding to a first baseline ECG signal of the patient during a first baselining period and a second ECG template corresponding to a second baseline ECG signal of the patient during a second baselining period different than the first baselining period; and
a cardiac event detector configured to
filter the ECG signal of the patient with each respective ECG template of the plurality of ECG templates;
determine a quality score for each respective ECG template based on a degree to which the filtered ECG signal corresponds to the ECG signal of the patient, wherein determining the quality score for each respective ECG template comprises measuring a deviation of at least one of a zero phase crossing or a magnitude of the filtered ECG signal and the ECG signal of the patient;
select the respective ECG template having a highest quality score to use as a current ECG template; and
compare a current ECG signal of the patient with the current ECG template to determine whether the patient is experiencing the cardiac event.
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