System and method for avoiding undersensing of ventricular fibrillation

A medical device for detecting and treating tachyarrhythmia, comprising:

• a plurality of electrodes to sense a cardiac signal;
• a sensing module coupled to the plurality of electrodes to sense cardiac events in response to the cardiac signal;
• and
• a first processing module coupled to the sensing module and configured to:
• determine a first morphology metric for each sensed cardiac event occurring during a time segment of the cardiac signal;
• determine a count of the first morphology metrics corresponding to an event originating in a ventricular chamber;
• determine a second morphology metric for the time segment of the cardiac signal in response to the count of the first morphology metrics meeting a threshold number of events;
• and
• classify the time segment as a shockable segment in response to the second morphology metric meeting a detection criterion.

A non-transitory, computer-readable medium storing a set of instructions, which when executed by a processor of a medical device causes the device to:

• determining a cardiac signal using a plurality of electrodes coupled to a sensing module;
• determine cardiac events in response to the cardiac signal;
• determine a first morphology metric for each sensed cardiac event occurring during a time segment of the cardiac signal;
• determine a count of the first morphology metrics corresponding to an event originating in a ventricular chamber;
• determine a second morphology metric for the time segment of the cardiac signal in response to the count of the first morphology metrics meeting a threshold number of events;
• and
• classify the time segment as a shockable segment in response to the second morphology metric meeting a detection criterion.