A medical device is configured to deliver a shock to a patient's heart via electrodes coupled to the medical device and set an escape interval timer to start running an escape interval after delivering the electrical shock. A sensing module of the medical device is configured to sense a cardiac event in response to a cardiac electrical signal received by the medical device crossing a sensing threshold. The medical device determines if the cardiac event meets reset criteria and allows the escape interval timer to continue running the escape interval if the cardiac event does not meet the reset criteria.