A medical device comprising: a sensing circuit configured to sense at least one cardiac electrical signal; a control circuit in communication with the sensing circuit, the control circuit configured to: determine an amplitude metric from a cardiac signal segment of the at least one cardiac electrical signal sensed by the sensing circuit over a time interval; determine if the amplitude metric meets an amplitude threshold; and perform one of: a first analysis of the cardiac electrical signal segment for detecting a first arrhythmia in response to the amplitude metric not meeting the amplitude threshold; or a second analysis of the cardiac electrical signal segment for detecting a second arrhythmia different than the first arrhythmia in response to the amplitude metric meeting the amplitude threshold; and a therapy delivery circuit in communication with the control circuit, the therapy delivery circuit configured to deliver one of: a first electrical stimulation therapy in response to the control circuit detecting the first arrhythmia based on at least the first analysis; or a second electrical stimulation therapy different than the first electrical stimulation therapy in response to the control circuit detecting the second arrhythmia based on at least the second analysis. a sensing circuit configured to sense at least one cardiac electrical signal; a control circuit in communication with the sensing circuit, the control circuit configured to: determine an amplitude metric from a cardiac signal segment of the at least one cardiac electrical signal sensed by the sensing circuit over a time interval; determine if the amplitude metric meets an amplitude threshold; and perform one of: a first analysis of the cardiac electrical signal segment for detecting a first arrhythmia in response to the amplitude metric not meeting the amplitude threshold; or a second analysis of the cardiac electrical signal segment for detecting a second arrhythmia different than the first arrhythmia in response to the amplitude metric meeting the amplitude threshold; and a therapy delivery circuit in communication with the control circuit, the therapy delivery circuit configured to deliver one of: a first electrical stimulation therapy in response to the control circuit detecting the first arrhythmia based on at least the first analysis; or a second electrical stimulation therapy different than the first electrical stimulation therapy in response to the control circuit detecting the second arrhythmia based on at least the second analysis. determine an amplitude metric from a cardiac signal segment of the at least one cardiac electrical signal sensed by the sensing circuit over a time interval; determine if the amplitude metric meets an amplitude threshold; and perform one of: a first analysis of the cardiac electrical signal segment for detecting a first arrhythmia in response to the amplitude metric not meeting the amplitude threshold; or a second analysis of the cardiac electrical signal segment for detecting a second arrhythmia different than the first arrhythmia in response to the amplitude metric meeting the amplitude threshold; and a first analysis of the cardiac electrical signal segment for detecting a first arrhythmia in response to the amplitude metric not meeting the amplitude threshold; or a second analysis of the cardiac electrical signal segment for detecting a second arrhythmia different than the first arrhythmia in response to the amplitude metric meeting the amplitude threshold; and a therapy delivery circuit in communication with the control circuit, the therapy delivery circuit configured to deliver one of: a first electrical stimulation therapy in response to the control circuit detecting the first arrhythmia based on at least the first analysis; or a second electrical stimulation therapy different than the first electrical stimulation therapy in response to the control circuit detecting the second arrhythmia based on at least the second analysis. a first electrical stimulation therapy in response to the control circuit detecting the first arrhythmia based on at least the first analysis; or a second electrical stimulation therapy different than the first electrical stimulation therapy in response to the control circuit detecting the second arrhythmia based on at least the second analysis.