A medical device comprising: a sensing circuit configured to receive a cardiac electrical signal from a patient's heart and sense R-waves and T-waves from the cardiac electrical signal; a therapy delivery circuit configured to generate and deliver anti-tachycardia pacing, ATP, pulses to the patient's heart via electrodes coupled to the therapy delivery circuit; and a control circuit coupled to the sensing circuit and to the therapy delivery circuit and configured to: detect a ventricular tachyarrhythmia from the cardiac electrical signal received by the sensing circuit; responsive to the detected ventricular tachyarrhythmia, control the therapy delivery circuit to: deliver a plurality of ATP pulses at alternating ATP time intervals, the alternating ATP time intervals comprising at least a first ATP time interval separating a first pair of the plurality of the ATP pulses and a second ATP time interval separating a second pair of the plurality of ATP pulses, the second ATP time interval being different than the first ATP time interval and consecutively following the first ATP time interval, wherein: the first pair comprises a first ATP pulse and a second ATP pulse consecutively following the first ATP pulse at the first ATP time interval, the second pair comprises the second ATP pulse and a third ATP pulse consecutively following the second ATP pulse at the second ATP time interval, and the control circuit is configured to control the therapy delivery circuit to deliver a fourth ATP pulse consecutively following the third ATP pulse at the first ATP time interval. a sensing circuit configured to receive a cardiac electrical signal from a patient's heart and sense R-waves and T-waves from the cardiac electrical signal; a therapy delivery circuit configured to generate and deliver anti-tachycardia pacing, ATP, pulses to the patient's heart via electrodes coupled to the therapy delivery circuit; and a control circuit coupled to the sensing circuit and to the therapy delivery circuit and configured to: detect a ventricular tachyarrhythmia from the cardiac electrical signal received by the sensing circuit; responsive to the detected ventricular tachyarrhythmia, control the therapy delivery circuit to: deliver a plurality of ATP pulses at alternating ATP time intervals, the alternating ATP time intervals comprising at least a first ATP time interval separating a first pair of the plurality of the ATP pulses and a second ATP time interval separating a second pair of the plurality of ATP pulses, the second ATP time interval being different than the first ATP time interval and consecutively following the first ATP time interval, detect a ventricular tachyarrhythmia from the cardiac electrical signal received by the sensing circuit; responsive to the detected ventricular tachyarrhythmia, control the therapy delivery circuit to: deliver a plurality of ATP pulses at alternating ATP time intervals, the alternating ATP time intervals comprising at least a first ATP time interval separating a first pair of the plurality of the ATP pulses and a second ATP time interval separating a second pair of the plurality of ATP pulses, the second ATP time interval being different than the first ATP time interval and consecutively following the first ATP time interval, wherein: the first pair comprises a first ATP pulse and a second ATP pulse consecutively following the first ATP pulse at the first ATP time interval, the second pair comprises the second ATP pulse and a third ATP pulse consecutively following the second ATP pulse at the second ATP time interval, and the control circuit is configured to control the therapy delivery circuit to deliver a fourth ATP pulse consecutively following the third ATP pulse at the first ATP time interval. the first pair comprises a first ATP pulse and a second ATP pulse consecutively following the first ATP pulse at the first ATP time interval, the second pair comprises the second ATP pulse and a third ATP pulse consecutively following the second ATP pulse at the second ATP time interval, and the control circuit is configured to control the therapy delivery circuit to deliver a fourth ATP pulse consecutively following the third ATP pulse at the first ATP time interval.