An example medical device system includes therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry. The ATP therapy includes one or more ATP trains. The medical device system also includes processing circuitry configured determine a first propagation time based on a comparison of features in a local electrogram and a far-field electrogram, such as the time from a fiducial point in the local electrogram and QRS onset in the far-field electrogram. The processing circuitry is also configured to determine, based on the first propagation time, a number of pulses to achieve a second propagation time and control the therapy delivery circuitry to deliver the ATP train of at least the number of pulses.