Techniques are disclosed for determining, by an extracardiovascular implantable cardioverter defibrillator (ICD) implanted in a patient, whether one or more test therapy signals generated by another medical device implanted in the patient is detected. In response to detecting the one or more test therapy signals, the extracardiovascular ICD provides an indication that the extracardiovascular ICD has detected the one or more test therapy signals. In some examples, the indication is an audible tone provided to a clinician. In some examples, the other medical device is an intracardiac cardiac pacing device, and the one or more test therapy signals comprises a plurality of anti-tachycardia pacing (ATP) pulses.
