An extra-cardiovascular implantable cardioverter defibrillator comprising: a sensing module for acquiring a cardiac electrical signal; a high voltage therapy module comprising a high voltage charging circuit, a high voltage capacitor, and switching circuitry configured to couple the high voltage capacitor to a plurality of implantable extra-cardiovascular electrodes; and a control module configured to: control the high voltage therapy module to induce a tachyarrhythmia by controlling the high voltage therapy module to: charge the high voltage capacitor to a first voltage amplitude; deliver a first series of pulses having a first inter-pulse interval between consecutive pulses (102a-102n and 104a-104n) to a patient's heart by enabling the switching circuitry to discharge the high voltage capacitor via an extra-cardiovascular electrode vector of the plurality of implantable extra-cardiovascular electrodes; recharge the high voltage capacitor during the first inter-pulse interval between consecutive pulses of the first series of pulses; determine from the cardiac electrical signal if tachyarrhythmia is induced after the first series of pulses; in response to determining that tachyarrhythmia is induced, control the high voltage therapy module to charge the high voltage capacitor to a second voltage amplitude greater than the first voltage amplitude, the second voltage amplitude corresponding to a therapeutic shock energy; and discharge the high voltage capacitor to deliver the therapeutic shock energy to the patient's heart. a sensing module for acquiring a cardiac electrical signal; a high voltage therapy module comprising a high voltage charging circuit, a high voltage capacitor, and switching circuitry configured to couple the high voltage capacitor to a plurality of implantable extra-cardiovascular electrodes; and a control module configured to: control the high voltage therapy module to induce a tachyarrhythmia by controlling the high voltage therapy module to: charge the high voltage capacitor to a first voltage amplitude; deliver a first series of pulses having a first inter-pulse interval between consecutive pulses (102a-102n and 104a-104n) to a patient's heart by enabling the switching circuitry to discharge the high voltage capacitor via an extra-cardiovascular electrode vector of the plurality of implantable extra-cardiovascular electrodes; recharge the high voltage capacitor during the first inter-pulse interval between consecutive pulses of the first series of pulses; determine from the cardiac electrical signal if tachyarrhythmia is induced after the first series of pulses; in response to determining that tachyarrhythmia is induced, control the high voltage therapy module to charge the high voltage capacitor to a second voltage amplitude greater than the first voltage amplitude, the second voltage amplitude corresponding to a therapeutic shock energy; and discharge the high voltage capacitor to deliver the therapeutic shock energy to the patient's heart. control the high voltage therapy module to induce a tachyarrhythmia by controlling the high voltage therapy module to: charge the high voltage capacitor to a first voltage amplitude; deliver a first series of pulses having a first inter-pulse interval between consecutive pulses (102a-102n and 104a-104n) to a patient's heart by enabling the switching circuitry to discharge the high voltage capacitor via an extra-cardiovascular electrode vector of the plurality of implantable extra-cardiovascular electrodes; recharge the high voltage capacitor during the first inter-pulse interval between consecutive pulses of the first series of pulses; charge the high voltage capacitor to a first voltage amplitude; deliver a first series of pulses having a first inter-pulse interval between consecutive pulses (102a-102n and 104a-104n) to a patient's heart by enabling the switching circuitry to discharge the high voltage capacitor via an extra-cardiovascular electrode vector of the plurality of implantable extra-cardiovascular electrodes; recharge the high voltage capacitor during the first inter-pulse interval between consecutive pulses of the first series of pulses; determine from the cardiac electrical signal if tachyarrhythmia is induced after the first series of pulses; in response to determining that tachyarrhythmia is induced, control the high voltage therapy module to charge the high voltage capacitor to a second voltage amplitude greater than the first voltage amplitude, the second voltage amplitude corresponding to a therapeutic shock energy; and discharge the high voltage capacitor to deliver the therapeutic shock energy to the patient's heart.