A cardiac arrhythmia may be induced by delivering a sequence of pulses to a patient via one or more extravascular electrodes. In one example, one or more pacing pulses may be delivered to a patient via an extravascular electrode and a shock pulse may be delivered to the patient the extravascular electrode. In some examples, the pacing pulses and the shock pulse may be generated with energy from a common energy storage module and without interim charging of the module. For example, the pacing and shock pulses may be generated as the energy storage module dissipates. In another example, a cardiac arrhythmia may be induced in a patient by delivering a burst of pulses to a patient via an extravascular electrode. In some cases, the burst of pulses may be generated with energy from a common energy storage module and without interim charging of the energy storage module.