A system comprising: a first therapy module configured to deliver electrical stimulation to a tissue site within a patient according to a set of stimulation parameter values; a second therapy module configured to deliver at least one of a pacing, cardioversion or defibrillation therapy to a heart of the patient; a sensing module configured to sense a cardiac signal of the heart of the patient; a processor configured to detect, during a time in which the first therapy module delivers electrical stimulation to the tissue site according to the set of stimulation parameter values, a potential arrhythmia of the heart based on the cardiac signal, to control the first therapy module to adjust the delivery of electrical stimulation to the tissue site in response to detecting the potential arrhythmia, to determine whether the potential arrhythmia is detected after the adjustment to the delivery of electrical stimulation to the tissue site by the first therapy module, and, in response to determining the potential arrhythmia is not detected after the adjustment to the delivery of electrical stimulation to the tissue site by the first therapy module, to initiate a modification to at least one stimulation parameter value of the set of stimulation parameter values, characterised in that: the processor is configured to, in response to detecting the potential arrhythmia based on the cardiac signal after modifying the at least one stimulation parameter of the set of stimulation parameter values of the first therapy module, determine whether the potential arrhythmia comprises a true arrhythmia and to control the second therapy module to deliver therapy to the heart of the patient in response to determining the potential arrhythmia comprises a true arrhythmia. a first therapy module configured to deliver electrical stimulation to a tissue site within a patient according to a set of stimulation parameter values; a second therapy module configured to deliver at least one of a pacing, cardioversion or defibrillation therapy to a heart of the patient; a sensing module configured to sense a cardiac signal of the heart of the patient; a processor configured to detect, during a time in which the first therapy module delivers electrical stimulation to the tissue site according to the set of stimulation parameter values, a potential arrhythmia of the heart based on the cardiac signal, to control the first therapy module to adjust the delivery of electrical stimulation to the tissue site in response to detecting the potential arrhythmia, to determine whether the potential arrhythmia is detected after the adjustment to the delivery of electrical stimulation to the tissue site by the first therapy module, and, in response to determining the potential arrhythmia is not detected after the adjustment to the delivery of electrical stimulation to the tissue site by the first therapy module, to initiate a modification to at least one stimulation parameter value of the set of stimulation parameter values, characterised in that: the processor is configured to, in response to detecting the potential arrhythmia based on the cardiac signal after modifying the at least one stimulation parameter of the set of stimulation parameter values of the first therapy module, determine whether the potential arrhythmia comprises a true arrhythmia and to control the second therapy module to deliver therapy to the heart of the patient in response to determining the potential arrhythmia comprises a true arrhythmia.