An implantable medical system comprising: a physiological sensor configured to produce a physiological signal correlated to a motion of a patient; at least one medical electrical lead (14, 16,18) including: a plurality of electrodes (20, 22, 26, 30, 32, 34, 36, 40, 42) carried by the at least one medical electrical lead; and a plurality of electrical conductors (62, 64), each of the plurality of electrical conductors electrically connected to a respective one of the plurality of electrodes; an implantable medical device adapted to be coupled to the at least one medical electrical lead, the implantable medical device including: a sensing module electrically coupled to the plurality of electrical conductors when the at least one medical electrical lead is coupled to the implantable medical device, the sensing module configured to sense a first cardiac signal using at least one of the plurality of electrodes, the first cardiac signal comprising a first plurality of cardiac event signals attendant to the depolarization of a heart of the patient; and a controller electrically coupled to the sensing module and the physiological sensor and configured to: determine whether a lead monitoring condition is met in response to the physiological signal; acquire the first cardiac signal when the lead monitoring condition is met; analyze the first cardiac signal to detect an abnormality of the first cardiac signal; and detect a short circuit of the medical electrical lead in response to detecting the abnormality. a physiological sensor configured to produce a physiological signal correlated to a motion of a patient; at least one medical electrical lead (14, 16,18) including: a plurality of electrodes (20, 22, 26, 30, 32, 34, 36, 40, 42) carried by the at least one medical electrical lead; and a plurality of electrical conductors (62, 64), each of the plurality of electrical conductors electrically connected to a respective one of the plurality of electrodes; a plurality of electrodes (20, 22, 26, 30, 32, 34, 36, 40, 42) carried by the at least one medical electrical lead; and a plurality of electrical conductors (62, 64), each of the plurality of electrical conductors electrically connected to a respective one of the plurality of electrodes; an implantable medical device adapted to be coupled to the at least one medical electrical lead, the implantable medical device including: a sensing module electrically coupled to the plurality of electrical conductors when the at least one medical electrical lead is coupled to the implantable medical device, the sensing module configured to sense a first cardiac signal using at least one of the plurality of electrodes, the first cardiac signal comprising a first plurality of cardiac event signals attendant to the depolarization of a heart of the patient; and a controller electrically coupled to the sensing module and the physiological sensor and configured to: determine whether a lead monitoring condition is met in response to the physiological signal; acquire the first cardiac signal when the lead monitoring condition is met; analyze the first cardiac signal to detect an abnormality of the first cardiac signal; and detect a short circuit of the medical electrical lead in response to detecting the abnormality. a sensing module electrically coupled to the plurality of electrical conductors when the at least one medical electrical lead is coupled to the implantable medical device, the sensing module configured to sense a first cardiac signal using at least one of the plurality of electrodes, the first cardiac signal comprising a first plurality of cardiac event signals attendant to the depolarization of a heart of the patient; and a controller electrically coupled to the sensing module and the physiological sensor and configured to: determine whether a lead monitoring condition is met in response to the physiological signal; acquire the first cardiac signal when the lead monitoring condition is met; analyze the first cardiac signal to detect an abnormality of the first cardiac signal; and detect a short circuit of the medical electrical lead in response to detecting the abnormality. determine whether a lead monitoring condition is met in response to the physiological signal; acquire the first cardiac signal when the lead monitoring condition is met; analyze the first cardiac signal to detect an abnormality of the first cardiac signal; and detect a short circuit of the medical electrical lead in response to detecting the abnormality.