A system comprising: a first implantable medical device being an implantable cardiac device that senses a first electrical signal within a patient; a second IMD being an implantable neurostimulator that delivers a second electrical signal to a tissue site within the patient, wherein the first IMD senses the first electrical signal while the second IMD delivers the second electrical signal to a tissue site within the patient; and means for determining a noise characteristic of the first electrical signal sensed by the first IMD while the second IMD is delivering the second electrical signal to the tissue site; means for comparing the noise characteristic of the first electrical signal to a threshold value and determining the presence of a neurostimulation signal artefact due to crosstalk based on the comparison; and means for modifying at least one of a stimulation parameter with which the second IMD generates electrical stimulation that is delivered to the tissue site or a sensing parameter with which the first IMD senses the first electrical signal based on the determination of the presence of an artefact; wherein the means for determining the noise characteristic of the first electrical signal is configured to determine the characteristic by at least: controlling the second implantable medical device to suspend delivery of the second electrical signal; controlling the first IMD to sense a third electrical signal while said delivery is suspended, and deriving a baseline signal; controlling the second IMD to deliver the second electrical signal to the tissue site; controlling the first IMD to sense the first electrical signal with the first IMD while the second IMD delivers the second electrical signal to the tissue site; and determining a difference between at least one signal characteristic of the first electrical signal and the baseline signal. a first implantable medical device being an implantable cardiac device that senses a first electrical signal within a patient; a second IMD being an implantable neurostimulator that delivers a second electrical signal to a tissue site within the patient, wherein the first IMD senses the first electrical signal while the second IMD delivers the second electrical signal to a tissue site within the patient; and means for determining a noise characteristic of the first electrical signal sensed by the first IMD while the second IMD is delivering the second electrical signal to the tissue site; means for comparing the noise characteristic of the first electrical signal to a threshold value and determining the presence of a neurostimulation signal artefact due to crosstalk based on the comparison; and means for modifying at least one of a stimulation parameter with which the second IMD generates electrical stimulation that is delivered to the tissue site or a sensing parameter with which the first IMD senses the first electrical signal based on the determination of the presence of an artefact; the means for determining the noise characteristic of the first electrical signal is configured to determine the characteristic by at least: controlling the second implantable medical device to suspend delivery of the second electrical signal; controlling the first IMD to sense a third electrical signal while said delivery is suspended, and deriving a baseline signal; controlling the second IMD to deliver the second electrical signal to the tissue site; controlling the first IMD to sense the first electrical signal with the first IMD while the second IMD delivers the second electrical signal to the tissue site; and determining a difference between at least one signal characteristic of the first electrical signal and the baseline signal. controlling the second implantable medical device to suspend delivery of the second electrical signal; controlling the first IMD to sense a third electrical signal while said delivery is suspended, and deriving a baseline signal; controlling the second IMD to deliver the second electrical signal to the tissue site; controlling the first IMD to sense the first electrical signal with the first IMD while the second IMD delivers the second electrical signal to the tissue site; and determining a difference between at least one signal characteristic of the first electrical signal and the baseline signal.