Oversensing of a Particular Transient Noise Appearing After the Implantation of an Implantable Cardiac Device

We experienced 2 cases in which oversensing of a particular noise after the implantation of an implantable cardiac device was observed in the acute phase. These were unusual cases in which the noise exhibited a low frequency pattern and appeared several hours after the implantation, but disappeared within 1 week. Here we present these cases and the details of an experiment investigating the origin of the noise and the methods for its prevention.The noise in these cases led to pacing inhibition and could have induced an inappropriate shock due to oversensing, but its morphology and electromagnetic interference were atypical for a lead failure or myopotentials. The noise spontaneously disappeared from the analysis of the data stored in the device. In an experiment based on the Irnich model, in which it was assumed that blood invaded a damaged grommet, low frequency noise occurred which was similar to the noise in the two cases. We concluded that care must be exercised when handling grommets.