The disclosure describes an enhancement to lead monitoring techniques, which uses a sensing integrity counter (SIC). The techniques of this disclosure may enhance lead monitoring techniques by detecting possible sensing issues based on a significant increase in periodic, e.g., daily, SIC counts relative to previous periods. Some issues with sensing cardiac signals via implantable cardiac leads can result in an implantable medical device (IMD) measuring very short intervals between what appears to be sensed heart beats. Examples of issues include insulation breach, conductor fracture, or poor electrical connection, which may cause noise that appears to be an R-wave. The IMD may detect the noise, along with actual R-waves, and determine that there are relatively short (e.g., less than a threshold) intervals between the “R-waves.” A significant increase in the number or frequency of very short intervals between R-waves may indicate the date/time of a significant sensing issue.