A medical device system comprising: a plurality of electrodes configured to sense electrical activity of a heart of a patient; and processing circuitry configured to: receive a cardiac signal generated in response to monitoring the electrical activity of a heart of a patient using the plurality of electrodes; determine a baseline amplitude value of the cardiac signal within a first detection window, the first window comprising a first time period extending for a predefined amount of time from a sample time; determine a plurality of amplitude values for the cardiac signal within a second detection window, the second detection window comprising a second time period extending for a predefined amount of time following the sample time; calculate an area-under-the-curve value based on the plurality of amplitude level values within the second detection window and the baseline amplitude value; compare the area-under-the-curve value to a noise signal threshold value; and determine that the cardiac signal includes a noise signal in response to a determination that the area-under-the-curve value exceeds the noise signal threshold value. a plurality of electrodes configured to sense electrical activity of a heart of a patient; and processing circuitry configured to: receive a cardiac signal generated in response to monitoring the electrical activity of a heart of a patient using the plurality of electrodes; determine a baseline amplitude value of the cardiac signal within a first detection window, the first window comprising a first time period extending for a predefined amount of time from a sample time; determine a plurality of amplitude values for the cardiac signal within a second detection window, the second detection window comprising a second time period extending for a predefined amount of time following the sample time; calculate an area-under-the-curve value based on the plurality of amplitude level values within the second detection window and the baseline amplitude value; compare the area-under-the-curve value to a noise signal threshold value; and determine that the cardiac signal includes a noise signal in response to a determination that the area-under-the-curve value exceeds the noise signal threshold value. receive a cardiac signal generated in response to monitoring the electrical activity of a heart of a patient using the plurality of electrodes; determine a baseline amplitude value of the cardiac signal within a first detection window, the first window comprising a first time period extending for a predefined amount of time from a sample time; determine a plurality of amplitude values for the cardiac signal within a second detection window, the second detection window comprising a second time period extending for a predefined amount of time following the sample time; calculate an area-under-the-curve value based on the plurality of amplitude level values within the second detection window and the baseline amplitude value; compare the area-under-the-curve value to a noise signal threshold value; and determine that the cardiac signal includes a noise signal in response to a determination that the area-under-the-curve value exceeds the noise signal threshold value.