The insertable cardiac monitors (ICMs) used for diagnosing and managing abnormal heart activities can falsely detect heart rhythms due to respiration, device rotation/orientation, device position, device flipping, and body mass that alter the amplitudes and morphologies. The objective of this paper is to investigate the effects of these key variables on ICM sensing by using computer simulations and virtual human family. We observed in these simulations that sensing amplitudes can vary greatly depending on device flipping, orientation/rotation, and migration; change significantly due to respiration effect; and are most sensitive to it when body mass is large. Those findings support identification of the key variables impacting clinical false detections.