Additionally, in Expert Plus mode or otherwise when playing with the “alarm when KO” custom difficulty setting enabled, a guard's Heart Monitor also raises the alarm tracker by 1 step when he is knocked out, unless he is already knocked out.
Heart Monitors can be permanently disabled using EMP Packs or Dr. Xu's Subdermal Tools. Heart Monitors are also bypassed by ranged weapons using the Anatomy Analysis augment. When a guard's Heart Monitor is disabled or bypassed, killing him or knocking him out does not raise the alarm tracker.
All human guards have a Heart Monitor, except for OMNI Harbingers who instead have a Consciousness Monitor and an Improved Heart Monitor. Note that when hovering over an OMNI Harbinger in the user interface, the tooltip additionally shows that he has a standard Heart Monitor, but this is misleading; an OMNI Harbinger's Heart Monitor never has any effect, so practically speaking OMNI Harbingers do not have Heart Monitors.