Unconfirmed media reports say Nancy Guthrie's pacemaker stopped syncing with her Apple devices. Here's what that means.

In addition to recording heart activity, pacemakers can also help document inactivity, such as confirming time of death.

The heart devices do not track location, nor do they transmit across large distances. Like an estimated three million Americans, Nancy Guthrie, the 84-year-old mother of the NBC News anchor Savannah ...

Nancy Guthrie’s 2 a.m. pacemaker spike on the day she vanished could mean that the elderly woman was involved in a heart rate ...