Heart rate variability or HRV is the variation in the time interval between heartbeats, within a specific time frame. Even healthy hearts have irregularities. A heart that is maintaining a rating of 60 beats per minute does not necessarily beat at one-second intervals. In other words, you can't keep time with a heartbeat like you can with a clock. Longer intervals happen when you exhale, and shorter ones occur when you inhale. When an EKG measures HRV, it indicates whether your heartbeats are constant. If they are, then your HRV is low. If the intervals vary, then your HRV is high. HRV readings give important information about the autonomic nervous system, which regulates heart and respiration rate as well as digestion. Your HRV reading tells your doctor if both the resting and activated branches of your autonomic nervous system are functioning properly.

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