Glossary
Ectopic beat
Also called ectopic beats, premature beat, extra heartbeat, PVC, PAC
A heartbeat that starts outside the heart's normal pacemaker and usually comes early. Ectopic beats are common, but they distort HRV unless removed or corrected.
A normal heartbeat starts in the sinus node, the heart’s natural pacemaker. An ectopic beat starts somewhere else. If it starts in the upper chambers it is called a premature atrial contraction (PAC); if it starts in the lower chambers, a premature ventricular contraction (PVC).
They are common. Peltola’s review notes that almost everyone has ectopic beats at some point, and they turn up in healthy people as well as in people with heart disease.
For HRV, the problem is timing. An ectopic beat arrives early, so the interval before it is short, and a ventricular one is usually followed by a longer pause. That short-long pair looks like a huge beat-to-beat swing, and it is not caused by your nervous system. Left in, even a few of these can push RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next. It mainly reflects vagal activity. More about RMSSD and other metrics away from your real value. The Task Force standards recommend using recordings free of ectopic beats where possible, and correcting them, for example by interpolation, when they cannot be avoided. A sudden, unexplained jump in your HRV is worth a second look for this reason.
Ectopic beats in an HRV app are not a diagnosis. Talk to a doctor if you often feel skipped or racing beats, or if they come with dizziness, chest pain, shortness of breath or fainting.
The lesson How to take a good HRV reading explains how to spot and avoid distorted readings.