A thump in the chest, a skipped beat, a pause that feels too long. That is often a PVC. Here is what one looks like on a real single-lead recording, and how to recognize it on your own Apple Watch ECG.
What a PVC is
A normal heartbeat starts in the sinus node, high in the upper chambers, and travels down a fast conduction pathway to the lower chambers, the ventricles. A PVC starts somewhere in the ventricles instead, before the next regular beat is due. Because the signal spreads slowly through the heart muscle rather than along the fast pathway, the beat looks different on an ECG.1
PVCs are very common. They occur in up to three quarters of people at some point, and most are not dangerous.2
A real example
This is a real recording in lead I, the lead closest to what an Apple Watch records, with every beat labeled by experts. ECG Tracker+ ran the same analysis it runs on your recordings and marked one beat as a possible PVC. It is the beat the experts labeled as a PVC, and the app marked no other extra beats in the 30 seconds.
The regular beats here arrive about every 625 ms, a heart rate of about 96 bpm. The marked beat arrived only 477 ms after the beat before it. The gap after it lasted 791 ms.
Four signs to look for
- It comes early. The gap before it is clearly shorter than the gaps between regular beats. In the example it is 477 ms instead of about 625 ms.
- It looks different. The QRS, the tall spike of the beat, is wider than usual, often more than 120 ms, and its shape differs from the beats around it.1
- There is no P wave in front of it. The small bump that normally comes just before each QRS is missing, because the beat did not start in the upper chambers.1
- A longer pause follows. The heart often waits longer before the next regular beat. When the gaps before and after add up to about two regular beats, clinicians call it a compensatory pause.1 In the example they add up to 1,268 ms, close to two regular beats of about 1,250 ms.
Not every PVC shows all four signs. A PAC, an early beat from the upper chambers, also arrives early, but its QRS usually stays narrow and looks like its neighbors. The guide to PACs and PVCs compares the two.
How ECG Tracker+ shows it
In the app, the beat is highlighted on the waveform with a Possible PVC label. Tap the finding to focus the waveform on that beat and see the R-R interval before and after it. Comparing those two gaps is often the clearest sign that a beat was early.
Why the app says possible
On a single lead, the details that separate a PVC from other early beats are not always clear. Noise and movement can distort a beat, and an early beat from the upper chambers can sometimes look wide. Medical experts note that consumer ECG devices cannot currently classify PACs and PVCs the way a clinical assessment does.3 That is why ECG Tracker+ calls it a possible PVC. A marker is a cue to look closer and, if it matters to you, to show a clinician. It is not a confirmed finding.
When PVCs form a pattern
Sometimes PVCs repeat in a steady rhythm. When every second beat is a PVC, it is called bigeminy. When every third beat is, it is called trigeminy. ECG Tracker+ marks these patterns as possible bigeminy or possible trigeminy when they continue for at least four cycles in a row.
What one strip cannot tell you
A 30-second recording is a tiny sample of your day. One PVC on a strip says nothing about how often they happen. When clinicians want to know that, they use a Holter or patch monitor that records for a day or more. A burden above about 10% of all beats is where they begin to consider effects on the heart muscle.4 No 30-second strip can measure that.
Call emergency services if extra beats come with chest pain, fainting, dizziness or shortness of breath.2 See a clinician if extra beats keep happening, get worse or worry you.
Frequently asked questions
Can an Apple Watch ECG show a PVC?
Yes, a PVC often shows up on the waveform even when the result says Sinus Rhythm. Apple's ECG app does not label PVCs. ECG Tracker+ marks possible PVCs on your Apple Watch recordings for review.
Is one PVC on my ECG dangerous?
A single PVC is very common and usually harmless. What matters to a clinician is how often they happen, whether you have symptoms and the health of your heart, which one strip cannot show.
What is the difference between a PVC and a PAC?
Both are early beats. A PVC starts in the lower chambers and usually looks wide and different. A PAC starts in the upper chambers and usually has a narrow QRS that looks like the beats around it.
Why does ECG Tracker+ say possible PVC?
A single-lead recording cannot always show where a beat started, and noise can resemble an early beat. The marker tells you where to look. A clinician confirms what it is.
