What Premature Junctional Contraction (PJC) Looks Like on Your Watch ECG

PJC ECG
Qaly Heart
Qaly is built by Stanford engineers and cardiologists, including Dr. Marco Perez, a Stanford Associate Professor of Medicine, Stanford Cardiac Electrophysiologist, and Co-PI of the Apple Heart Study.

Key Takeaways

  • Tell-tale signs of a PJC include a missing or inverted P wave, a narrow QRS complex, and a compensatory pause.
  • PJCs can feel similar to other irregular heartbeats like PACs and PVCs, so they're easy to confuse with PACs or PVCs.
  • The occasional PJC is generally not a cause for concern. Frequent PJCs, on the other hand, may be a sign of a more serious heart condition called junctional rhythm.

Got other questions on PJC? See the Qaly guides on PJC:

Introduction

Hello, heart hero. In your quest to identify that irregular heartbeat you just felt, you may have come across the term Premature Junctional Contraction, or Premature Junctional Complex, or PJC. With your trusty watch ECG now in hand, you may be wondering, "What does a PJC look like on my watch ECG?" In this guide, we'll help you see PJCs on your watch ECG. Let's dive in.

What's a PJC?

Before trying to identify a PJC on your ECG, it's helpful to remind yourself what a PJC actually is. (If you're confident in your PJC knowledge, though, skip on ahead to the next section for some visual examples of a PJC ECG).

Your heart has this great structure called the atrioventricular node, or AV node. It's a fancy word for the part of your heart that connects your heart's upper chambers, or atria, with your heart’s lower chambers, or ventricles. Interestingly, the way your heart beats is by producing an electrical signal that squeezes and unsqueezes your heart, which pumps blood to your lungs for oxygen, and then to the rest of your body. Your AV node sits between your atria and your ventricles, which is why it's called the "atrioventricular" node. Neat, huh?

Sometimes, your heartbeat starts in this "junction," where it isn't supposed to. This "premature junctional contraction" messes with your heart’s normal rhythm, which may have felt to you like a skipped heartbeat.

So What Does a PJC Look Like on My Watch ECG?

To identify a PJC on your ECG, here are some tell-tale signs to look for:

For visual examples, take a look at some PJCs seen on Qaly members' watch ECGs.

Here's a single PJC caught on a Qaly member's Apple Watch ECG. Notice the inverted or missing P wave in the PJC. Also, notice how narrow the QRS complex is.
Here's a single PJC caught on a Qaly member's Apple Watch ECG. Notice the inverted or missing P wave in the PJC. Also, notice how narrow the QRS complex is.

Here's another PJC caught on a Qaly member's Apple Watch ECG. Notice here that the PJC has no P wave, and as a result, no PR interval. Also, see that long pause after the PJC?
Here's another PJC caught on a Qaly member's Apple Watch ECG. Notice here that the PJC has no P wave, and as a result, no PR interval. Also, see that long pause after the PJC?

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Here are multiple PJCs caught on a Qaly member's Apple Watch ECG. Again, notice those missing or inverted P waves in the PJCs, along with those long pauses after them. Tell-tale signs.
Here are multiple PJCs caught on a Qaly member's Apple Watch ECG. Again, notice those missing or inverted P waves in the PJCs, along with those long pauses after them. Tell-tale signs.

Are PJCs a Cause for Concern?

The occasional PJC is generally not a cause for concern. Frequent PJCs, on the other hand, may be a sign of a more serious heart condition called junctional rhythm. If you're curious, here's what junctional rhythm looks like on your watch ECG.

Also, PJCs are less common than other irregular heartbeats like PACs or PVCs. PJCs can also feel similar to PACs or PVCs, so they're easy to confuse with each other. If you're curious, here's what a PAC looks like on your watch ECG, and here's what a PVC looks like on your watch ECG.

As always, if you show signs of PJCs or any other weird heartbeats, contact your healthcare provider immediately to rule out the presence of harmful underlying conditions.

Conclusion

Well, that just about wraps up our guide on what a PJC looks like on your watch ECG. We hope this could be of some help to you.

If you still need help interpreting your ECGs, don't worry, we understand how scary and confusing it can be to experience irregular heartbeats. That's why we created the Qaly app for you and for the hundreds of millions of people around the world who live with heart palpitations and abnormal heart rhythms. On the Qaly app, human experts will interpret your ECGs within minutes for clarity and peace of mind.

To get started with the Qaly app for free, grab the Qaly app from the App Store or Play Store today. If you have any more questions, or if you need our help in any other way, don't hesitate to reach out to us at support@qaly.co.

As always from the team at Qaly, stay heart healthy ❤️

Wondering if it's a PJC? On the Qaly app, human experts will interpret your ECGs for PJC within minutes. Get started for free today.

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Wondering if it's a PJC? On the Qaly app, human experts will interpret your ECGs for PJC within minutes. Get started for free today.

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