What Second-Degree AV Block Type 1 (Wenckebach) Looks Like on Your Watch ECG

Key Takeaways

Tell-tale signs of Second-Degree AV Block Type 1 (aka Wenckebach) include normal P Waves and a PR Interval that gets longer and longer, until there's a missing QRS Complex on your ECG.
Wenckebach is almost always harmless, and typically doesn't require treatment.
As always, if you believe you have Wenckebach, discuss it with your healthcare provider to rule out more serious heart conditions like cardiomyopathy that may be causing the Wenckebach.

Tell-tale signs of Second-Degree AV Block Type 1 (aka Wenckebach) include normal P Waves and a PR Interval that gets longer and longer, until there's a missing QRS Complex on your ECG.
Wenckebach is almost always harmless, and typically doesn't require treatment.
As always, if you believe you have Wenckebach, discuss it with your healthcare provider to rule out more serious heart conditions like cardiomyopathy that may be causing the Wenckebach.

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Introduction

Hello, heart hero. In your quest to identify that irregular heart rhythm you just felt, you may have come across the terms Second-Degree Atrioventricular Block Type 1, or Second-Degree AV Block Type 1, Mobitz I, or Wenckebach. Wow, that's a lot of terms for the same abnormal heart rhythm... With your trusty watch ECG now in hand, you may be wondering, "What does Wenckebach look like on my watch ECG?" In this guide, we'll help you see Wenckebach on your watch ECG. Let's dive in.

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What's Wenckebach?

Before trying to identify Wenckebach on your ECG, it's helpful to remind yourself what Wenckebach actually is. (If you're confident in your Second-Degree AV Block Type 1 knowledge, though, skip on ahead to the next section for some visual examples of a Wenckebach ECG).

To start, remember how your heart beats? It produces an electrical signal, which squeezes and unsqueezes your heart, which in turn pumps your blood to your lungs for oxygen and then out to the rest of your body.

Your heart produces that electrical signal from your "sinus node" to generate a normal heartbeat. Then, that electrical signal travels from your heart's upper chambers, or atria, to your heart's lower chambers, or ventricles. To do this, your heart's electrical signal moves through a "gatekeeper" called your atrioventricular node, or AV node. In Wenckebach, your sinus node is healthy and fires on time, so your ECG's P Waves look completely normal. However, your heart's electrical signal incorrectly slows down as it travels through your AV node, taking longer and longer to move through it at each subsequent heartbeat. This causes your PR Interval to get longer and longer on your ECG, until one of your heartbeats' electrical signal is completely blocked from passing through your AV node, resulting in a QRS Complex not appearing on your ECG. After this "dropped" QRS Complex, the cycle repeats. Lastly, note that Second-Degree AV Block Type 1 results in a slowed heart rhythm called Bradycardia, with more P Waves than QRS Complexes on your ECG.

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So What Does Wenckebach Look Like on My Watch ECG?

To identify Wenckebach on your ECG, look for these tell-tale signs:

A normal P Wave.
A PR Interval that gets longer and longer, until there's a missing QRS Complex, after which the cycle repeats.
A narrow or normal QRS Complex, for the QRS Complexes that aren't dropped.

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

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Here's Second-Degree AV Block Type 1 caught on a Qaly member's Apple Watch ECG. Although this is a Wenckebach ECG, the dropped beat is missing, making it hard to identify as Second-Degree AV Block Type 1. This is either because it’s merged with T Waves on the ECG or because it's' a Low Voltage ECG.

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Here's another Wenckebach caught on a Qaly member's Apple Watch ECG. For example, see those T Waves after the missing QRS Complexes, between the 4s mark and the 5s mark, and also between the 16s mark and the 17s mark?

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Here's a third Wenckebach caught on a Qaly member's Apple Watch ECG. Here, too, notice that it's difficult to see the PR Interval before the dropped QRS Complex, making it hard to identify as Second Degree AV Block Type 1. This is either because it’s merged with the subsequent T Waves on the ECG or because it's' a Low Voltage watch ECG, which is a common problem with watch ECGs.

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Is Wenckebach a Cause for Concern?

Second-Degree AV Block Type 1 is almost always harmless, and it usually doesn't require treatment.

That being said, if you believe you have Wenckebach, discuss it with your healthcare provider to rule out more serious heart conditions like cardiomyopathy that may be causing the Wenckebach to occur.

If you're curious to learn about other heart blocks, here's what First-Degree AV Block looks like on your watch ECG, here's what 2:1 AV Block looks like on your watch ECG, here's what Second-Degree AV Block Type 2 looks like on your watch ECG, and here's what Complete Heart Block looks like on your watch ECG.

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Conclusion

Well, that just about wraps up our guide on what Second-Degree AV Block Type 1 (Wenckebach) 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 ❤️