What P Waves Look Like on Your Watch ECG

P Wave 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

  • Your ECG's P Wave shows you how long it takes for your heart's upper chambers, or atria, to squeeze during each heartbeat.
  • Abnormal P Waves often indicate that either there's an abnormality in your atria, or that your heartbeats start from a place in your heart other than your heart's sinus node.
  • Missing P Waves can also be a sign of abnormal heart rhythms, like Atrial Fibrillation.

Got other questions on your PQRST Intervals? See the complete set of Qaly guides on PQRST Intervals:

Introduction

Hello, heart hero. In your quest to identify that irregular heart rhythm you just felt, you may have come across the term P Wave. With your trusty watch ECG now in hand, you may be wondering, "What does a P Wave look like on my watch ECG?" Or you might be thinking, "What's does an abnormal P Wave on my watch ECG mean for my heart health?" In this guide, we'll help answer these questions. Let's dive in.

What's an Electrocardiogram?

Before diving into P Waves, it's important to understand exactly what an electrocardiogram, or ECG is. (If you're confident in your understanding of an ECG and how it relates to P Waves, though, skip on ahead to the next section for some visual examples of P Waves).

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.

As that electrical signal flows through your heart, your ECG on your watch sees it, and shows it to you as those awesome-looking waves you know as an ECG. Every time your heart completes one heartbeat, it completes one full cycle of that electrical signal flowing through your heart. And as that electrical signal flows through your heart, it produces different waves on your ECG that capture the squeezing and relaxing of your heart with each heartbeat, which are represented on your ECG as PQRST waves.


So What's a P Wave?

The first wave in your ECG's PQRST cycle during each of your heartbeats is the P Wave. Once your heart's electrical signal starts at the beginning of a heartbeat, it causes your heart's upper chambers, or atria, to squeeze. This squeezes the blood coming into your heart's atria down into your heart's lower chambers, or ventricles. The P Wave on your ECG captures this first squeeze in your heartbeats.

In your P Wave, your heart's electrical signal, seen here in gold, spreads through your heart's upper chambers and squeezes them.
In your P Wave, your heart's electrical signal, seen here in gold, spreads through your heart's upper chambers and squeezes them.

On each heartbeat in your ECG, the P Wave is the first small wave at the beginning of each cycle. It's typically a small, positive wave that comes right before the large QRS complex, which represents your heart's electrical signal spreading through your heart's lower chambers, or ventricles. The ability to identify P waves — and your ECG’s PR interval — is important in interpreting your ECG for abnormal heart rhythms.

Your PR Interval, in blue.
Your PR Interval, in blue.

What Do P Waves Look Like on My ECG?

P Waves can provide important information about your heart's atrial activity. Regular P Waves that have the same shape across your heart rhythm usually indicate Normal Sinus Rhythm, where your heart's electrical signal originates correctly from your heart's natural "pacemaker," or sinus node.

Here's Sinus Rhythm seen on a Qaly member's Apple Watch ECG. Notice the upright P Waves that have the same shape throughout the heart rhythm, a clue that this is a Sinus Rhythm ECG.
Here's Sinus Rhythm seen on a Qaly member's Apple Watch ECG. Notice the upright P Waves that have the same shape throughout the heart rhythm, a clue that this is a Sinus Rhythm ECG.


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What Are Common P Wave Abnormalities?

On the other hand, abnormalities in your P Waves can hint at specific abnormal heart rhythms. On one hand, your heart's electrical signal might start normally in your sinus node, but it has to go through abnormal atria to pass through your heart. In this case, a weirdly large P Wave might be a sign of your atria being abnormally large, called "atrial enlargement." On the other hand, P Waves that look upside-down, or "inverted," can suggest that your heart's electrical signal starts from a different part of your heart than your sinus node, such as your atria or your AV node. If your heartbeat starts from these or other places in your heart that aren't your sinus node, the abnormality in your P Wave is a clue for a possible heart rhythm abnormality like ectopic atrial rhythm on your watch ECG or junctional rhythm on your watch ECG. Lastly, missing P Waves could also suggest Atrial Fibrillation on your watch ECG. This is what makes understanding your ECGs' P Waves so important when you're self-managing your heart health.

Here's Junctional Rhythm seen on a Qaly member's Apple Watch ECG. Notice the inverted P Waves and narrow QRS Complexes, signs of a Junctional Rhythm ECG.
Here's Junctional Rhythm seen on a Qaly member's Apple Watch ECG. Notice the inverted P Waves and narrow QRS Complexes, signs of a Junctional Rhythm ECG.

Here's Atrial Fibrillation seen on a Qaly member's Fitbit Watch ECG. Notice the missing P Waves and "irregularly irregular" rhythm, tell-tale signs of an Afib ECG.
Here's Atrial Fibrillation seen on a Qaly member's Fitbit Watch ECG. Notice the missing P Waves and "irregularly irregular" rhythm, tell-tale signs of an Afib ECG.

Conclusion

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

If you still need help identifying your ECGs' P Waves, 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 identify your ECGs' P Waves within minutes for clarity and peace of mind.

To get started with the Qaly app, 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 ❤️

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Have trouble identifying your P Wave? On the Qaly app, human experts will identify your ECGs' P Wave within minutes. Get started today.

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