Sinus Arrhythmia Vs. Premature Atrial Contraction (Multiple) on Your Watch ECG

Sinus Arrhythmia PAC 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

Got other questions on Sinus Arrhythmia or PAC? See the Qaly guides on Sinus Arrhythmia and PAC:

Introduction

In an era where we can track our heart health from our wrists, it's crucial to understand the language of our hearts. Electrocardiograms (ECGs) captured by smartwatches are a powerful tool for monitoring heart rhythms, and today we're exploring two rhythms: sinus arrhythmia and premature atrial contractions (PACs). Understanding the difference between these two — sinus arrhythmia vs PAC — can provide vital insights into your heart health.

What’s Sinus Arrhythmia?

Sinus arrhythmia is a type of normal variation in heart rhythm that's often more pronounced in young, healthy people. It’s characterized by a heart rate that increases when you breathe in and decreases when you breathe out.

Sinus Arrhythmia read on a Fitbit ECG through the Qaly app.
Sinus Arrhythmia read on a Fitbit ECG through the Qaly app.

On an ECG, sinus arrhythmia appears as a regular variation in the “RR interval,” which is the time between each heartbeat, so long as it is accompanied by uniform and upright P waves. Here’s more on what sinus arrhythmia looks like on your watch ECG.

Sinus Arrhythmia read on a Samsung Watch ECG through the Qaly app.
Sinus Arrhythmia read on a Samsung Watch ECG through the Qaly app.

What’s a Premature Atrial Contraction (PAC)?

On the other hand, premature atrial contractions are early beats that originate from the atria — the upper chambers of the heart. When multiple PACs occur, they appear as irregular early beats on an ECG. While occasional PACs are usually benign, frequent PACs can sometimes indicate underlying heart disease or trigger other arrhythmias. 

PACs read on a Kardia ECG through the Qaly app.
PACs read on a Kardia ECG through the Qaly app.


Get your ECG checked by certified experts within minutes on the Qaly app.

Try Qaly for Free
App Store - Download Qaly | ECG Reader
Try Qaly for Free
Google Play - Download Qaly | ECG Reader
Try Qaly for Free
3 days free, cancel any time
QALY app - ecg reviews, ecg reader, ecg interpretations, review your ecg

On an ECG, PACs are identified by an early and often different-looking P wave, followed by a QRS complex and a compensatory pause. Here’s more on what a PAC looks like on your watch ECG.

PACs read on a Samsung ECG through the Qaly app.
PACs read on a Samsung ECG through the Qaly app.

What’s the Difference Between Sinus Arrhythmia and PAC?

When comparing PAC vs sinus arrhythmia, a key difference lies in the rhythm's regularity. Sinus arrhythmia maintains a consistent pattern despite slight variations, while multiple PACs present as irregular, early beats that are followed by compensatory pauses, and that disrupt the rhythm.

Furthermore, while sinus arrhythmia is a normal physiological phenomenon often associated with breathing, multiple PACs may be indicative of other underlying conditions. Hence, while a single PAC is usually not cause for concern, frequent PACs should prompt further evaluation.

Monitoring these rhythms on your smartwatch ECG can provide a snapshot of your heart's health. However, it's always important to discuss any concerns or findings with your healthcare provider. Stay informed, stay proactive, and stay heart healthy!

Still Not Sure if It’s Sinus Arrhythmia or PAC (Multiple) on Your ECG?

Differentiating between Sinus Arrhythmia vs PAC on your ECG isn’t always easy. If you’re still looking for help interpreting your ECG, check out the Qaly app on App Store or Play Store. On Qaly, human experts will interpret your ECGs within minutes, day or night. Try out the Qaly app for free today!

Wondering if it's Sinus Arrhythmia or PACs? On the Qaly app, human experts will interpret your ECGs for Sinus Arrhythmia and PACs within minutes. Get started for free today.

Try free, cancel any time
Try Qaly for Free
App Store - Download Qaly | ECG Reader
Try Qaly for Free
Google Play - Download Qaly | ECG Reader
Try Qaly for Free
3 days free, cancel any time
QALY app - ecg reviews, ecg reader, ecg interpretations, review your ecg

Get 3 days of unlimited ECG reviews for free -->

Get 3 days of unlimited ECG reviews for free -->

Wondering if it's Sinus Arrhythmia or PACs? On the Qaly app, human experts will interpret your ECGs for Sinus Arrhythmia and PACs within minutes. Get started for free today.

Try Qaly for Free