Supraventricular Tachycardia (Non-Sustained) Vs. Atrial Fibrillation on Your Watch ECG

SVT Afib 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 SVT or Afib? See the Qaly guides on SVT and Afib:

Introduction

Life's rhythms are beautiful, and perhaps, none more so than the one our heart dances to. The ECG, or electrocardiogram, captures this rhythm, detailing each beat's tale. In the play of heart rhythms, two characters often steal the limelight – Afib and SVT. In this guide, we’ll simplify these terms and understand the appearance of Afib vs SVT on your watch ECG. Let’s dive in.

What’s Atrial Fibrillation?

Atrial Fibrillation or Afib, in simpler terms, is akin to a jazz ensemble gone rogue. The heart's upper chambers or atria beat chaotically, disrupting the symphony of a regular heartbeat. It's not just the rhythm that's affected. Afib can take a toll on the efficient flow of blood, paving the way for debilitating conditions like stroke or heart failure.

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

On your Apple Watch or Fitbit or Samsung ECG, Afib looks like a seismograph capturing an intense earthquake – erratic and unpredictable. Distinct P waves, which usually depict atrial contractions, are not visible. Instead, you’ll see irregular oscillations known as fibrillatory waves. Here’s more on what Afib looks like on your watch ECG.

Afib read on a Fitbit ECG through the Qaly app.
Afib read on a Fitbit ECG through the Qaly app.


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What’s Supraventricular Tachycardia (SVT)?

In the SVT vs Afib debate, the Supraventricular Tachycardia (SVT) segment serves a different rhythmic story. Imagine a drummer playing a very fast, regular beat – that's SVT. Originating from above the ventricles, the rapid heart rate can escalate up to an overwhelming 150-250 beats per minute, which can sometimes be confused with sinus tachycardia.

SVT read on a Fitbit ECG through the Qaly app.
SVT read on a Fitbit ECG through the Qaly app.

On an ECG, SVT appears as a rapid, regular rhythm, with typically narrow QRS complexes. The drum roll is so quick that the P waves are often difficult to see. Sometimes P waves may be buried in the preceding T waves. 

SVT read on a Samsung Watch ECG through the Qaly app.
SVT read on a Samsung Watch ECG through the Qaly app.

“Non-sustained” SVT lasts less than 30 seconds, whereas “sustained” SVT lasts longer, sometimes even up to several hours. Here’s more on what SVT looks like on your watch ECG.

What’s the Difference Between Afib and SVT?

When tackling the Afib vs SVT question as you read your own ECG, keep an eye out for the distinguishing characteristics of each. Afib is an “irregularly irregular” rhythm, which means that there isn’t always a clear pattern to the irregularity in the rhythm. On the other hand, SVT is typically “regularly irregular.” While both are fast-paced, the inconsistencies of Afib often appear irregular and chaotic, whereas in SVT, the rhythm is regular.

Both rhythms bear different health implications. Afib, if unmanaged, can heighten the risk of stroke and heart failure, while non-sustained SVT, although not usually life-threatening, may lead to palpitations, rapid heartbeat, and bouts of chest discomfort.

Still Not Sure if It’s Supraventricular Tachycardia (Non-Sustained) or Atrial Fibrillation on Your ECG?

Differentiating between SVT vs Afib on your watch ECG can be tricky. If you’re still looking for help interpreting your ECG further, 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 Afib or SVT? On the Qaly app, human experts will interpret your ECGs for Afib and SVT within minutes. Get started for free today.

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

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