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

‍Got other questions on SVT or Afib? See the Qaly guides on SVT and Afib:

• What SVT Looks Like on Your ECG
• What Afib Looks Like on Your ECG
• ‍How to Read an ECG: Stanford Cardiologist Explains
• ‍The Ultimate Cardiologist's Guide to the Smartwatch ECG

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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.

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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.

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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.

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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.

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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. 

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“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.

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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.

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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 today!