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

QALY Team
Wenckebach (Second Degree AV Block Type 1) on smartwatch ECG (Apple Watch, Kardia, Samsung, Fitbit)

Key Takeaways

Second-degree type 1 or Wenckebach is characterized by a gradual prolongation of the PR interval over a few heart cycles until an atrial impulse (P-wave) is completely blocked, which manifests on the ECG as a P-wave not followed by a QRS complex.

How to Spot Second Degree AV Block Type 1 (Wenckebach) on Your Watch ECG

In second-degree AV block type 1, the sinus node is healthy and fires right on time, so the P waves come at regular intervals. However, atrial impulses traveling through the AV node take longer and longer to conduct at each subsequent impulse, causing a progressive prolongation of the PR interval until one impulse is completely blocked. As a result, QRS complexes are periodically dropped, resulting in a slowed heart rhythm (bradycardia), with more P waves than QRS complexes on the ECG.

These are the defining characteristics of second-degree AV block type 1:

  • Rhythm: Irregular
  • P wave: Normal
  • P-R interval: Progressively longer until a QRS complex is missed, then cycle repeats
  • QRS: Normal or Narrow

Second Degree AV Block Type 1 (Wenckebach) on smartwatch ECG (Apple Watch, Fitbit, Samsung, Kardia)
Example of Second Degree AV Block Type 1 caught with Apple Watch

Second Degree AV Block Type 1 (Wenckebach) on smartwatch ECG (Apple Watch, Fitbit, Samsung, Kardia)
Example of Second Degree AV Block Type 1 caught with Apple Watch

Common Symptoms of Second Degree AV Block Type 1 (Wenckebach)

Most people with second-degree AV block type 1 do not present any symptoms. Some individuals may occasionally feel:

  • Light-headedness
  • Dizziness
  • Fatigue

More rarely, second-degree AV block type 1 may lead to a sudden and temporary loss of consciousness, also known as syncope, caused by a brief decrease in the oxygen supply to the brain.

Any Cause for Concern?

Second-degree AV block type 1 (Wenckebach) is often a benign condition that does not usually progress to more severe types of heart block. However, in some people, it may cause symptoms or indicate that a person has an underlying medical condition.

As always, if you show signs of a potential second-degree AV block type 1, contact your healthcare provider as soon as possible to rule out the presence of harmful underlying conditions.

Still Not Sure How to Spot Second Degree AV Block Type 1 (Wenckebach) on Your Watch ECG?

Your smartwatch can be your partner in looking after your heart. If you’re concerned about second-degree AV block type 1 (Wenckebach), get your smartwatch ECGs analyzed by experts within minutes on the QALY app: iOS and Android.

Get second opinions of your ECGs by human experts on the QALY app!

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