What Junctional Rhythm Looks Like on Your Watch ECG

What Is Junctional Rhythm?

Junctional rhythm (JR) is a type of irregular heartbeat. A normal heartbeat relies on electrical activation by signals originating from the sinoatrial (SA) node, located in the heart's upper-right-hand chamber (right atrium). However, in junctional rhythm, the electrical signals originate from the atrioventricular (AV) node or the His bundle, instead. This phenomenon typically results in a slower rhythm or heartbeat. However, it can sometimes be faster and is then referred to as an accelerated junctional rhythm. A number of junctional rhythms exist:

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• Junctional bradycardia: heart rate below 40 beats per minute 
• Junctional escape rhythm: heart rate of 40 to 60 beats per minute 
• Accelerated junctional rhythm: heart rate of 60 to 100 beats per minute
• Junctional tachycardia: heart rate above 100 beats per minute

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Junctional rhythm is common among people with a sinus node dysfunction (SND), people with sick sinus syndrome, and young children and athletes with increased vagal nerve activity. It’s documented equally in women and men.

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Can Your Watch ECG Detect It?

While smartwatch ECGs can capture a 1-lead ECG during junctional rhythm, the smartwatch ECG software will not automatically tell you if you have a junctional rhythm ECG. ECGs found in smartwatches like the Apple Watch and Samsung watch are used for the basic monitoring of the heart. This includes checking for irregular heartbeats, known as arrhythmias, or observing the effects of exercise, but is limited to only a few arrhythmias. It’s important to consult your physician if you notice any symptoms typical of junctional rhythm, even if no abnormalities are detected.

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How To Spot Junctional Rhythm in Your ECG

The characteristic feature of a junctional rhythm ECG is that QRS complexes are observed without a preceding P wave. There may or may not be P waves that come after the QRS complexes or that are independent of or dissociated from the QRS complexes. The QRS complexes are often narrow, and the rhythm slow (less than 60bpm). 

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Any Cause for Concern?

A junctional rhythm ECG is often no cause for concern, especially when presenting in healthy individuals showing no accompanying symptoms. However, it can be an indicator of an underlying condition. Conditions such as sinus node dysfunction (SND), which is present in 1 in 600 cardiac patients above the age of 65 in the US, typically result in junctional rhythm. Other possible causes for junctional rhythm ECGs include:

• Hypokalemia or low potassium
• Cardiac surgery
• Digoxin toxicity
• Irritable or electrically over-active tissue near the AV junction
• Acute inflammatory processes like rheumatic fever and Lyme disease
• Drugs like beta-blockers and calcium blockers that cause bradycardia

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Your medical practitioner should identify other conditions and medications causing junctional rhythm before proceeding with appropriate treatment, especially if you notice accompanying symptoms.

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What Are Common Symptoms and Treatment Options?

There can be a large variety of symptoms that present due to a junctional rhythm. This is because a junctional rhythm is usually a result of multiple possible underlying conditions. Symptoms caused by junctional rhythm itself can be due to the reduced heart rate (less than 60bpm) or loss of AV synchrony. These generalized symptoms include:

• Light-headedness
• Heart palpitations 
• Chest heaviness 
• Neck tightness or pounding 
• Shortness of breath 
• Dizziness 
• Fatigue and weakness. 

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If the underlying cause is heart failure exacerbation, the patient may also experience wheezing and lower extremity edema (swelling). Another variation of symptoms can occur in patients with rheumatic fever.

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As junctional rhythm can be due to various causes, treatment depends on the underlying condition that the patient has. In some cases, no treatment is required when the patient is otherwise healthy and asymptomatic, or if the patient has an underlying sinus node dysfunction. This is because it’s sometimes a natural response to increased vagal nerve activity often found in athletes and young children. It can also be a response to the SA node's inability to regulate the heartbeat, in which case it’s necessary for the AV node to take over.

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Still Not Sure How to Spot Junctional Rhythm on Your Watch ECG?

Using smartwatch apps to monitor your health can help you identify arrhythmias like junctional rhythm early on. If you’re concerned about the ECG tracings from your smartwatch, get them reviewed by experts within minutes through the QALY app on iOS and Android. As always, if you show signs of a potential junctional rhythm, contact your healthcare provider as soon as possible to rule out the presence of harmful underlying conditions.

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