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Lown-Ganong-Levine (LGL) Syndrome - ECG

Lown Ganong Levine (LGL) syndrome, Short PQ syndrome, Clerc Levy Cristesco (CLC) syndrome

Accessory Pathways
Lown-Ganong-Levine (LGL) Syndrome
LGL Syndrome and Shortened PQ Interval
Accelerated AV Conduction and Shortened PQ Interval
ECG and LGL Syndrome

12-lead ECG

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Accessory Pathways

Physiologically, the atria are electrically isolated from the ventricles

The only electrical connection is the AV junction
If the AV junction is disrupted, a third-degree AV block occurs (electrical isolation of the atria from the ventricles)

0.5% of the population has an additional accessory pathway besides the AV junction

Thus, the atria and ventricles are electrically connected via two pathways:

AV junction
Accessory pathway

10% of patients with an accessory pathway have an additional secondary accessory pathway

which is often inactive

Based on location, there are three main accessory pathways:

Kent bundle

Connects the atria and ventricles
(Atrio-Ventricular bypass)
Creates WPW syndrome

James bundle

Connects the atria to the His bundle
(Atrio-Hisian bypass)
Creates LGL syndrome

Mahaim bundle

Connects the AV junction to the ventricles
(Nodo-Ventricular bypass)
Creates Mahaim syndrome

Lown-Ganong-Levine (LGL) Syndrome

LGL syndrome, Atrio-Hisian bypass, James bundle

James Bundle

Connects the atria to the His bundle (Atrio-Hisian bypass)
Does not slow down impulse conduction like the AV node

The James bundle has non-decremental conduction (without slowing)
The AV junction has decremental conduction (with slowing)

The PQ interval is shortened (<0.12s)

Because the impulse reaches the ventricles without slowing (bypasses the AV node)

LGL Syndrome and Shortened PQ Interval

LGL syndrome, decremental (AV node), non-decremental (James bundle) conduction

ECG Short PR interval, LGL syndrome, decremental, non-decremental conduction

James Bundle

Connects the atria to the His bundle, bypassing the AV node
(Atrio-Hisian bypass)

The PQ interval is shortened (<0.12s)

Because the impulse reaches the ventricles without slowing (bypasses the AV node)

Narrow QRS complex

The ventricles are activated through the conduction system (as in sinus rhythm)

May lead to Atrioventricular Reentry Tachycardia (AVRT)
The same ECG pattern can be seen in Accelerated Junctional Conduction

Accelerated AV Conduction and Shortened PQ Interval

Enhanced atrioventricular nodal conduction (EAVNC), nondecremental AV junction conduction

ECG short PR interval, Enhanced atrioventricular nodal conduction (EAVNC), non-decremental AV node conduction

Enhanced atrioventricular nodal conduction (EAVNC)
AV junction has non-decremental conduction

Conduction without slowing
The ventricles are thus activated earlier

On ECG there is also a shortened PQ interval (<0.12s)
Patient does not have an accessory pathway: James bundle
Atrioventricular reentry tachycardia cannot occur (AVRT)
LGL syndrome and Accelerated AV conduction both create a shortened PQ interval (<0.12s)

Approximately 30% of patients with a shortened PQ interval have accelerated AV conduction
For differential diagnosis, electrophysiological examination is used

ECG and LGL Syndrome

ECG Short PR interval, LGL syndrome, Enhanced atrioventricular nodal conduction

Shortened PQ interval (< 0.12s)
Narrow QRS complexes (< 0.12s)
Sometimes the shortened PQ interval is evaluated as follows:
Accelerated AV conduction:

Shortened PQ interval + Normal QRS complex

LGL syndrome:

Shortened PQ interval + Normal QRS complex + Frequent AVRT

Atria and ventricles are connected via 2 pathways
therefore AV reentry tachycardia (AVRT) can occur

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers

Home /

Lown-Ganong-Levine (LGL) Syndrome - ECG

Lown Ganong Levine (LGL) syndrome, Short PQ syndrome, Clerc Levy Cristesco (CLC) syndrome

Accessory Pathways
Lown-Ganong-Levine (LGL) Syndrome
LGL Syndrome and Shortened PQ Interval
Accelerated AV Conduction and Shortened PQ Interval
ECG and LGL Syndrome

12-lead ECG

Smartwatch ECG

Have a doctor’s or smartwatch ECG?

Upload your 12-lead, smartwatch or smart device ECG.
Get a physician’s report within 24 hours.

Get my ECG reviewed →

Reviewed by a physician · Your questions answered · Not AI

Accessory Pathways

Physiologically, the atria are electrically isolated from the ventricles

The only electrical connection is the AV junction
If the AV junction is disrupted, a third-degree AV block occurs (electrical isolation of the atria from the ventricles)

0.5% of the population has an additional accessory pathway besides the AV junction

Thus, the atria and ventricles are electrically connected via two pathways:

AV junction
Accessory pathway

10% of patients with an accessory pathway have an additional secondary accessory pathway

which is often inactive

Based on location, there are three main accessory pathways:

Kent bundle

Connects the atria and ventricles
(Atrio-Ventricular bypass)
Creates WPW syndrome

James bundle

Connects the atria to the His bundle
(Atrio-Hisian bypass)
Creates LGL syndrome

Mahaim bundle

Connects the AV junction to the ventricles
(Nodo-Ventricular bypass)
Creates Mahaim syndrome

Lown-Ganong-Levine (LGL) Syndrome

James Bundle

Connects the atria to the His bundle (Atrio-Hisian bypass)
Does not slow down impulse conduction like the AV node

The James bundle has non-decremental conduction (without slowing)
The AV junction has decremental conduction (with slowing)

The PQ interval is shortened (<0.12s)

Because the impulse reaches the ventricles without slowing (bypasses the AV node)

LGL Syndrome and Shortened PQ Interval

James Bundle

Connects the atria to the His bundle, bypassing the AV node
(Atrio-Hisian bypass)

The PQ interval is shortened (<0.12s)

Because the impulse reaches the ventricles without slowing (bypasses the AV node)

Narrow QRS complex

The ventricles are activated through the conduction system (as in sinus rhythm)

May lead to Atrioventricular Reentry Tachycardia (AVRT)
The same ECG pattern can be seen in Accelerated Junctional Conduction

Accelerated AV Conduction and Shortened PQ Interval

Enhanced atrioventricular nodal conduction (EAVNC)
AV junction has non-decremental conduction

Conduction without slowing
The ventricles are thus activated earlier

On ECG there is also a shortened PQ interval (<0.12s)
Patient does not have an accessory pathway: James bundle
Atrioventricular reentry tachycardia cannot occur (AVRT)

LGL syndrome and Accelerated AV conduction both create a shortened PQ interval (<0.12s)

Approximately 30% of patients with a shortened PQ interval have accelerated AV conduction
For differential diagnosis, electrophysiological examination is used

ECG and LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complexes (< 0.12s)
Sometimes the shortened PQ interval is evaluated as follows:
Accelerated AV conduction:

Shortened PQ interval + Normal QRS complex

LGL syndrome:

Shortened PQ interval + Normal QRS complex + Frequent AVRT

Atria and ventricles are connected via 2 pathways
therefore AV reentry tachycardia (AVRT) can occur

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

LGL Syndrome

Shortened PQ interval (< 0.12s)
Narrow QRS complex (< 0.12s)
It may also be due to accelerated AV conduction

Differential diagnosis is performed using electrophysiological examination

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers