Lown‑Ganong‑Levine (LGL) syndrome
Overview
Lown‑Ganong‑Levine (LGL) is an uncommon pre‑excitation/conduction phenotype characterised on the surface ECG by a very short PR interval, narrow QRS complexes and absence of a delta wave.
It is associated with paroxysmal supraventricular tachycardia (SVT) but - unlike Wolff-Parkinson-White (WPW) - does not show clear ventricular pre‑excitation on the ECG.
The electrophysiological substrate is heterogeneous (enhanced AV nodal conduction, junctional/low‑atrial rhythms, or fast conducting atrioventricular fibres historically termed “James fibres”) and is less well defined than for WPW.
There is no dedicated UK national guideline for LGL; investigation and referral in the emergency setting should follow established syncope and arrhythmia pathways and ED tachyarrhythmia algorithms.
Key ECG features (classical phenotype)
- Very short PR interval: classically < 120 ms (measure from the earliest onset of the P wave to the earliest onset of the QRS).
- Narrow QRS complexes (no QRS prolongation).
- Absence of a delta wave (no slurred initial upstroke of the QRS).
- During symptomatic episodes, SVT is usually a regular, narrow‑complex tachycardia (commonly AVNRT or orthodromic AV re‑entry).
Pathophysiology (concise)
LGL reflects accelerated atrioventricular conduction. Proposed mechanisms include enhanced AV nodal conduction or fast conducting atrioventricular fibres that bypass part of the AV node (historically called James fibres). Unlike the Kent bundles of WPW, these pathways do not produce ventricular pre‑excitation; hence no delta wave is...