What is the management of Lown-Ganong-Levine (LGL) syndrome?

Lown-Ganong-Levine Syndrome: Definition and Management

What is Lown-Ganong-Levine Syndrome?

Lown-Ganong-Levine (LGL) syndrome is a rare pre-excitation disorder characterized by a short PR interval (<0.12 seconds), normal QRS complex, and paroxysmal supraventricular tachyarrhythmias. 1, 2, 3

Pathophysiology

The underlying mechanism involves:

• An accessory pathway (James fibers) connecting the atria directly to the AV node or His bundle, bypassing normal AV nodal delay 2
• Alternatively, enhanced atrioventricular nodal conduction (EAVNC) through a fast pathway to the AV node 2
• This results in shortened AH conduction intervals and enhanced AV conduction properties 4

Clinical Presentation and Arrhythmia Spectrum

LGL syndrome presents with a broader spectrum of arrhythmias than traditionally recognized:

• Paroxysmal supraventricular tachycardia (50% of cases) 4
• Atrial fibrillation (17% of cases) 4
• Ventricular tachycardia (33% of cases) - a critical finding indicating that symptomatic arrhythmias require specific diagnosis 4
• Reciprocating tachycardia with significantly shorter cycle lengths compared to normal controls 4

A key pitfall: LGL syndrome can produce ventricular tachycardia, not just supraventricular arrhythmias, making electrophysiologic diagnosis essential. 4

Management Approach

Initial Assessment and Diagnosis

Electrophysiologic study is the gold standard for diagnosis and should be performed in all symptomatic patients to characterize the specific arrhythmia mechanism. 2, 4

Key diagnostic findings include:

• Unusually short AH conduction interval with normal HV interval 2
• Shorter AV node refractory periods compared to normal controls 4
• Enhanced AV conduction present in 58% of LGL patients 4
• During atrial fibrillation, shortest R-R intervals are significantly shorter than controls (254 ± 42 msec vs 325 ± 64 msec) 4

Pharmacological Management

Beta-blockers are the first-line preventative therapy to reduce the risk of tachyarrhythmias in LGL syndrome. 1

Alternative medical options based on clinical context:

• Digoxin can be used effectively, particularly in pregnancy, with good outcomes 3
• Medical therapy should be initiated promptly when diagnosis is established 1, 3

Definitive Treatment

Catheter ablation of the accessory pathway or AV nodal region is the definitive treatment option. 2

Ablation results in:

• Normalized AH interval 2
• Restoration of decremental conduction properties 2
• Elimination of the arrhythmia substrate 2

Monitoring and Follow-up

All patients require outpatient cardiac monitoring and cardiology follow-up to assess the need for electrophysiology study, even if initially asymptomatic. 1

This is critical because:

• LGL syndrome can be discovered incidentally in patients without prior arrhythmia history 1
• The syndrome permits development of more rapid heart rates during arrhythmias compared to normal individuals 4
• Specific arrhythmia diagnosis is mandatory given the spectrum includes ventricular tachycardia 4

Special Populations

In pregnancy, LGL syndrome can be safely managed medically with digoxin, with hospitalization during acute episodes and good maternal-fetal outcomes. 3

The syndrome most commonly affects young to middle-aged women and can be controlled medically throughout pregnancy 3

Critical Clinical Pearls

• Do not assume all arrhythmias in LGL are supraventricular; ventricular tachycardia occurs in one-third of cases 4
• Enhanced AV conduction characteristics allow faster arrhythmia rates than in normal controls, increasing hemodynamic compromise risk 4
• The presence of LGL can coexist with other cardiac pathology (such as hypertrophic cardiomyopathy), requiring comprehensive evaluation 5
• Electrophysiologic study findings may show dual AV nodal pathways with intranodal reentry as the mechanism 5