Lown–Ganong–Levine syndrome

Overview

Lown–Ganong–Levine syndrome (LGL syndrome) is a rare heart rhythm disorder that falls under the category of pre-excitation syndromes. It is characterized by episodes of supraventricular tachycardia (SVT), a rapid heart rate originating above the ventricles, in the absence of the delta wave typically seen in other pre-excitation conditions like Wolff–Parkinson–White (WPW) syndrome. LGL syndrome involves an abnormally short PR interval on an electrocardiogram (ECG), indicating rapid conduction of electrical impulses from the atria to the ventricles.

Causes

The exact anatomical and electrophysiological mechanism of LGL syndrome remains a topic of debate, but the most widely proposed causes include:

• James fibers – accessory pathways that bypass the normal AV node delay and connect the atria directly to the bundle of His

• Enhanced AV nodal conduction – where the AV node itself conducts impulses unusually fast without the presence of an accessory pathway

LGL syndrome is considered a congenital condition, though it may go undetected until symptoms appear later in life. It is not usually inherited in a Mendelian pattern, and genetic causes have not been clearly established.

Symptoms

Symptoms of Lown–Ganong–Levine syndrome result from episodes of rapid heart rate and can vary in frequency and severity. Common symptoms include:

• Palpitations – awareness of rapid or irregular heartbeat

• Dizziness or lightheadedness

• Shortness of breath

• Chest discomfort

• Fatigue

• Fainting (syncope) – in severe or prolonged cases

Some individuals with LGL syndrome may remain asymptomatic and only discover the condition incidentally during an ECG for another reason.

Diagnosis

Diagnosis of Lown–Ganong–Levine syndrome is based on clinical evaluation, ECG findings, and exclusion of other arrhythmia syndromes. Key diagnostic criteria include:

• Short PR interval – typically less than 120 milliseconds

• Normal QRS complex – without a delta wave, differentiating it from WPW syndrome

• Episodes of supraventricular tachycardia (SVT)

Further testing may include:

• Holter monitor – continuous ECG monitoring to capture intermittent arrhythmias

• Electrophysiological study (EPS) – an invasive procedure to map electrical conduction pathways and confirm the presence of accessory fibers

• Exercise stress test – to observe heart rhythm response to physical activity

Treatment

Treatment of LGL syndrome depends on the severity and frequency of arrhythmic episodes. Management options include:

• Observation – for asymptomatic individuals or those with infrequent, mild symptoms

• Medications – such as beta-blockers or calcium channel blockers to control heart rate and prevent episodes of SVT

• Antiarrhythmic drugs – in some cases to suppress arrhythmias

• Catheter ablation – for patients with frequent or disabling symptoms, electrophysiology-guided ablation can target and eliminate the accessory pathway if identified

Emergency care may be required in the event of sustained or hemodynamically unstable tachycardia episodes.

Prognosis

The prognosis for individuals with Lown–Ganong–Levine syndrome is generally good. The condition is not typically associated with an increased risk of sudden cardiac death, unlike some other pre-excitation syndromes. With appropriate treatment, most people can manage symptoms effectively and maintain normal daily activities. In many cases, symptoms may lessen with age. For those undergoing successful catheter ablation, long-term resolution of arrhythmias is common.