Lown–Ganong–Levine syndrome (LGL) is a

pre-excitation syndrome Pre-excitation syndrome is a heart condition in which part of the cardiac ventricles are activated too early. Pre-excitation is caused by an abnormal electrical connection or accessory pathway between or within the cardiac chambers. Pre-excitatio ...

of the heart. Those with LGL syndrome have episodes of abnormal heart racing with a short

PR interval In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization) ...

and normal

QRS complex The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the ri ...

es seen on their electrocardiogram when in a normal

sinus rhythm A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly oriented P waves on the electrocardiogram (ECG). Sinus rhythm is necessary, but not su ...

. LGL syndrome was originally thought to be due to an abnormal electrical connection between the atria and the ventricles, but is now thought to be due to accelerated conduction through the

atrioventricular node The atrioventricular node or AV node electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the lower back section of t ...

in the majority of cases. The syndrome is named after

Bernard Lown Bernard Lown (June 7, 1921February 16, 2021) was a Lithuanian-American cardiologist and inventor. Lown was the original developer of the direct current defibrillator for cardiac resuscitation, and the cardioverter for correcting rapid disordered ...

, William Francis Ganong, Jr., and

Samuel A. Levine Samuel Albert Levine (January 1, 1891 – March 31, 1966) was an American cardiologist. The Levine scale, Levine's sign and Lown–Ganong–Levine syndrome are named after him. The Samuel Albert Levine Cardiac Unit at Brigham and Women's Hospita ...

Signs and symptoms

Pathophysiology

LGL syndrome was originally thought to involve a rapidly conducting

accessory pathway An accessory pathway is an additional electrical connection between two parts of the heart. These pathways can lead to abnormal heart rhythms or arrhythmias associated with symptoms of palpitations. Some pathways may activate a region of ventricula ...

(bundle of James) that connects the atria directly to the

bundle of His The bundle of His (BH) or His bundle (HB) ( "hiss"Medical Terminology for Health Professions, Spiral bound Version'. Cengage Learning; 2016. . pp. 129–.) is a collection of heart muscle cells specialized for electrical conduction. As part of t ...

, bypassing the slowly conducting

. However, the majority of those with LGL in whom electrophysiological studies have been performed do not have any evidence of an accessory pathway or structural abnormality. Whilst in a minority of cases some form of intranodal or paranodal fibers that bypass all or part of the atrioventricular node can be found with subsequent conduction down the normal His-Purkinje system, in most cases the short PR interval is caused by accelerated conduction through the atrioventricular node. LGL syndrome is therefore felt to represent a clinical syndrome with multiple different underlying causes.

Diagnosis

LGL syndrome is diagnosed in a person who has experienced episodes of abnormal heart racing (arrhythmias) who has a

less than or equal to 0.12 second (120 ms) with normal

configuration and duration on their resting

ECG Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the hear ...

. A short PR interval found incidentally on an ECG without episodes of tachycardia is simply a benign ECG variant. LGL can be distinguished from WPW syndrome because the delta waves seen in WPW syndrome are not seen in LGL syndrome. The QRS complex will also be narrow in LGL syndrome, as opposed to WPW, because ventricular conduction is via the His-Purkinje system. Lown–Ganong–Levine syndrome is a clinical diagnosis that came about before the advent of electrophysiology studies. It is important to be aware that not all WPW ECGs have a delta wave; the absence of a delta wave does not conclusively rule out WPW.

Prognosis

Individuals with LGL syndrome do not carry an increased risk of sudden death. The only morbidity associated with the syndrome is the occurrence of paroxysmal episodes of tachycardia which may be of several types, including

sinus tachycardia Sinus tachycardia is an elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the sinoatrial node. In adults, sinus tachycardia is defined as a heart rate greater than 100 beats per minute (bpm). The ...

, atrioventricular nodal re-entrant tachycardia, atrial fibrillation, or

atrial flutter Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart. When it first occurs, it is usually associated with a fast heart rate and is classified as a type of supraventricular tachycardia. Atrial f ...

References

External links