Lown–Ganong–Levine Syndrome
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Lown–Ganong–Levine syndrome (LGL) is a pre-excitation syndrome 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 necessary, but not sufficient, for normal electrical activity within the heart. On the electrocardiogram (ECG), a sinus rhythm ...
. 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 (AV node, or Aschoff-Tawara 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 ...
in the majority of cases. The syndrome is named after Bernard Lown, William Francis Ganong, Jr., and Samuel A. Levine.


Signs and symptoms

In general, patients will be asymptomatic at baseline. During their tachyarrhythmia however, they may report palpitations, shortness of breath, syncope or presyncope. They will have a tachycardia. How well they tolerate their tachyarrhythmia is dictated by their physiologic reserve. A young, well patient may just have palpitations and the tachycardia alone. However, an older patient with pre-existing (discrete) cardiovascular disease may additionally experience hypotension and syncope. Very fast heart rates can be detrimental even in well patients though.


Pathophysiology

LGL syndrome was originally thought to involve a rapidly conducting
accessory pathway In cardiology, an accessory pathway is an additional electrical connection between two parts of the heart. These pathways can lead to abnormal heart rhythms ( arrhythmias) associated with symptoms of palpitations. Some pathways may activate a regi ...
(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 ...
, bypassing the slowly conducting
atrioventricular node The atrioventricular node (AV node, or Aschoff-Tawara 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 ...
. 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
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 ...
less than or equal to 0.12 second (120 ms) with 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 ...
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 through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of ...
. . LGL can be distinguished from
Wolff–Parkinson–White syndrome Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart involving an accessory pathway able to conduct electrical current between the atria and the ventricles, thus byp ...
( WPW) syndrome because the delta waves seen in WPW syndrome are not seen in LGL syndrome. The QRS complex is often normal but can 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 a sinus rhythm of the heart, with an increased rate of electrical discharge from the sinoatrial node, resulting in a tachycardia, a heart rate that is higher than the upper limit of normal (90–100 beats per minute for adu ...
, atrioventricular nodal re-entrant tachycardia,
atrial fibrillation Atrial fibrillation (AF, AFib or A-fib) is an Heart arrhythmia, abnormal heart rhythm (arrhythmia) characterized by fibrillation, rapid and irregular beating of the Atrium (heart), atrial chambers of the heart. It often begins as short periods ...
, 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 (SVT). ...
.


See also

*
Cardiac electrophysiology Cardiac electrophysiology is a branch of cardiology and Basic Science, basic science focusing on the electrical activities of the heart. The term is usually used in clinical context, to describe studies of such phenomena by invasive (intracardiac ...
* Electrocardiogram *
Electrophysiology study A cardiac electrophysiology study (EP test or EP study) is a Invasiveness of surgical procedures, minimally invasive procedure using catheters introduced through a vein or artery to record electrical activity from within the heart. This electric ...
*
Premature ventricular contraction A premature ventricular contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as ...
*
Wolff–Parkinson–White syndrome Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart involving an accessory pathway able to conduct electrical current between the atria and the ventricles, thus byp ...


References


External links

{{DEFAULTSORT:Lown-Ganong-Levine syndrome Cardiac arrhythmia Syndromes affecting the heart Rare syndromes