Lown–Ganong–Levine syndrome (LGL) is a pre-excitation syndrome of the heart due to abnormal electrical communication between the atria and the ventricles. Once thought to involve an accessory conduction pathway, it is grouped with Wolff–Parkinson–White syndrome as an atrioventricular re-entrant tachycardia (AVRT). Individuals with LGL syndrome have a short PR interval with normal QRS complexes and paroxysms of clinically-significant tachycardia. The syndrome is named after Bernard Lown, William Francis Ganong, Jr., and Samuel A. Levine.
Individuals with a short PR interval found incidentally on EKG were once thought to have LGL syndrome. However, subsequent studies have shown that a short PR interval in the absence of symptomatic tachycardia is simply a benign EKG variant.
Unlike WPW syndrome, the pathophysiology underlying LGL syndrome is poorly understood. The syndrome was once thought to involve an accessory pathway (bundle of James) that connects the atria directly to the bundle of His. However, EP studies have been unable to identify a single accessory pathway or structural abnormality in all individuals with LGL syndrome. Therefore, most consider the disorder to be a clinical syndrome with multiple different underlying causes, all involving some form of intranodal or paranodal fibers that bypass all or part of the atrioventricular (AV) node with subsequent conduction down the normal His-Purkinje system.
LGL syndrome is diagnosed on the basis of the surface EKG in a symptomatic individual with a PR interval less than or equal to 0.12 second (120 ms) with normal QRS complex configuration and duration. It 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 EKG's have a delta wave; the absence of a delta wave does not conclusively rule out WPW.
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, supraventricular tachycardia, atrial fibrillation, atrial flutter, or even ventricular tachycardia.
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