science

Lown–Ganong–Levine syndrome

Lown–Ganong–Levine syndrome is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lown–Ganong–Levine syndrome rather than just read about it. In short: 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 and normal QRS complexes seen on their electrocardiogram when in a normal sinus rhythm.

Key takeaways

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Reproduce the core statement of Lown–Ganong–Levine syndrome from memory before moving on to harder problems.

Reference excerpt

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 and normal QRS complexes seen on their electrocardiogram when in a normal 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 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 (bundle of James) that connects the atria directly to the bundle of His, bypassing the slowly conducting atrioventricular node. 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 less than or equal to 0.12 second (120 ms) with normal QRS complex configuration and duration on their resting ECG. . LGL can be distinguished from Wolff–Parkinson–White syndrome (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, atrioventricular nodal re-entrant tachycardia, atrial fibrillation, or atrial flutter.

See also Cardiac electrophysiology Electrocardiogram Electrophysiology study Premature ventricular contraction Wolff–Parkinson–White syndrome

References

External links

Worked examples

Example 1 — a first encounter with Lown–Ganong–Levine syndrome

Start with the simplest possible case. Write down what Lown–Ganong–Levine syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lown–Ganong–Levine syndrome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lown–Ganong–Levine syndrome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lown–Ganong–Levine syndrome

In research: Lown–Ganong–Levine syndrome appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lown–Ganong–Levine syndrome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lown–Ganong–Levine syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cardiac arrhythmia, Rare syndromes, Syndromes affecting the heart, so understanding it makes those chapters shorter.
In everyday life: Look for Lown–Ganong–Levine syndrome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lown–Ganong–Levine syndrome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lown–Ganong–Levine syndrome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lown–Ganong–Levine syndrome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lown–Ganong–Levine syndrome in simple terms?

Why does Lown–Ganong–Levine syndrome matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lown–Ganong–Levine syndrome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lown–Ganong–Levine syndrome.