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The AV Block Family

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Atrioventricular block (AV Block ) is an interruption of the electrical activity between the atria and the ventricle of the heart. The effect may be total, partial or result in a delay of conduction. The severity of the AV block is usually defined as; first, second or third-degree block and this is the story of "The AV Block Family" which aims to help in differentiating them.
AV Block Family
ECG Components

Normal Sinus Rhythm

The wife (P wave) waits at home for the husband (QRS complex). The husband (QRS complex) comes home on time every night.

NOTE: PR interval is less than 0.2 seconds (one large block on the ECG), there is one P wave per QRS complex, and the rhythm is regular.
Normal Sinus Rhythm

First Degree AV Block

The wife (P wave) is waiting at home. The husband (QRS complex) comes home late every night, but he always comes home, and it is the same every night.

NOTE: The impulse is delayed at the AV node, and PR interval is greater than 0.2 seconds (more than one large on the ECG).
First Degree AV Block

Second Degree AV Block, Type 1 (Wenckeback)

The wife (P wave) is waiting at home. The husband (QRS complex) come home later and later every night until one night he doesn't come home at all.

Husband (QRS complex) must come home at least two nights in a row to see this pattern.

NOTE: PR interval will become greater and greater until there will be a dropped QRS complex and there are two consecutive P waves, after which the pattern will reoccur.
Wenckebach

Second Degree AV Block, Type 2

The wife (P wave) is waiting at home. Sometimes the husband (QRS complex) comes home, sometimes he doesn't. When he does come home, it is always at the same time.

This is usually more serious than Type 1 (Wenckeback), and will sometimes require counselling (pacing).

NOTE: PR and R to R intervals will remain constant, but there will be absent QRS complexes.

Second-degree AV Block 2:1

2:1 AV Block

Second-degree AV Block 3:1

3:1 AV Block

Third Degree AV Block

Wife (P wave) is no longer waiting at home. She and her husband (QRS complex) are now on separate schedules, have no relationship to one another, and are no longer talking. Each spouse has a regular, individual schedule.

This frequently requires counselling (pacing (either temporarily or permanently)).

NOTE: Atrial depolarisation will continue with P waves in a ventricular standstill while the ventricles (QRS complex) are depolarising in an idioventricular rhythm. Both will be regular, but they will be uncoordinated.
Third-degree (complete) AV Block


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