The Story of the AV Block Family

Atrioventricular block (AV block) is a type of heart block where the conduction between the atria and ventricles of the heart is impaired and this is their story.

Wife = P Wave     Husband = QRS Complex    Pacer = Counselling 


Normal Sinus Rhythm

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

[PR Interval is less than 0.2 seconds (One large block on the EKG paper), there is one P wave per QRS complex, and the rhythm is regular.]

1st Degree AV Block

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

[Impulse is held at AV node, and PR Interval is greater than 0.2 seconds, or one large box on the EKG paper.]

2nd Degree Block, Type 1 ("Wenckebach")

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

Note: Husband (QRS) must come home at least 2 nights in a row to see this pattern.

[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 restart.]

2nd Degree Block, Type 2

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

Note: This is usually more serious than Type I, and will sometimes require counselling (pacing).

[PR and R to R intervals will remain consistent, but there will be "missing" QRS complexes.]

3rd Degree AV Block

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

Note: This frequently requires Counselling  in the form of a temporary or permanent pacer.

[Atrial depolarisation will continue with P waves in a "ventricular standstill" while the ventricles (QRS) are depolarising in an idioventricular rhythm - both will be regular, but will be uncoordinated.]