Atrioventricular Conduction Abnormalities (Heart Block)

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What is Atrioventricular Conduction Abnormalities?

Heart block is a disorder of the electrical conduction system of the heart.

There are three degrees of heart block:

1st degree: There is a delayed conduction between the atria and ventricles, but all beats are conducted;
2nd degree: Some beats from the atria are not conducted to the ventricles;
3rd degree: The atria and the ventricles beat completely independent of each other.

Who gets Atrioventricular Conduction Abnormalities?

First degree heart block is common, but is usually asymptomatic (without obvious signs or symptoms). Higher degrees can be common, particularly in elderly populations.

Predisposing Factors

A previous heart attack (myocardial infarction) is the most common cause of heart block. It may also be caused by degeneration with fibrosis and calcification of the conducting system (Lev's and Lenegre's diseases). Other causative factors include drugs that interfere with conduction, electrolyte disturbances, cardiac surgery, pericarditis, myocarditis, cardiomyopathy and rheumatic heart disease.

Progression

First degree heart block is by itself of no significance, provided it does not progress to second or third degree, but this does not often happen. Most cases of second degree heart block are also asymptomatic, and these patients should be closely observed for potential progression to complete heart block.

In complete heart block no atrial impulses conduct to ventricular contraction. Spontaneous escape rhythms either from the ventricles maintain life in the person, but symptoms such as syncope (brief loss of consciousness) are usually seen.

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