Atrioventricular Blocks

Atrioventricular block is a type of arrhythmia of heart in which there is disturbances in impulse conduction. Atrioventricular blocks are of three types, which are as follow-

1. First degree block.

2. Second degree block.

3. Third degree block.


1. First degree heart block-
First degree heart block is usually asymptomatic and in it there is prolongation of P-R interval more than 0.20 seconds. This type of atrioventricular block is caused by electrolyte imbalance, side effects of digitalis, beta-blockers and sometimes due to acute myocardial infarction.

2. Second degree heart block-
Second degree heart block is of two types-

Mobitz type I.
b) Mobitz type II.

a) Mobitz type I-
Mobitz type I heart block is caused due to side effects of digitalis, beta-blockers, calcium channel blockers and acute inferior wall myocardial infarction. This type of heart block is usually asymptomatic. In it there is continuous slowing of AV conduction until it is totally blocked. There is progressive prolongation of successive P-R intervals until one P wave is blocked or not conducted.

b) Mobitz type II-
It usually occurs after anterior wall myocardial infarction. Patient is symptomatic. In it there is continuous P-R interval

and QRS is often abnormal. There is intermittent failure of atrial impulses to conduct to the ventricles.


3. Third degree heart block-
Third degree heart block is also known as complete heart block or complete AV block. In it there is a constant P-P and R-R intervals but with complete AV dissociation that is the atria and ventricles beat independently. None of the atrial impulses reach the ventricles and atria are activated by one pacemaker and the ventricles by another pacemaker. Complete heart block is caused by Lenegre’s disease, Lev’s disease, myocardial infarction, side effects of digitalis, tumors and infections of conducting system.

Do you know about- Causes of Acute Onset Dyspnoea

Reference taken from- Book- Medicine by Methew and Parveen Aggarwal.

Article Written By Dr.Simran

Doctor, Professional Medical Writer and Moderator

Last updated on 22-07-2016 246 0

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