Third Degree or Complete AV Block

Third Degree AV Block or Complete AV Block

Rate	Atrial rate is usually normal; ventricular rate is usually less than 70/bpm. The atrial rate is always faster than the ventricular rate.
P wave	Normal with constant P-P intervals, but not "married" to the QRS complexes.
QRS	May be normal or widened depending on where the escape pacemaker is located in the conduction system
Conduction	Atrial and ventricular activities are unrelated due to the complete blocking of the atrial impulses to the ventricles.
Rhythm	Irregular

Complete block of the atrial impulses occurs at the A-V junction, common bundle or bilateral bundle branches.

Another pacemaker distal to the block takes over in order to activate the ventricles or ventricular standstill will occur.

May be caused by:

digitalis toxicity

acute infection

MI and

degeneration of the conductive tissue.

Treatment modalities include:

external pacing and atropine for acute, symptomatic episodes and

permanent pacing for chronic complete heart block.

Instant Feedback:

In a third degree heart block, the P waves are "married" to the QRS complexes.

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