Atrio-Ventricular Block

2. AV Block

• The delay or failure of the atrioventricular node to conduct impulses.

1st Degree (Partial AV Block)

• Delayed conduction through the AV node

Causes Electrolyte imbalance, drug reactions, degenerative changes in the AV node

ECG Appearance: Longer P-R interval

Treatment Treat the underlying cause

2nd Degree (Partial AV Block)

• Intermittent failure of conduction through the AV node

Mobitz Type I.= prolonged P-R interval

Mobitz Type II.= no prolongation of the P-R interval

Type A: normal QRS length; block is above the bundle of His division (Most commonly seen with Mobitz Type I.)

Type B: longer QRS length; block is below the bundle of His division (Most commonly seen with Mobitz Type II.)

Causes Electrolyte imbalance, drug reactions, degenerative changes in the AV node

ECG Appearance: Some P waves are not followed by QRS complexes

Treatment

Mobitz Type I.: Treat underlying cause if necessary

Mobitz Type II. Treat with atropine etc. or surgical implantation of a pacemaker

3rd Degree (Total AV Block)

• Total failure of AV conduction causing uncoordinated and independent atrial and ventricular depolarisations

Causes Electrolyte disturbances, drug toxicities (e.g. digitalis), acquired nodal diseases, cardiomyopathies, hypothyroidism, endocarditis, Lyme disease etc.

ECG Appearance: Independent regular and fast P waves; independent regular and slow QRS waves

Treatment Treat underlying disease, atropine etc., implantation of a cardiac pacemaker