What is First Degree AV Block

It is the prolongation of PR >0.22 sec. Every atrial depolarisation is followed by conduction to
the ventricles, but with delay.

Causes of First Degree AV Block

• Normally found in athletes (due to increased vagal tone).
• Drugs (digitalis toxicity).
• Acute myocardial infarction (common in inferior MI).
• Acute rheumatic carditis.
• In elderly (atherosclerosis).
• Hyperkalaemia.


Usually asymptomatic.

ECG findings

• PR interval—prolonged >0.22 second (normal 0.12–0.20 second).
• QRS—normal.
• Rhythm—normal.

Treatment of First Degree AV Block

No specific treatment is required.