First-degree AV Block

Created by team@ekgdx.com on Dec. 14, 2023

Let’s talk about first-degree, AV block.

First-degree AV block is characterized by a prolonged PR interval in the setting of sinus rhythm, but all impulses are conducted.

Criteria

  • Sinus rhythm
  • PR interval >0.20 sec. 

Possible causes: Normal variant, increased vagal tone, athletes, inferior myocardial infarction, status post cardiac surgery, myocarditis, hyperkalemia, drug induced (beta-blockers, calcium channel blocks, adenosine, digitalis, and amiodarone). Additionally infiltrative heart diseases, neuromuscular disorders and Lyme disease have been identified as causes of first-degree AV block.

NOTE: For some authors, a first-degree AV block is not really a block, but rather a delay in conduction.

NOTE: The isolated finding of this type of "block" may not clinically significant.

NOTESometimes the PR interval is as long as 1.0 second and can exceed the PP interval, a condition termed skipped P waves.

NOTE: Marked first-degree AV block can reduce cardiac output and may not be well tolerated, especially in patients with left ventricular dysfunction. 

 

 

Marked first-degree AV block with PR interval of 520 ms. 

 

First-degree AV block in the setting of inferior acute MI.

 

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References

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Thanks for joining us. 

Dr. Roig

First-degree AV Block