The PR interval of a first-degree AV block _____. a. is ...

[scienceeasy]

The PR interval of a first-degree AV block _____.
 
  a. is constant and less than 0.12 seconds in duration
  b. is constant and more than 0.20 seconds in duration
  c. is generally progressive until a P wave appears without a QRS complex
  d. gradually decreases in duration until a P wave appears without a QRS complex

Question 2

The PR interval is considered prolonged if it is more than _____ seconds in duration.
 
  a. 0.06
  b. 0.12
  c. 0.18
  d. 0.20

[mrphibs]

Answer to Question 1

B
A first-degree AV block is present when there is a 1:1 relationship between P waves and QRS complexes and the PR interval is prolonged (i.e., more than 0.20 seconds) and constant.

Answer to Question 2

D
A PR interval is considered short if it is less than 0.12 seconds and long if it is more than 0.20 seconds.