Because of this, medications such as beta-blockers can lengthen the PR interval and result in a first-degree AV block. Also, a longer PR interval can cause the first heart sound (S1) to sound soft ...

A PR interval consistently longer than 0.20 seconds (greater than 5 small boxes) indicates a first-degree AV block. Note: There is a 1:1 ratio between P waves and QRS complexes, unlike 2nd degree ...

"First-degree Fetal Heart Block May Be Reversible." ScienceDaily. www.sciencedaily.com / releases / 2007 / 02 / 070210170613.htm (accessed May 8, 2025). Explore More ...

First-degree heart block: This is when the signals slow down. ... Mobitz type I causes a progressive prolongation of the PR interval, which eventually builds to a non-conducting P wave.

In 8 (7%) patients the PR interval lengthened with increasing doses of verapamil, but it remained below the 0.2 s threshold for first-degree heart block; however, two of these patients did develop ...