Rate: The underlying rate Rhythm: Regular P Wave: Normal PR Interval: Prolonged (>0.20 sec) QRS: Normal (0.06-0.10 sec)
Will look like a typical sinus rhythm. The P-R interval will be constant throughout the tracing and measure greater than 0.20 seconds.
A first degree Heart block occurs when electrical impulses moving through the Atrioventricular (AV) node are delayed (but not blocked). First degree indicates slowed conduction without missed beats. External Source: http://www.uptodate.com/contents/first-degree-atrioventricular-block