In a sinus block, how do the lengths of two R to R intervals compare to the block?

In the context of a sinus block, the R-R intervals surrounding the block are equal in length to the block itself. This occurs because a sinus block represents the failure of a sinus impulse to be conducted, resulting in a pause in the cardiac cycle. During this pause, the underlying rhythm continues, and when the impulse resumes, it does so from the same point as prior. Therefore, the length of the R-R intervals on either side of the block remains unchanged, mirroring precisely the duration of the blocked interval. This characteristic helps healthcare professionals identify and confirm the presence of a sinus block on an electrocardiogram.