Rate

The standard paper speed of an EKG is 25mm/sec, which means the EKG covers a 10 second period. The rates of the various waves can be calculated based on this with a few different methods. As a quick side note, the paper speed can be changed; if it is sped up to 50mm/sec, the EKG covers a 5 second period and spreads this out; this sometimes reveals findings that may be hidden in a quicker EKG. Quickening the paper speed may be most useful to help differentiate various narrow complex tachycardias. At the standard speed, one small box is 0.04 seconds and one large box is, therefore, 0.2 seconds.

The two main methods are either the 300 divisional method of the sixfold multiplication method (not actual names as far as I am aware):

Rate=300/(the number of large boxes between R waves)

Rate=number of R waves on the strip x6

Again, these are based on the standard EKG paper speed and would need to be adjusted if this speed is changed. These provide the ventricular rates. The sixfold multiplication method is better with irregular rhythms as the number of large boxes between R waves would vary in these rhythms. These methods can also be used to calculate atrial rates, though one must be cautious to properly evaluate for all P waves on the strip as some rhythms (ie atrial flutter) may have multiple P waves for every QRS. The atrial rate is important to be able to identify/calculate to differentiate between the various heart blocks.

Adult Heart Rates:

1. bradycardia: HR<60bpm

2. normal rate: HR 60-100bpm

3. tachycardia: >100bpm

Normal Pediatric Heart Rates:

• newborn: 110-150bpm

• 2 years: 85-125bpm

• 4 years: 75-115bpm

• 6+ years: 60-100bpm

Note that these can have variations between these age groups listed (2 week old may be different than 9 month old).