Regularity: R-R intervals are regular, overall rhythm is regular.
Rate: The rate is between 100 and 180 beats/min.
P WAVE: P waves will usually be absent. If present, they will be inverted.
PRI: If P waves are present, they will measure between 0.12 and 0.20 seconds in duration. If not present, PRI cannot be measured. Occasionally there will only be intermittent P waves in the rhythm.
QRS: Measures less than 0.12 seconds.