Regularity

March the calipers down the strip and decide whether the rhythm is regular.

Understand the measurements

March out the RR

Marching is how regularity is judged on paper: set the span once, then walk it. If every R falls on a stamp the rhythm is regular.

Classify the regularity

Regular means the RR never changes. Regularly irregular means a repeating pattern of change. Irregularly irregular means no pattern at all, which is the hallmark of atrial fibrillation.