: R-R Interval Measurement by Electrocardiography

: What Is Being Measured

: The R-R interval is the time, usually expressed in milliseconds or seconds, between one R wave and the next on an ECG tracing. Because each R wave marks a ventricular beat, the interval corresponds to the cycle length of the heartbeat and is used to calculate heart rate and evaluate rhythm regularity.

: How the Test Is Done

: The measurement is taken from an ECG recording, which may be a standard resting 12-lead ECG, a rhythm strip, or a longer monitor such as a Holter or event recorder. Small electrodes are placed on the skin to record the heart's electrical activity, and the intervals are then measured from the tracings.

: Why Your Clinician May Order It

: R-R interval assessment is used to check heart rate, look for irregular rhythms such as atrial fibrillation or premature beats, and evaluate pauses or racing episodes. It may also be part of monitoring during treatment with certain heart medications.

: What the Results Can Mean

: Variation in R-R intervals is normal and reflects the heart's natural responsiveness to breathing and activity. Markedly irregular intervals can suggest an arrhythmia, while very long pauses or consistently very short intervals may warrant further evaluation. Your clinician interprets the intervals together with your symptoms and the rest of the ECG.