MinRR
MinRR — the minimum RR interval — is the shortest time between two successive normal heartbeats during the recording. It corresponds to the highest instantaneous heart rate reached and shows how far the heart accelerated under sympathetic influence, physical effort, emotion or inhalation.
What MinRR shows
Even at rest the heartbeat intervals are not constant: they shorten with every inhalation (respiratory sinus arrhythmia) and with short bursts of sympathetic activity. MinRR captures the shortest of these intervals. Together with the maximum interval (MaxRR) it defines the variation range ΔX = MaxRR − MinRR used in Baevsky's indices.
Reading it on an ECG
On standard ECG paper (25 mm/s) one large square equals 0.2 s. Heart rate can be estimated as 300 divided by the number of large squares between two R waves: 3 squares = 600 ms ≈ 100 bpm, 4 squares = 800 ms ≈ 75 bpm, 5 squares = 1000 ms ≈ 60 bpm.
Interpretation
- MinRR at rest is shorter than MeanRR; the difference grows with stronger respiratory sinus arrhythmia and is small when the rhythm is rigid.
- A MinRR below about 600 ms in a resting recording means that the heart rate exceeded 100 bpm at least briefly — check for stress, movement, coffee, fever, or an episode of tachycardia.
- A single extremely short interval often results from an extrasystole or an artefact; such beats must be excluded from HRV calculation.
- During exercise testing the minimum RR interval reflects the peak heart rate; a failure to accelerate adequately (chronotropic incompetence) may indicate sinus node disease or medication effect.
Consult a doctor if very short intervals (fast heart rate) appear at rest, start suddenly, or are accompanied by palpitations, chest pain, dizziness or fainting — an ECG or Holter recording can show whether an arrhythmia is present.
References
- Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation. 1996;93(5):1043–1065. doi:10.1161/01.CIR.93.5.1043
- Baevsky RM, Chernikova AG. Heart rate variability analysis: physiological foundations and main methods. Cardiometry. 2017;(10):66–76.
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153–156. doi:10.1016/S0735-1097(00)01054-8
This article is for general information and does not replace a consultation with a doctor.
Published on 24 June 2019