TP
TP — total power — is the overall variance of heartbeat intervals obtained by spectral (frequency-domain) analysis of heart rate variability. It is the sum of the power in all frequency bands — very low (VLF), low (LF) and high (HF) frequency in short recordings — and reflects the total activity of all regulatory influences on the heart rhythm.
The idea of spectral analysis
The sequence of heartbeat intervals contains several overlapping rhythmic oscillations: fast ones linked to breathing, slower ones linked to blood-pressure regulation, and very slow ones linked to hormones, thermoregulation and other processes. Spectral analysis (fast Fourier transform or autoregressive modelling) separates these oscillations and shows how much variance — "power" — each frequency band contains. The Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology defined the standard bands used worldwide.
| Band | Frequency | Main physiological sources |
|---|---|---|
| HF — high frequency | 0.15–0.40 Hz | Breathing; vagal (parasympathetic) modulation — respiratory sinus arrhythmia |
| LF — low frequency | 0.04–0.15 Hz | Baroreflex control of blood pressure; mixed sympathetic and vagal influences |
| VLF — very low frequency | 0.0033–0.04 Hz | Thermoregulation, renin–angiotensin system, hormonal and other slow mechanisms |
| ULF — ultra low frequency | < 0.0033 Hz | Circadian rhythm — only in 24-hour recordings |
How TP is calculated and interpreted
Because power is variance, TP of a recording is approximately equal to the square of SDNN of the same recording. TP therefore carries the same overall information as SDNN, in a frequency-resolved form. Absolute power values differ widely between individuals (often by an order of magnitude), depend on age, heart rate, breathing, posture and recording length, and are not normally distributed; many programs therefore also report the natural logarithm (ln TP).
Low total power
- Reduced overall variability and adaptability of heart-rate regulation
- Stress, fatigue, lack of sleep, acute illness, high heart rate
- Ageing, low physical fitness, obesity
- Persistently low values: heart failure, after myocardial infarction, diabetic autonomic neuropathy — associated with higher cardiovascular risk
High total power
- Rich, flexible regulation: young age, good fitness, rest, sleep
- Slow breathing or movement during the recording
- Falsely high values: extrasystoles, artefacts, atrial fibrillation
Spectral indices require stationary, artefact-free recordings of at least 2–5 minutes (and longer for VLF). Compare only recordings made with the same duration, posture and breathing conditions, and follow your own trend rather than absolute population numbers.
Discuss your results with a doctor if total power and other HRV indices remain low over a long period, especially with palpitations, breathlessness, high blood pressure, diabetes or known heart disease.
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
- Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Front Public Health. 2017;5:258. doi:10.3389/fpubh.2017.00258
- Nunan D, Sandercock GRH, Brodie DA. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing Clin Electrophysiol. 2010;33(11):1407–1417. doi:10.1111/j.1540-8159.2010.02841.x
- Tarvainen MP, Niskanen JP, Lipponen JA, Ranta-aho PO, Karjalainen PA. Kubios HRV — heart rate variability analysis software. Comput Methods Programs Biomed. 2014;113(1):210–220. doi:10.1016/j.cmpb.2013.07.024
This article is for general information and does not replace a consultation with a doctor. HRV values depend on the device, recording length and conditions.
Published on 1 July 2019