Heart Rate Variability, HRV for Chinese Medicine

Heart rate variability (HRV, Heart Rate Variability) refers to the small variations in the time interval between each heartbeat.

In simple terms, the heart does not beat like a metronome, with one fixed beat every second. Even if your heart rate is 60 beats per minute, the interval between two heartbeats may be 0.98 seconds, 1.03 seconds, 0.95 seconds, and so on. These variations are what we call heart rate variability.

How is it measured?

These variations are very small and are measured in milliseconds. Assessing HRV requires specialised measuring equipment and accurate analytical tools. At present, the most accurate method is to place electrodes on the chest to record an electrocardiogram, and then calculate HRV from the results. Wrist-worn devices do not measure the electrocardiogram directly, so their results may be subject to inaccuracies.

What do HRV results indicate?

HRV is related to the balance of the autonomic nervous system (ANS). A large body of research has shown that various HRV indicators are associated with the respiratory system, endocrine system, immune system, glucose metabolism, psychological functions, and heart health. The association is particularly strong in relation to cardiovascular disease.

HRV and heart disease

In 1987, Kleiger’s study analysed the HRV of 808 patients who had survived acute myocardial infarction (heart attack). After an average follow-up period of 31 months, the study found that patients with HRV (SDNN) below 50 ms had a mortality risk 5.3 times higher than those with HRV above 100 ms. This was the first study to apply HRV in research on cardiac mortality among patients with coronary heart disease.

Applications of HRV

HRV cannot be used for diagnosis, but it can serve as a tool for disease prevention. In general, chronic diseases often develop gradually over many years, as abnormalities in daily mental and physical states, sleep, blood pressure, blood glucose, blood lipids, and other factors accumulate over time. In routine clinical practice, healthcare practitioners use different questionnaires to assess a patient’s sleep quality, mental state, and psychological condition. However, these results inevitably contain subjective elements. Today, HRV results can provide an objective indication of a patient’s mental and psychological state, helping guide treatment, monitoring, and evaluation of outcomes. From cardiovascular and psychological perspectives, HRV may support the treatment of cardiovascular-related diseases as well as various conditions that may be associated with psychological factors, such as dermatological, gynaecological, and neurological conditions.