A Chinese doctor named Wang Shu-he documented this in his writings known as Mai Ching or The Knowledge of Pulse Diagnosis, which is still today a classic in the "pulse literature" field. One of the sentences he set down is often quoted today:

If the heartbeat gets as regular as the knocking of the woodpecker or the dripping of the rain on the roof, the patient will die within four days.

• 1891 - Müller reveals a lower increase in heart rate in heart disease patients on atropine
• 1927 - Winterberg and Wenkelbach describe respiratory sinus arrhythmia
• 1965 - Hon and Lee describe changes to the RR intervals during fetal distress
• 1972 - Hinkel et al. relate increased risk of cardiac death to reduced respiratory sinus arrhythmia
• 1978 - Wolf et al. describe a connection between HRV and heart attack mortality
• 1981 - (Akselrod et al. 1981) "The spectral analysis of HRV is meaningful as a noninvasive, quantitative indicator of the functionality of cardiovascular control systems"
• 1990 - HRV analysis is first used in clinical cardiology and diabetology
• 2000 - HRV is included in the risk stratification for sudden cardiac death
• 2011 - HRV analysis is included in the Curriculum for Special Pain Medicine and Psychosomatics at the Hannover Medical School
• 2010 -HRV analysis is added to German Disease Management Guidelines Program in the topic of diabetic neuropathy in adults

In 1925, scientist Heinrich Hering prophesized:

The wise use of the autonomic system will someday represent the core skill in the art of healing.

Dr. Johann Diederich Hahn-Godeffroy:

The autonomic nervous system, the maintaining of a harmonic balance between tension and relaxation  is the art of life.