Assesses the balance between the two divisions of the Autonomic (involuntary) Nervous System (ANS) – the Sympathetic (SNS) and Parasympathetic (PSNS).

The ANS regulates all body functions, the heart rate being one. The first human response to any stimulus, physical or emotional and beneficial or harmful, is processed initially by the ANS.

The SNS controls the “flight or fight” reaction by increasing blood pressure, heart rate, and blood flow to the necessary muscles. It can be thought of as the “energy-boosting” or “mobilizing” division in order to prepare the body to expend energy for stressful or emergency situations. The damaging effects of the SNS on HRV is an indication of biological aging. On the other hand, the PSNS controls “rest and feed” functions and restores our bodies back to a calm restful state after a period of SNS activation.

There is a large body of evidence that indicates that the sympathetic nervous system plays a significant role in the genesis of cardiac arrhythmias, including malignant ventricular arrhythmias, such as ventricular tachycardia and v’entricular fibrillation. The parasympathetic nervous system plays a protective role, decreasing the likelihood of malignant ventricular arrhythmias.

In healthy responses to stimuli, these two systems balance each other. An imbalance of the ANS is a biological marker of aging and in various pathologies such as hypertension and predictor of the risk of death after a heart attack.

Therefore, HRV assesses the early signs of pathological developments or functional disorders which may not be revealed by routine physical examinations.