Autonomic Nervous System Physiology

Heart rate variability (HRV) power spectral analysis is one of many means of analyzing the electrocardiogram. Analysis of this kind can provide relative measures of the power or tone of various underlying physiologic influences on heart rate control, including hormonal and enzymatic, circadian, respiratory, and neural influences. Primary neural control of the heart is maintained by the autonomic nervous system (ANS).

The ANS influences every cell in the body through its two branches:

The sympathetic nervous system (sympathetic) and the parasympathetic nervous system (parasympathetic). In general, the sympathetic is responsible for mediating energy expenditure, while the parasympathetic is responsible for energy conservation and restoration. For example, the sympathetic mediates the "fight or flight" response and the body's response to stress, pain, and cold. Thus, the sympathetic causes higher heart rates and respiratory rates, shunting blood from the extremities to core organs and muscles (e.g., running or shivering), etc. The parasympathetic mediates resting states after meals and at night, digestion and nutrient storage, and recovery states by helping to coordinate immune responses and healing. Thus, the parasympathetic causes slower heart rates and respiratory rates, sleep, increased gastrointestinal track motility, increased peripheral vascular flow, blood flow to all cells, liver and kidneys, and venous return to the heart. The sympathetic and parasympathetic branches of the ANS work together to maintain homeostasis.
When the ANS affects a change in the body (e.g., heart rate or respiratory rate), it works only to cause the change. The ANS then returns to its baseline state. So, periodic excursions in one or the other branch from baseline are normal and expected as long as the ANS returns to baseline in a timely manner. Persistently elevated levels of tone in one or the other branch are not healthy. The general action of each of the branches of the ANS is to oppose the other. As one branch begins to work the other branch begins to return it to baseline. Consequently, persistently elevated tone in one branch can result in a persistently depressed tone in the other. This only serves to compound an unhealthy situation. So, balance between the branches is as important as overall tone in each of the branches.

It has been learned that the parasympathetic nervous system can change faster than the sympathetic nervous system. Thus, as the sympathetic starts to mediate a stress response the parasympathetic immediately begins to counter it. If the parasympathetic is not faster than the sympathetic, then any stress response could send the heart into tachycardia and onto ventricular fibrillation before the parasympathetic could act to prevent it. The parasympathetic, through the Vagus, is the main controlling influence on respiratory activity. Changes in respiration are influenced by changes in parasympathetic tone. Parasympathetic input to the heart is through fibers that synapse deep in the myocardium. Sympathetic influence on the heart is through surface synapses. Due to this arrangement the parasympathetic is more sensitive to heart damage (i.e.: infarct, ischemia, or cardiomyopathies). Since the parasympathetic is faster to respond, it is usually the branch that is first to indicate changes in health status anywhere in the body.

What Makes the Intellewave Different from other ANS Testing Devices?

Patented Spectral Analysis
Intellewave developed a proprietary algorithm based on artificial intelligence methods.
This device can automatically detect ectopic beats & artifacts to provide high quality HRV analysis.

Why is this important? Because spectral analysis of R-R intervals is sensitive to any artifact or ectopic beat  (i.e. one artifact in the center of the selected data segment dramatically increases the power of high frequency spectral function of R-R intervals variability making PSNS assessment completely wrong)

Proprietary Sophisticated Algorithm Based on Artificial Intelligence
This proprietary algorithm allows Physicians to recognize up to 81 different variations in the relationship between sympathetic & parasympathetic activities.

Method of Data Selection
Intellewave uses the “definite number of R-R Intervals” selection method. Other companies use the “5 minutes approach”. However the “Theory of Random Processes” states that to make a statistical analysis of any random process we must take the same number of random events. Therefore a time based approach cannot get consistency & reproducibility for any HRV statistical analysis.

WHY ANS MONITORING?

Syncope
Peak Sympathetic response to postural change approximately the same or higher than peak response to valsalva is associated with syncope in young people. Too much Parasympathetic response throughout the test is associated with Syncope in older people.

Sleep Apnea
With Sleep Apnea the Sympathetics are exceedingly high & the Parasympathetics are low normal to low.

Diabetes
With Diabetics the Parasympathetic & Sympathetic systems are both out of balance. The more out of balance these 2 branches of the ANS system are, the faster the disease will progress & the less effective their medications.

Hypertension
Parasympathetic tone is low & Sympathetic tone is high. Another situation that arises is Autonomic Hypertension. In this case, Parasympathetic tone is high & the Sympathetic tone is abnormally high.

Orthostatic Hypotension
During the postural change the Parasympathetic tone abnormally increases and/or the sympathetic tone abnormallydecreases in patients with Orthostatic Hypotension.

Cardiac Autonomic Neuropathy
Both the Parasympathetic & Sympathetic tones are low in patients with Cardiovascular Autonomic Neuropathy. If the relative Sympathetic tone is low but still much higher than Parasympathetic tone, the patient is at risk for SUDDEN CARDIAC DEATH.

Benefits for Determining Treatment Plan

(Based on feedback from Physicians)

• Rule out other factors such as hormonal, enzymatic, circadian, respiratory, baroreceptor, etc.
• Able to identify patients at risk for sudden cardiac death syndrome.
• Determine if meds affecting ANS needed versus other treatments.
• To determine optimal dose beta blockers. HR data not sufficient since it only indirectly provides info. about the level of sympathetic activity.
• Test can confirm or exclude beta blocker overdose (when both Parasympathetic and Sympathetic activity is low).
• Evaluate treatment
• For patients may not report symptoms
• Parasympathetic changes faster than sympathetic
• Determining progression of Diabetes: The more out of balance the 2 branches, faster disease will progress.
• Reduced autonomic function is earliest indicator of CAN