The Autonomic Nervous System – New Assessment Measures for Cardiovascular Risk
Part I: HRV – Are you stressing out towards a heart attack? How your Autonomic Nervous System regulates heart health.
When it comes to diagnosing the risks of cardio-vascular disease, we now know we need to look beyond cholesterol. Statistics show that over half of all new diagnosed heart disease patients have normal cholesterol and that there are other factors to look out for when it comes to heart disease risk.1 The real revolution in the prevention and assessment of heart disease risk is the assessment of the Autonomic Nervous System (ANS). The ANS controls sub-consciously all of our our internal organ functions including the heart.
The ANS is divided into the sympathetic or ‘flight and fight’ mode and the parasympathetic ‘rest and digest’ mode. The activation of the sympathetic nervous system is by the secretion of adrenalin from our adrenal glands, which helps release more glucose into the bloodstream for the impending demands on energy expenditure. The activation of the parasympathetic nervous system is through the release of acetylcholine, nitric oxide and other compounds together with the vagus nerve, which innervates the heart directly by slowing it down and relaxing it.
It is the imbalance of these two branches of the ANS that is responsible for most heart disease. In terms of assessing the ANS, the most accurate method is through Heart Rate Variability (HRV), that is, the variation between the beats of the heart determines whether you are more sympathetic or parasympathetic dominant. One study has shown that patients with heart disease have on average 33% less parasympathetic activity2 and typically the more severe the heart disease, the lower the parasympathetic activity.3
In further supportive evidence, 80% of ischemic events are preceded by chronic reductions in parasympathetic activity. 4 These are typically brought on by lifestyle factors like smoking, sedentary lifestyle, emotional stress or hypertension and this is further exacerbated by a period of intense sympathetic nervous system activity characterized by some intense acute trauma or physical exertion. To protect yourself from a heart attack we need to have normal parasympathetic activity which can buffer bouts of intense sympathetic activity. What is chronically happening right now in the health of people is chronically low levels of parasympathetic life restoring activity.
Therefore, maintaining vagal tone and activity is key. Comorbid factors of heart disease like having high blood pressure, diabetes or insulin resistance, decrease the vagal tone.
What happens in the lead up to a heart attack event? In the majority of cases there is an underlying low parasympathetic tone, then there is some big increase in sympathetic activity for example some physical or emotional stressor. This stimulates the myocardial cells to break down glucose via the glycolysis pathway and a subsequent increase in lactic acid production in myocardial cells. This happens in 100% of myocardial infarctions (heart attacks), with no coronary artery mechanism involved.7 This increase in lactic acid causes localized acidosis, which makes calcium unable to enter the cells and the cells less able to contract. This causes diminished muscle function in the walls of the heart. The continued build up lactic acid in the cells causes necrosis of the tissue which then leads to a heart attack.
Further we see localized edema, which causes increase pressure that ruptures unstable plaques which further blocks the arteries and worsens the hemodynamics of the heart. This is the only explanation why plaques rupture.
So in essence we need to nourish our parasympathetic activity, with more outside nature exposure like walks in the parks and forests. More loving and nurturing relations with our loved ones, and more stability in our lives. There are herbal and supplemental interventions that can stimulate the parasympathetic activity and in Part II I will be explaining these interventions in more detail.
For more information regarding stress and heart health, please contact Functional Medicine Practioner, Miles Price at 2881 8131 or email@example.com
- Normal LDL-Cholesterol Levels Are Associated With Subclinical Atherosclerosis in the Absence of Risk Factors Leticia Fernández-Friera, Valentín Fuster et al. J Am Coll Cardiol. 2017 Dec, 70 (24) 2979-2991
- Baroldi, Giorgio, Malcolm D. Silver, and Giorgio Baroldi. The Etiopathogenesis of Coronary Heart Disease: A Heretical Theory Based on Morphology. Georgetown, Tex: Landes Bioscience, 2004
- Sroka, K. On the genesis of myocardial ischemia. Z Kardiol93, 768–783 (2004)
- Takase et al., “Heart Rate Variability in Patients with Diabetes Mellitus, Ischemic Heart Disease and Congestive Heart Failure,” Journal of Electrocardiology 25, no. 2 (April 1992): 79–88,
- James Scheuer and Norman Brachfeld, “Coronary Insufficiency: Relations between Hemodynamic, Electrical, and Biochemical Parameters,” Circulation Research (1966): 178–189.
Written by Miles Price