Health Complaints
Hypertension (High Blood Pressure) |
It seems that we live in an age that has come to accept conditions such as hypertension, hypercholesterolemia/hyperlipidema (raised blood cholesterol) as a natural part of aging rather than something that we can directly influence by the way in which we care for ourselves. It is certainly true that there is a degree of degredation of the vascular system that accompanies advancing age, but the extent to which this is occuring, and the rates of mortality as a result of it are more a reflection of our liestyle habits and choices.
A large amount of cases of hypertension have an unknown cause and are referred to as ‘essential’ hypertension. There can be a miriad of influences that may be associating factors in such cases. These are genetic issues, obesity, smoking, alcohol intake, dietary habits etc. In cases where there is a known underlying pathology responsible for the increased pressure, it is referred to as ‘secondary’ hypertension. This can be due to medications, renal disease, or vascular pathologies such as arteriosclerosis. It is this cause that is the most common worldwide. Ateriosclerosis is the term given to the narrowing of the lumen of an artery and an accompanying loss of flexibility of the vessel wall. This is an issue for two important reasons. If the lumen size of a vessel decreases, the blood flowing through it will be under greater pressure. This wouldnt necessarily be an issue if the wall of the vessel was nice and flexible and could accomodate for the increase in pressure (and bring it back into equanimity). The consequences of this narrowing and rigidity can be illustrated using this example. Imagine your garden hose pipe when it gets old. The rubber becomes hard and almost brittle. One day you turn on the tap full blast and the pressure within the pipe causes it to burst! This narrowing is caused by a process called atherosclerosis.
Atherosclerosis
This is a slowly progressive condition that involves the formation of fibro-fatty plaques within the muscular wall of the artery. The latest theory surrounding the formation of these plaques is surrounding inflammation. The walls of the vessels become inflamed as a result of injury, exposure to toxic materials, or some other influence. These areas of inlammation alter the functioning of the vascular endothelium, thus increasing its permeability (Robbins et al 1999:260). This increased permeability allows monocytes to migrate past the endothelium and into the intima (1999:260). Once in the intima, monocytes develop into macrophages and absorb likpids to become foam cells (1999:260). Lipoproteins then also migrate through the cell wall and are oxidised by local macrophages. Platelets then attach themselves to this site, and their growth factors cause smooth muscle cells to migrate from the media into the intima (1999:260). All of these processes will make the lumen narrower and the lesions created can rupture and encourage the formation of a thrombus, which can dislodge and travel through the vascular system until it causes occlusion and the infarction of tissue. The atherosclerotic lesions themselves can dislodge and become an atheroembolus.
There are other elements to consider in the maintenance of blood pressure.
Renal System
The kidneys are responsible for assisting in the maintenance of blood pressure by regulating blood volume. They conserve or eliminate water in the urine. The retension of water will increase the plasma volume. The greater the volume within a vessel, the greater the pressure within it. The kidneys also play a role in the regulation of blood pressure via the renin-angiotensin system. When blood flow to the kidney decreases (in a healthy person this can be due to a drop in blood pressure, and in a patient with cardiovascular disease, this can be due to poor circulation due to ateriosclerosis), the jusxtaglomerular cells within the kidney secretes the hormone renin into the general circulation (Tortora & Grabowski 2003:712). Renin and angiotensin converting enzyme (ACE) go through a sequence of events to produce the hormone angiotensin II which increases blood pressure via stimulating both vasoconstriction and sodium reabsorption in the kidney - which increases plasma volume.
Vasoconstriction
The diameter of the artery lumen is altered in size to increase or decrease the pressure within the vessel. This is controlled by several groups of chemicals. As the walls of these vessels are smooth muscle, the alteration in size can be instigated simply by ions such as potassium. Nitric oxide (NO), also named ‘endothelium-derived relaxation factor (EDRF) is an important vasodilatory chemical (2003:712).
Herbs for hypertension:
Crataegus laevigata - otherwise known as hawthorn. This shrub which is common to the British countryside has a long standing tradition as a remedy for both the direct treatment, and maintenance of the cardiovascular system. This herb affects both cardiac contraction and blood pressure. It is essentially a peripheral vasodilator - it widens the vessels thus reducing the pressure within them. The active chemicals in this herb that are believed to be responsible for this activity are the flavanoid group known as oligomeric proanthocyanidins (OPC’s). These substances seem to be able to inhibit the action of angiotensin converting enzyme described above (Heinrich et al 2004:217).
Viburnum opulus - also known as cramp bark. This herb is another to have a high content of flavanoid compounds, although research seems to point out that it is not 100% clear precisely which compounds are responsible for its actions. This herb is primarily a smooth muscle relaxant, therefore can relax the musculature of the vessel wall and act as a vasodilator.
Achillea millifolium - also known as yarrow. This lovely plant that seems to just be growing in every direction near my home, has so many applications. It has commonly be used as a ‘hypotensive’ herb. This term is a little vague as there is no clear indication as to why it is able to reduce blood pressure (even though there is an abundance of empirical evidence to support this). The hypotensive action may arise as a result of yarrow’s diuretic action.
Tillia europea - also known as Lime flower. This lovely herb is most commonly applied as a relaxing nervine, so can prove to be a fabulous addition to a prescription where the patient has a stress element associated with their hypertension. It has developed a reputation as a hypotensive agent, although the reason for this is not 100% clear, although this too maybe as a result of its diuretic action. It does this by having a gentle irritant action upon the nephron.
Taraxacum officinalis fol - also known as dandelion. This herb is in my opinion the king of the diuretics. It has a powerful diuretic effect - comparible to the commonly prescribed (or dished out like sweeties) drug bendrofluazide. Diuretic herbs are disireable in patients with hypertension as they will stimulate urine output and help to reduce plasma volume. If the volume of fluid within a vessel is reduced, there will be less pressure within the vessel, and less risk of damage to the endothelium and thrombus formation.
References
Heinrich M, Barnes J, Gibbons S, Williamson EM (2004). Fundamentals of Pharmacognosy and Phytotherapy. USA, Philadelphia: Churchill Livingstone.
Robbins SL, Cotran RS, Kumar V, Collins T (1999). Pathological Basis of Disease. USA, Philadelphia: W.B Saunders & Co.
Tortora GJ, Grabowski SR (2003). Principles of anatomy and physiology. USA, New York: John Wiley & Sons. Inc