The most common medical condition and leading cause of death in Ireland today is Hypertension, accounting for nearly 1/3 of the total number of deaths and killing around 10,000 people each year. Hypertension or high blood pressure is where the force of the blood against the arterial walls as it circles the body is more forceful than it should be. It is the main cause of death in Ireland due to the fact that it is a condition that usually gives no symptoms, and goes unnoticed unless it is checked regularly or when a health problem arises. It is the lack of symptoms that gives the condition its other name The Silent Killer. To check total blood pressure a measurement of both systolic and diastolic pressure must be taken. Systolic pressure measures the blood pressure while the heart beats and diastolic pressure measures the blood pressure while the heart rests. Normal blood pressure is considered to be 120/80 mmHg, 120 being the measurement of systolic output and 80 being measurement of the diastolic output. Today, there are 4 categories of blood pressure; normal, pre-hypertension, hypertension stageI and hypertension stageII. Normal blood pressure as stated previously is 120/80, pre-hypertension is considered to be between 121-139 systolic and 80-89 diastolic while both stages of hypertension are 140 systolic or higher with 90 diastolic or higher.blood-pressure.gif
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With Hypertension, as stated previously both the systolic and diastolic may be chronically higher than 140/90mmHg or just one of the measurements may be chronically higher than the normal number. Hypertension is split into 2 different blood pressure categories; hypertension stage I and hypertension stage II. Stage I categorically has a systolic of between 140 and 159 with a diastolic of 90 to 99 while stage II is marked by a systolic reading of 160 or higher with a diastolic of 100 or more. There are 2 types of hypertension, the first is called essential hypertension and the second is called secondary hypertension. Essential or primary hypertension is high blood pressure with no identified cause while secondary hypertension is high blood pressure caused by another underlying condition or the medication used to treat it. When considering the pathogenesis of primary hypertension, the change in systemic vasculature could be as a result of continuously increased blood volume, cardiac output or purely due to sustained elevation of the systemic vascular resistance. The increased resistance is as a result of a reduction in diameter of the lumen and thickening of the walls of resistant blood vessels. Vascular tone is also another factor to take into consideration when considering pathogenesis as studies show that vascular endothelium of patients with hypertension produce very little nitric oxide. Nitric oxide is the body’s natural vasodilator but due to the reduction in production the vascular smooth muscle becomes less sensitive to its activity. This lack of nitric oxide and desensitized smooth muscle coupled with increased production of endothelin can lead to enhanced vasoconstriction of the vascular tissue. This vasoconstriction causes the arterial walls to become more rigid and to increase resistance to the flow of blood, which in turn causes the heart to beat more forcefully. The stiffening of the arterial walls also leads to a wider pulse which is a characteristic of isolated systolic hypertension which is where the systolic reading is 140 but the diastolic reading is still below 90.blood_vessel.gif
Today, essential hypertension accounts for more than 90% of all hypertension related cases while secondary hypertension namely accounts for the rest. The cause of essential hypertension is unknown but there are 7 factors that could potentially be responsible for this type of blood pressure. These are a high salt diet, age, ethnicity such as African American, Renal insufficiency, weight problems, genetics and susceptibility. Secondary hypertension is less common but is generally a result of an underlying condition or due to medication; some underlying causes include renal insufficiency, thyroid insufficiency, pregnancy, stress and many more. Renal artery stenosis is the narrowing of the renal artery lumen, this results in a reduction of pressure in the arteriole and a reduction in renal perfusion. This reduction in renal perfusion and constriction of the artery stimulates the release of rennin which increases the concentration of the hormones angiotensin II and aldosterone. The increase in these hormones results in the increased uptake of sodium and water thus increasing the blood volume leading to hypertension due to the Frank-Starling mechanism. The pathogenesis of hyperaldosteronism is similar to that of renal artery stenosis, as the increased secretion of aldosterone results in increased sodium and water uptake thus increasing the blood volume and cardiac output. The Frank-Starling mechanism is physiologically involved in balancing the output of the 2 ventricles of the heart; it is the hearts ability to change its force of contraction thus changing the stroke volume as a response to changes in the venous return. An example of this is an increase in output of the right ventricle would lead to an increase in the flow into the left ventricle. Without the Frank-Starling mechanism to react to the imbalance then a major malfunction would occur.primary hyperaldosteronism
One of the most prevalent links with secondary hypertension in today’s society is stress. It acts as an indirect cause of the condition by repeatedly stimulating the sympathetic nervous system; this overstimulation leads to large amounts of vasoconstricting hormones such as norepinephrine to be released. Stimulation of the sympathetic nervous system due to stress also increases the circulating angiotensin II, vasopressin and aldosterone levels. The constant and repeated constriction of the arteries due to increased cardiac output and vascular resistance elevates the blood pressure. On top of the sympathetic nervous system stimulation, stress also stimulates the adrenal medulla to produce more catecholamines such as norepinephrine and epinephrine. It is the combination of increased catecholamines and angiotensin II that maintains the elevated blood pressure causing the hypertension.
To treat the condition it is often necessary to look at the underlying cause if any and to try treat that where possible. For essential hypertension there is no identifiable cause so the treatment plan is trial and error, while with secondary hypertension; the underlying condition that is putting stress on the heart can be treated with the hopes that it will alleviate the strain. There are 4 main classes of antihypertensive drugs these are; Diuretics, vasodilators, sympathetic nervous system suppressors and rennin-angiotensin system drugs.
Diuretics such as Thiazides, potassium sparing and loop are the main types used in the treatment of hypertension. They are often called ‘water pills’ as they act on the kidneys to increase the elimination of sodium and water from the body in order to decrease blood volume. Vasodilators are another important category of drugs in the treatment of hypertension as they help in the relaxation of the muscles in the blood vessels. Calcium channel antagonists (blockers) and potassium channel agonists are 2 main examples of vasodilators used to treat hypertension. The calcium channel blockers aid in the relaxation by blocking the calcium conduction of L type calcium channels on vascular smooth muscle. K+ channel agonists on the other hand cause local relaxation of smooth muscle by increasing the permeability of the membrane to K+ ions. The activation of potassium ions switches off the calcium channels thus stopping the production of action potentials.
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Alpha and beta blockers/ antagonists are 2 main sympathetic nervous system suppressors or peripheral sympatholytic drugs used in the treatment of hypertension. The alpha antagonist blocks the alpha receptors in the smooth muscle of peripheral arteries which blocks the mechanism of contraction through the IP3 signal transduction pathway thus reducing the blood pressure. The beta antagonists however, only act on reducing the cardiac output and are found to be not so effective on their own and so they are generally prescribed with the use of diuretics like the Thiazides. Alpha agonists are the third type of sympathetic nervous system suppressor or centrally acting sympatholytic drugs, they block the sympathetic activity of the brain by binding to the alpha 2 receptor and activating it. This activation of the alpha 2 receptor reduces the outflow to the heart thus decreasing the cardiac output, heart rate and contraction. Generally the alpha agonists are prescribed in conjunction with diuretics due to the drugs fluid accumulation side effects which when left untreated can lead to cell edema.
The last category of drugs used to treat hypertension is the Renin-angiotensin targeting drugs. The 2 main targeting drugs used are ACE inhibitors and angiotensin II receptor antagonists. ACE inhibitors or angiotensin-converting enzyme inhibitors; block the enzyme from producing angiotensin II which is responsible for the narrowing of blood vessels and stimulation of hormones that raise blood pressure. By blocking this enzyme, the blood vessels remain relaxed and blood pressure remains normal. On the other hand, the angiotensin II receptor antagonists block the action of angiotensin not the formation thus the blood vessels remain relaxed.
Herbal and complementary treatment
In today’s medical world, diet and exercise are the best recommended treatments where possible or when medication can be avoided. Simple things such as to quit smoking, exercising for 30 minutes a day, limiting salt and alcohol intake, eating a heart healthy diet and reducing stress are all things that could dramatically lower blood pressure. Supplements in the diet are another friendly way of lower blood pressure, supplements such as omega3 fish and cod liver oils, coenzyme Q10, ALA, garlic, calcium and cocoa are all indicated for the treatment of hypertension. Where supplements and diet don’t have the desired efficacy, herbs can help boost the effects or can even be used in conjunction with prescribed anti-hypertensive medications.
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