Pathophysiology of Essential Hypertension
Introduction
Hypertension or high blood pressure is a condition that occurs as a result of higher than normal pressure (tension) within the arterial vessels that carry blood from the heart to other organs. Normal blood pressure should be below 120/80 whereas, pressure higher than 140/90 is considered as high blood pressure. The pressure range between 120/80 to 139/89 is termed as pre-hypertension pressure. The numerator in these pressure recordings indicates the systolic pressure in the arteries as the heart’s contraction pumps blood into the arteries. The denominator represents diastolic blood pressure within the arteries as the heart relaxes from the contraction. This diastolic blood pressure is the lowest that arteries get exposure.
Essential Hypertension
Essential hypertension is also referred to as idiopathic or primary hypertension. This is a type of hypertension that has no cause that can be identified by definition. This form of high blood pressure is most prevalent and affects about 95 percent of hypertensive people. The condition has a familial tendency and is influenced by environment and genetic factors. Research attaches gene influence as one of the major causative factors of essential hypertension. The probability of getting primary hypertension gets higher with age and is higher in individuals who have high blood pressure at a young age (Oudiz, 2010).The condition can further bring cardiac, cerebral and renal complications.
Pathophysiology of essential hypertension
Blood pressure in the arteries is determined by peripheral resistance and the cardiac output. Therefore, the blood pressure depends on the balance between these two determinants. Stroke volume and heart rate influence the cardiac output, whereas; the stroke volume is determined by vascular compartment size and myocardial contractility. Anatomic and functional changes in arterioles and arteries influence the peripheral resistance. Pathophysiology of primary hypertension is not well comprehended and is still under research. However, several theories have been postulated in a bid to explain essential hypertension. The known fact is that cardiac output rises in the early stages of the disease whereas, the cumulative peripheral resistance remains normal (TPR). As the condition progresses with time the total peripheral resistance increases and the cardiac output reduces to normal levels (Medicine Net Incorporation, 2010). There are three proposed theories and these include:These possible causes include a more active than normal sympathetic nervous system. This leads to increased stress response which in turn furthers high blood pressure. A highly active rennin-angiotensin system causes blood vessels to constrict (vasoconstriction) and this in turn causes high blood pressure. The system also causes the body to retain a lot of sodium and water that increases the volume of blood and therefore causing hypertension.The failure of kidneys to eliminate sodium results in secretion of natriuretic factors like atrial natriuretic factor. This factor promotes excretion of salt but on the other hand causes the side effects that result in the rising of the total peripheral resistance.High blood pressure is often heritable and caused a number of genes (polygenic). A number of genes have been postulated as possible causative agents that cause essential hypertension. Several genes have been examined in association with hypertension. One of them is the angiotensinogen (AGT) gene studied by Kim et al. They were able to show that increasing the number of Angiotensinogen would raise blood pressure and therefore, this can cause hypertension.
The role of essential hypertension in causing heart disease
Any elevation in the diastolic and/or systolic blood pressure raises the chances of developing cardiac disease and could also cause arteries to harden (Arteriosclerosis or atherosclerosis). These hypertension caused complications are called end-organ damage. This is because the damage on these organs comes by as a result of a prolonged high blood pressure period. Previously a rise in diastolic pressure was thought to be more risky than systolic pressure rise however; it is now well known that systolic hypertension poses a great danger to people who are 50 years or older. The estimation of American heart association shows that hypertension affects one in three American adults. It is also estimated to affect approximately two million children and teenagers. As a result hypertension is regarded as a great challenge to health. When the blood pressure is continuously very high the walls of arteries get weakened and are more likely to develop atherosclerosis (The layering of inner arterial walls with fatty substances). As the walls thicken the arteries develop a smaller lumen which constricts the flow of blood through the veins. As a result, the heart must work extra hard to pump the oxygenated blood through the clogged arteries to the destination organs. This restricted flow over-works the heart to an extent that can cause ischemic heart disease. The clogged arteries are likely to have blood clots. These clots further impede blood flow and can result in entire blockage. Constricted flow coupled with a very high blood pressure can cause veins to burst leading to hemorrhage or bulge (aneurysm). The accumulation of plaque material on the walls of arteries causes coronary artery disease (CAD).
The breaking of a section of the plaque can cause blood clots. These clots could cause a heart attack if they get large enough to cut off the blood supply completely or to a big extent. The impeded flow stops oxygenated blood from reaching the part of the heart muscles that it was intended for and in turn, the lack of oxygen causes the heart muscle damage. If there is no quick correctional treatment the part of the damaged heart muscle starts to die. Persistent essential high blood pressure can cause congestive heart failure.Hypertrophic cardiomyopathy is also caused by hypertension. This condition makes the muscles of the heart to thicken abnormally. This prevents the heart valves from functioning properly. At times it stops blood from flowing out or into the heart. The disease is prevalent amongst all ages (Maron, McKenna, Seidman & Spirito, 1997).The persistent hypertension causes a thickened heart, a condition referred to as a hypertrophy heart.
The heart enlarges due to increased stress on the heart. This usually involves one of the lower chambers of the heart or ventricles. The extra work that the heart does in pumping blood against high blood pressure in the lungs or body causes the heart’s ventricle to thicken with time. Hypertension is the common cause of the left ventricular hypertrophy.According to Roy (Roy, 2008) aortic dissection is another common condition caused by essential hypertension. In this condition blood surges through a tear in the aortic layer called intima which creates a false lumen. This dissection can occur anywhere in the aorta and extend distally or proximally. The situation may lead to aortic regurgitation and hamper circulation in the arterial branches. Ventricular tachycardia is a rhythm that is regular and fast. It begins in the heart’s lower ventricles. If left untreated the condition can cause ventricular fibrillation that is a risky medical condition. In the later condition the rhythm will be irregular and fast. In this condition the heart beats fast and irregularly till it ceases to pump blood and eventually causing sudden death. This condition is caused by other heart conditions whose primary causes include primary hypertension; for example, hypertrophic or dilated cardiomyopathy. Therefore essential hypertension can be a secondary cause of ventricular tachycardia (Health Wise, 2008).
Bibliography
Health Wise. (September 17th 2008). Ventricular tachycardia. [online]. Available from http://www.webmd.com/heart-disease/tc/ventricular-tachycardia. [Accessed on 2nd may 2010].
Maron, J. B, McKenna, J.W, Seidman, E. C. and Spirito, P. (March 13th 1997). The Management of Hypertrophic Cardiomyopathy: The New England Journal of Medicine, Volume 336:775-785, Number 11. [online]. [Accessed on 2nd may 2010].
Medicine Net Incorporation (2010). High Blood Pressure, [online]. Available from http://www.medicinenet.com/high_blood_pressure. [Accessed on 2nd may 2010].
Roy, S. (n.d). Systemic Hypertension. [online]. Available from http://www.histopathology-india.net/HypertHD.htm. [Accessed on 2nd may 2010].
Oudiz, J. R. (March 23rd 2010). Pulmonary Hypertension, Primary, [online]. Available from http://emedicine.medscape.com/article/301450-overview. [Accessed on 2nd may 2010].
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