Hypertension, commonly referred to as “high blood pressure” or HTN, is a medical condition in which the blood pressure is chronically elevated. Hypertension may occur when the body's smaller blood vessels (arterioles) constrict, causing an increase in blood pressure. Because the blood vessels constrict, the heart must work harder to maintain blood flow at the higher pressures. Although the body may tolerate short periods of increased blood pressure, sustained hypertension may eventually result in damage to multiple body organs, including the kidneys, brain, eyes and other tissues, causing a variety of maladies associated therewith. The elevated blood pressure may also damage the lining of the blood vessels, accelerating the process of atherosclerosis and increasing the likelihood that a blood clot may develop. This could lead to a heart attack and/or stroke. Sustained high blood pressure may eventually result in an enlarged and damaged heart (hypertrophy), which may lead to heart failure.
Hypotension, on the other hand, refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it.
Hypertension or hypotension is not something that only affects the whole vascular system, sometimes it is a local part of the vascular system that is affected. By locally dilate or constrict the blood vessel creating the local problem of hypo- or hypertension this problem could be treated. To avoid any kind of damage to the blood vessel a system using heat or cold could be used to regulate the constriction or dilatation of the blood vessel.
Hypertension may occur in the pulmonary system with too high blood pressure in the pulmonary artery. This could be caused by defective heart valves but often the cause is unknown.
Hypotension may occur in the renal artery only causing general hypertension because regulation factors are produced in the kidney, which wrongly detects that hypotension is on hand.