Hypertension
Differential Diagnosis
There are three general types of hypertension. Essential hypertension occurs when the condition has no known cause (may be accumulation of several factors). When hypertension is caused by another condition or disease process, it is called secondary hypertension. When only the systolic blood pressure number is high, it is called isolated systolic hypertension, which is common in older adults.
Secondary hypertension
1. Renal(kidney) hypertension
How does narrowing of the renal artery cause hypertension? First, the narrowed renal artery impairs the circulation of blood to the affected kidney. This deprivation of blood then stimulates the kidney to produce the hormones, renin and angiotensin. These hormones, along with aldosterone from the adrenal gland, cause a constriction and increased stiffness (resistance) in the peripheral arteries throughout the body, which results in high blood pressure.
Renal hypertension is usually first suspected when high blood pressure is found in a young individual or a new onset of high blood pressure is discovered in an older person
Screening for renal artery narrowing then may include renal isotope (radioactive) imaging, ultrasonographic (sound wave) imaging, or magnetic resonance imaging (MRI) of the renal arteries.
2. Adrenal gland tumors
Two rare types of tumors of the adrenal glands are less common, secondary causes of hypertension. The adrenal glands sit right on top of the kidneys. Both of these tumors produce excessive amounts of adrenal hormones that cause high blood pressure. These tumors can be diagnosed from blood tests, urine tests, and imaging studies of the adrenal glands. Surgery is often required to remove these tumors or the adrenal gland (adrenalectomy), which usually relieves the hypertension.
One of the types of adrenal tumors causes a condition that is called primary hyperaldosteronism because the tumor produces excessive amounts of the hormone aldosterone. In addition to the hypertension, this condition causes the loss of excessive amounts of potassium from the body into the urine, which results in a low level of potassium in the blood.(blood test)
3. Coarctation of the aorta
Coarctation of the aorta is a rare hereditary disorder that is one of the most common causes of hypertension in children. This condition is characterized by a narrowing of a segment of the aorta, the main large artery coming from the heart. The aorta delivers blood to the arteries that supply all of the body's organs, including the kidneys.
The narrowed segment (coarctation) of the aorta generally occurs above the renal arteries, which causes a reduced blood flow to the kidneys. This lack of blood to the kidneys prompts the renin-angiotensin-aldosterone hormonal system to elevate the blood pressure. Treatment of the coarctation is usually the surgical correction of the narrowed segment of the aorta.
Because blood pressure is maintained by an adequate blood volume, an adequate cardiac output, and appropriate vasomotor tone, it follows that hypertension may result from an increase in any one or more of these three factors.
1. Increased blood volume. This results in most cases from an increase in sodium in the blood from primary aldosteronism (adrenal tumors) or from secondary aldosteronism (renovascular hypertension from glomerulonephritis and other primary renal diseases or obstruction of the renal arteries by atherosclerotic plagues or fibromuscular hyperplasia). Administration of corticosteroid drugs may cause hypertension by the same mechanism. Polycythemia vera(bone marrow makes too many RBC) is often associated with moderate hypertension because of increased red cell mass.
2. Increased cardiac output. This mechanism accounts for the systolic hypertension in hyperthyroidism, aortic insufficiency, patent ductus arteriosus, arteriovenous shunts, and Paget disease.
3. Increased vasomotor tone. Increased output of epinephrine and norepinephrine as occurs in pheochromocytoma is one example of this type of hypertension. Administration of sympathomimetic drugs is another. Essential hypertension is probably based on this mechanism, but increased total body sodium leading to an increased blood volume may also be a pathophysiologic mechanism. Unfortunately, this approach omits dissecting aneurysm and coarctation of the aorta, two important causes of hypertension.
Diagnosis
The latest blood pressure guidelines, issued in 2003 by the National Heart, Lung, and Blood Institute, divide blood pressure measurements into four general categories:
§ Normal blood pressure. Your blood pressure is normal if it's below 120/80 mm Hg. However, some doctors recommend 115/75 mm Hg as a better goal. Once blood pressure rises above 115/75 mm Hg, the risk of cardiovascular disease begins to increase.
§ Prehypertension. Prehypertension is a systolic pressure ranging from 120 to 139 mm Hg or a diastolic pressure ranging from 80 to 89 mm Hg. Prehypertension tends to get worse over time. Within four years of being diagnosed with prehypertension, nearly one-third of adults ages 35 to 64 and nearly half the adults age 65 or older develop high blood pressure.
§ Stage 1 hypertension. Stage 1 hypertension is a systolic pressure ranging from 140 to 159 mm Hg or a diastolic pressure ranging from 90 to 99 mm Hg.
§ Stage 2 hypertension. The most severe hypertension, stage 2 hypertension is a systolic pressure of 160 mm Hg or higher or a diastolic pressure of 100 mm Hg or higher.
Your doctor will likely take two to three blood pressure readings each at two or more separate appointments before diagnosing you with high blood pressure.
This is because blood pressure normally varies throughout the day — and sometimes specifically during visits to the doctor, a condition called white-coat hypertension.
Borderline high blood pressure
Borderline hypertension is defined as mildly elevated blood pressure higher than 140/90 mm Hg at some times, and lower than that at other times.
If, during the follow-up of a patient with borderline hypertension, the blood pressure becomes persistently higher than 140/ 90 mm Hg, an anti-hypertensive medication is usually started. Even if the diastolic pressure remains at a borderline level (usually under 90 mm Hg, yet persistently above 85)treatment may be started in certain circumstances.
http://www.medicinenet.com/high_blood_pressure/page4.htm#borderline
No comments:
Post a Comment