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Essential hypertension

Hypertension or high blood pressure is a medical condition where the blood pressure is chronically elevated. While it is formally called arterial hypertension, the word "hypertension" without a qualifier usually refers to arterial hypertension. more...

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Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurysm, and is a leading cause of chronic renal failure.

Definition

Blood pressure is a continuous variable, and risks of various adverse outcomes rise with it. A blood pressure of less than 120/80 mmHg is defined as "normal" in adults. Hypertension is usually diagnosed on finding blood pressure of 140/90 mmHg or above, measured on both arms on three occasions over a few weeks.

Recently, the JNC VII (The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure) has defined blood pressure 120/80 mmHg to 140/90 mmHg as "prehypertension". Prehypertension is not a disease category. Rather, it is a designation chosen to identify individuals at high risk of developing hypertension (JNC VII).

In patients with diabetes mellitus or kidney disease studies have shown that blood pressure over 130/80 mmHg should be considered a risk factor and may warrant treatment.

Etiology

Essential hypertension

  • Age. Over time, the number of collagen fibres in artery and arteriole walls increases, making blood vessels stiffer. With the reduced elasticity comes a smaller cross-sectional area in systole, and so a raised mean arterial blood pressure.
  • High salt intake
  • Sedentary lifestyle
  • Tobacco smoking
  • Alcohol abuse
  • High levels of saturated fat in the diet
  • Obesity. In obese subjects, losing a kilogram of mass generally reduces blood pressure by 2 mmHg.
  • Stress
  • Low birth-weight
  • Diabetes mellitus
  • Various genetic causes

Secondary hypertension

While most forms of hypertension have no known underlying cause (and are thus known as "essential hypertension" or "primary hypertension"), in about 5% of the cases, there is a known cause, and thus the hypertension is secondary hypertension.

Pathophysiology

The mechanisms behind the factors associated with inessential hypertension are generally fully understood, and are outlined at secondary hypertension. However, those associated with essential hypertension are far less understood. What is known is that cardiac output is raised early in the disease course, with total peripheral resistance normal; over time cardiac output drops to normal levels but TPR is increased. Three theories have been proposed to explain this:

  • Inability of the kidneys to excrete sodium, resulting in natriuretic factor (note: the existence of this substance is theoretical) being secreted to promote salt excretion with the side-effect of raising total peripheral resistance.
  • An overactive renin / angiotension system leads to vasoconstriction and retention of sodium and water. The increase in blood volume leads to hypertension.
  • An overactive sympathetic nervous system, leading to increased stress responses.

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Home Monitoring in Patients with Essential Hypertension
From American Family Physician, 1/15/02 by Richard Sadovsky

Results of studies using self-reporting of blood pressure measurement by way of telecommunication systems have demonstrated declines in both systolic and diastolic blood pressure, but patients are known to often report inaccurate blood pressures, especially when the blood pressure is high. Rogers and associates conducted a randomized, controlled trial that used 24-hour ambulatory blood pressure monitoring measurements to more accurately identify changes in blood pressure and reported these results by electronic transmission to physicians.

Patients with essential hypertension were included in the study if they were being considered for a change in antihypertensive therapy because of elevated blood pressure despite antihypertensive treatment; adverse side effects from hypertensive medication; an office systolic pressure of at least 180 mmHg or a diastolic pressure of at least 110 mmHg, and no current use of antihypertensive agents. All patients received printed material on nonpharmacologic approaches to blood pressure control including weight reduction, increased physical activity and a change in diet, when necessary. Baseline height, weight, and body mass index were recorded.

Of the 121 patients in the trial, 60 were randomly assigned to the home-service group and 61 to the usual-care group. The intervention was automatic blood pressure recording at home. Patients in the intervention group took their blood pressure three times in the morning before eating or drinking and three times in the evening before going to bed at least three times weekly for a minimum of eight weeks. Data were automatically transmitted to a support center at Welch Allyn, the manufacturer of the telecommunication devices. Weekly reporting of systolic and diastolic pressures and heart rate was provided to both the primary physician and the patient. Physicians adjusted medications by telephone or office visit.

The usual-care group had no home blood pressure monitoring. The primary study end point was change in mean arterial pressure during the trials. This was obtained using a 24-hour ambulatory blood pressure monitoring device at baseline and at the conclusion of the study. The median time of the study was 11 weeks.

The mean arterial blood pressure decreased in patients receiving the home service regardless of gender, age, or ethnicity. Medication changes were significantly more common in the study (home-service) group, but the mean decrease in arterial pressure was not related to a medication change.

The authors conclude that patients with essential hypertension who use a telecommunication service to report measurements have a greater decrease in blood pressure than patients receiving usual care. Part of this beneficial effect may have been caused by more frequent medication changes, but blood pressure also decreased in home-service patients who did not have a change of medication. Patients may have been more motivated to make healthy lifestyle changes or were more adherent to their medication regimens when they were able to see their pressure readings on the home device.

COPYRIGHT 2002 American Academy of Family Physicians
COPYRIGHT 2002 Gale Group

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