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Hypertension

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Arterial hypertension, or high blood pressure is a medical condition where the blood pressure is chronically elevated. Persistent hypertension is one of the risk factors for strokes, heart attacks and heart failure, 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. Hypertension is usually diagnosed on finding blood pressure above 140/90 mmHg measured on both arms on three occasions over a few weeks. (Also see urgency below). In patients with diabetes mellitus studies have shown that blood pressure over 130/80 mmHg should be considered a risk factor and may warrant treatment. Recently there have been calls to define blood pressure over 120/80 mmHg as "pre-hypertension", even in non-diabetic populations.

Signs and symptoms

Hypertension

Hypertension does not normally present with any symptoms. It is commonly detected through "case finding" by doctors. Malignant hypertension (or accelerated hypertension) is a distinct condition, which presents with headaches, blurred vision and end-organ damage. It is recognised that stressful situations can increase the blood pressure; if a normally normotensive patient has a high blood pressure when being reviewed by a health care professional, this is colloquially termed white coat hypertension.

Hypertension is often confused with mental tension, stress and anxiety. While chronic anxiety is associated with poor outcomes in people with hypertension, it alone does not cause it.

Emergencies

Hypertension is rarely severe enough to cause symptoms. These only surface with a systolic blood pressure over 240 mmHg and/or a diastolic blood pressure over 120 mmHg. These pressures without signs of end-organ damage (such as renal failure) are termed accelerated hypertension. When end-organ damage is present, but in absence of raised intracranial pressure, it is called hypertensive urgency. Hypertension under this circumstance needs to be controlled, but hospitalization is not required. When hypertension causes increased intracranial pressure, it is called malignant hypertension. Increased intracranial pressure causes papilledema, which is visible on ophthalmoscopic examination of the retina.

Complications

While elevated blood pressure alone is not an illness, it often requires treatment due to its short- and long-term effects on many organs. The risk is increased for:

Pregnancy

See the main article: hypertension of pregnancy

Although few women of childbearing age have high blood pressure, up to 10% develop hypertension of pregnancy. While generally benign, it may herald three complications of pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-up and control with medication is therefore often necessary.

Diagnosis

Over 90% of all hypertension has no known cause and is therefore called "essential/primary hypertension". Often, it is part of the metabolic "syndrome X" in patients with insulin resistance: it occurs in combination with diabetes mellitus (type 2), combined hyperlipidemia and central obesity.

Important causes of secondary hypertension are:

Blood tests commonly performed in a newly diagnosed hypertension patient are:

Epidemiology

The level of blood pressure regarded as deleterious has been revised down during years of epidemiological studies. A widely quoted and important series of such studies is the Framingham Heart Study carried out in an American town: Framingham, Massachusetts. The results from Framingham and of similar work in Busselton, Western Australia have been widely applied. To the extent that people are similar this seems reasonable, but there are known to be genetic variations in the most effective drugs for particular sub-populations. Recently (2004) the Framingham figures have been found to overestimate risks for the UK population considerably. The reasons are unclear. Nevertheless the Framingham work has been an important element of UK health policy.

Treatment

Doctors recommend weight loss and regular exercise, as well as discontinuing smoking, as the first steps in treating mild to moderate hypertension. These steps are highly effective in reducing blood pressure. Unfortunately these actions are easier to suggest than to achieve and most patients with moderate or severe hypertension end up requiring indefinite drug therapy to bring their blood pressure down to a safe level.

Mild hypertension is usually treated by diet, exercise and improved physical fitness. A diet rich in fruits and vegetables and fat-free dairy foods and low in fat and sodium lowers blood pressure in people with hypertension. Dietary sodium (salt) causes hypertension in some people and reducing salt intake decreases blood pressure in a third of people. Regular mild exercise improves blood flow, and helps to lower blood pressure.

There are many medications for treating hypertension, together called antihypertensives, which—by varying means—act by lowering blood pressure. Evidence suggests that reduction of the blood pressure by 10 mmHg can decrease the risk for complications by about 25%.

In the ALLHAT trial, the diuretic hydrochlorothiazide was found to be the most effective antihypertensive medication in terms of reduction in risk of heart attacks and strokes. ACE inhibitors and calcium channel blockers were found to have no effect on these outcomes. Results in patients treated with Alpha blockers but not diuretics were found to be definitely less good (heart failure was more likely) and this arm of the trial was terminated early.

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