The US National Heart, Lung, and Blood Institute (NHLBI) has published the latest guidelines for managing high blood pressure, known as "JNC-7". The last guidelines were issued in November 1997. Here is an edited version of the NHLBI on-line releases. These guidelines recognize the need for greatly improved blood pressure control in the USA, and should have important implications for both physicians and their patients. Robert Griffith, Editor.

Introduction

New clinical practice guidelines for the prevention, detection, and treatment of high blood pressure have just been released by the US National Heart, Lung, and Blood Institute (NHLBI).¹ The guidelines, which were prepared by a special committee of the National High Blood Pressure Education Program (NHBPEP), feature altered blood pressure categories, including a new "prehypertension" level - which covers about 22% of American adults or about 45 million persons. They also streamline the steps by which doctors diagnose and treat patients, and recommend the use of diuretics as part of the drug treatment plan for high blood pressure in most patients.

"Americans' lifetime risk of developing hypertension is much greater than we'd thought", says NHLBI Director Dr. Claude Lenfant. "For instance, those who do not have hypertension at age 55 have a 90% risk of going on to develop the condition. We also now know that damage to arteries begins at fairly low blood pressure levels - those formerly considered normal. Studies show that the risk of death from heart disease and stroke begins to rise at blood pressures as low as 115 over 75, and that it doubles for each 20 over 10 millimeters of mercury (mm Hg) increase. So the harm starts long before people get treatment. The new prehypertension category reflects this risk and, we hope, will prompt people to take preventive action early."

Awareness and treatment levels

According to a national survey, 70% of Americans are aware of their high blood pressure, 59% are being treated for it, and 34% of those with hypertension have it under control. Those percentages represent a slight improvement over rates for 10 years ago, when 68% of Americans were aware of their high blood pressure, 54% were being treated for it, and 27% of those with hypertension had it under control.

"Though improved, the treatment and control rates are still too low," said Dr Aram Chobanian, the Chairman of the Joint National Committee. The new guidelines focus on this problem, recommending factors that often lead to inadequate control, such as not prescribing sufficient medication. The guidelines stress that most patients will need more than one drug to control their hypertension and that lifestyle measures are a crucial part of treatment.

Categories of high blood pressure

The classification of blood pressure has been redefined, to allow for the new prehypertension category, and to simplify treatment approaches:

Category	Systolic BP (mm Hg)		Diastolic BP (mm Hg)
Normal	below 120	and	below 80
Prehypertension	120 - 139	or	80 - 89
Hypertension Stage 1	140 -159	or	90 - 99
Hypertension Stage 2	160 and above	or	100 and above

Those with prehypertension are not considered to need drug therapy, unless it's required by another condition, such as diabetes or chronic kidney disease; but they should make any necessary changes in lifestyle.

Treatment of hypertension

The guidelines recommend use of a diuretic, either alone or in combination with another drug class, as part of the treatment plan in most patients. Even though many studies have found diuretics to be effective in preventing hypertension's cardiovascular complications, they are currently not being sufficiently used.

Treatment depends on the type of patient with hypertension: those with stage 1 hypertension without associated conditions, those with more severe, or stage 2, hypertension but also without associated conditions; and those with associated conditions that indicate the need for specific classes of blood pressure-lowering medication; these are called "compelling indications", and they are heart failure, a high risk of a heart attack (MI), after a heart attack, diabetes, chronic kidney disease, and after a stroke.

For patients with stage 1 or stage 2 uncomplicated hypertension, the goal blood pressure is less than 140/90. In some patients in the third group - those with diabetes or chronic kidney disease - a goal blood pressure of less than 130/80 may be desirable. Many effective drugs are available. The most important of these are diuretics, beta blockers, ACE inhibitors, angiotensin receptor blockers, and calcium channel blockers.

In stage 1 uncomplicated hypertension, thiazide-type diuretics are recommended for most patients, although treatment with other drugs also may be considered. Two-thirds or more of patients require two or more drugs to control hypertension; the selection of the initial medication is probably less important than the need to achieve blood pressure control.

In Stage 2 hypertension it is very likely that more than one medication will be required, and treatment may be initiated with two drugs, one of which should generally be a diuretic.

Patients with hypertension associated with a "compelling indication" require more specific therapy. For example, for those who have had a heart attack, beta blockers and ACE inhibitors are preferred; for those at high risk for coronary heart disease, ACE inhibitors, beta blockers, calcium channel blockers, as well as diuretics are recommended; and for chronic kidney disease, ACE inhibitors and angiotensin receptor blockers are drugs of first choice.

To obtain maximum benefits from blood pressure lowering, emphasis should also be placed on treating other cardiovascular risk factors including high blood cholesterol levels, smoking, diabetes, and overweight and obesity. People with high blood pressure are at greater than average risk for having such associated conditions, and their management is essential for achieving maximal cardiovascular health.

The benefits of adequate treatment

Overall, antihypertensive therapy has been associated with 35% to 40% average reductions in the incidence of stroke, 20% to 25% in heart attacks, and more than 50% in heart failure. It's estimated from clinical data that, in patients with other cardiovascular risk factors (e.g. smoking, diabetes, etc), a sustained 12-point reduction in systolic blood pressure over a 10-year period will prevent one death for every 10 patients treated. The risk of dementia in the elderly also appears to be reduced by blood pressure lowering.

The important lifestyle changes people can make are: maintain a healthy weight; be physically active; if you drink alcoholic beverages, do so in moderation; follow a heart-healthy eating plan, which includes limiting the amount of sodium in your diet; and do not smoke. The guidelines encourage those in the new normal category to adopt these measures as well.

This summary of the main recommendations is merely an overview. Anyone with high blood pressure, or caring for someone with hypertension, should get more information from the NHLBI website "Your Guide to Lowering High Blood Pressure" at: http://www.nhlbi.nih.gov/hbp/index.html