An estimated 45 million Americans who were previously considered as having normal blood pressure levels are now being informed that''s no longer the case.

The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) has convinced federal health officials to issue new national guidelines and label this new group of Americans as "prehypertensive."

The prehypertensive group, added to the estimated existing 50 million Americans who have hypertension, means that roughly one in three adults is at an increased risk of stroke, heart failure and kidney disease.

The two numbers that make up the blood pressure readings indicate the pressure on the artery walls, measured in millimeters of mercury, when the heart contracts - the top figure - and when it''s between beats - the bottom figure.

Normal blood pressure is considered anything less than 120 over 80. According to federal health officials, clinical studies and observational studies have revealed the possibility of death from heart disease and stroke begins to increase at levels as low as 115 over 75.

BJC experts say the new prehypertensive guidelines that define 120 to 139 for systolic blood pressure and 80 to 89 for diastolic pressure will save lives, because the earlier hypertension is identified, the better it is in preventing long-term damage to the heart.

Angela Brown, MD, a Washington University internist specializing in hypertension management at Barnes-Jewish Hospital, says it''s important that practicing physicians take an aggressive approach to blood pressure control. "The numbers of patients with heart failure and end-stage renal disease continue to rise," Dr. Brown says. "Part of this is due to poor blood pressure control. In simple terms, control the blood pressure, decrease the risk."

Dr. Brown says JNC 7 clinical trials showed there was a need to simplify the blood pressure classification. The diagnosis and management of hypertension, however, extends beyond blood pressure control. Other cardiovascular risk factors such as diabetes, dyslipidemia, obesity, diet and exercise play an important role in hypertension management.

"The JNC 7 report recognizes that when multiple risk factors are present in addition to hypertension, patients are at increased risk for adverse events and outcomes," Dr. Brown says. "In addition, we need to be more aggressive in treating hypertension. It''s clear from the data that increased blood pressure carries an increased risk for cardiovascular and renal disease. For every 20/10 mmHg increment in blood pressure over 115/75, the risk of cardiovascular disease doubles. It''s also been shown that people with normal blood pressure at age 55 have a 90 percent lifetime risk of developing hypertension.

"The new designation of prehypertension is to bring greater awareness to a new group of people. This is the point at which the most can be done toward prevention. These people shouldn''t be diagnosed with hypertension or treated with medication, but should engage in lifestyle changes to decrease their individual risk, and collectively decrease the population risk for developing hypertension. Prehypertension can be viewed as a ''wake-up call.''"

The JNC 7 also endorses the American Public Health Association resolution for a reduction in sodium in processed foods and restaurants during the next 10 years.

"The largest source of sodium in the diet comes from processed and prepackaged foods," Dr. Brown says. "It''s been well documented that some people are more salt-sensitive than others, and therefore have higher blood pressures as a result of their overall salt intake. When the amount of salt - and, therefore, water retained - is decreased, the blood pressure goes down. In order to show benefits to the general population, it''s important to decrease the amounts of sodium in foods."

The new guidelines won''t affect the work of Lisa de las Fuentes, MD, a Washington University cardiovascular fellow at Barnes-Jewish Hospital. Dr. de las Fuentes is in the early stages of a five-year study to determine whether genes influence the way the heart thickens in response to high blood pressure and how it uses different sources of energy, such as fat and sugar found in the bloodstream, to function.

"The new guidelines won''t significantly affect the study because we''ve been including a normal control population in addition to our known hypertensive subjects,"

Dr. de las Fuentes says. "Because our analyses use blood pressure as a continuous variable - meaning the actual blood pressure measurements, and not just a yes-or-no categorization as to whether participants have hypertension - there''s no need to increase the number of participants for the study, nor to re-study patients. Many of the subjects we have evaluated have come to us thinking they were normal, and have subsequently been diagnosed with hypertension."

Dr. de las Fuentes suggests that the majority of pre-hypertensive patients make some lifestyle modifications.

"Eat right, lose weight, exercise and get regular follow-ups with your physician to watch for progression to overt hypertension," she says. "We also need to evaluate for other cardiovascular risk factors, including cholesterol levels, diabetes, family history, and other medical problems that may be causing hypertension, such as sleep apnea and kidney disease. These are things that we should be recommending to just about all patients."

For a referral to a WU heart specialist at Barnes-Jewish Hospital, call 314-TOP-DOCS (314-867-3627) or toll-free 1-866-867-3627.

By Brian Bretsch of BJC Today, June 2, 2003