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Taking blood pressure to new lows

The lower-is-better rule doesn’t just apply to cholesterol.

Once upon a time, in a land not far away at all, a healthy blood pressure was thought to be 100 plus your age. That simple rule of thumb has gone the way of hats for men, cordiality in politics, and affordable health insurance. It was replaced in 1977 by a cutoff of 160/95 separating “normal” from high blood pressure. That cutoff continues to drift downward, steadily eroding what we think of as normal or healthy blood pressure.

National guidelines, published in 2003, took a range of blood pressures — 120/80 to 139/89 — that had been squarely in the normal camp and redefined them as prehypertension, or high blood pressure waiting to happen. Many people and their doctors thought that the hypertension experts got carried away. How does being labeled as having a “pre-disease” help anything, they wondered, especially when the guidelines didn’t recommend any specific treatment for prehypertension beyond awareness and lifestyle changes?

Research suggests that the stricter definition of healthy blood pressure is right on target, and that “the lower, the better” applies as much to blood pressure as it does to cholesterol.

Strategies for lowering blood pressure

There are many ways to attack high blood pressure. If it’s in the prehypertension zone, try lifestyle changes first (though with the CAMELOT results, doctors may be quicker to prescribe blood pressure-lowering medications). If it is truly high (a systolic pressure above 140 or a diastolic pressure above 90), then lifestyle changes and medications are in order.

Lifestyle changes:

  • Exercise more.

  • Eat more fruits, vegetables, and low-fat dairy products and less saturated fat (the DASH diet).

  • If you are overweight, try to lose some weight.

  • If you smoke, stop.

Drug therapy. The drug or drug combination used to control blood pressure doesn’t matter nearly as much as sticking with it to get blood pressure under control. Options include ACE inhibitors, angiotensin-receptor blockers, beta blockers, calcium-channel blockers, and diuretics.

How good is normal?

The simple question — Is so-called normal blood pressure best for us? — led to a large trial known as CAMELOT (Comparison of Amlodipine versus Enalapril to Limit Occurrences of Thrombosis). The results were presented at the American Heart Association meeting in November 2004 and published simultaneously in the Nov. 10, 2004, Journal of the American Medical Association.

An international team compared the effects of two different blood pressure-lowering drugs among almost 2,000 volunteers with coronary artery disease (one or more blocked arteries) and without high blood pressure. The average pressure was 129/78, which would be considered normal in any doctor’s office in the country.

One-third of the volunteers took the calcium-channel blocker amlodipine (Norvasc), one-third took the ACE inhibitor enalapril (Vasotec), and one-third took a placebo. The active drugs lowered systolic blood pressure by 5 points and diastolic pressure by 2.5.

During two years of follow-up, the volunteers taking amlodipine or enalapril did better than those taking the placebo. Fewer of the volunteers in the drug groups died of cardiovascular disease, had nonfatal heart attacks and strokes, needed bypass surgery or angioplasty, or were hospitalized for chest pain or heart failure than in the placebo group.

The differences weren’t huge — 23% of the people in the placebo group had one of these cardiovascular problems, compared to 20% in the enalapril group and 17% in the amlodipine group. But apply the findings to the millions of people with heart disease and normal-ish blood pressure, and they translate into thousands of saved lives and averted procedures.

But wait, there’s more. Some of the volunteers in each group agreed to undergo before-and-after tests in which a tiny ultrasound probe was inserted via a vein in the groin into one of the arteries feeding the heart. This test, called intravascular ultrasound, can map the movement of atherosclerotic plaque, much like satellite cameras track the advance and retreat of glaciers. The amount and placement of cholesterol-filled plaque barely changed in the volunteers who took a blood pressure-lowering drug, while it grew and advanced among the placebo-taking volunteers.

Blood pressure scale

How low can you go?

Blood pressure seems to be following cholesterol in the lower-is-better movement. In 2004, PROVE-IT and other trials challenged the target of 100 mg/dL for LDL (bad) cholesterol for people with heart disease. This work suggests that getting down to 75 mg/dL or even lower might be better.

Low LDL doesn’t seem to pose any problems. People who live primitive hunter-gatherer lifestyles have LDL levels around 65 — about half that of the average American. And no safety issues have emerged in people who use a statin to drive LDL below 70.

Blood pressure is different. You can lower it only so much before the body starts to rebel. At a systolic pressure below 90 or 80 mm Hg, the heart has trouble getting enough blood to the brain, and most people get lightheaded or perhaps even pass out.

Sliding scale

The CAMELOT study received a lot of attention because it supports the belief that treating even modestly elevated blood pressure can do some good. The sad fact, though, is that more than 50 million Americans have blood pressures far above the average in CAMELOT, and that two of every three people with hypertension don’t have their blood pressure under control, meaning below 140/90.

Blood pressure tends to climb with age, a sign of slow, steady damage to blood vessels. High blood pressure isn’t really a matter of cutoffs, but a matter of degrees. Moving from 138/89 to 142/92 certainly catapults you from prehypertension to hypertension on the charts. In reality, at 138/89 you were already at increased risk for having a heart attack or stroke. For every 20 mm Hg increase in systolic pressure or 10 mm Hg increase in diastolic pressure, your chances of dying from one of those conditions doubles.

If you have high blood pressure, guidelines call for getting it below 140/90, and even lower for people with diabetes or kidney disease. The word from CAMELOT suggests that the benefits of striving for an even lower blood pressure exceed the risks.

Posted by: Dr.Health

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