High blood pressure: Definitions and priorities

For the media, the top health story of 2003 was SARS. It’s no surprise; SARS was new, dramatic, and deadly. It deserved the attention it got, and so did the other hot newsmakers, such as the perennial favorites: cholesterol, cancer, heart disease, hormone replacement, and Alzheimer’s. Everyone needs to learn as much as possible about these major problems — but the publicity they received overshadowed the disease that’s responsible for one of every eight deaths in the world. As usual, in 2003 hypertension earned its reputation as a silent killer.

Why don’t we pay more attention to high blood pressure? Perhaps because it’s so common. Since 50 million Americans have hypertension, it may be viewed as an inevitable, even normal, part of life. And because most people with high blood pressure feel perfectly well for decades, the disease is often dismissed with a shrug — until it causes a heart attack or stroke.

Hypertension does not get the respect it deserves. Indeed, a third of all hypertensive Americans don’t even know they have the illness. And even when high blood pressure is diagnosed correctly, it’s often treated incorrectly; in all, only 27% of Americans with hypertension are being adequately treated (see Harvard Men’s Health Watch, June 2003).

It’s time for another look at hypertension. To make progress against the disease that affects about a third of all American adults — including two-thirds of those older than 60 — both patients and physicians have to understand and implement new standards for diagnosis and treatment.

Blood pressure: The flow of life
Blood pressure is the driving force of the circulation, providing the energy that propels oxygen-rich blood to all the body’s tissues. Blood pressure depends on two factors: the pumping force of the heart and the diameter of the arteries that receive blood from the heart. The stronger the heartbeat, the higher the pressure; the narrower the arteries, the higher the pressure.

Blood pressure is not static, like a man’s height or weight, but a dynamic function that can vary from moment to moment, quite literally within the span of a heartbeat. The body’s control mechanisms allow pressure to rise at times of stress and to fall during repose. In healthy people, blood pressure falls to its lowest during sleep, spikes to its highest on awakening, and ranges up and down during the day according to circumstances.

Since blood pressure can fluctuate rapidly and widely, any one measurement represents just a snapshot of a person’s average pressure. When it comes to predicting complications, the average pressure is more important than the peaks and valleys, but for most people, one reading in a doctor’s office is the only view they’ll get. In most cases it’s good enough — if it’s done properly.

Measuring blood pressure
To get an accurate reading, you should avoid caffeine, nicotine, and exercise before your pressure is checked; they can all produce a temporary spike. Since stress can boost blood pressure more than nearly anything else, you should be relaxed. That’s easier said than done, especially in a medical setting. Your doctor should always repeat your reading if it’s borderline or high. Often, he’ll leave the cuff on your arm so you get used to it while you rest quietly for several minutes before taking a second reading. And if your pressure is still high, your doctor may arrange to have a nurse or technician measure it in more familiar surroundings, at home or work, to minimize the “white coat” effect. Even better, he can order a 24-hour ambulatory monitor to measure your pressure around the clock during normal activities. It’s the gold standard for checking blood pressure, but it’s expensive and cumbersome. Fortunately, most people can learn to check their own pressures accurately with an automated digital arm cuff; it’s an excellent way to separate the white coat effect from true hypertension, and it’s also valuable for monitoring therapy when blood pressure control is tricky.

No matter who is taking your pressure, it’s important to do it the right way. You should be sitting or lying quietly with your arm supported comfortably at the level of your heart. And it’s even more important to use the right size cuff. The inflatable bladder in the cuff should cover 80% of your arm’s circumference; if the cuff is too small, it will overestimate your pressure, and too large, underestimate it.

Although medical science is discovering new facts about hypertension, the basic method behind the measurement that could save your life dates from 1896, when Dr. Scipione Riva-Rocci invented the sphygmomanometer, or blood pressure cuff. Nine years later, Dr. Nikolai Korotkoff learned how to use a stethoscope with the cuff to determine both the systolic and diastolic pressures.

The systolic reading is the pressure in the arteries while your heart is pumping blood; the diastolic, while the heart is relaxed and refilling with blood between beats. The systolic pressure is always higher and is recorded first. By convention, the systolic pressure is written over the diastolic number; an excellent reading, for example, would be written as 110/70 and announced as “one-ten over seventy.”

Because Dr. Riva-Rocci’s original instrument used a column of mercury to calibrate pressure, it was measured in millimeters of mercury (mmHg). Since mercury is now recognized as a health hazard, today’s doctors use aneroid pressure cuffs; they are safer and just as accurate, but are still calibrated in mmHg. And although the newest devices rely on Doppler technology rather than sound to detect blood flow and pressure, they retain the same measurement.