Diagnosed with hypertension nearly 40 years ago, Jerry Hartley knows the importance of tracking his blood pressure.
"The problem with the silent killer is that it is working every day," says Hartley, a self-employed sales consultant in Torrance.
But exactly how hard the silent killer is working is difficult to know. When the 73-year-old goes for his quarterly checkup, the reading taken by the nurse is generally higher than his physician gets when she examines him a few minutes later. And when Hartley checks his blood pressure at home, the reading is almost always higher than at the doctor's office.
So what is Hartley's true blood pressure level? Like everyone else's, it fluctuates constantly, so any reading is a point-in-time snapshot.
That can be unsettling, considering that physicians use blood pressure readings to decide how to treat hypertension -- and that poorly controlled blood pressure is a significant health threat.
To address this problem, three medical organizations -- the American Heart Assn., the American Society of Hypertension and the Preventive Cardiovascular Nurses Assn. -- recently issued a call to action for the 73 million Americans with hypertension, urging them to monitor their blood pressure at home.
Many with hypertension are already doing just that and have been since home monitors began flooding the market a few years ago. Indeed, 55% of patients reported monitoring their blood pressure at home in 2005, up from 38% five years earlier, according to the May issue of the Journal of the American Society of Hypertension.
Much of that home monitoring has been of questionable use, however.
"Patients come in with an index card, and it will have a haphazard number of readings they've taken in the last six months. It's different dates and different times -- you can't make heads or tails of it," says Dr. William B. White, a professor at the University of Connecticut School of Medicine's division of hypertension and clinical pharmacology and a co-author of the position paper recommending home monitoring. "You have no idea what to do with that information."
That is why the call to action gives detailed directions on how to measure and record blood pressure. By systematically monitoring it -- two readings in the morning and two in the evening every day for one week each quarter -- patients can provide their physicians with a better understanding of their true blood pressure level.
"We then have an idea of the relationship between time of day, blood pressure and medication administration," White says. "That way you can really get a good handle on whether or not the person's blood pressure is controlled."
Although conventional wisdom says blood pressure readings at a doctor's office are more reliable than those taken at home, a growing number of studies disputes that. A patient's "true" blood pressure is the average level over a period of time. Properly trained patients using reliable monitors at home obtain readings closer to their 24-hour average than professionals who measure the levels at the doctor's office, according to research conducted by White and others. That is because as many as 20% of patients diagnosed with hypertension suffer "white-coat effect," meaning their blood pressure climbs only when they are in a medical setting. And about 10% of patients may have lower readings at the doctor's office than in other situations, a condition known as masked hypertension.
Either situation provides misleading information to the physician responsible for creating and monitoring the patient's treatment plan.
Recording their blood pressure levels leaves some patients nervous, but training and experience generally win them over, White says.
"Patients feel a little empowered to be more in charge of what they're doing," he says. "They get a feeling of security if their blood pressure is well controlled. They get a feeling of insecurity if it's not -- but then they can do something about it -- which is the important thing."
Nancy Houston Miller, associate director of cardiac rehabilitation at Stanford University Medical Center and a co-author of the call-to-action paper, expects it will take years for home monitoring to become standard practice. She predicts that it will eventually be as common as self-monitoring of blood glucose by diabetics.
"People have to be educated as to how to use BP monitors correctly, when to notify their physicians about unusual readings and how to obtain the most accurate BP machines," says Miller, former president of the Preventive Cardiovascular Nurses Assn.