March 28, 2011-- Up to one-third of people who were thought to have treatment-resistant high blood pressure may actually have "white coat hypertension" -- blood pressure that spikes in the doctor's office.
The new findings appear in the journal Hypertension.
Treatment-resistant high blood pressure occurs when a person's blood pressure remains high despite taking at least three different drugs to lower it.
Of 8,295 people included in the study, 37% of those who were believed to have treatment-resistant hypertension actually had "white coat hypertension." That's according to 24-hour blood ambulatory pressure monitoring. In that type of monitoring, blood pressure is measured at regular intervals outside the doctor's office throughout the day.
"Ambulatory blood pressure monitoring continues to be needed and must be encouraged for a correct diagnosis and management of all hypertensive patients not controlled on three or more antihypertensive drugs," conclude the researchers, who were led by Alejandro de la Sierra, MD, director of internal medicine at Hospital Mutua Terrassa at the University of Barcelona in Spain.
A higher percentage of women than men had white coat hypertension, the study shows. People who really had treatment-resistant hypertension were more likely to smoke, have a history of diabetes, and other heart disease risk factors.
The researchers were unable to check adherence to medications, which is a problem with high blood pressure and may affect some of the findings.
Question of Cost
"There is no question that ambulatory blood pressure monitoring is the gold standard, but the question is, can everyone afford it. And the answer is probably not at the present time with the technology that we have," says Thomas D. Giles, MD. Giles is professor of medicine at Tulane University School of Medicine in New Orleans and the current president of American Society of Hypertension specialists' program.
The cost for ambulatory blood pressure monitoring can be up to $500 at some clinics, and only some plans reimburse for the test.
"Hard-to-treat hypertension means giving a lot of drugs and the blood pressure is not coming down," he says.
If it is truly resistant hypertension, there will be other signs in addition to elevated blood pressure, including kidney disease, he says.
"We go through a whole inventory," Giles says. "If your pressure is high in the office and there is nothing else associated with it, it's always fair to say ‘do you think I may have excitement?'" or white coat hypertension.
Other factors include the use of certain types of drugs and high-salt diet, which may affect blood pressure or treatment.
Dana Simpler, MD, an internist at Mercy Medical Center in Baltimore, says that ambulatory monitoring is important, but it's not always covered by insurers. "I would love to send them out with a 24-hour cuff and find out their readings, but that doesn't always happen."
To circumvent insurance issues, Simpler has some patients purchase a home blood pressure cuff and bring it to the office to make sure it is accurate, and then has them record their blood pressure at home.
"When it is up in the office and normal at home, we do nothing," she says. In these cases treatment may cause low blood pressure, which can result in lightheadedness and fainting.
The new findings seem plausible to Robert A. Phillips, MD, PhD, director of the Heart and Vascular Center of Excellence and senior vice president of UMass Memorial Medical Center in Worcester, Mass.
"If they don't have diabetes, kidney disease, are not a smoker, and don't have sleep apnea and other target organ damage, then we can say go ahead and do home monitoring to see if they have white coat hypertension," he says.
While white coat hypertension does not typically require treatment it should still be monitored every year, Phillips says.
The opposite of white coat hypertension is masked hypertension. This occurs when blood pressure is normal in the doctor's office, but elevated elsewhere, he explains.
"We don't have enough data to say what to do about masked hypertension, but people with masked hypertension may be the ones who need ambulatory monitoring because these people think they are well-controlled, but they are not and may be a higher risk," he says.
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