Tracking Top Number in Blood Pressure May Be Enough
TUESDAY June 17, 2008 -- For patients over 50, doctors tracking hypertension may only need to monitor systolic blood pressure, ignoring diastolic blood pressure, British experts suggest.
Systolic blood pressure -- the top number in a reading -- is the pressure exerted at the beginning of the heart's pumping cycle, while diastolic pressure records the lowest pressure during the heart's resting cycle. Both pressures are routinely measured when taking blood pressure.
"We felt that trying to communicate two pressures to patients is a very confusing message," said Dr. Bryan Williams, a professor of medicine at the University of Leicester and Leicester Royal Infirmary, U.K., and co-author of a Viewpoint article in the June 17 online issue of The Lancet.
"If we could just get patients to focus on a single number, and recognize that that number needed to be lowered, it might help in both communicating the message and also improving treatment," Williams said.
Because there is such an emphasis on diastolic pressure, patients are not getting their systolic blood pressure adequately controlled, Williams contends. "We felt the best way of dealing with this was to say that people over the age of 50 probably didn't even need to measure diastolic -- it's only the systolic we should be focusing on," he said.
Some experts in the United States have long pushed for the change. In 2000, a National Institutes of Health-sponsored group published an advisory in the journal Hypertension that supported a clinical focus on systolic pressure.
As the population ages, a rise in systolic pressure resulting in what is called systolic hypertension is becoming more common, especially in people over 50, compared with diastolic hypertension, Williams noted.
Generally, systolic blood pressure continues to increase with age, while diastolic pressure starts to drop after age 50, which is the same time cardiovascular risk begins to rise. Therefore, there is an increased prevalence of systolic hypertension past age 50, whereas diastolic hypertension is practically nonexistent.
"It's pretty pointless to measure diastolic pressure, since it's falling anyway," Williams said. "Rising systolic pressure is the most significant factor in causing strokes and heart disease," he said. "That's what we need to be focusing on."
Using systolic blood pressure alone after age 50 should simplify treatment for doctors, policymakers and even drug companies by getting them to focus on ways to lower systolic pressure, Williams said.
Using systolic pressure alone focuses physicians' attention on what needs to be treated, since many may still be using diastolic pressure to guide treatment decisions, Williams said.
For people under 50, the scenario may be different. About 40 percent of adults under 40 years of age have diastolic hypertension, and about a third of those between 40 and 50 have the problem. For these patients, there needs to be a continued emphasis on both systolic and diastolic blood pressures, Williams's group said. However, controlling systolic blood pressure, even among these younger patients, almost always results in adequate control of diastolic blood pressure, too, they noted.
For people 50 or older, systolic pressure is high if it is 140 mmHg or above, according to the U.S. National Heart, Lung, and Blood Institute.
But one expert believes that there are still important reasons to concentrate on systolic and diastolic blood pressure for patients of any age.
"Inadequate control of hypertension contributes to a substantial proportion of preventable cardiovascular events worldwide," said Dr. Gregg C. Fonarow, director of the Ahmanson-UCLA Cardiomyopathy Center at the University of California, Los Angeles. "Elevations in systolic as well as diastolic blood pressure contribute to this cardiovascular risk, although in patients over age 50, elevations in systolic blood pressure impart greater relative risk," he said.
The proposal in this Viewpoint to only use systolic hypertension for the diagnosis and treatment of hypertension in patients age 50 and over, while thought-provoking and having the laudable aim to improving treatment and control of systolic blood pressure, may have unintended consequences that require further consideration, Fonarow said.
"Gains made in achieving better control of diastolic blood pressure in the last few decades may be lost if the sole focus of hypertension guidelines becomes systolic blood pressure," Fonarow said. "Studies have suggested that drops in diastolic blood pressure to very low levels may increase cardiovascular risk for patients with coronary artery disease; under this single dimension proposal, this risk could be obscured," he said.
"Furthermore, measurement of both systolic and diastolic blood pressure are essential components of global cardiovascular risk assessment using the Framingham and other risk assessment scores, hence the need to retain routine diastolic blood pressure measurement," Fonarow said.
Posted: June 2008