A Better Way to Measure Blood Pressure?
Measuring Blood Pressure Closer to Heart Better Shows if Blood Pressure Drugs Are Working
Nov. 14, 2005 (Dallas) -- The standard inflated arm cuff is not the best way to check whether a blood pressure-lowering drug is working, a new study suggests.
Measurement of central aortic blood pressure can better predict the risk of heart attack and stroke than the traditional arm blood pressure measurement, the researchers say.
Using the aortic blood pressure measurement, they found that newer blood pressure drugs known as calcium-channel blockers work better than the old standbys in keeping blood pressure under control.
But when an arm cuff was used, the two treatments lowered blood pressure equally.
"It's been assumed that blood pressure in the arm represents blood pressure elsewhere in the body, such as in the brain and heart," says researcher Bryan Williams, MD, professor of medicine at the University of Leicester in England.
"But this may not always be the case," he tells WebMD. "For patients in this study, measurement of the pressure in the arm underestimated the benefits of the calcium-channel blocker."
Getting Close to the Heart
The study, presented at the annual meeting of the American Heart Association, included 2,199 people. Nearly half got the calcium-channel blocker Norvasc plus an ACE inhibitor if necessary to control blood pressure, while the others got the conventional treatment of a beta-blocker drug plus a diuretic if needed.
In addition to having standard blood pressure measurements taken with the arm cuff, central aortic pressure was measured with the SphygmoCor system, which uses a computer program to interpret the shape of pulse waves measured at the wrist.
The calcium-channel blocker regimen reduced central aortic pressure by 4.3 points more than the beta-blocker regimen, the study showed.
"That translates into as much as a 30% reduction in risk of stroke," Williams says. "It is not insignificant."
Further Study Needed
Despite the findings, Williams says it's too soon to routinely ask doctors to check aortic blood pressure.
"The device is very promising and should be used in more clinical trials to see how different drugs affect blood pressure nearer the heart. But using the cuff is still easier and cheaper," he says, noting the SphygmoCor system costs nearly $17,500.
Timothy Gardner, MD, chairman of the committee that chose which studies would be highlighted at the meeting and a heart surgeon at Christiana Care Health Services in Wilmington, Del., agrees. "It's too expensive to do routinely -- at least for now. We have to do more studies to make sure it's worth it."
Nevertheless, "This is an important significant finding. Blood pressure obtained by a cuff may not necessarily reflect the effect of a drug on the heart," he tells WebMD.