Blood pressure may predict recurrent cardiovascular events in women

03/10/04

American Heart Association rapid access journal report:

DALLAS, March 16 The risk of repeat heart attacks, strokes and other cardiovascular events in women increases as blood pressure rises, researchers report in today's rapid access issue of Circulation: Journal of the American Heart Association.

The study is one of the first to examine prospectively the relationship between blood pressure and secondary risk exclusively in women, according to lead author Peter J. Mason, M.D., M.P.H.

"We found a strong continuous relationship between increasing blood pressure and the risk of secondary cardiovascular (CVD) events in women, and that even borderline elevations in blood pressure are associated with an increased risk," Mason said.

Mason did the research as a National Heart, Lung, and Blood Institute-sponsored cardiovascular epidemiology fellow at the Brigham and Women's Hospital Division of Preventive Medicine. He is currently a cardiology fellow at Boston Medical Center.

The prospective study of 5,218 female health professionals (average age 62) found that for each 10 millimeters of mercury (mm Hg) increase in systolic blood pressure (the top number in a reading), a woman's CVD risk increased 9 percent.

High blood pressure causes the heart to work harder than normal to pump blood, causing it to enlarge and weaken over time. Most of the earlier studies that have examined the association between blood pressure and CVD risk focused on patients without known heart or blood vessel disease.

The women in this study -- followed an average of 6 years -- are part of the larger Women's Antioxidant Cardiovascular Study. The WACS is an ongoing double-blind, placebo-controlled secondary prevention trial of the benefits and risks of antioxidant vitamins, folic acid and vitamins B6 and B12 among women with CVD or three or more coronary risk factors. Women in the current study had confirmed CVD events such as heart attack or stroke, coronary artery bypass graft or angioplasty.

Systolic blood pressure (SBP) is the pressure when the heart beats. The lower number in a blood pressure reading is called the diastolic blood pressure (DBP) and is the pressure between beats. Normal blood pressure is defined as SBP below 120 mm Hg and DBP below 80 mm Hg. High blood pressure is defined as blood pressure of 140/90 mm Hg or greater.

"Our prospective data demonstrate that SBP is a strong independent predictor of CVD events among middle-aged and older women with known CVD," Mason said.

Although diastolic pressure was a weaker predictor of CVD risk compared to SBP, Mason said it's still an important component and doctors need to consider both numbers. "Both measures are important but, relatively speaking, in our cohort of women systolic blood pressure proved to be the stronger predictor of risk," he said.

The researchers found increased risk starting at systolic blood pressures of 130 mm Hg, a level called "prehypertension" in people without known CVD. In a multivariate analysis that adjusted for other risk factors, SBP of 130-139 mm Hg increased a women's relative risk by 28 percent compared to the risk of a woman with SBP at the level of 120-129 mm Hg, Mason said.

"Our finding that CVD risk increases with borderline SBP elevation is consistent with previous findings in primary prevention, as well as recommendations from the Seventh Report of the Joint National Committee on Prevention, Detection, and Treatment of High Blood Pressure (JNC 7) that call for initiating antihypertensive therapy in patients with diabetes or chronic kidney disease with SBP equal or greater than 130 mm Hg," he said. "Our data suggest that women with CVD and borderline elevations in SBP are at increased risk of future events and might benefit from a lower targeted blood pressure."

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