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Low Blood Pressure Risky for Heart Patients?

Controversial Study Shows Very Low Blood Pressure May Raise Risk of Heart Attack, Stroke
By
WebMD Health News
Reviewed by Louise Chang, MD

May 7, 2009 -- In patients with cardiovascular disease, very low blood pressure may actually boost their risk of stroke and heart attack, according to a new -- and controversial -- report.

"There is a point at which blood pressure lowering becomes counterproductive," says Franz H. Messerli, MD, a professor of clinical medicine at Columbia University College of Physicians and Surgeons and director of the hypertension program in the division of cardiology at St. Luke's-Roosevelt Hospital in New York.

Messerli is the senior author on the report linking very low pressures with a higher risk of heart attack and stroke, scheduled to be presented today at the annual meeting of The American Society of Hypertension in San Francisco.

The "danger" points, according to Messerli's analysis, are 110 or lower for systolic pressure (the top number of the reading) and 60 or lower for diastolic pressure (the bottom number).

For the general population, a blood pressure of 140/90 or above is considered high; blood pressure between 120/80 and 139/89 is considered prehypertension, according to the National Institutes of Health.

But another hypertension expert criticized the study on a number of fronts. "In my opinion this analysis should be ignored," says Henry Black, MD, a nephrologist and clinical professor of internal medicine at New York University School of Medicine.

Blood Pressure: The Lower the Better?

Messerli and colleagues extracted data from the Treating to New Targets (TNT) trial, which enrolled 10,001 patients with known coronary artery disease and assigned them to two different doses of Lipitor, trying to evaluate whether aggressive lowering of LDL "bad" cholesterol would reduce heart attacks and strokes. The patients were followed for nearly five years.

Messerli's team looked at the relationship between systolic blood pressure or diastolic blood pressure and major cardiovascular events such as heart attack and stroke.

"If you go down to 130, 120, it's no big deal," Messerli tells WebMD. But in his analysis, he found that reducing systolic blood pressure to 110 was associated with a 3.1-fold increased risk of major cardiovascular events.

As for diastolic pressure, those in the group with diastolic pressures of 60 or less had a 3.3-fold increased risk of heart attack and stroke.

In the study, a pressure of 140.6/79.8 was linked with the lowest rate of heart attack and stroke.

In general, Messerli says, doctors have long believed "the lower the better" when it comes to blood pressure. His study suggests that may not be so for those with known coronary artery disease. "The dictum 'the lower the better' does not apply for the TNT coronary heart disease population," he tells WebMD.

He concludes that a so-called J-curve relationship exists -- that is, pressures either too high or too low adversely affect the risk of heart attack and stroke. Why low pressure would do that is not certain, he says.

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