Blood pressure: questioning a maxim.

Blood Pressure: Questioning a Maxim

In treating patients with high blood pressure, doctors routinely follow the maxim "the lower the better." Now some new research calls that practice into question. In a study of people with mild to moderate hypertension, epidemiologists found that when drug treatment caused a large drop in blood pressure, a person's risk of heart attack was nearly four times that of patients with more moderate decreases.

Patients with very small blood pressure reductions, indicating ineffective treatment, also suffered more heart attacks -- about three times more than those with moderate changes. The trend in stroke rates resembled that in heart attack rates. Blood pressure reductions of about 10 percent appeared safest overall, the researchers conclude.

Of the 50 million to 60 million people in the United States with hypertension, 80 percent fall into the mild to moderate category -- with a diastolic blood pressure (the pressure between heart contractions) of 90 to 104 millimeters mercury. They are at risk for stroke and for heart and kidney disease, but about 80 percent of deaths among these patients result from heart attack. Because the new findings suggest that aggressive, uniform therapy for hypertension may increase the risk of heart attack in some individuals, blood pressure goals should be kept in the moderate range, says Michael H. Alderman of the Albert Einstein College of Medicine in the Bronx.

Alderman and his co-workers determined the baseline blood pressures of 1,765 people entering treatment for hypertension, 25 percent of whom had abnormal electrocardiograms. Using these readings and measurements taken after treatment, the team calculated changes in blood pressure. And such changes, rather than a particular pressure reading or any other factor, predicted the risk of heart attack, they report in the Aug. 18 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

"The implication is you have to individualize treatment goals," Alderman says. "You can't just have a single number that everybody's blood pressure should be driven down to."

The physiological relationship between blood pressure cuts and heart attacks remains unclear. Too much pressure can damage artery walls, but too little pressure might reduce flow, especially in the many hypertension patients with atherosclerosis. A large drop in pressure could flip the balance and cause blood flow to the heart to plummet, Alderman speculates. Alternatively, he suggests that a patient's strong response to blood pressure drugs -- resulting in a drastic drop -- may indicate an unknown risk factor for heart attack in that individual. "Maybe it's some sort of vascular reactivity which is reflected in the measure of blood pressure," he says.

Although the epidemiologic results are difficult to explain, Alderman says, "they nevertheless have profound clinical implications." Not all blood pressure experts agree on that. Jeffrey A. Cutler, of the National Heart, Lung, and Blood Institute in Bethesda, Md., remains unconvinced. "The hard data to support doing anything other than lowering blood pressure as far as possible are not available," he contends. On the other hand, calling the report "not in keeping with politically popular thinking," John H. Laragh of the New York Hospital-Cornell Medical Center says it "shows that a moderate blood pressure decrease is the right goal. Too much reduction is as bad as no treatment."