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Blood Pressure Numbers Warn of Heart Rhythm Risk

Difference between high and low readings can point to abnormal heartbeat, research shows

TUESDAY, Feb. 20, 2007 (HealthDay News) -- Increased pulse pressure -- the difference between the high and the low numbers that designate blood pressure -- is an important indicator of the risk of developing the dangerous abnormal heartbeat called atrial fibrillation, data from a major heart study show.

"The normal value of pulse pressure is about 40," explained cardiologist Dr. Gary F. Mitchell, president of Cardiovascular Engineering, a private company that does research funded by the U.S. National Institutes of Health. "When you get into the 50 range, the risk of atrial fibrillation starts to go up substantially."

Mitchell's team tracked more than 5,300 participants in the Framingham Heart Study for an average of 16 years.

Reporting in the Feb. 21 issue of the Journal of the American Medical Association., they found that a 20-point rise in pulse pressure was associated with a 34 percent increase in the risk of developing atrial fibrillation.

In atrial fibrillation, the upper chambers of the heart tend to quiver, rather than beat steadily. The condition can lead to formation of blood clots that travel to the brain, causing stroke. It is also associated with other major problems, including heart failure. An estimated 2.3 million Americans are diagnosed with atrial fibrillation, and the incidence is expected to increase as the population grows older.

Stiffness of the arteries is an indicator of atrial fibrillation risk, Mitchell said. "We have been doing various measurements of arterial stiffness, and it occurred to us that pulse pressure was a very good measure of arterial stiffness that is frequently ignored," he said.

Determining pulse pressure is a simple matter of subtraction. For example, someone with a blood pressure reading of 120 over 80 (the top number is the systolic pressure, the bottom number diastolic pressure) has a pulse pressure of 40. If systolic pressure goes up to 130 and diastolic pressure remains the same, the pulse pressure reading is 50.

"The key here is that if you can identify people at high risk of atrial fibrillation because of stiffening of the arteries, you can intervene and prevent such problems as atrial fibrillation," Mitchell said.

To Dr. Andrea Natale, medical director of the Cleveland Clinic's atrial fibrillation center, the report is another reminder of the importance of high blood pressure in cardiovascular disease.

Having a pulse pressure increase because of a low diastolic pressure "is theoretically possible but highly unlikely," Natale said. Almost invariably, a high pulse pressure is an indicator of high blood pressure, "and high blood pressure is the number one risk factor for atrial fibrillation," he said.

The connection between pulse pressure and atrial fibrillation risk needs more study, the researchers wrote. "Further research is needed to determine whether interventions that reduce pulse pressure will limit the growing incidence of atrial fibrillation," their report said.

Mitchell and Natale agreed that a high pulse pressure calls for intervention to reduce all the risks associated with high blood pressure. "If we intervene pharmacologically, we can affect that risk," Natale said.

In addition to medications, Mitchell called attention to lifestyle changes that can help keep blood pressure in the normal range. "Watching your weight, getting exercise, keeping the amount of sodium in your diet low, all these can help," he said.

More information

There's more on atrial fibrillation at the American Heart Association.

SOURCES: Gary F. Mitchell, M.D., president, Cardiovascular Engineering, Waltham, Mass; Andrea Natale, M.D., director, Cleveland Clinic Atrial Fibrillation Center; Feb. 21, 2007, Journal of the American Medical Association
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