By Fackelmann, Kathy A.
Science News , Vol. 139, No. 16
Blood enzyme foretells heart attack threat
Elevated blood levels of a kidney-secreted enzyme may prove a potent predictor of heart attack risk among people with moderate hypertension, according to a new epidemiologic study. If further research confirms that finding, blood tests for the enzyme should help identify hypertensive people especially vulnerable to heart attack.
Years of high blood pressure can damage the heart and blood vessels. Some people with hypertension fall victim to a heart attack, while others escape that fate. Nearly 20 years ago, a retrospective study of hypertensive patients linked heart attack risk to the enzyme renin, but subsequent studies of similar patients showed no such association.
A research team in New York City has now reopened the case, adding significant weight to the renin/heart attack theory.
Renin "provides a powerful tool to identify [mild hypertensives] who are most likely to have a heart attack," says study coauthor Michael H. Alderman of the Albert Einstein College of Medicine. In the previous studies, investigators may have had trouble measuring the enzyme, he suggests.
Alderman and John H. Laragh of the Cornell University Medical College led a study of 1,717 men and women in New York City who belonged to various worker unions. All volunteers had a systolic (heart-pumping) blood pressure of at least 160 millimeters of mercury (mm Hg) and a diastolic (heart-resting) pressure of at least 95 mm Hg. (Hypertension is defined as systolic pressure of at least 140 and researchers measured blood renin at the study's start, detecting high levels in 12 percent of the volunteers. All participants received antihypertensive drugs for the next eight years.
At the end of the study period, the researchers discovered a fivefold greater incidence of heart attack in the high-renin subgroup compared with the rest of the sample. And among volunteers who had no other known cardiovascular risk factors -- such as smoking, diabetes or elevated blood cholesterol -- those with high renin levels were seven times more likely to suffer a heart attack than were those with low to normal renin, the team reports in the April 18 NEW ENGLAND JOURNAL OF MEDICINE. …