DALLAS, NOV. 12 -- A protein that a researcher calls the "heart-attack maker" is elevated in black Americans and could explain their increased rate of heart attacks, according to a study released today.

"It is helpful in explaining why some individuals have heart attacks at early ages," said Thomas Pearson of the Mary Imogene Bassett Research Institute in Cooperstown, N.Y.

A study of white and black doctors in their fifties revealed that levels of the protein were more than twice as high in the blacks, Pearson said at the annual scientific meeting of the American Heart Association.

The protein, called lipoprotein (a), or Lp(a), is related to and probably works like LDL, the so-called bad cholesterol, Pearson said.

"I call it the heart-attack maker," he said, because it packs a double punch. Like LDL, it encourages the clogging of arteries. But, unlike LDL, it also interferes with an enzyme that helps to dissolve the resulting clots.

Last year, Pearson's study found the risk of heart disease in the black doctors to be 2.4 times the risk for white doctors. The discovery of a corresponding difference in Lp(a) levels "may be a new area to help explain that," he said.

"We think that Lp(a) is a major, major risk factor -- right up there with hypertension -- for coronary heart disease in blacks," Pearson said.