Cardiac culprit: autopsies implicate C-reactive protein in fatal heart attacks. (This Week).

The blood chemical called C-reactive protein (CRP)--an indicator of inflammation--is elevated in many heart disease patients. A new study of people who died suddenly of various causes finds that those who succumbed to a heart attack had an abundance of CRP in the blood, even though few had had outward signs of heart problems.

The finding bolsters the case for using CRP as a diagnostic tool to detect heart ailments because autopsies revealed that high CRP concentrations in blood coincide with the presence of dangerously unstable athero-sclerotic plaques in the coronary arteries.

Plaques can be fat-filled or fibrous. In a coronary artery, either type can cause a heart attack. Unstable, fat-filled plaques can burst, and the blood's clotting factors rush to the site and block the vessel. Sometimes fibrous plaques also come apart, attracting clotting agents, or they remain intact but narrow the vessel and short-circuit the heart's signals, says Allen P. Burke, a pathologist at the Armed Forces Institute of Pathology (AFIP) in Washington, D.C.

Fatty, unstable plaques "are accidents waiting to happen," says Burke's colleague, Renu Virmani, also a pathologist at AFIP. Their study, the first to use data from autopsied heart attack victims to assess CRP's role in such deaths, will appear in the April 30 Circulation.

The researchers autopsied 302 people who had died suddenly of heart attacks, auto accidents, or other misfortunes.

The autopsies showed that 71 people who had died of heart attacks had stable plaques in their arteries. Another 73 of the heart attack deaths resulted from clotting due to rupture of fatty plaques or erosion of fibrous plaques inside a coronary artery. The heart attack victims had significantly higher CRP concentrations in blood than did the 158 people who died of noncardiac causes. Those who died from ruptured fatty plaques had the highest average concentrations.

During all the autopsies, the team counted the unstable, fatty plaques in the coronary arteries. People with the greatest number of these plaques were most likely to have high CRP concentrations in the blood.

"This is a very interesting study" because it ties plaque instability to CRP concentrations, says Edward T. H. Yeh, a cardiologist at the University of Texas M.D. Anderson Cancer Center in Houston.

A growing body of research demonstrates CRP's potential as a warning sign of a heart attack in otherwise healthy individuals (SN: 6/14/97, p. 374). Some physicians measure patients' CRP, but that's not routine, says Virmani.