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Maybe your cholesterol test came in with good numbers, and you're feeling safe from a heart attack. Don't get too comfortable. Almost half of all cases of heart disease show up in people with normal cholesterol levels, according to Dr. Paul Ridker.
Ridker, director of the Center for Cardiac Rehabilitation at Brigham & Women's Hospital in Boston and faculty member with Harvard Medical School, points to C-reactive protein -- a substance associated with inflammation -- as a marker that predicts heart disease better than cholesterol.
But don't look for the test to be part of your regular check-up very soon. While C-reactive protein testing may be the wave of the future, it's not ready for prime time yet, according to some local doctors.
"I think it's coming. But we need to figure out guidelines of whom to measure it in and why," said Dr. Jonathan Abrams, cardiologist and professor at the University of New Mexico School of Medicine. Abrams organized the Santa Fe Colloquium on Cardiovascular Therapy at which Ridker spoke earlier this month.
Research on C-reactive protein is "very provocative," said Dr. Dan Friedman, director of preventive cardiology and cardiac rehabilitation at the Presbyterian Healthplex. But studies so far don't tell whether certain treatments reduce heart attacks or deaths in people with high levels, he said.
Until that information is available, it doesn't make sense to use the test to screen people for heart disease, he said.
C-reactive protein can be high in people with other diseases, so it may not work as a screening tool for heart disease risk, said Dr. Allen Adolphe, chairman of internal medicine for Lovelace Health Systems. If it were used to screen the general population, too many false positives -- people identified as being at risk for heart disease who really aren't -- would crop up, he said.
But Ridker said he and his colleagues have been impressed by how well C-reactive protein levels predict future heart attacks and even strokes in people who show no other risk factors, such as smoking or diabetes.
One study of a group of 27,139 women who experienced about 700 cardiovascular "events" (such as a heart attack) showed that survival rates were worst among women who had high C-reactive protein levels, but low levels of LDL (low-density lipoproteins, the "bad" cholesterol), he said.
"If you reduce LDL, you get rid of 19 percent of heart disease," Ridker said. "But if you get rid of the inflammatory response, you get rid of 40 percent of the risk. That's why clinical trials in the future will be focused on inflammation."
Scientists believe that inflammation plays some role in the buildup of plaque on the linings of blood vessels. People with high C-reactive protein levels tend to get heart attacks from a sudden rupture of a plaque, as opposed to a blockage from stable plaque in the blood vessel, he said. Those sudden ruptures can happen even in people who don't show a major narrowing of the blood vessels from plaque build-up.
Some research shows that people whose heart attack has been related to the inflammatory process do better with invasive interventions, such as insertion of a stent, Ridker said.
Statin drugs, which are used to lower cholesterol levels, also appear to reduce levels of C-reactive protein, he said. That suggests that some people with low cholesterol but high C-reactive protein might benefit from taking statins.
That's where more research still needs to be done.
"I wouldn't be surprised, when new data is digested, that there will be further impetus" to test people for C-reactive protein levels, Abrams said. Besides the statins, other cholesterol-lowering drugs also appear to bring down C-reactive proteins, he said.
Adolphe said he finds the test most useful in evaluating people who already have heart disease or high risk factors for the disease, such as diabetes, high blood pressure or high cholesterol. If their C-reactive protein levels are high, he might give those patients statins or increase the dosage if they already have a prescription, Adolphe said.
C-reactive proteins might not merely be warning signs of inflammation, Abrams added.
"CRP is probably not good in and of itself. It probably does things on the subcellular level that are harmful," he said.
Friedman said some of his patients have read newspaper articles about C-reactive proteins and have asked if they should have the test. Most, though, already have heart disease and are being treated for it, he said. Knowing their CRP level would not change their treatment, he said.
The screening question was examined as recently as last April in the journal Archives of Internal Medicine. That article concluded that many questions remain to be answered.
"Until these questions are resolved, we must agree with the reservations expressed by others that it is not yet time for ... testing to become an accepted practice," wrote authors Irving Kushner and Ashwini Sehgal, both physicians from Case Western Reserve University in Cleveland. "Otherwise, large numbers of people could be needlessly alarmed and a great deal of money unnecessarily spent on tests, office visits and medications."
Copyright 2002 Albuquerque Journal
