(CBS/AP) It's a familiar story for doctors and patients. People report to the emergency room feeling symptoms and pass a cardiac checkup, only to have a heart attack days later. It's an issue scientists have grappled with as they've tried to develop a test that can predict when heart attacks will happen.
The researchers behind a new study say they're now closer than ever to finding this test.
Most heart attacks happen when fatty deposits in an artery burst open, and a blood clot then forms to seal the break. If the clot is too big, it blocks off blood flow.
The problem with today's best tests is that, "We don't have a way to get at whether an artery's going to crack, the precursor to a heart attack," said study author Dr. Eric Topol, director of California's Scripps Translational Science Institute.
Scripps researchers reported a new lead in the March 22 issue of Science Translational Medicine by searching people's blood for specific cells that appear to flake off the lining of a severely diseased artery.
For the study, researchers measured high levels of those cells, deformed ones, floating in the blood of 50 people who'd just had a heart attack. The cells are called "circulating endothelial cells" and shed from the endothelium, or the lining of blood vessels, into the bloodstream.
First, Topol's team paired with Veridex LLC, a Johnson & Johnson unit that makes technology used to find cancer cells floating in blood. Could it find these cardiovascular cells, too?
The researchers took blood samples from 50 heart attack patients - before they had any artery-disturbing tests or treatments - and from 44 healthy volunteers. They found lots of the endothelial cells floating in the heart attack victims' blood, and very little in the healthy people's blood.
The big surprise they found was the cells in the heart patients were grossly deformed. "Sick cells," Topol said.
Next, Topol said his team soon will begin needed studies to learn how early those cells might appear before a heart attack, and if spotting them could allow use of clot-preventing drugs to ward off damage. Some San Diego emergency rooms will study an experimental blood test with chest-pain sufferers whose standard exams found no evidence of a heart attack, he said.
Don't expect a test to predict heart attacks any time soon - a lot more research is needed, caution heart specialists not involved with the study. But they're intrigued.
"This study is pretty exciting," said Dr. Douglas Zipes of Indiana University and past president of the American College of Cardiology. It suggests those cells are harmed "not just in the minutes prior" to a heart attack, he said, "but probably hours, maybe even days" earlier.
"It's a neat, provocative first step," added Dr. William C. Little, cardiology chief at Wake Forest Baptist Medical Center. "But it is not a biomarker ready for prime time."
The study couldn't tell when the flaky abnormal cells first appeared - and that's key, Little said. It's not clear how many heart attacks happen too suddenly for any warning period.
But Topol theorizes there are plaques that break apart gradually and may shed these cells for up to two weeks before the heart attack. He cites autopsy studies that found people's arteries healed several plaque ruptures before the final one that killed them.
About 935,000 people in the U.S. have a heart attack every year, according to government figures. Doctors can tell who's at risk: People with high blood pressure and cholesterol, who smoke, have diabetes, are overweight or sedentary.
According to the American Heart Association, signs of a heart attack include chest pain or discomfort that lasts for more than a few minutes, pain or discomfort in both arms, the back, neck, jaw or stomach, shortness of breath, cold sweat, nausea or lightheadedness.
But there's no way to tell when a heart attack is imminent. Tests can spot that an artery is narrowing, or if a heart attack is under way or already has damaged the heart muscle. They can't tell if the plaque inside arteries is poised to rupture. So it's not that uncommon for someone to suffer a heart attack shortly after passing a stress test or being told that their chest pain was nothing to worry about.
WebMD has more on heart attacks.