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Cardiologists have called it their greatest unmet need — a test to predict when a patient is about to have a heart attack.
Scientists in California last year detected elevated clusters of endothelial cells in the blood of heart attack victims. Now researchers at Utah's Intermountain Medical Center have identified a genetic signal in the blood that surfaces days before a heart attack.
"We think it's an interesting signal that may help us anticipate and prevent heart attacks through aggressive treatment," said one of the study's authors, Jeffrey Anderson, director of cardiovascular research at Intermountain's Heart Institute.
Surgical, drug and diagnostic interventions have come a long way, said Anderson, explaining that early in his career, "When someone came in with [heart attack] symptoms, we'd put them in bed and shock them if they had cardiac arrest."
Then came therapies to remove blood clots and surgeries to open arterial flows, he said.
"But as a cardiologists, one of our challenges and disappointments is we just have no way of predicting when someone is going to have a heart attack in advance. So we're always playing catch up, and sometimes help comes too late."
With heart disease, plaques — cholesterol, calcium and other molecules — build in the blood and become stuck to artery walls. Some remain stable and stay there, but others break free, which can lead to a heart attack or stroke.
Molecular biologists have discovered a relationship between instable arterial plaques and a type of ribonucleic acid (RNA) called microRNA, which regulates a host of processes involved in heart disease.
Changes in the levels of certain microRNA could theoretically signal when danger lurks, Anderson explained. But the only way to identify those changes is to find patients who had suffered a heart attack shortly after having their blood collected.
As it happens, in the early 1990s, Intermountain Healthcare physicians created a Heart Study Registry, which today contains the records and blood samples of more than 30,000 heart patients.
Oxana Galenko, a scientist at Intermountain, scoured the registry for patients who had suffered a heart attack within 44 days of having their blood collected and found 30 individuals.
She then analyzed their blood samples for about a dozen microRNAs that had been cited in other studies as being involved in heart disease.
She found that weeks before a heart attack, patients' microRNA 122 and 126 dramatically dropped.
Galenko believes that something about these microRNAs being present prevents people with heart disease from having a heart attack.
"MicroRNAs turn things off. Whatever they usually turn off in people with heart disease before a heart attack isn't being turned off when microRNA levels are reduced, which may be causing something else to be activated," she says. "MicroRNAs act like a watch dog, and when their levels are reduced, heart disease takes a turn for the worse and heart attacks are likely to occur."
Intermountain presented results of the study at a meeting of the American College of Cardiology on Sunday.
Anderson said the study needs to be replicated using larger samples. "We're talking with other health systems that might have blood banks and we'll continue to draw samples from patients here too," he said.
But the findings inspire hope of one day being able to detect looming heart attacks with a simple blood test.
It's not uncommon for doctors to see high-risk patients every one to three months, he said. "At that time you could take a blood sample."
It might also be possible to develop a finger prick test kit similar to that used by diabetics, Anderson said. "Patients could literally do the test every few days or weekly."
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