Patients who have a heart attack have unique cells floating in their blood, say US researchers.
Their study on 111 people, published in the journal Physical Biology, could spot the difference between healthy and heart-attack patients.
They are investigating whether testing for the cells can be used to predict those about to have a heart attack.
The British Heart Foundation said it was unlikely to change practice in the short term.
The team, at the Scripps Research Institute in California, looked for circulating endothelial cells in the blood of patients.
Fatty plaques build up on the walls of blood vessels and can ultimately rupture, releasing fragments of the plaque into the bloodstream. This can block the flow of blood in the vessels around the heart and cause a heart attack.
During this process endothelial cells were also released into the blood, the researchers said.
Tests in 79 patients after a heart attack were compared with 25 healthy people and seven having treatment for diseased blood vessels.
One of the researchers, Prof Peter Kuhn, said: “The goal of this paper was to establish evidence that these circulating endothelial cells can be detected reliably in patients following a heart attack and do not exist in healthy controls, which we have achieved.
“Our results were so significant relative to the healthy controls that the obvious next step is to assess the usefulness of the test in identifying patients during the early stages of a heart attack.”
Commenting on the findings, Dr Mike Knapton, from the British Heart Foundation, said: “In the short to medium term, it is unlikely to change how people in the UK are treated as we already have good ways to treat and diagnose heart attacks, and targets to ensure rapid pain-to-treatment times.
“This study appears to be laying the groundwork for future research to see if this test could be used to identify patients in the early stages of a heart attack.”