A straight-forward scan can identify patients with high risk of heart attack, say scientists.
Experts have developed an imaging technique that can detect life-threatening blockages in arteries.
If left untreated, the blockages - which are made of fatty deposits known as plaques - can rupture causing heart attacks. But the newly developed test can detect fatty plaques on the brink of rupture.
Fatty plaques at risk of rupture 'lit up' in some patients while they had a PET-CT scan during a clinical trial.
More than 90% of people scanned, who had had a heart attack recently, had a lit-up area in one of their blood vessels, corresponding exactly to the location of the plaque that caused their heart attack.
Approximately 40% of patients with angina also had a plaque that lit up yellow, as well as high-risk features suggesting a heart attack may be imminent, and aggressive treatment would be required.
"Being able to identify dangerous fatty plaques likely to cause a heart attack is something that conventional heart tests can't do. This research suggests that PET-CT scanning may provide an answer - identifying 'ticking time bomb' patients at risk of a heart attack," Professor Peter Weissberg, British Heart Foundation's medical director, said in a statement.
He added: "Nearly 20 years of BHF-funded research has led us to this point. We now need to confirm these findings, and then understand how best to use new tests like this in the clinic to benefit heart patients."
According to the British Heart Foundation, who part-funded the University of Edinburgh study along with the Scottish Government, 200 people die each day from a heart attack.