A blood test can more than halve the number of people admitted to hospital with a suspected heart attack, say doctors.
They say the rapid test, which looks for a chemical in the blood, would reduce stress for patients, save money and ease pressure on hospital wards.
Trials on 6,304 people, published in the Lancet medical journal, suggested it was 99.6% accurate.
The British Heart Foundation said the test would produce faster answers without affecting patient safety.
About one million people attend A&E departments in the UK with chest pain, only for most of them to be sent home after a sometimes lengthy and anxious stay.
They have levels of troponin, a chemical released by damaged heart muscle, tested when they are admitted and again 12 hours later.
The new test also looks for troponin, but can detect much lower levels and needs to be done only once. So those given the all-clear can go straight home.
A dull pain, ache or "heavy" feeling in the chest
Mild discomfort in the chest that makes you feel generally unwell
Pain that spreads to the back, arm or stomach
Pain that feels bad indigestion
Feeling light-headed or dizzy
The study, led by the University of Edinburgh and taking place in Scottish and US hospitals, estimated that two-thirds of patients could be discharged much more quickly.
Dr Atul Anand, one of the researchers and a physician at the Edinburgh Royal Infirmary, told the BBC News website: "It's really exciting. When you look at patients who come to medical wards with chest pain, 80% are going home 12 hours later.
"This avoids the hassle, cost and patient stress."
He said the test cost less than £10 although not all hospitals currently had the facilities to perform the more sensitive test.
However, Dr Anand said it would be "pretty straightforward" to introduce and there was a "clamouring" to do it.
Prof Jeremy Pearson, from the British Heart Foundation, said: "A faster, more accurate diagnosis of whether chest pain is caused by a heart attack would be better for patients and save the NHS money.
"No-one wants to be in hospital unless they have to be.
"What's important about this study is that the evidence shows you can quickly and confidently rule out a heart attack without compromising patient safety."