Seven out of 10 people with suspected angina are not receiving appropriate X-rays, putting them at risk of heart attacks, researchers have said.
Women, elderly people and those of southern Asian descent are particularly unlikely to be given the test even if they are suitable for it, they said.
A study found that patients not given a type of X-ray known as a coronary angiography were more likely to die from heart disease. They were also more likely to be admitted to hospital with unstable angina or a heart attack.
The study, including experts from Barts and the London as well as the University College London Medical School, was published in the British Medical Journal.
It involved analysing more than 10,000 patients to determine whether they were offered coronary angiography.
This is a specialist X-ray which involves injecting dye into the arteries so clinicians can assess the extent of damage to the heart and any narrowing of the arteries.
The aim of the study was to see whether having an angiography in the early stages of heart disease, when a person has suspected stable angina characterised by chest pain after exertion, affects their outcome.
Patients with suspected stable angina attending six chest pain clinics in England between January 1996 and December 2002 took part in the study. An independent panel of doctors found that 1,375 of the patients were suitable for angiography.
Each patient was followed up three years later to determine whether their heart disease had progressed or whether they had suffered something like a heart attack.
The researchers concluded: "Overall, 69% of patients deemed appropriate for angiography did not undergo this investigation." They said there could be a number of possible explanations for the results, including different referral methods, or patients not wanting to undergo the procedure.