Researchers looked at data collected in 14 countries on 20,881 patients hospitalized for acute coronary syndromes. Of those, 1,763, or eight percent, did not report chest pain. Older patients, women and diabetics were more likely to fall into this group.

Researchers found that the conditions of about a quarter of such patients were initially misdiagnosed, compared with only two percent of patients with chest pain.

In their training, doctors are taught that not every heart attack or case of unstable angina is accompanied by chest pain, and that other symptoms can include faintness, shortness of breath, heavy sweating or nausea. But in the study, the patients without chest pain were less likely to be given drugs to thin their blood to reduce the risk of further damage, or to undergo surgical intervention. The difference continued up until the patients left the hospital, when they were less likely to be discharged with prescriptions for drugs to reduce blood pressure or cholesterol.

"If you feel particularly unwell, with shortness of breath, dizziness or faintness or persisting nausea or vomiting, seek medical attention," said the study's lead author, Dr. David Brieger of Concord Hospital in Sydney. "It is possible these symptoms may be related to your heart, even if they are not accompanied by chest pain."