People who have an intense fear of dying during a heart attack could suffer worse outcomes, research suggests.
Compared with people who had a less intense fear of dying, those with the most had a four times higher risk of suffering big inflammatory responses in the body.
These biological responses can damage the heart and lead to patients suffering poorer health in the longer term.
Fear of dying during a heart attack is quite common -- affecting one in five patients in the latest study.
Researchers led by a team at Imperial College London followed 208 patients with acute coronary syndrome (ACS).
ACS is a condition that needs immediate medical attention. It is caused by an artery blockage, leading to a heart attack or unstable angina.
Symptoms include chest pain, shortness of breath, sweating, nausea and vomiting.
Experts analysed the emotional responses of patients, including their levels of distress and fear of dying.
They also measured levels of tumour necrosis factor alpha (TNF alpha), a molecule involved in inflammation, within two to three days of hospital admission.
Three to four weeks later, researchers made a home visit to the patients to record their heart rate variability (HRV) and levels of the stress hormone cortisol.
Low HRV suggests the heart is not functioning well and could predict future heart problems while cortisol plays a key role in controlling inflammation.
Professor Andrew Steptoe, the British Heart Foundation professor of psychology at University College London, who worked on the study, said: "Although survival rates have improved tremendously over the last few decades, many patients remain quite frightened during the experience.
"Fear of dying is not just an emotional response, but is linked into the biological changes that go on during acute cardiac events."