People who have an intense fear of dying during a heart attack could suffer worse outcomes, research has suggested.
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 pain in the chest, 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.
“Large inflammatory responses are known to be damaging to the heart, and to increase the risk of longer-term cardiac problems such as having another heart attack.
“We found that, when compared with a low fear of dying, intense fear was associated with a four-fold increased risk of showing large inflammatory responses, measured by raised levels of TNF alpha.
“Interestingly, this was independent of demographic and clinical factors such as the severity of the cardiac event.
“Fear of dying and inflammatory responses in turn predicted biological changes in the weeks following an acute cardiac event, namely reduced heart rate variability and alterations in the output of the hormone cortisol.
“These processes may contribute to poor outcomes in the longer term.”
The research, carried out at St George’s Hospital in south London, was published in the European Heart Journal.
It found that the levels of distress experienced by patients had no link with whether they had suffered a previous heart attack.
However, those people with more intense distress could have been suffering more severe pain, and those who were economically deprived and had fewer social connections appeared to be affected the most.
More research is needed on the link between emotional responses and higher levels of TNF alpha, but the findings could suggest new ways of helping patients.
Prof Steptoe said: “This is an observational study, so we do not know whether helping people overcome their fears would improve the clinical outlook, or whether reducing the levels of acute inflammation would have beneficial emotional effects, but these are possibilities.”