Wednesday, March 3, 1999 Published at 19:07 GMT
Fear can kill
People died of fear during the Los Angeles earthquake
Scientists are launching a study to try to predict which people are in danger of dying from fright.
According to New Scientist magazine, researchers are now convinced that there is some truth in the old saying "I was scared to death".
In some cases, the body's own fight-or-flight response to danger appears to backfire and stop the heart completely. It may also trigger fatal heart attacks.
Doctors might be able to prevent this type of heart attack if they can identify the people at risk.
Dr James Muller, of Kentucky University, in Lexington, examines the causes of heart attacks.
Next month he begins a study of 2,000 people who have cardiac defibrillators implanted in their chests because they have already suffered one near-fatal heart attack.
He hopes to get a clearer picture of what types of physical and emotional stresses can induce abnormal heart rhythms.
Compelling evidence for the theory that fear can kill was provided by a study of deaths following the 1994 Los Angeles earthquake.
Dr Robert Kloner, a cardiologist at the Good Samaritan Hospital in Los Angeles, reviewed the records of the Los Angeles county coroner's department for the week before the earthquake, the day of the earthquake and corresponding control periods in 1991, 1992 and 1993.
His team found that on the day of the quake, the coroner recorded five times more sudden cardiac deaths than would ordinarily be expected.
This was nothing to do with people physically exerting themselves as they dug themselves out of the rubble, they said.
Dr Kloner said: "The typical story was that a patient clutched his chest, described chest pain, and dropped over dead."
During the early hours of 18 January, when the first attack occurred, 147 deaths were recorded.
Records for previous years showed that under normal circumstances only 93 deaths would have been expected during this time.
Most of these deaths were from heart attacks, and the increased mortality was limited to the first day of missiles.
Most people who die from fear have a long-standing condition - such as cholesterol problems - that puts them at additional risk.
But, in a tiny minority of cases, a healthy person may become so terrified that the brain triggers the release of a mix of chemicals so potent that it induces a massive influx of calcium into the heart cells.
This causes the heart to contract so fiercely that it never relaxes again.
Fight or flight
Terror, or any extreme emotional response, stimulates the fight-or-flight response.
The brain's hypothalamus tells the adrenal glands to start pumping hormones such as adrenaline and noradrenaline - also known as catecholamines - into the bloodstream.
The effect is to:
The brain also stimulates organs by causing nerves to secrete catecholamines directly into them - thus triggering the deadly contraction.
It appears the more common types of heart attacks can also be triggered by fear.
The release of hormones causes arteries to clamp down, for example, and platelets start to aggregate in readiness for clotting.
Blood rushing through narrowed vessels also generates shear forces against cholesterol plaques stuck to blood vessel walls.
If a plaque breaks, the debris can cause a clot and block blood flow to the heart muscle.