Emotional   stress may be a trigger of otherwise unexplained cases of cardiac arrest, new research shows.

An international research team found that survivors of unexplained, or “idiopathic,” cardiac arrest were likely to have been through a highly stressful event the day before suffering the often-fatal heart condition.

Of the 25 survivors the researchers interviewed, 9 said they’d dealt with a severely or moderately stressful event during the 24 hours before they went into cardiac arrest. Only 2 of 25 adults in a comparison group that had a Heart attack or Chest pain requiring invasive treatment reported a recent stressful event.

In addition, 20 of the cardiac arrest patients said they’d been through significant stress in the 6 months prior to their heart trouble, versus 10 patients in the comparison group.

Cardiac arrest occurs when the heart suddenly stops working, most commonly due to a heart-rhythm disturbance called ventricular fibrillation (VF). In VF, the electrical impulses controlling the heartbeat become chaotic, causing the ventricles - the heart’s main pumping chambers - to quiver instead of contracting as they should. Unless VF is corrected by an Electrical shock from a defibrillator machine, the person can die within minutes.

Usually, VF can be attributed to an underlying Heart disease. But there are cases, referred to as idiopathic VF, where doctors cannot pinpoint a heart problem as the cause.

The new findings suggest that psychological stress may play a role in such cases of unexplained cardiac arrest, according to lead study author Dr. Richard D. Lane, a professor of psychiatry at the University of Arizona in Tucson.

He and his colleagues report the findings in the journal Psychosomatic Medicine.

The study included 25 men and women who were interviewed an average of 5 years after suffering unexplained VF, and a comparison group of patients treated for heart attack or chest pain caused by impaired blood flow to the heart.

More than half of the VF patients said they’d been through severe stress in the 6 months before suffering cardiac arrest. One 44-year-old woman, for instance, said she had a difficult marriage and had worked long days without a weekend off for 3 years; shortly before her cardiac arrest, a relative underwent major surgery and the woman was denied a weekend off from work.

In addition, nine VF patients said they’d dealt with severe or moderate stress the day before their cardiac arrest. One 40-year-old woman, for instance, said she had just ended a serious relationship and was hurt and “furious.”

It is rare for ventricular fibrillation to be unexplained, and certainly for most people, a stressful event does not trigger such an extreme physiological reaction.

It’s possible, according to Lane, that in cases of unexplained VF, patients in fact have some genetic defect that makes them vulnerable to the heart arrhythmia, and stress helps trigger a cascade of events that leads to VF.

The survivors in this study, Lane said, may have had such a genetic abnormality, but did not receive testing for it after their cardiac arrest. Or they may have had some genetic vulnerability that researchers have yet to identify.

Exactly why stress might send some vulnerable people into cardiac arrest is not fully clear, but Lane said there is strong evidence that in people with existing heart disease, emotional stress may precipitate cardiac events like heart attack.

It’s thought that the effects of stress on the autonomic nervous system - which controls, among other vital processes, the working of the heart - may help explain the connection.

SOURCE: Psychosomatic Medicine, May/June 2005.