Previous studies have shown that earthquakes, war or even the loss of a World Cup Soccer match can increase rates of death from sudden cardiac arrest, in which the heart stops circulating blood.

"It's definitely been shown in all different ways that when you put a whole population under a stressor that sudden death will increase," said Dr Rachel Lampert of Yale University in New Haven, Connecticut, whose study appears in the Journal of the American College of Cardiology.

"Our study starts to look at how does this really affect the electrical system of the heart," Lampert said.

She and colleagues studied 62 patients with heart disease and implantable heart defibrillators or ICDs that can detect dangerous heart rhythms or arrhythmias and deliver an electrical shock to restore a normal heart beat.

"These were people we know already had some vulnerability to arrhythmia," Lampert said in a telephone interview.

Patients in the study took part in an exercise in which they recounted a recent angry episode while Lampert's team did a test called T-Wave Alternans that measures electrical instability in the heart.

Lampert said the team specifically asked questions to get people to relive the angry episode. "We found in the lab setting that yes, anger did increase this electrical instability in these patients," she said.

Next, they followed patients for three years to see which patients later had a cardiac arrest and needed a shock from their implantable defibrillator.

"The people who had the highest anger-induced electrical instability were 10 times more likely than everyone else to have an arrhythmia in follow-up," she said.

Lampert said the study suggests that anger can be deadly, at least for people who are already vulnerable to this type of electrical disturbance in the heart.

"It says yes, anger really does impact the heart's electrical system in very specific ways that can lead to sudden death," she said.

But she cautioned against extrapolating the results to people with normal hearts. "How anger and stress may impact people whose hearts are normal is likely very different from how it may impact the heart which has structural abnormalities," she said.

Lampert is now conducting a study to see if anger management classes can help decrease the risk of arrhythmia in this group of at-risk patients.