Heart attacks increased in the wake of 9/11

Doctors there believe that the psychological stress surrounding the event may have triggered dozens of extra "cardiac events".

News of the tragedy may have caused rises in blood pressure which increase the risk of heart attacks.

The study from New York Methodist Hospital was presented at a conference.

Other reports have suggested a direct link between stressful events such as major sporting events and natural disasters and an increase in heart attacks.

Experts think that these would not necessarily have been prevented if the "psychological trauma" never happened - but that the event simply precipitated the attack in a patient with dangerously hardened arteries.

Big rise

The team from the Brooklyn hospital looked at the records of more than 400 patients admitted with suspected heart problems in the 60 days after September 11.

Emotional trauma and stress can increase risk

They found that 15% of them were due to a full heart attack - compared with 11% of a similar sample of 400 taken from the previous 60 days.

A check of the same period in the previous year revealed a clear difference.

The proportion of patients admitted with unstable angina - acute chest pain - fell in the same period, suggesting it was perhaps some of these patients who had progressed to a full-blown heart attack as a result of watching the terrorist attack unfold on television.

The New York Methodist Center is only a few miles from Ground Zero, and doctors quickly noticed that the number of heart attacks was on the increase in the wake of the tragedy.

TV stress

Dr Jianwei Feng, addressing a meeting of the American Heart Association, said that it might be endlessly replayed television images of the attack that were the problem.

He admitted one man suffering from chest pain, who condition worsened considerably as he watched coverage of the disaster in the hospital.

"The more he watched the TV reports about the attack, the more upset he became," said Dr Feng.

"He began to have heart palpitations and shortness of breath."

He said that a chemical released in response to stress increased the risk.

Large variations in rates are possible from one 60-day period to the next Professor Doug Carroll, University of Birmingham

"Anytime a person experiences psychological or emotional stress, catecholamine levels rise, which increases heart rate and blood pressure."

This can directly trigger an attack by causing a rupture of a one of the hardened "plaques" which form on the arteries of people with heart disease.

The natural healing response of the damaged artery wall causes inflammation and makes the formation of a clot which causes a heart attack more likely.

However, Professor Doug Carroll, from the University of Birmingham, who has carried out research into sporting events and heart attacks, said that he would expect to see the biggest rise in attacks over just a three day period after the traumatic event - rather than 60.

He said: "Large variations in rates are possible from one 60-day period to the next.