Being angry or emotionally upset may increase the risk of a heart attack, a new international study involving Irish researchers has found.

Engaging in heavy physical exertion may also trigger an attack, the findings suggest.

The study involved over 12,400 people in 52 countries. The participants had an average age of 58 and all had suffered a heart attack for the first time.

"Previous studies have explored these heart attack triggers, however, they had fewer participants or were completed in one country, and data are limited from many parts of the world. This is the first study to represent so many regions of the world, including the majority of the world's major ethnic groups," explained the study's lead author, Dr Andrew Smyth, a researcher at the HRB Clinical Research Facility in Galway and at the Population Health Research Institute at McMaster University in Canada.

The study assessed the various triggers experienced by the participants prior to their heart attacks.

It found that experiencing anger or emotional upset, or undertaking heavy physical exertion, doubled the risk of a heart attack.

Furthermore, a combination of these factors was even more dangerous. Undertaking heavy physical exertion while angry or upset tripled the risk of a heart attack.

These triggers increased the risk irrespective of other known risk factors, such as smoking, obesity and high blood pressure. Dr Smyth said that it appears that these emotional and physical triggers have similar effects on the body.

"Both can raise blood pressure and heart rate, changing the flow of blood through blood vessels and reducing blood supply to the heart. This is particularly important in blood vessels already narrowed by plaque, which could block the flow of blood leading to a heart attack," he explained.

However, he insisted that when it comes to physical exertion, regular physical activity is still essential ‘so we want that to continue'.

"However, we would recommend that a person who is angry or upset who wants to exercise to blow off steam, not go beyond their normal routine to extremes of activity," he said.

Details of these findings are published in the American Heart Association's journal, Circulation.