It was found that those who suffered heart attacks had higher levels of fibrinogen and fewer naturally occurring anti-coagulating factors in their blood.
Fibrinogen is the part of the blood that forms into fibrin, long strands of fibre which trap red blood cells and platelets, developing into clots.
The research means that doctors can better identify a high risk group who would most benefit from surgery or who could be targeted with preventive drugs. The data also gives scientists more precise information into the causes of heart attacks, helping them to develop effective treatments.
The study, co-ordinated by the London School of Hygiene and Tropical Medicine, recruited 3,000 angina patients, aged 40 to 70, from nine European countries. They were monitored for two years and their blood analysed.
Dr Simon Thompson, senior lecturer in medical statistics, said: 'The results of this collaborative study are exciting. They give us a much better picture of the biology of a heart attack and show us how to identify people at higher risk and how to take care of them.
'We will be more able to see where we need to take drastic intervention, such as by-pass surgery.'
He said that aspirin was already used as an agent to help to thin blood but that the strong 'clot- buster' drugs, given after a heart attack, were too powerful to be used as a preventive drug for angina patients.
Dr Thompson said that the role of blood fats was still important in heart disease, though more and more scientists were investigating the role of fibrinogen.
The results of the study, which is part of a European Concerted Action on Thrombosis project, funded by the European Community, will be given in detail on Wednesday to the 14th Congress of the European Society of Cardiology, which opened in Barcelona yesterday .
The research is expected to show that results were consistent across the study, regardless of the country of origin of the patients and of their traditional diets. The nations were the United Kingdom, France, Switzerland, Austria, the Netherlands, Greece, Italy, Belgium and Germany.