The finding will add to the growing evidence that infection is an additional risk factor for heart disease along with smoking, poor diet, lack of exercise and family history. Heart disease rates in Britain have been falling for the past 25 years, despite little change in the national diet, and some scientists have speculated that only an infectious agent could explain the rise and fall of the "epidemic".
Researchers at St George's Hospital Medical School, London, tested the blood of 213 survivors for signs of infection with Chlamydia pneumoniae, a common cause of chest infections and believed to be present in up to half the population.
The survivors were followed for 18 months and those with the highest level of infection had up to four times the risk of further attacks or problems requiring bypass surgery or other treatment. However, when members of this group were treated with antibiotics their increased risk was virtually eliminated.
Dr Sandeep Gupta, of St George's Hospital Medical School, who led the research, published in the American journal Circulation, said: "I think this is very exciting news. For 10 years this link between infection and heart disease has been smouldering. This is a big new piece in the jigsaw. I would say it's a small breakthrough."
A much larger study, involving more than 2,000 patients, was needed to examine the importance of Chlamydia as a heart disease risk factor. But if the bug was implicated in just 10 per cent of the 300,000 deaths in Britain each year from heart disease, treatment with antibiotics could save lives. "It would be a shame not to explore it further," he said.Reuse content