A new study from researchers in Finland and the United Kingdom has raised the possibility that heart attacks may be linked to infection, challenging decades of medical understanding. The findings, published in the Journal of the American Heart Association, suggest that bacterial activity inside arteries could be a hidden trigger of myocardial infarction.

The study revealed that cholesterol-rich atherosclerotic plaques can contain bacterial biofilms—a gelatinous layer where microbes remain dormant for years, protected from both the immune system and antibiotics. At some point, however, a viral infection or another external factor can reactivate these bacteria, leading to inflammation. This inflammatory response may rupture the fibrous covering of the plaque, cause clot formation, and ultimately result in a heart attack.

Professor Pekka Karhunen, who led the research, explained that while coronary artery disease has long been attributed mainly to oxidized LDL cholesterol, the study provided direct evidence of bacterial DNA within arterial plaques, including bacteria commonly found in the mouth.

The research team confirmed the presence of these biofilms using antibodies that revealed their structures within arterial tissue. Bacteria released from the biofilms were observed in cases of myocardial infarction, provoking immune responses and inflammation that destabilized the arteries.

According to the scientists, the discovery could open new directions in diagnosis, treatment, and prevention. Most significantly, it raises the prospect of developing a vaccine against coronary artery disease and heart attacks.

The study is part of a broader EU-funded cardiovascular health program involving 11 countries, with contributions from Finnish universities, the Finnish Institute for Health and Welfare, and the University of Oxford. Tissue samples were collected from patients with atherosclerosis who underwent arterial surgery and from individuals who died of sudden cardiac death.