Dormant Bacteria Could Be Spark for Plaque Rupture, Study Shows

A pioneering study now suggests that heart attacks may, in some cases, result from infectious processes rather than solely lifestyle and cholesterol risks. Researchers from Finland and the UK have uncovered compelling evidence that bacterial biofilms hidden within arterial plaques can lie inactive for decades and, when triggered by a viral infection or other external stimulus, may ignite inflammation, rupture arterial plaques, and ultimately lead to myocardial infarction.

In the study, scientists from Tampere and Oulu Universities, the Finnish Institute for Health and Welfare, and the University of Oxford identified bacterial DNA—originating from oral bacteria—embedded within the atherosclerotic plaques of coronary arteries. These bacteria exist inside resilient biofilm structures that shield them from the immune system and antibiotics. The researchers also developed a targeted antibody that revealed these gelatinous biofilms in arterial tissue; in cases where individuals suffered a heart attack, bacteria appeared to have emerged from the biofilm, triggering immune responses that destabilised the arterial plaque.

Once awakened—by infections such as viral illness or other external triggers—the bacteria proliferate and prompt an inflammatory reaction. This inflammation can compromise the fibrous cap of the plaque, allowing it to rupture, which then instigates blood clot formation that may block the artery and provoke a heart attack.

Professor Pekka Karhunen, who led the investigation, noted that the prevailing view has held oxidised low-density lipoprotein cholesterol as the primary initiator of coronary artery disease. The presence of bacterial material within the plaques represents a significant shift in understanding the pathogenesis of myocardial infarction.

The findings open fresh prospects for diagnostics and prevention. Possibilities include development of antibodies to detect bacterial biofilms, antibiotic protocols targeting vulnerable patients, and even the design of vaccines against bacterial agents implicated in coronary events. The study forms part of a broader EU-funded cardiovascular research initiative involving 11 countries, with support from the Finnish Foundation for Cardiovascular Research and the Jane and Aatos Erkko Foundation.

Despite these groundbreaking findings, established risk factors—such as elevated cholesterol, hypertension, smoking, inadequate exercise and poor diet—retain their crucial role in cardiovascular health and prevention strategies.