Heart attacks, long thought to be caused mainly by cholesterol buildup in the arteries, may actually have an infectious trigger.
A groundbreaking new study from researchers in Finland and the UK suggests that dormant bacteria hiding inside arterial plaques could be responsible for many heart attacks, changing how scientists think about one of the world’s leading killers.
The research, published in the Journal of the American Heart Association, found that plaques in the arteries—fatty buildups of cholesterol that can block blood flow—often contain bacterial biofilms.
A biofilm is a sticky, protective layer created by bacteria that allows them to survive unnoticed for years, or even decades, without causing obvious symptoms. Because of this shield, the body’s immune system and antibiotics cannot easily reach the bacteria.
But the calm doesn’t last forever. The study found that a viral infection or another external stressor can “wake up” these dormant bacteria.
Once activated, they multiply rapidly, sparking inflammation in the surrounding artery.
This inflammation can weaken and rupture the fibrous cap covering the plaque. When the plaque bursts, it can form a blood clot, which blocks blood flow to the heart and causes a myocardial infarction, more commonly known as a heart attack.
Professor Pekka Karhunen, who led the study, said the discovery challenges decades of conventional wisdom.
Until now, experts believed that heart attacks were primarily triggered when the body reacted to oxidized low-density lipoprotein (LDL), often called “bad cholesterol.” While cholesterol remains an important factor, the new findings show bacteria may also play a direct role.
“Bacterial involvement in coronary artery disease has long been suspected, but direct and convincing evidence has been lacking,” Karhunen explained. “Our study demonstrated DNA from several oral bacteria inside atherosclerotic plaques.”
To confirm the discovery, the researchers developed an antibody that specifically targeted the bacteria they found. This revealed hidden biofilm structures in arterial tissue. In patients who had experienced a heart attack, bacteria released from these biofilms were observed, along with strong immune responses that led to the rupture of plaques.
The implications are wide-reaching. If bacterial biofilms contribute to heart attacks, doctors may one day be able to diagnose and treat coronary artery disease in new ways—potentially even using vaccines to prevent heart disease before it starts. This would mark a major shift in both prevention and treatment strategies.
The study was carried out by scientists from Tampere and Oulu Universities, the Finnish Institute for Health and Welfare, and the University of Oxford. They analyzed tissue samples from individuals who had died of sudden cardiac death as well as patients undergoing surgery for severe atherosclerosis.
For now, the research suggests that heart disease may not only be a condition of cholesterol and lifestyle but also an infectious disease. If confirmed by further studies, this discovery could transform how doctors understand, treat, and prevent heart attacks.
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