A study published in the Journal of the American Heart Association has identified specific bacteria commonly found in the mouth and throat inside the coronary artery plaque of people who died from sudden cardiac events. The bacteria in question belong to a group called viridans streptococci, organisms most people carry in their mouths without ever knowing it.
Researchers analyzed coronary plaque samples from 121 individuals who died from sudden cardiac death and 96 individuals who underwent endarterectomy, a procedure used to remove plaque buildup from arteries. Across both groups, viridans streptococci appeared consistently in the plaque samples, pointing to a pattern that researchers say warrants much closer attention.
Why bacteria in the mouth matter for the heart
Viridans streptococci are among the earliest colonizers in the formation of dental plaque. That detail matters because it suggests these organisms are not random visitors inside arterial plaque. They may arrive as part of a larger bacterial community, a biofilm made up of multiple species that travel from the mouth into the bloodstream and eventually embed themselves in vulnerable arterial walls.
Under normal circumstances, these bacteria cause no harm. They are a standard part of the oral microbiome and play a role in maintaining the mouth’s bacterial balance. The problem begins when they enter the bloodstream, particularly in people who already have atherosclerosis. Once inside an arterial plaque, they can trigger inflammation, and that inflammation is what makes a plaque unstable and more likely to rupture.
A ruptured plaque is the direct cause of most heart attacks.
What the lead researcher says
Dr. Pekka Karhunen, a professor at Tampere University in Finland and the study’s lead author, noted that advances in molecular microbiological techniques have renewed scientific interest in the role that infectious agents play in coronary plaque inflammation. For years, the connection between oral health and cardiovascular disease existed largely as a clinical observation. This study adds a layer of biological specificity to that conversation.
The findings do not establish that oral bacteria cause heart attacks outright. What they suggest is that these organisms may be active participants in the inflammation process that makes heart attacks more likely.
How cardiologists are interpreting the data
Cardiologists who reviewed the findings offered measured responses. Dr. Sergiu Darabant of Miami Cardiac and Vascular Institute noted that inflammation has long been understood as a significant driver of both plaque formation and plaque rupture. The study adds a new dimension to that picture by implicating oral bacteria as a possible source of that inflammatory activity.
Dr. Yu-Ming Ni of MemorialCare Heart and Vascular Institute acknowledged how common viridans streptococci are in the oral cavity but flagged a limitation in the study’s design. Because the research was observational, it cannot definitively establish when or how the bacteria became involved in the cardiac events studied. Timing matters enormously when trying to determine cause and effect, and that remains an open question.
What this means for everyday prevention
No approved vaccine exists for viridans streptococci. What does exist is a straightforward body of evidence connecting poor oral hygiene to elevated cardiovascular risk. Dental infections left untreated can allow bacteria to enter the bloodstream in significant numbers. Keeping teeth and gums healthy reduces that risk in a direct and practical way.
Dr. Brett Sealove, another cardiologist who reviewed the findings, reinforced that viridans streptococci are generally benign and serve useful functions in the oral environment. The danger is situational, arising specifically when these bacteria reach places they are not supposed to be, including heart valves, where they can cause endocarditis, and now potentially arterial plaque.
Staying current on vaccinations for influenza, COVID-19, and pneumococcal diseases also appears relevant, particularly for people with existing cardiovascular risk factors. Severe respiratory infections have their own documented associations with cardiac events, and reducing overall infectious burden is a reasonable protective strategy.
Where the research goes from here
Heart disease claimed approximately 19.8 million lives globally in 2022, with 85% of those deaths attributed to heart attacks and strokes. Research that identifies new biological mechanisms behind that toll has real implications for how prevention is approached.
The bacteria-to-heart-attack connection is still being mapped. But the consistency of viridans streptococci appearing in arterial plaque across two different patient populations gives researchers a specific target to investigate further. The mouth, it turns out, may be a more important window into cardiovascular health than previously understood.
