ST. LOUIS, Mo. Researchers in St. Louis are providing some much needed clarity about how COVID-19 impacts the human heart. COVID has been linked to cardiovascular complications for some time, but up until now its been a mystery as to how exactly the virus is interfering with the heart. For example, does the virus actually infect the heart itself? Or does it just cause inflammation which effects the cardiovascular system? Now, a team from Washington Universitys School of Medicine says theres evidence COVID-19 infects and replicates within carriers heart muscles cells.

This is of course bad news for the heart, which experiences cell death and muscle contraction issues as a result. In pursuit of an answer, the team used stem cells to create heart tissue modeling a COVID-19 infection.

Early on in the pandemic, we had evidence that this coronavirus can cause heart failure or cardiac injury in generally healthy people, which was alarming to the cardiology community, says senior author Kory J. Lavine, MD, PhD, in a university release.

Even some college athletes who had been cleared to go back to competitive athletics after COVID-19 infection later showed scarring in the heart. There has been debate over whether this is due to direct infection of the heart or due to a systemic inflammatory response that occurs because of the lung infection, the associate professor of medicine continues. Our study is unique because it definitively shows that, in patients with COVID-19 who developed heart failure, the virus infects the heart, specifically heart muscle cells.

Researchers also used stem cells to create tissues simulating heart muscle contractions. This process helped researchers to conclude that besides just killing heart muscle cells, COVID interferes with the organs contractions.

Notably, study authors add all of this heart damage can happen to an infected individual even if they show no signs of bodily inflammation.

Inflammation can be a second hit on top of damage caused by the virus, but the inflammation itself is not the initial cause of the heart injury, Lavine explains.

While this certainly isnt the first virus to impact the heart, the research team reports nothing is status quo when it comes to COVID-19. They explain that COVID-19 evokes a unique immune response dissimilar to anything seen when other viruses make contact with the heart.

COVID-19 is causing a different immune response in the heart compared with other viruses, and we dont know what that means yet, the researcher reports. In general, the immune cells seen responding to other viruses tend to be associated with a relatively short disease that resolves with supportive care. But the immune cells we see in COVID-19 heart patients tend to be associated with a chronic condition that can have long-term consequences. These are associations, so we will need more research to understand what is happening.

Researchers further confirmed their stem cell findings when they examined the real heart tissues from four COVID-19 patients.

Even young people who had very mild symptoms can develop heart problems later on that limit their exercise capacity, Lavine concludes. We want to understand whats happening so we can prevent it or treat it. In the meantime, we want everyone to take this virus seriously and do their best to take precautions and stop the spread, so we dont have an even larger epidemic of preventable heart disease in the future.

The study is published in JACC: Basic to Translational Science.

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COVID-19 kills heart muscle cells, interferes with a patients heartbeat - Study Finds