Decoded: How COVID-19 disease causes heart muscle damage, affects heart rate

Heart damage in COVID-19 patients is caused by the novel coronavirus infecting cardiac muscle cells, leading to cell death which interferes with the muscle's contraction, according to a study that may lead to the development of new drugs to treat the viral infection. While studies since the beginning of the pandemic have linked COVID-19 with heart problems such as reduced ability to pump blood, scientists, including those from the Washington University School of Medicine in the US, said it was unknown until now if these are directly caused by the virus infecting the organ, or due to inflammation elsewhere in the body.

In the current research, published in the Journal of the American College of Cardiology: Basic to Translational Science, they used stem cells to engineer cardiac tissue and modelled how the coronavirus infected the heart. The researchers found that viral infection not only kills heart muscle cells but destroys the muscle fibre units responsible for heart muscle contraction. According to the scientists, this cell death and loss of heart muscle fibres can happen even in the absence of 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," said study senior author Kory J Lavine from the Washington University School of Medicine.

Based on the study results, the researchers said the coronavirus is unique in the effect it has on the heart, especially in the immune cells that respond to the infection.

For most other viruses that affect the heart, they said the immune system's T cells and B cells are on the site of infection, however in COVID-19, the study found that the body's immune cells called macrophages, monocytes, and dendritic cells dominate the counter response.

"COVID-19 is causing a different immune response in the heart compared with other viruses, and we don't know what that means yet," Lavine said. "In general, the immune cells seen responding to other viruses tend to be associated with a relatively short disease that resolves with supportive care," he added.

According to the scientists, these immune cells are associated with a chronic condition that can have long-term consequences.

While the researchers could validate their findings by studying tissue from four COVID-19 patients who had heart injury associated with the infection, they said more research is still needed to "understand what is happening."

"Even young people who had very mild symptoms can develop heart problems later on that limit their exercise capacity," Lavine said.

"We want to understand what's 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 don't have an even larger epidemic of preventable heart disease in the future," he added.

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