New clues have emerged on the link between Covid-19 and heart health. Researchers have conducted a series of experiments and shown that SARS-CoV-2’s spike protein can lead to heart muscle injury through an inflammatory process.
“It’s already known from the clinical side that Covid-19 infection can induce heart injury. However, what we don’t know is the mechanistic details of how this occurs. What we suspect is that the spike protein from SARS-CoV-2 has unknown pathological roles. Our data shows that it causes heart muscle damage,” said Dr Zhiqianq Lin, lead author of the study and an assistant professor at the Masonic Medical Research Institute in Utica, New York.
SARS-CoV-2 enters healthy cells via its spike protein on its surface. It then latches on to receptors known as angiotensin-converting enzyme 2 (ACE2) on healthy cells and may enter them. “Host natural immunity is the first line of defence against pathogen invasion, and heart muscle cells have their own natural immune machinery,” explained Dr Lin. But the study has now shown that SARS-CoV-2 may damage the heart via immune responses that are independent of ACE2, leading to inflammation.
The researchers also examined heart biopsies from a deceased patient with COVID-19-associated myocarditis or an inflamed heart muscle and a healthy heart. Whereas both the spike protein and the TLR4 protein were detected in cardiac muscle cells and other cell types in the Covid-19 patient, neither protein was detected in the healthy heart. “That means once the heart is infected with SARS-CoV-2, it will activate TLR4 signalling. Besides directly damaging the heart muscle cells, the spike protein itself is very inflammatory and may cause systemic inflammation that indirectly causes heart problems,” said Dr Lin.
Reacting to the new findings, Dr Nishith Chandra, Principal Director, Interventional Cardiology, Fortis Escorts Heart Institute, said, “We have seen a marked increase in numbers of heart patients during the last two years of Covid. In one study, it was found that almost 62 per cent of patients hospitalised for Covid had some or other form of heart issues. Even patients, who were not hospitalised, were at high risk for developing heart issues. There are a few common ways the heart is affected by Covid. One is inflammation of the heart muscle, called myocarditis, which ultimately weakens the heart and causes its failure. The other way Covid affects the heart is by causing clots in the small arteries of the heart, thus triggering attacks. We have seen a number of young patients recover from Covid and come to emergency with a heart attack. The third and very common presentation of the post-Covid syndrome is in the form of disturbances in the heart’s rhythm. Patients complain of fast heart rates and palpitation. Some also complain of slow heart rates.”
So, how does the virus affect the heart? “It is by two mechanisms. First, it enters healthy heart cells through its spike protein and directly injures the host heart cells, leading to heart muscle dysfunction. The other mechanism is by causing widespread inflammation, by stimulating the host’s own defence mechanism as is borne out by the new study,” added Dr Chandra.
He also dispelled the widespread myth that mRNA vaccines of Covid could cause heart muscle inflammation. “Detailed research has proven that since the mRNA vaccine does not contain spike protein, it does not damage the heart. Thus, vaccines are safe and do not cause myocarditis, as is widely believed.”
So, how do we treat Covid-related heart complications? “The best course is prevention. Don’t allow Covid to cause serious illness by getting yourself vaccinated. The judicious use of blood thinners and anticoagulants in critically sick Covid patients has also been found to reduce risk of clotting and heart attacks,” said Dr Chandra.
Moving forward, the researchers intend to investigate how SARS-CoV-2 spike proteins cause inflammation in the heart. So far, they have outlined two potential ways this may happen. The first possibility is that the spike protein directly activates inflammation in virus-infected heart muscle cells. The second possibility is that the spike protein is shed into the bloodstream and damages the heart as it circulates.