About seventy-five percent of people who died of COVID-19 are found to have harbored the SARS-CoV-2 virus in their hearts according to the most detailed study of cardiac tissue to date.
Those people, according to a report from Science, were more likely as well to experience irregular heart rhythms prior to death compared to patients without cardiac attack.
The research provides an understanding of how the infection may impair the heart, not to mention, the manner certain treatments may contribute.
Mayo Clinic cardiovascular pathologist Joseph Maleszewski, who was not part of the study said that the finding is painting "a really nice picture" of the link between COVID-19 and heart problems.
Ample Evidence of Heart Impairment
Researchers have ample evidence of heart impairment. Some people, for instance, exhibit elevated troponin levels. Troponins are molecules emitted in the blood when the heart is injured.
Others, on the other hand, have suffered from inflammation of the sac that surrounds the heart, as well as the heart's inflammation itself.
However, it has been unclear if these issues were the results of the SAS-CoV-2 virus that directly attacks the heart or the impairment is because of an overactive immune reaction.
Part of the problem is that past studies are mixed on whether the COVID-19-causing virus can enter heart tissue.
According to cardiovascular pathologist James Stone from Massachusetts General Hospital, SARS-CoV-2 uses real-time polymerase chain reaction or RT-PCR. It works by detecting viral RNA in tissue then making many DNA copies of it.
Once there is adequate DNA, a fluorescent tag or a molecule can stick to it and shine to expose its presence. However, Stone explained, the heart tissue is frequently processed and preserved through the use of chemicals such as paraffin which can collapse the RNA and avert detection.
Presence of the Virus in Patients' Hearts
Stone, together with his team, used a different method known as the 'in situ hybridization' and 'NanoString transcriptomic profiling'.
Like RT-PCR, these approaches utilize special molecules to attach to and identify pieces of viral RNA, although they do so without the need to make DNA copies first.
This method can detect viral RNA even if it has collapsed into smaller pieces. The scientists also analyzed around 1,000 pieces of heart tissue-- over 20 samples from each of the 41 COVID-19 subject patients. The cardiovascular pathologist added that said number is twice the number of samples from each patient in most studies.
The virus, as indicated in the team's report in Modern Pathology, was found to be present in 20 of the hearts and only these patients experienced new atrial fibrillations, both fast and irregular heart rhythms, or early or extra heartbeats as compared to others in the study. Stone calls such a correlation "pretty phenomenal."
Use of Steroid Dexamethasone
It remains unclear if COVID-19 directly attacked the heart in these cases. Most of the infested cardiac cells were immune cells, which could have been invaded by SARS-CoV-2 elsewhere in the body before they traveled to the heart.
It remains unclear too, if the virus, instead of the immune cells themselves, is the one that's causing the problems.
Nevertheless, the study may contribute to the explanation the steroid dexamethasone is quite helpful to some of the patients. The drug was one of the first discovered to prevent deaths from severe cases of COVID-19. A related report came out in USA Today in June 2020.
Stone said that it lowers inflammation and thus may have curbed the existence of SARS-CoV-2-concealing immune cells in the heart.
Only half of the patients treated with the said drug were found to have the virus in their hearts, compared with 90 percent of patients who were not on dexamethasone.
A related report on the link between COVID-19 and a patient's heart is shown on NHLBI's YouTube video below:
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