It’s believed to be the first evidence of direct infection of heart muscle cells by the virus; viral particles were identified in different cell lineages of the heart, including cardiomyocytes, endothelial cells, mesenchymal cells, and inflammatory cells.
The case was described in a reportAugust 20 in The Lancet Child & Adolescent Health.
“The presence of the virus in various cell types of cardiac tissue, as evidenced by electron microscopy, shows that myocarditis in this case is likely a direct inflammatory response to the virus infection in the heart,” first author Marisa Dolhnikoff, MD, department of pathology, University of São Paulo, said in an interview.
There have been previous reports in adults with COVID-19 of both SARS-CoV-2 RNA by reverse transcription–polymerase chain reaction (RT-PCR) and viral particles by electron microscopy in cardiac tissue from endomyocardial specimens, the researchers noted. One of these reports, published in April by Tavazzi and colleagues, “detected viral particles in cardiac macrophages in an adult patient with acute cardiac injury associated with COVID-19; no viral particles were seen in cardiomyocytes or endothelial cells.
“Our case report is the first to our knowledge to document the presence of viral particles in the cardiac tissue of a child affected by MIS-C,” they added. “Moreover, viral particles were identified in different cell lineages of the heart, including cardiomyocytes, endothelial cells, mesenchymal cells, and inflammatory cells.”
‘Concerning’ case report
“This is a concerning report as it shows for the first time that the virus can actually invade the heart muscle cells themselves,” C. Michael Gibson, MD, CEO of the Baim Institute for Clinical Research in Boston, said in an interview.
“Previous reports of COVID-19 and the heart found that the virus was in the area outside the heart muscle cells. We do not know yet the relative contribution of the inflammatory cells invading the heart, the release of blood-borne inflammatory mediators, and the virus inside the heart muscle cells themselves to heart damage,” Dr. Gibson said.
The patient was a previously healthy 11-year-old girl of African descent with MIS-C related to COVID-19. She developed cardiac failure and died after 1 day in the hospital, despite aggressive treatment.
SARS-CoV-2 RNA was detected on a postmortem nasopharyngeal swab and in cardiac and pulmonary tissues by RT-PCR.
Postmortem ultrasound examination of the heart showed a “hyperechogenic and diffusely thickened endocardium (mean thickness, 10 mm), a thickened myocardium (18 mm thick in the left ventricle), and a small pericardial effusion,” Dr. Dolhnikoff and colleagues reported.
Histopathologic exam revealed myocarditis, pericarditis, and endocarditis characterized by infiltration of inflammatory cells. Inflammation was mainly interstitial and perivascular, associated with foci of cardiomyocyte necrosis and was mainly composed of CD68+ macrophages, a few CD45+ lymphocytes, and a few neutrophils and eosinophils.
Electron microscopy of cardiac tissue revealed spherical viral particles in shape and size consistent with the Coronaviridae family in the extracellular compartment and within cardiomyocytes, capillary endothelial cells, endocardium endothelial cells, macrophages, neutrophils, and fibroblasts.
Microthrombi in the pulmonary arterioles and renal glomerular capillaries were also seen at autopsy. SARS-CoV-2–associated pneumonia was mild.
Lymphoid depletion and signs of hemophagocytosis were observed in the spleen and lymph nodes. Acute tubular necrosis in the kidneys and hepatic centrilobular necrosis, secondary to shock, were also seen. Brain tissue showed microglial reactivity.
“Fortunately, MIS-C is a rare event and, although it can be severe and life threatening, most children recover,” Dr. Dolhnikoff commented.
“This case report comes at a time when the scientific community around the world calls attention to MIS-C and the need for it to be quickly recognized and treated by the pediatric community. Evidence of a direct relation between the virus and myocarditis confirms that MIS-C is one of the possible forms of presentation of COVID-19 and that the heart may be the target organ. It also alerts clinicians to possible cardiac sequelae in these children,” she added.