The COVID-19 literature has been peppered with reports about myocarditis accompanying the disease. If true, this could, in part, explain some of the observed cardiac injury and arrhythmias in seriously ill patients, but also have implications for prognosis.
But endomyocardial biopsies and autopsies, the gold-standard confirmation tests, have been few and far between.
Predictors of death in COVID-19 are older age, cardiovascular comorbidities, and elevated troponin or NT-proBNP – none of which actually fit well with the epidemiology of myocarditis due to other causes, Alida L.P. Caforio, MD, of Padua (Italy) University said in an interview. Myocarditis is traditionally a disease of the young, and most cases are immune-mediated and do not release troponin.
Moreover, myocarditis is a diagnosis of exclusion. For it to be made with any certainty requires proof, by biopsy or autopsy, of inflammatory infiltrates within the myocardium with myocyte necrosis not typical of myocardial infarction, said Dr. Caforio, who chaired the European Society of Cardiology’s writing committee for its 2013 position statement on myocardial and pericardial diseases.
“We have one biopsy-proven case, and in this case there were no viruses in the myocardium, including COVID-19,” she said. “There’s no proof that we have COVID-19 causing myocarditis because it has not been found in the cardiomyocytes.”
Emerging evidence
The virus-negative case from Lombardy, Italy, followed an early case series suggesting fulminant myocarditis was involved in 7% of COVID-related deaths in Wuhan, China.
Other case reports include cardiac magnetic resonance (CMR) findings typical of acute myocarditis in a man with no lung involvement or fever but a massive troponin spike, and myocarditis presenting as reverse takotsubo syndrome in a woman undergoing CMR and endomyocardial biopsy.
A CMR analysis in May said acute myocarditis, by 2018 Lake Louise Criteria, was present in eight of 10 patients with “myocarditis-like syndrome,” and a study just out June 30 said the coronavirus can infect heart cells in a lab dish.
Among the few autopsy series, a preprint on 12 patients with COVID-19 in the Seattle area showed coronavirus in the heart tissue of 1 patient.
“It was a low level, so there’s the possibility that it could be viremia, but the fact we do see actual cardiomyocyte injury associated with inflammation, that’s a myocarditis pattern. So it could be related to the SARS-CoV-2 virus,” said Desiree Marshall, MD, director of autopsy and after-death services, University of Washington Medical Center, Seattle.
The “waters are a little bit muddy,” however, because the patient had a coinfection clinically with influenza and methicillin-susceptible Staphylococcus aureus, which raises the specter that influenza could also have contributed, she said.
Data pending publication from two additional patients show no coronavirus in the heart. Acute respiratory distress syndrome pathology was common in all patients, but there was no evidence of vascular inflammation, such as endotheliitis, Dr. Marshall said.
SARS-CoV-2 cell entry depends on the angiotensin-converting enzyme 2 (ACE2) receptor, which is widely expressed in the heart and on endothelial cells and is linked to inflammatory activation. Autopsy data from three COVID-19 patients showed endothelial cell infection in the heart and diffuse endothelial inflammation, but no sign of lymphocytic myocarditis.