Eduardo Oliver
Head of the Experimental Pharmacology and New Targets in Cardiopulmonary Disorders Group at the Margarita Salas Biological Research Centre - CSIC
This multi-centre retrospective study analyses the evolution of 112 patients, from 23 mainly European and three US hospitals, with suspected acute myocarditis - a highly lethal inflammatory disorder of the heart if not treated in time - among a total of nearly 57,000 patients who have had covid-19 during the first four waves between February 2020 and April 2021.
The study confirms suspicions based on previous observations that SARS-CoV-2 infection may be implicated in causing acute myocarditis in some patients.
While the study shows that the percentage of patients with covid-19 who develop this type of cardiac disorder is relatively low (between 2-4 per 1,000), it highlights the seriousness of the effect and the importance of early detection and proper treatment to prevent associated deaths.
The study shows that those patients with acute myocarditis who also showed severe respiratory complications associated with covid-19 were almost 40% more likely to experience fulminant shock and 15% more likely to die. None of the patients with acute myocarditis but without pneumonia died.
While the study shows robust conclusions, it is important to be aware of the potential bias that can be introduced by such retrospective observational studies, as the authors themselves point out. In addition, diagnosis of acute myocarditis is generally difficult and requires specific markers and standardised criteria, which may have helped to underestimate the number of patients with acute myocarditis.
Finally, it is important to note that the study was conducted in patients under 70 years of age, during the first four waves, so it is not possible to estimate what impact the omicron variant, currently widespread worldwide, might be having on the incidence of acute myocarditis. In addition, none of the patients had been vaccinated before the onset of acute myocarditis symptoms, so we cannot extrapolate the results to vaccinated individuals.