Two Distinct Phenotypes of COVID-Related Myocarditis Emerge

Researchers from France have identified two distinct phenotypes of fulminant COVID-19-related myocarditis in adults, with different clinical presentations, immunologic profiles, and outcomes.

Differentiation between the two bioclinical entities is important to understand for patient management and further pathophysiologic studies, they say.

The first phenotype occurs early (within a few days) in acute SARS-CoV-2 infection, with active viral replication (PCR+) in adults who meet criteria for multisystem inflammatory syndrome (MIS-A+).

In this early phenotype, there is “limited systemic inflammation without skin and mucosal involvement, but myocardial dysfunction is fulminant and frequently associated with large pericardial effusions. These cases more often require extracorporeal membrane oxygenation [ECMO],” Guy Gorochov, MD, PhD, Sorbonne University, Paris, told theheart.org | Medscape Cardiology.

The second is a delayed, postinfectious, immune-driven phenotype that occurs in adults who fail to meet the criteria for MIS-A (MIS-A–).

This phenotype occurs weeks after SARS-CoV-2 infection, usually beyond detectable active viral replication (PCR–) in the context of specific immune response and severe systemic inflammation with skin and mucosal involvement. Myocardial dysfunction is more progressive and rarely associated with large pericardial effusions, Gorochov explained.

The study was published in the July 26 issue of the Journal of the American College of Cardiology.

Evolving Understanding

The findings are based on a retrospective analysis of 38 patients without a history of COVID-19 vaccination who were admitted to the intensive care unit (ICU) from March 2020 to June 2021 for suspected fulminant COVID-19 myocarditis.

Patients were confirmed to have SARS-CoV-2 infection by PCR and/or by serologic testing. As noted in other studies, the patients were predominantly young men (66%; median age, 27.5 years). Twenty-five (66%) patients were MIS-A+ and 13 (34%) were MIS-A–.

In general, the MIS-A– patients were sicker and had worse outcomes.

Specifically, compared with the MIS-A+ patients, MIS-A– patients had a shorter time between the onset of COVID-19 symptoms and the development of myocarditis, a shorter time to ICU admission, and more severe presentations assessed using lower left ventricular ejection fraction (LVEF) and sequential organ failure assessment (SOFA) scores.

MIS-A– patients also had higher lactate levels, were more likely to need venoarterial ECMO (92% vs 16%), had higher ICU mortality (31% vs 4%), and a had lower probability of survival at 3 months (68% vs 96%) compared with their MIS-A+ peers.

Immunologic Differences

The immunologic profiles of these two distinct clinical phenotypes also differed.

In MIS-A– early-type COVID-19 myocarditis, RNA polymerase III autoantibodies are frequently positive and serum levels of antiviral interferon-alpha and granulocyte-attracting interleukin-(IL)-8 are elevated.

In contrast, in MIS-A+ delayed-type COVID-19 myocarditis, RNA polymerase III autoantibodies are negative and serum levels of IL-17 and IL-22 are highly elevated.

“We suggest that IL-17 and IL-22 are novel criteria that should help to assess in adults the recently recognized MIS-A,” Gorochov told theheart.org | Medscape Cardiology. “It should be tested whether IL-17 and IL-22 are also elevated in children with MIS-C,” he added.

The researchers also observed “extremely” high serum IL-10 levels in both patient groups. This has been previously associated with severe myocardial injury and an increase in the risk for death in severe COVID-19 patients.

The researchers say the phenotypic clustering of patients with fulminant COVID-19-related myocarditis “seems relevant” for their management.

MIS-A– cases, owing to the high risk for evolution toward refractory cardiogenic shock, should be “urgently” referred to a center with venoarterial ECMO and closely monitored to prevent a “too-late” cannulation, especially under cardiopulmonary resuscitation, known to be associated with poor outcomes, they advise.

They note that the five patients who died in their series had late venoarterial ECMO implantation, while undergoing multiple organ failures or resuscitation.

Conversely, they say, the risk for evolution to refractory cardiogenic shock is lower in MIS-A+ cases. However, identifying MIS-A+ cases is “all the more important given that numerous data support the efficacy of corticosteroids and/or intravenous immunoglobulins in MIS-C,” Gorochov and colleagues write.

The authors of a linked editorial say the French team should be “commended on their work in furthering our understanding of fulminant myocarditis related to COVID-19 infection.”

Ajith Nair, MD, Baylor College of Medicine, and Anita Deswal, MD, MPH, University of Texas M.D. Anderson Cancer Center, both in Houston, note that fulminant myocarditis is rare and can result from either of two mechanisms: viral tropism or an immune-mediated mechanism.

“It remains to be seen whether using antiviral therapy vs immunomodulatory therapy on the basis of clinical and cytokine profiles will yield benefits,” they write.

“Fulminant myocarditis invariably requires hemodynamic support and carries a high mortality risk if it is recognized late. However, the long-term prognosis in patients who survive the critical period is favorable, with recovery of myocardial function,” they add.

“This study highlights the ever-shifting understanding of the pathophysiology and therapeutic approaches to fulminant myocarditis,” Nair and Deswal conclude.

This research was supported in part by the Foundation of France, French National Research Agency, Sorbonne University, and Clinical Research Hospital. The researchers have filed a patent application based on these results. Nair and Deswal have no relevant disclosures.

J Am Coll Cardiol. 2022;80:299-312, 313-315. Abstract, Editorial

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