Good News for CV Recovery After COVID-19 Vaccine Myocarditis

Myocarditis attributed to COVID-19 mRNA vaccination is associated with fewer cardiovascular complications compared with conventional myocarditis or that attributed to SARS-CoV-2 infection itself, according to new French data.

Previous studies in this space have confirmed that myocarditis is rare and usually resolves quickly after vaccination for COVID-19, but it seems to affect some groups more than others.

While the new data are consistent with what has been seen before, they underscore the need for “medical disease management for up to several months after hospital discharge” in certain affected patients, write Laura Semenzato, MSc (PI-PHARE, Saint-Denis, France), and colleagues.

Peter Liu, MD (University of Ottawa Heart Institute, Canada), who was not involved in the study, told TCTMD it’s “reassuring” that vaccination-related myocarditis is usually mild, but agreed that the medical community must remain vigilant in following up with these patients, especially given their young age and unknowns about how this condition can affect them years later.

“A lot of people now don't even bother following up carefully patients with vaccine-related myocarditis,” he said. “This data does suggest that they do require follow-up care even though it does not need to be very prolonged.” Since many of these patients present to the emergency room as opposed to an outpatient clinic, setting a checkup appointment upon discharge is not always straightforward, but should be done for at least 3 months, Liu advised.

Additionally, many of these patients are college-aged and “not amenable to follow-up,” he said, but that is all the more reason that potentially university health clinics should get involved in making sure that follow-up care is accessible.

The length of follow-up needed to rule out conditions like late gadolinium enhancement—which remains an unclear risk signal in patients with vaccine-related myocarditis—will depend on patient symptoms as well as the “severity and ability to actually decipher comorbidities,” he continued. “Fortunately, most people are young, so it's less of an issue, but nevertheless, the patient with severe symptoms, particularly rhythm disturbances and LV function abnormalities and also comorbidities, should be followed more closely.”

Fewer CV Complications

For the analysis, published online this week in JAMA, the researchers included all 4,635 individuals ages 12 to 49 years who were hospitalized for myocarditis in France between December 2020 and June 2022. Patients were allocated to the postvaccine or post-COVID-19 infection myocarditis groups based on whether they had received a COVID-19 mRNA vaccine or experienced a COVID-19 infection within the last 7 or 30 days.

The 558 patients with postvaccine myocarditis were on average younger (25.9 years) and more often male (84%) compared with the 298 and 3,779 patients, respectively, with post-COVID-19 (31.0 years; 67% male) and conventional myocarditis (28.3 years; 79% male). About two-thirds (67%) of postvaccine myocarditis occurred after the patient received two vaccine doses.

Compared with conventional myocarditis, the standardized incidence of the primary composite endpoint of hospital readmission for myopericarditis, other cardiovascular events, or all-cause death at 18 months was lower following postvaccine myocarditis (weighted HR 0.55; 95% CI 0.36-0.86), but the risk was similar with post-COVID-19 myocarditis (weighted HR 1.04; 95% CI 0.70-1.52).

The results were maintained in a historical analysis replacing the conventional myocarditis cohort with a group of 2,191 patients hospitalized for myocarditis in 2018 (weighed HR 0.65; 95% CI 0.40-1.05).

Notably, patients with postvaccine and post-COVID-19 myocarditis received similar care according to the frequency of medical procedures and drugs prescribed over the 18-month study period compared with patients with conventional myocarditis.

Liu said the classification of 18 months in these patients as long term is “reasonable,” adding that more data out to 4 or 5 years are still needed, especially because mRNA vaccines and treatments continue to be developed for conditions other than COVID-19.

“There will be more vaccines using this delivery method and there will be more treatments potentially taking advantage of it, mainly because of the success of this whole strategy,” he said. “Understanding why some people get it is still important so that we can identify who may be at risk and also understand the true nature of this unusual complication.”