Adolescents and adults younger than age 21 who develop myocarditis after mRNA COVID-19 vaccination frequently have abnormal findings on cardiac MRI (cMRI) but most have a mild clinical course with rapid resolution of symptoms, a new study concludes.
“This study supports what we’ve been seeing. People identified and treated early and appropriately for the rare complication of COVID-19 vaccine-related myocarditis typically experienced only mild cases and short recovery times,” American Heart Association President Donald M. Lloyd-Jones, MD, said in a podcast.
“Overwhelmingly, the data continue to indicate [that] the benefits of COVID-19 vaccine far outweigh any very rare risks of adverse events from the vaccine, including myocarditis,” Dr. Lloyd-Jones added.
The study was published online Dec. 6 in Circulation.
Using data from 26 pediatric medical centers across the United States and Canada, the researchers reviewed the medical records of 139 patients younger than 21 with suspected myocarditis within 1 month of receiving a COVID-19 vaccination.
They made the following key observations:
- Most patients were male (90.6%), White (66.2%) and with a median age of 15.8 years.
- Suspected myocarditis occurred in 136 patients (97.8%) following mRNA vaccine, with 131 (94.2%) following the Pfizer-BioNTech vaccine; 128 cases (91.4%) occurred after the second dose.
- Symptoms started a median of 2 days (range 0 to 22 days) following vaccination administration.
- Chest pain was the most common symptom (99.3%), with fever present in 30.9% of patients and shortness of breath in 27.3%.
- Patients were treated with nonsteroidal anti-inflammatory drugs (81.3%), intravenous immunoglobulin (21.6%), glucocorticoids (21.6%), colchicine (7.9%) or no anti-inflammatory therapies (8.6%).
- Twenty-six patients (18.7%) were admitted to the intensive care unit; 2 received inotropic/vasoactive support; none required extracorporeal membrane oxygenation or died.
- Median time spent in the hospital was 2 days.
- A total of 111 patients had elevated troponin I (8.12 ng/mL) and 28 had elevated troponin T (0.61 ng/mL).
- More than two-thirds (69.8%) had abnormal electrocardiograms and/or arrhythmias (7 with nonsustained ventricular tachycardia).
- Twenty-six patients (18.7%) had left ventricular ejection fraction (LVEF) less than 55% on echocardiogram; LVEF had returned to normal in the 25 who returned for follow-up.
- 75 of 97 patients (77.3%) who underwent cMRI at a median of 5 days from symptom onset had abnormal findings; 74 (76.3%) had late gadolinium enhancement, 54 (55.7%) had myocardial edema, and 49 (50.5%) met Lake Louise criteria for myocarditis.
“These data suggest that most cases of suspected COVID-19 vaccine–related myocarditis in people younger than 21 are mild and resolve quickly,” corresponding author Dongngan Truong, MD, Division of Pediatric Cardiology, University of Utah and Primary Children’s Hospital, Salt Lake City, said in a statement.
“We were very happy to see that type of recovery. However, we are awaiting further studies to better understand the long-term outcomes of patients who have had COVID-19 vaccination-related myocarditis. We also need to study the risk factors and mechanisms for this rare complication,” Dr. Truong added.
Dr. Lloyd-Jones said these findings support the AHA’s position that COVID-19 vaccines are “safe, highly effective, and fundamental to saving lives, protecting our families and communities against COVID-19, and ending the pandemic.”
The study received no funding. Dr. Truong consults for Pfizer on vaccine-associated myocarditis. A complete list of author disclosures is available with the original article.
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