Trending Clinical Topic: Myocarditis

Ryan Syrek


December 17, 2021

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Myocarditis has been an ongoing concern during the pandemic because it has been associated with COVID-19 infection and, to a much lesser degree, with vaccination. New studies that help to clarify both links resulted in this week's top trending clinical topic. According to the Centers for Disease Control and Prevention (CDC), myocarditis after mRNA vaccination occurs after 70 per 1 million doses given among boys aged 16-17 years, who are at highest risk. A new review of data from 26 pediatric medical centers across the United States and Canada provided reassuring information regarding those affected (see Infographic).

The study was published in Circulation and found that symptoms started a median of 2 days (range, 0 -22 days) after vaccine administration. Chest pain was the most common symptom (99.3%). Fever was present in 30.9% of patients, and shortness of breath was reported in 27.3%. "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, said in a statement.

F. Perry Wilson, MD, MSCE, found the data mostly encouraging. He pointed to "a rhythm strip of a 15-second run of nonsustained V-tach in a 17-year-old" and reduced function on echocardiology in 20% of the young people included as somewhat concerning signs. Still, Wilson concludes, "we have to resist the urge to compare the effects of vaccine to the effects of no vaccine. Given the contagiousness of SARS-CoV-2, we need to compare the effects of the vaccine to the effects of COVID itself."

The CDC has found that patients with COVID-19 have nearly 16 times the risk for myocarditis. The cardiac manifestations of COVID range far beyond myocarditis. In a recent review, researchers say clinicians "should be cognizant of some of the reported ECG changes, such as abnormal QRS axis in nearly 20% of patients, conduction abnormalities in approximately 20%, atrioventricular block in about 2.5%, and premature beats in nearly 10% of patients." More than 9% of patients admitted with COVID-19 infection have arrhythmias, mostly atrial fibrillation. The authors recommend baseline and follow-up ECG for QTc monitoring in hospitalized patients.

Given the myriad of cardiac concerns associated with SARS-CoV-2 infection, news that the myocarditis associated with mRNA vaccination is mostly mild and resolves quickly in the rare instances in which it occurs was welcome news. The findings continue to tip scales in favor of vaccination and resulted in this week's top trending clinical topic.

Learn more about myocarditis.


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