Covid-19 has many potential sequelae, secondary conditions directly resulting from the infection. Perhaps one of the most concerning is myocarditis, which is defined as inflammation of the heart muscle and is commonly associated with a viral infection, according to the American Heart Association.
The Mayo Clinic indicates that common symptoms of myocarditis can include chest pain and shortness of breath, as well as arrhythmias and fatigue. In more severe cases, myocarditis can lead to heart failure, a heart attack, stroke, and even sudden cardiac arrest. While the connection between Covid-19 and myocarditis has not been identified, several theories are currently being studied and point to either the virus itself or potentially the immune response to the virus. There is physiological credence to both theories. In the former, a study published in September 2020 by Siripanthong and colleagues in Heart Rhythm indicates that the virus can enter heart tissue through the ACE2 receptor. In the latter, a review article by Tschöpe and colleagues published in Nature a month later argues that the adaptive immune system’s response to SARS-CoV-2 infection can result in inflammation to the heart muscle. Both theories, however, need further evaluation in relation to Covid-19.
The incidence of Covid-19-induced myocarditis is not well established. In late July, shocking findings from a study published in JAMA Cardiology suggested that after being screened via cardiac magnetic resonance imaging, 60% of Covid-19 survivors (independent of the severity of the illness) had developed myocarditis. Moreover, a later study also published in JAMA showed that 12 of 26 athletes had indications of either current or past myocarditis. Given the vast amount of Covid-19 cases that are asymptomatic to moderate, if these findings are to be extrapolated to the general population, then there are likely many cases among individuals who may not know they are at risk. This is particularly relevant for young adults, who are more likely to develop myocarditis and less likely to develop a severe case of the disease.
Evidence to suggest that myocarditis develops after Covid-19 and its incidence need to be further investigated, however. Myocarditis is challenging to diagnose, making it challenging to systematically approximate incidence among Covid-19 survivors. Given the rising case numbers, such research and screening among patients experiencing myocarditis symptoms after recovery are of great importance to prevent and mitigate further complications.