Diagnostic Considerations
Myocarditis should be considered in young patients with the following [20] :
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Apparent cardiovascular conditions that often present as more common cardiac conditions (eg, acute coronary syndrome, acute heart failure)
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Cardiovascular symptoms but without having typical cardiovascular risk factors and a history of signs/symptoms of recent viral upper respiratory infection or enteroviral infection
Consider fulminant myocarditis in the presence of shock, electric instability, or rapidly evolving conduction anomalies (eg, widening QRS complex, PR prolongation). [20] It is also important to recognize the typical signs/symptoms of right heart failure (eg, right upper quadrant pain, anomalies in liver function tests, jaundice, elevated neck veins, peripheral edema, hepatomegaly with liver pulsatility). Differentiate right heart failure early (before progressive cardiogenic shock) from primary hepatobiliary disease (eg, cholecystitis). [20]
Consider hypersensitivity myocarditis, which generally presents as fulminant myocarditis with peripheral eosinophilia, rash, or elevated liver function tests. [20] Common causes include antibiotics (eg, beta lactams, minocycline) and some central nervous agents (eg, clozapine, carbamazepine). These patients are often febrile and have a high risk of death, transplantation, or placement of ventricular assist device at 120 days. Definitive diagnosis typically requires an endomyocardial biopsy. [20]
Takotsubo cardiomyopathy
A transient cardiac dysfunction known as takotsubo cardiomyopathy or transient apical ballooning syndrome is characterized by severe hypokinesis of the anteroapical and inferoapical regions of the heart for unclear reason, and often with complete resolution. Many cases have been associated with a psychological or stressful event. Some have suggested a myocarditis nature of the condition, but the precise understanding of this syndrome remains unclear.
Differential diagnosis
Other conditions to consider in the differential diagnosis of myocarditis include the following:
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Coronary artery vasospasm
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Isolated coronary artery anomalies
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Myocardial infarction
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Myocardial ischemia
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Cardiogenic pulmonary edema
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High-altitude pulmonary edema
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Neurogenic pulmonary edema
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Interstitial (nonidiopathic) pulmonary fibrosis
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Sudden cardiac death
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Unstable angina
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Ventricular tachycardia
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Sepsis [20]
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Coronavirus disease 2019 (COVID-19) mRNA vaccines (see below)
COVID-19 messenger RNA (mRNA) vaccine-related myocarditis
Cases of myocarditis and pericarditis in adolescents and young adults emerged in April 2021, potentially correlated with administration of COVID-19 mRNA vaccines. A case series of seven adolescent males presenting with symptomatic acute myocarditis described similar symptom onset of within a few days (ie, 2-4 days) after vaccine administration, particularly after the second dose. [31] Diagnostic test results were also similar among the patients, including elevated troponin levels, ST elevation, and diffuse myocardial edema. None were critically ill, all responded quickly to treatment with nonsteroidal anti-inflammatories (NSAIDs), and several also received glucocorticoids. [31] A case report of 23 male military members (22 previously healthy) with myocarditis within 4 days of receiving an mRNA COVID-19 vaccine has been published. [32] Of these 23 patients, 20 were diagnosed following the second vaccine dose.
A total of 1,226 preliminary myocarditis/pericarditis cases were reported to VAERS (Vaccine Adverse Event Reporting System) following the approximately 300 million mRNA doses administered through June 11, 2021. [33] Most occurred after the second dose, and nearly 80% have been in males. The Centers for Disease Control and Prevention (CDC) and American Academy of Pediatrics (AAP) stress the benefit of the vaccine at preventing severe COVID-19, hospitalization, and death, and they recommend vaccination.
The CDC has published clinical considerations relevant to myocarditis and pericarditis with mRNA COVID-19 vaccines. Instruct patients to seek immediate medical attention if they experience chest pain, dyspnea, or palpitations after receiving the vaccine. Treatment consists of anti-inflammatory agents including NSAIDs, intravenous immunoglobulin (IVIG), and glucocorticoids. Additionally, athletic activity restrictions may be necessary, depending on when serum markers of myocardial injury and inflammation, ventricular systolic function, and clinically relevant arrhythmias return to normal.
The US Food and Drug Administration (FDA) is adding a warning to the fact sheets for the Pfizer/BioNTech and Moderna mRNA COVID-19 vaccines as medical experts continue to investigate cases of heart inflammation. [34]
Differential Diagnoses
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Myocarditis. Hematoxylin and eosin staining. Low power. This image shows numerous lymphocytes with associated myocyte damage. Photo courtesy of Dr Donald Weilbaecher.
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Myocarditis. Hematoxylin and eosin staining. High power. Toxoplasmosis (numerous purple granular-like structures within a myocyte) is demonstrated.
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Myocarditis. Hematoxylin and eosin staining. High power. Lymphocytes, histiocytes, and a multinucleated giant cell representing sarcoidosis (a diagnosis of exclusion) is shown.
