The following are key points to remember from the American Heart Association (AHA) scientific statement on recognition and initial management of fulminant myocarditis (FM):

1. We must strive to recognize the diagnosis of FM early so that guideline-directed medical therapy can target inflammation and preservation of end-organ function, eventually leading to remission and/or survival.
2. The current working definition of FM is "sudden and severe inflammation of the myocardium resulting in myocyte necrosis, edema, and cardiogenic shock."
3. FM can present with symptoms that range from common complaints such as dyspnea, chest pain, and arrhythmias to more severe cases such as cardiogenic shock and sudden cardiac death.
4. Key tips to help assist in diagnosis:
1. An electrocardiogram can show the following: low QRS voltage due to myocardial edema, ST-segment elevation, frequent ectopy, ventricular arrhythmias, conduction abnormalities.
2. Elevated cardiac enzymes include: serum cardiac troponin, erythrocyte sedimentation rate, C-reactive protein, natriuretic peptides.
5. Key tips in cardiac imaging:
1. Echocardiography
1. Features may include normal left ventricular (LV) diastolic dimension with increased wall thickness from myocardial edema and pericardial effusion versus LV dilatation.
2. Segmental LV dysfunction, diastolic dysfunction, right ventricular (RV) dysfunction, and cardiac thrombus can occur.
3. Tissue Doppler imaging and strain imaging are usually abnormal.
4. Note: Presence of RV dysfunction and persistent diastolic dysfunction are poor prognostic features.

2. Cardiac magnetic resonance imaging (CMR)
1. Myocardial edema, fibrosis and inflammation, and myocardial hyperemia.
2. Consider CMR tissue mapping.

3. Nuclear imaging
1. Perfusion defects without epicardial coronary artery.

4. Right-sided heart catheterization and coronary angiography
5. Consider endomyocardial biopsy (EMB) if patient has:
1. New-onset unexplained heart failure <2 weeks' duration associated with hemodynamic compromise.
2. Unexplained new-onset heart failure between 2 weeks and 3 months' duration that is associated with a dilated LV and new bradyarrhythmia, new ventricular arrhythmias, or a failure to respond to standard care within 1-2 weeks of diagnosis.
3. EMB should be considered in heart failure that is rapidly progressing when there is high suspicion that the cause can only be confirmed by histology.

6. Early management: Be prepared to treat for arrhythmias and cardiogenic shock. Activate shock teams when present and have available hemodynamic temporary/permanent mechanical support when warranted. If needed, transfer to a cardiac transplant center in a timely manner. The goal is hemodynamic/cardiac recovery.
7. Conditions associated with FM:
1. Lymphocytic myocarditis: autoimmune, toxic, and infectious etiologies (viral 30-40% of cases).
2. Giant cell myocarditis (GCM): may require biventricular mechanical support. It is important to get tissue diagnosis since this type rarely recovers. There are limited data to guide immunosuppression medication doses and optimal duration of therapy in the setting of GCM for long-term maintenance of remission.
3. Acute necrotizing eosinophilic myocarditis: eosinophilic myocarditis, drug hypersensitivity. Presentation is more indolent, usually with less arrhythmia.
4. Cancer therapies: anthracyclines and immune checkpoint inhibitors.
5. Although cardiac sarcoidosis is an infrequent cause of FM, it should be considered on the differential diagnosis in patients presenting with new heart failure associated with conduction abnormalities, ventricular arrhythmias, or hemodynamic compromise.
8. Most inflammatory cases are treated with high-dose steroids; however, depending on the cause, other therapeutic agents such as antivirals can be considered but are not guideline based due to lack of evidence to date.
9. It is not recommended to use empirical, upfront, immunomodulatory agents before a diagnosis of myocarditis.
10. Patients who recover from FM should abstain from competitive sports for at least 3-6 months due to risk of ventricular arrhythmias and inflammation. If after 3-6 months the patient has a normal exercise tolerance test, echocardiogram, and Holter monitor, they may resume competitive sports.
11. The future of diagnosing FM will possibly use more CMR guidance, viral genome analysis, and immunohistochemical markers to guide management.

Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Pericardial Disease, Sports and Exercise Cardiology, Vascular Medicine, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Cardiac Surgery and Arrhythmias, Cardiac Surgery and Heart Failure, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Heart Transplant, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Sports and Exercise and Imaging

Keywords: Arrhythmias, Cardiac, Bradycardia, Cardiac Catheterization, Chest Pain, Coronary Angiography, C-Reactive Protein, Death, Sudden, Cardiac, Dyspnea, Echocardiography, Edema, Electrocardiography, Exercise Tolerance, Fibrosis, Genome, Viral, Giant Cells, Heart Transplantation, Hemodynamics, Hyperemia, Inflammation, Magnetic Resonance Imaging, Myocarditis, Myocardium, Natriuretic Peptides, Neoplasms, Pericardial Effusion, Sarcoidosis, Shock, Cardiogenic, Sports, Thrombosis, Troponin

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