Fulminant myocarditis refers to an acute, severe form of myocardial inflammation with rapid progression and hemodynamic compromise (low output syndrome or cardiogenic shock) requiring inotropic medications or mechanical circulatory support 1-6.
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Epidemiology
Fulminant myocarditis is uncommon 1. The frequency of heart failure in the setting of acute myocarditis has been estimated at approximately 2.5-10% 2,4,6.
Associations
Fulminant myocarditis has been associated with the following 1-4:
cardiogenic shock and cardiac arrest
Diagnosis
Diagnosis of fulminant myocarditis is established by a combination of characteristic clinical findings including severe hemodynamic compromise requiring hemodynamic support in the absence of coronary artery disease and can be confirmed by imaging e.g. cardiac MRI. Histology should be performed in most patients with the presentation of fulminant myocarditis to secure the diagnosis 1 including immunohistology and viral genome analysis for treatment decisions and prognosis 1.
The following criteria have been proposed for the diagnosis 3:
rapid onset of heart failure or quick deterioration
prodromal symptoms of precedent infection
rapid hemodynamic compromise requiring inotropic drugs or mechanical circulatory support
myocarditis confirmed by cardiac MRI or proven on endomyocardial biopsy
exclusion of other cardiac causes especially myocardial ischemia and coronary artery disease
Clinical presentation
Clinical symptoms are variable and include dyspnea, chest pain, arrhythmias such as atrial fibrillation, heart block or ventricular tachycardia and also sudden cardiac death 1,6. Patients can present with cardiogenic shock or cardiac arrest at onset, or with initially mild symptoms rapidly progressing into a fulminant condition requiring intravenous inotropes and/or mechanical circulatory support 2.
As in non-fulminant acute myocarditis, prodromal preceding symptoms, including flu-like symptoms, sore throat, respiratory infections and gastrointestinal illness may be present 2,4.
Electrocardiogram (ECG) may show a low QRS voltage due to myocardial edema or a nonvascular distribution of ST-elevations or left bundle branch block 1,3,6.
Elevated troponin levels are common and may reach peaks similar to those in patients with myocardial infarction 1. Continuously rising cardiac enzyme levels in the absence of coronary artery disease can indicate this condition 5.
Pathology
Fulminant myocarditis is characterized by a severe and often diffuse inflammatory infiltrate of the myocardium 4 resulting in myocardial edema, myocardial necrosis with the presence of damaged cardiomyocytes and cardiogenic shock 1,7. The main pathological phenotypes of fulminant myocarditis include lymphocytic, eosinophilic and giant cell myocarditis and cardiac sarcoidosis 1-4,6,8. In the setting of fulminant myocarditis, histology is not only important but also for treatment decisions and prognosis 8.
Etiology
Causes of acute myocarditis are manifold 1,2 – see acute myocarditis.
The main etiologies of fulminant myocarditis include the following 1-3:
infection (most commonly virus-induced myocarditis, but also bacterial, fungal, and parasitic causes)
autoimmune (immune-mediated)
drug toxicity (drug-induced, hypersensitivity, immune checkpoint-associated)
Immunophenotype
Immunohistochemistry can aid in the setting of equivocal histologic results 2.
Radiographic features
Echocardiography
Echocardiography is a main imaging modality for monitoring patients in the setting of fulminant myocarditis and findings include 1-3,5,6:
progressive left ventricular wall motion abnormalities
progressive decrease in left ventricular ejection fraction and cardiac output
impairment in both left and right ventricular function
left ventricular wall thickening, indicating myocardial edema
near normal left ventricular diastolic dimensions
MRI
Due to patient instability cardiac MRI might be performed not early, but some time later in the course 1 and is particularly important in institutions, where the capacity of endomyocardial biopsy is limited 2,3. As for any cause of myocardial inflammation, evaluation involves the Lake Louise criteria for the diagnosis 5,10.
Lake Louis criteria
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main criteria
myocardial edema: abnormal T2 mapping, elevated signal in STIR/T2 imaging
myocardial injury: abnormal T1 mapping, elevated ECV, LGE in a non-ischemic pattern
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supportive criteria
pericarditis: evidence of pericardial effusion and/or pericardial enhancement
systolic dysfunction: regional or global wall motion abnormalities
Late gadolinium enhancement (LGE) has been described as often more diffuse than in patients with non-fulminant myocarditis 1,3.
Coronary angiography
Coronary angiography is essential to guide management and to rule out coronary artery disease in the setting of cardiogenic shock 1. In addition, patients presenting with symptoms of fulminant myocarditis should undergo endomyocardial biopsy 1-3. However endomyocardial biopsy suffers from sampling errors leading to false-negative results 1-3.
Radiology report
The radiology report should include a description of the following:
morphology and functional analysis
changes compared to the previous examination
MRI
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myocardial tissue properties including:
presence, pattern and distribution of late gadolinium enhancement
presence and/or persistence as well as location and extent of myocardial edema
abnormal T1 and T2 mapping values (if performed)
Treatment and prognosis
Management includes inotropic medications and circulatory support including ventilation, intra-aortic balloon pumps (IABP) and even extracorporeal membrane oxygenation (ECMO) in refractory cases if necessary 1-3. It also includes cause specific therapy 1 which can be adjusted to the underlying etiology (e.g. immunosuppression in autoimmune etiologies). The treatment possibilities nowadays have shifted the prognosis to more favorable outcomes compared to the past 1,3.
Not surprisingly, fulminant myocarditis is associated with a poorer outcome than the non-fulminant form of acute myocarditis, resulting in higher rates of death and cardiac transplantation both in short and long term 6,10. Most deaths occur in the acute phase of fulminant myocarditis 5 with a cumulative risk of death or heart transplant of approximately 20-25% after one month and almost 30% after 3 months according to a study 7. However, contractile recovery is often more pronounced than in acute non-fulminant myocarditis.
The presence of right ventricular dysfunction, increased pulmonary wedge pressures, persistent diastolic dysfunction, as well as granulomatous etiologies or giant cell myocarditis are associated with a poorer prognosis 1,2,7.
History and etymology
The word ‘fulminant’ means ‘coming on suddenly with great severity’ 1.
A classification of myocarditis introduced by the American cardiologist Eric Bruce Liebermann and colleagues in 1991 included the term ‘fulminant myocarditis’ 12.
Differential diagnosis
The main differential diagnosis of fulminant myocarditis includes the following 3,4:
other causes of acute heart failure
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