Clinical Presentation of Acute Myocarditis
Acute myocarditis presents with a broad spectrum of symptoms ranging from mild chest pain to dramatic clinical features resembling acute myocardial infarction, including angina pectoris, ST-segment elevations on ECG, elevated cardiac biomarkers, and potentially life-threatening complications such as acute heart failure, cardiogenic shock, and arrhythmias. 1
Common Presenting Symptoms
Chest pain (82-95% of adult patients) 2
- May be sharp, pleuritic, or pseudoischemic
- Often reflective of epicardial inflammation involving the pericardium 1
Dyspnea (19-49% of patients) 2
- At rest or with exercise
- New onset (days up to 3 months) or worsening
Fatigue and exercise intolerance 1
- Often related to myocardial dysfunction
Palpitations (common) 1
- Due to supraventricular or ventricular arrhythmias
Syncope (5-7% of patients) 2
- May indicate severe conduction abnormalities or arrhythmias
Cardiac Manifestations
Heart Failure Signs and Symptoms
- Acute congestive heart failure with or without cardiogenic shock 1
- Jugular venous distension and cold extremities (in severe cases) 3
- Progressive chronic heart failure 1
Arrhythmias
- Supraventricular tachyarrhythmias 1
- Ventricular tachyarrhythmias 1
- Bradyarrhythmias 1
- Intraventricular conduction delays 1
ECG Abnormalities
- ST-segment elevation (mimicking myocardial infarction) 1
- T-wave changes 1
- First to third-degree atrioventricular block 1
- Bundle branch block 1
- Reduced R-wave height 1
- Widened QRS complex 1
- Abnormal Q waves 1
- Low voltage 1
- Frequent premature beats 1
Laboratory Findings
Elevated cardiac troponin 1
- Present in most hospitalized cases but may be elevated in only 34% of less severe cases 1
Elevated inflammatory markers
Imaging Findings
Echocardiography
- Regional wall motion abnormalities (often in non-coronary distribution) 1
- Ventricular dilatation 1
- Global systolic or diastolic dysfunction 1
- Increased wall thickness due to edema 1
- Pericardial effusion 1
Cardiac MRI
- Myocardial edema on T2-weighted images 1
- Late gadolinium enhancement in classic myocarditic pattern (subepicardial or mid-myocardial) 1, 4
- Pericardial enhancement 1
Clinical Course and Severity Spectrum
Uncomplicated course (75% of hospitalized patients) 2
- Minimal symptoms with preserved ventricular function
- Very low mortality rate
Complicated course 2
- Acute heart failure or ventricular arrhythmias (12% rate of in-hospital mortality or need for heart transplant)
- Hemodynamic instability (2-9% of patients) requiring inotropic support or mechanical circulatory support
Fulminant myocarditis 3
- Rapid onset of severe heart failure
- High mortality rate
- Refractory malignant ventricular arrhythmias
Special Types of Myocarditis
- Aggressive, noninfectious autoimmune disorder
- Rapidly fatal without advanced heart failure treatment
- Fulminant course with overt heart failure
Eosinophilic myocarditis 2
- Associated with hypersensitivity reactions to drugs or vaccines
- May respond to immunosuppression
Clinical Pitfalls and Caveats
Mimics acute coronary syndrome - Always rule out obstructive coronary artery disease in patients presenting with chest pain and ST-segment elevation 1
Variable presentation - The absence of specific pathognomonic features makes diagnosis challenging 4
Rapid progression - The acute phase of viral myocarditis lasts only 1-3 days but can quickly progress to life-threatening complications 1
Diagnostic window - Optimal sensitivity for diagnostic imaging is limited to a few weeks from presentation 1
Risk stratification - Patients with myocarditis who develop heart failure and arrhythmias usually show larger late gadolinium enhancement distribution on CMR 4
The clinical presentation of acute myocarditis requires prompt recognition and risk stratification to guide appropriate management and prevent adverse outcomes such as sudden cardiac death, progression to dilated cardiomyopathy, or refractory heart failure.