Dr. Sharma treated us to a noon report featuring a young guy who developed acute myocarditis! It was a good opportunity to review acute myocarditis.
What is it?
Myocarditis is an inflammatory process of the cardiac muscle. It is most commonly seen in patients 20 to 50 years of age.
Myocarditis has a wide-range of causative agents, but consider them broadly in terms of infectious versus autoimmune versus drug-induced.
It is important to note that viruses are considered to be the MOST frequent cause and while many viruses can cause myocarditis, the most common etiologies are considered to be Coxsackie B virus, Adenovirus, Hepatitis C, CMV, Echovirus, and Influenza but Parvovirus B-19 and human herpes virus 6 are viruses now most frequently found.
How does it present?
The presentation of myocarditis is variable: it can be a subclinical, asymptomatic disease that goes undetected or present as florid heart failure!
Typically, it presents with heart failure symptoms over a few days to weeks. Viral myocarditis is also classically preceded by fever, myalgias, and upper respiratory symptoms but this prodrome is NOT required for diagnosis.
Otherwise, symptoms can include fatigue, chest pain (classically more anginal than the pain seen in pericarditis), signs of volume overload, cfardiogenic shock, arrhythmias, and even sudden death.
When Should I Suspect Myocarditis?
Suspect myocarditis in patients with or without cardiac signs and symptoms who have
A rise in cardiac biomarkers
EKG changes suggestive of acute myocardial injury
Arrhythmias
Global or regional abnormalities of LV systolic function (particularly if clinical findings are new and unexplained)
Clinical signs and symptoms of an acute MI (Particularly if patient lacks cardiovascular risk factors or coronary angiogram is normal)
How do I work up suspected myocarditis?
A good place to start after your history and physical is with the following:
EKG- This can be normal or show non-specific abnormalities ranging from atrial or ventricular arrhythmias, non-specific ST changes, or even ST elevations and Q waves.
Cardiac enzymes- These are generally elevated given myocardial involvement.
CXR- This may show signs of heart failure, including pulmonary edema, vascular congestion, enlarged heart silhouette
BNP- Can be elevated
Acute phase reactants (ESR/CRP)- May also be elevated but this is very nonspecific.
CBC with diff- May show a leukocytosis. Eosinophils will be elevated in eosinophilic myocarditis.
Echocardiogram- You want to evaluate both regional and global ventricular function as well as valvular function and rule out other causes of cardiac dysfunction
Cardiac MR- This is very useful in patients with suspected myocarditis with elevated troponin and or ventricular dysfunction without a clear cause. We recommend you use gadolinium to help enhance areas of damage; this can also show edema and scarring.
Coronary Angiography
Endomyocardial biopsy- This is the gold standard test. It can define myocarditis with evidence of myocardial necrosis, degeneration, or both, with an adjacent inflammatory infiltrate. Indications for endomyocardial biopsy include unexplained fulminant heart failure (defined as new onset heart failure of less than 2 weeks duration associated with hemodynamic compromise), unexplained new onset heart failure of 2 weeks to 3 months duration associated with dilated LV and new arrhythmias, ventricular arrhythmias in general, Type II or III conduction block or lack of response to usual heart failure therapy.
How do I diagnose myocarditis?
There is a 2013 European Society of Cardiology position statement that is helpful! Myocarditis can be clinically diagnosed if:
1. The patient has at least one of the following clinical presentations of myocarditis
Acute chest pain
New onset or worsening of dyspnea at rest or exercise, and/or fatigue with or without left and/or right heart failure signs
Palpitations and/or unexplained arrhythmia symptoms and/or syncope and/or aborted sudden cardiac death
And
2. At least one diagnostic criteria
ECG/Holter/Stress test features
Elevated cardiac enzymes
Functional and structural abnormalities on cardiac imaging
Tissue characterization by Cardiac MRI
It also defines other supporting features:
Fever >38 C at presentation or during prior 30 days with or without associated symptoms
Exposure to toxic agents
Absence of other clinical conditions that could explain clinical findings such as CAD, valve disease, congenital heart disease
How do I manage myocarditis?
The treatment of myocarditis largely focuses on supportive care, including:
Treatment of heart failure and arrhythmias
Restriction of physical activity to reduce work of heart during acute phase of myocarditis
Immunosuppressive therapy is suggested for specific auto-reactive disorders although placebo-controlled immunosuppressive trials have not demonstrated improvements in mortality or ejection fraction.
Patients should avoid NSAIDS as these are not effective and can actually enhance myocarditis process and increase mortality.
References:
1. Friedrich et al. "Cardiovascular Magnetic Resonance in Myocarditis: A JACC White Paper". Journal of the American College of Cardiology Volume 53, Issue 17, April 2009.
2. MKSAP 17- Myocarditis.
3. Up-to-date
4. International Society and Federation of Cardiology
5. European Society of Cardiology
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