Type:
Educational Exhibit
Keywords:
Infection, Haemodynamics / Flow dynamics, Acute, Contrast agent-intravenous, MR, Echocardiography, CT, Cardiovascular system, Cardiac
Authors:
C. Lacroix, D. Bélanger, P. Martin, P. Farand, F. Belzile, G. Gahide; Sherbrooke, QC/CA
DOI:
10.1594/ecr2012/C-1954
Background
Myocarditis : definition
Incidence and symptoms
- Autopsy series have reported myocarditis in up to 22% of young adults presenting with sudden death.
[1,
2]
- Important underlying etiology of dilated cardiomyopathy (9%) [2]
- Extreme diversity of clinical manifestations ranging from non specific systemic symptoms to fulminant hemodynamic collapse and sudden death.
[3]
- Challenges of establishing the diagnosis in standard clinical settings makes true incidence of non-fatal myocarditis difficult to determine,
likely higher than actually diagnosed.
[2]
Etiologies
Multiple triggers for myocardial inflammation are possible: infection,
toxic,
ischemic or mechanical injury,
immune reactions.
[3]
- Infectious disease accounts for the majority of cases
- Viral Coxsackie A and B,
HHV-6,
parvovirus B19,
adenoviruses and echoviruses most common [1]
- Bacterial: mycobacterial,
Streptococcal species,
Mycoplasma pneumoniae
- Fungal: Aspergillus,
Candida,
Coccidiodes,
Cryptococcus
- Parasitic: Schistosomiasis,
Larva migrans,
- Toxins: anthracyclines,
cocaine,
interleukin-2
- Immunologic syndromes: Churg-Strauss,
inflammatory bowel disease,
giant cell myocarditis,
sarcoidosis,
systemic lupus erythematosus…
Natural History
- The natural history of myocarditis is as varied as its clinical presentations.
- May progress to dilated cardiomyopathy in up to 10% of patients.
- Previously healthy adults that present with myocarditis mimicking myocardial infarction almost always fully recover their cardiovascular status.
- Patients who present with heart failure:
- Mild left ventricular dysfunction (LVEF of 40% to 50%): typically improve within weeks to months.
- Advanced left ventricular dysfunction (LVEF 35%, left ventricle (LV) end-diastolic dimension > 60 mm): 50% of patients will develop chronic ventricular dysfunction,
and 25% of patients will progress to transplantation or death,
the remaining 25% of patients will have spontaneous improvement in their ventricular function
Endomyocardial biopsy (EMB)
- EMB is the gold standard for unequivocally establishing the diagnosis.
[1]
- Performed via central venous access (more often the right internal jugular vein).
- Myocarditis more often localized at the left ventricular free wall; however,
because of increased risks associated with biopsy of the left ventricle,
samples are usually taken from the right ventricle (RV) or right side of interventricular septum (right ventricular free wall and pulmonary outflow track are too thin to biopsy).
Weaknesses
- Sampling error limits its sensitivity.
[1,
2]
- A minimum of 5 samples taken to improve sensitivity:
- 1 sample sensitivity = 20%,
- 5 samples sensitivity = 66%
- EMB is also limited by a large interobserver variation.
[2]
- Of note,
multiple investigators have described strong clinical,
ventriculographic,
and laboratory evidence of myocarditis among patients with negative biopsies.
- ≈ 0,5% of complications (ex : perforation) [1,
2]
Indications
- Recent societal consensus recommends biopsies only in patients with heart failure or myocardial disorders with specific treatment recommendations.
[1,
2]
- Therefore,
EMB is not recommended in many patients with myocarditis.
- With the actual recommendations,
only 10% of patients with suspected myocarditis are sent for endomyocardial biopsy.
[2]
Myocardial biopsy optimization
Mahrholdt et al. (Circulation,
2004) used cardiac magnetic resonance (CMR) imaging to guide endomyocardial biopsies (EMB):
- Foci were most frequently located in the lateral free wall of the left ventricle
- Improved EMB sensitivity to 90%:
- histopathologic analysis revealed active myocarditis in 19 of the 21 patients in whom biopsy was obtained from the region of contrast enhancement,
patients (parvovirus B19,
n=12; HHV-6,
n=5).
Electrocardiogram (ECG) findings in myocarditis [2,
3]
- Diagnostic value limited: low specificity
- Sensitivity of ECG for myocarditis is low: abnormalities are observed in less than 50% of patients.
[2,
3]
Biomarkers
- Increased levels of creatinine kinase and troponin can be observed (related to inflammatory injury); troponin I is more commonly increased than CK-MB in myocarditis.
[3]
- Elevated levels of troponin I is associated with a 34% sensitivity and a 89% specificity for myocarditis.
[3]
- Prevalence of an increased troponin T in biopsy-proven myocarditis is 35–45% [2] conferring this finding a low sensitivity and high specificity.
Lauer et al.
using troponin T (>0.1 ng/mL) obtained: sensitivity 53%; specificity 94%; PPV 93%; NPV 56% for myocarditis. [4]
Ultrasonography
- Provides excellent anatomical and functional assessment.
- Wall thickness and presence of pericardial effusion can be assessed.
[2]
- The highly variable echocardiographic findings in myocarditis lack specificity; diagnostic value also limited by the fact that many patients have a normal echocardiogram.
Nuclear medicine [2]
- 111Indium antimyosin antibody and 67Gallium nuclear imaging have been used to diagnose myocarditis in the past.
- Findings had low specificity.
- Limited availability of the tracers
- Poor spatial resolution
- Radiation issues