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Myocarditis Workup

  • Author: Wai Hong Wilson Tang, MD; Chief Editor: Henry H Ooi, MD, MRCPI  more...
 
Updated: Sep 05, 2014
 

Approach Considerations

Laboratory studies may include the following:

  • Complete blood count (CBC) - Leukocytosis (may demonstrate eosinophilia)
  • Elevated erythrocyte sedimentation rate (and other acute phase reactants, such as C-reactive protein)
  • Rheumatologic screening - To rule out systemic inflammatory diseases
  • Elevated cardiac enzymes - Creatine kinase or cardiac troponins
  • Serum viral antibody titers - For viral myocarditis

Cardiac enzymes

Elevated cardiac enzymes are an indicator for cardiac myonecrosis. Cardiac troponin (troponin I or T), in particular, is elevated in at least 50% of patients with biopsy-proven myocarditis. Cardiac enzymes may also help to identify patients with resolution of viral myocarditis.

The test has 89% specificity and 34% sensitivity and increases more frequently than creatine kinase MB subunits (elevated in only 5.7% of patients with biopsy-proven myocarditis). However, these studies have been performed using standard clinical assays, and the sensitivity of newer-generation high-sensitivity cardiac troponin assays in diagnosing myocarditis may differ.

Viral antibody titers

Common viral antibody titers available for clinical evaluation include coxsackievirus group B, human immunodeficiency virus (HIV), cytomegalovirus, Ebstein-Barr virus, hepatitis virus family, and influenza viruses. Titers increase 4-fold or more, with a gradual fall during convalescence (nonspecific); hence, serial testing is required.

Antibody titer testing is rarely indicated in the diagnosis of viral myocarditis or any dilated cardiomyopathies, owing to its low specificity and the delayed rising of viral titers, which would have no impact on therapeutic decisions.

Viral genome

The presence of viral genome in endomyocardial biopsy samples is considered the criterion standard for viral persistence. However, the test lacks specificity, because the presence of viral genome can also be present in healthy controls. The most common viral genomes found include those of parvovirus and herpes simplex.

Histologic findings

Biopsy specimens from EMB should reveal the simultaneous findings of lymphocyte infiltration and myocyte necrosis.

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Echocardiography

Echocardiography is performed to exclude other causes of heart failure (eg, amyloidosis or valvular or congenital causes) and to evaluate the degree of cardiac dysfunction (usually diffuse hypokinesis and diastolic dysfunction). It also may allow gross localization of the extent of inflammation (ie, wall motion abnormalities, wall thickening, pericardial effusion). In addition, echocardiography may distinguish between fulminant and acute myocarditis by identifying near-normal left ventricular diastolic dimensions and increased septal thickness in fulminant myocarditis (versus increased left ventricular diastolic dimensions and normal septal thickness in acute myocarditis), with marked improvement in systolic function in time.

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Scintigraphy

Antimyosin scintigraphy (using antimyosin antibody injections) can identify myocardial inflammation with high sensitivity (91-100%) and negative predictive power (93-100%) but has low specificity (31-44%) and low positive predictive power (28-33%). In contrast, gallium scanning is used to reflect severe myocardial cellular infiltration and has a good negative predictive value, although specificity is low. Positron emission tomography (PET) scanning has been used in selected cases (eg, sarcoidosis) to assess the degree and location of inflammation.

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Additional Imaging Techniques

Cardiac angiography is often indicated to rule out coronary ischemia as a cause of new-onset heart failure, especially when clinical presentation mimics acute myocardial infarction. It usually shows high filling pressures and reduced cardiac outputs.

Gadolinium-enhanced magnetic resonance imaging (MRI) is used for assessment of the extent of inflammation and cellular edema, although it is still nonspecific. Delayed-enhanced MRI has also been used to quantify the amount of scarring that occurred following acute myocarditis.[25]

Monney et al suggested that cardiac magnetic resonance (CMR) scanning may be useful in patients with suspected acute coronary syndrome who are found not to have coronary artery disease. Despite preserved systolic function, a significant proportion of these patients were subsequently diagnosed with acute myocarditis on the basis of the CMR scan findings.[26]

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Endomyocardial Biopsy

Endomyocardial biopsy (EMB) is the criterion standard for the diagnosis of myocarditis, although it has limited sensitivity and specificity, as inflammation can be diffuse or focal. However, the use of routine EMB in establishing the diagnosis of myocarditis rarely is helpful clinically, since histologic diagnosis seldom has an impact on therapeutic strategies, unless giant cell myocarditis is suspected.[2, 3]

However, the Heart Failure Society of America 2010 comprehensive heart failure practice guideline recommends considering endomyocardial biopsy for patients with acute deterioration of heart function of unknown origin that is not responding to medical treatment.[4]

The risk of adverse events in endomyocardial biopsy approaches 6%, including complications in 2.7% of patients on sheath insertion and 3.3% on the biopsy procedure; there is also a 0.5% probability of perforation.[3]

Because of sampling technique, sensitivity may increase with multiple biopsies (50% for 1 biopsy, 90% for 7 biopsies). The standard is to obtain at least 4 or 5 biopsies, although false-negative rates still may be as high as 55%.

False-positive rates are also high, owing to small numbers of normally occurring lymphocytes in the myocardium and the difficulty in distinguishing between lymphocytes and other cells (such as eosinophils in hypersensitive/eosinophilic myocarditis). Moreover, wide interobserver variability in histologic interpretations is also a factor.

Noncaseating granulomas for sarcoid myocarditis are found in only 5% of cases by biopsies and in as many as 27% in autopsy series.

Persistent viral messenger ribonucleic acid (mRNA), which can be found in only 25-50% of patients with biopsy-proven acute myocarditis, often confers a poor prognosis. Epidemiologic results from the European Study on the Epidemiology and Treatment of Cardiac Inflammatory Disease (ESETCID) database found that only 11.8% of patients with suspected acute or chronic myocarditis and reduced ejection fractions had detectable viral genomes in biopsy samples.[27]

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Electrocardiogram

Electrocardiograms are often nonspecific (eg, sinus tachycardia, nonspecific ST- or T-wave changes). Occasionally, heart block (atrioventricular block or intraventricular conduction delay), ventricular arrhythmia, or injury patterns, with ST- or T-wave changes mimicking myocardial ischemia or pericarditis (pseudoinfarction pattern), may indicate poorer prognosis. Arrhythmia is common in Chagas heart disease. The following may be seen: right bundle-branch block with or without bifascicular block (50%), complete heart block (7-8%), atrial fibrillation (7-10%), and ventricular arrhythmia (39%).

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Staging

The Dallas classification (1987) and the World Health Organization (WHO) Marburg classification (1996) are commonly used based on the patterns in the following histologic characteristics[6] :

  • Cell types - Lymphocytic, eosinophilic, neutrophilic, giant cell, granulomatous, or mixed
  • Amount - None (grade 0), mild (grade 1), moderate (grade 2), or severe (grade 3)
  • Distribution - Focal (outside vessel lumen), confluent, diffuse, or reparative (in fibrotic areas)

The Dallas classification on initial biopsy is as follows:

  • Myocarditis - Myocardial necrosis, degeneration, or both, in the absence of significant coronary artery disease with adjacent inflammatory infiltrate with or without fibrosis
  • Borderline myocarditis - Inflammatory infiltrate too sparse or myocyte damage not apparent
  • No myocarditis

The Dallas classification on subsequent biopsy is as follows:

  • Ongoing (persistent) myocarditis with or without fibrosis
  • Resolving (healing) myocarditis with or without fibrosis
  • Resolved (healed) myocarditis with or without fibrosis

WHO Marburg criteria (1996) defines myocarditis as a minimum of 14 infiltrating leukocytes/mm2, preferably T cells (CD45RO), with as many as 4 macrophages possibly included.[27]

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Contributor Information and Disclosures
Author

Wai Hong Wilson Tang, MD Professor of Medicine, Section of Heart Failure and Cardiac Transplantation Medicine, Cleveland Clinic Foundation

Wai Hong Wilson Tang, MD is a member of the following medical societies: American College of Cardiology, American Heart Association, American Society for Clinical Investigation, International Society for Heart and Lung Transplantation, Heart Failure Society of America

Disclosure: Nothing to disclose.

Chief Editor

Henry H Ooi, MD, MRCPI Director, Advanced Heart Failure and Cardiac Transplant Program, Nashville Veterans Affairs Medical Center; Assistant Professor of Medicine, Vanderbilt University School of Medicine

Disclosure: Nothing to disclose.

Acknowledgements

Paul Blackburn, DO, FACOEP, FACEP Attending Physician, Department of Emergency Medicine, Maricopa Medical Center

Paul Blackburn, DO, FACOEP, FACEP is a member of the following medical societies: American College of Emergency Physicians, American College of Osteopathic Emergency Physicians, American Medical Association, and Arizona Medical Association

Disclosure: Nothing to disclose.

Ethan A Booker, MD Attending Physician, Department of Emergency Medicine, Washington Hospital Center

Ethan A Booker, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

David FM Brown, MD Associate Professor, Division of Emergency Medicine, Harvard Medical School; Vice Chair, Department of Emergency Medicine, Massachusetts General Hospital

David FM Brown, MD is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Steven J Compton, MD, FACC, FACP Director of Cardiac Electrophysiology, Alaska Heart Institute, Providence and Alaska Regional Hospitals

Steven J Compton, MD, FACC, FACP is a member of the following medical societies: Alaska State Medical Association, American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, and Heart Rhythm Society

Disclosure: Nothing to disclose.

David S Howes, MD Professor of Medicine and Pediatrics, Section Chief and Emergency Medicine Residency Program Director, University of Chicago Division of the Biological Sciences, The Pritzker School of Medicine

David S Howes, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physicians-American Society of Internal Medicine, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Eric M Kardon, MD, FACEP Attending Emergency Physician, Georgia Emergency Medicine Specialists; Physician, Division of Emergency Medicine, Athens Regional Medical Center

Eric M Kardon, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

George A Stouffer III, MD Henry A Foscue Distinguished Professor of Medicine and Cardiology, Director of Interventional Cardiology, Cardiac Catheterization Laboratory, Chief of Clinical Cardiology, Division of Cardiology, University of North Carolina Medical Center

George A Stouffer III, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, American College of Physicians, American Heart Association, Phi Beta Kappa, and Society for Cardiac Angiography and Interventions

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

James B Young, MD Chairman, Professor of Medicine, Department of Medicine, Cleveland Clinic Foundation

Disclosure: National Institute of Health Grant/research funds Independent Contractor

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H and E, low power, showing numerous lymphocytes with associated myocyte damage (photo courtesy of Dr. Donald Weilbaecher)
H and E, high power, showing toxoplasmosis (numerous purple granular-like structures within a myocyte)
H and E, high power, showing lymphocytes, histiocytes and a multinucleated giant cell representing sarcoidosis (a diagnosis of exclusion)
 
 
 
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