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Heart & vascular pathology

Inflammatory disease

Noninfective myocarditis

Author: R. Amita, M.D.

Last author update: 1 March 2015

Last staff update: 31 December 2020

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PubMed Search: Noninfective myocarditis

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Table of Contents

Cite this page: Amita R. Noninfective myocarditis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/heartnoninfecmyo.html. Accessed May 12th, 2024.

Definition / general

Myocarditis is an inflammatory disease of the myocardium caused by different infectious and noninfectious triggers
Non infectious types include lymphocytic, eosinophilic and giant cell myocarditis (GCM)

Terminology

GCM has been termed idiopathic GCM, pernicious myocarditis, Fiedler myocarditis, acute idiopathic interstitial myocarditis, giant cell granulomatous myocarditis, and granulomatous myocarditis

Epidemiology

Incidence difficult to determine as most cases are believed to be subclinical or underdiagnosed

Pathophysiology

Most cases of lymphocytic myocarditis are idiopathic
A primary autoimmune etiology has been suggested for GCM, based on the antimyosin GCM Lewis rat model and a high prevalence of associated autoimmune disorders, especially inflammatory bowel disease

Diagrams / tables

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Etiology of Myocarditis

Clinical features

Asymptomatic or nonspecific symptoms of chest pain, fever, sweats, chills, dyspnea
Palpitations, syncope or sudden cardiac death may develop because of underlying ventricular arrhythmias or atrioventricular block
In necrotizing eosinophilic myocarditis (NEC), a previously healthy patient experiences a rapid, acute progression to systolic failure and hemodynamic compromise which is usually fatal

Diagnosis

Definitive diagnosis requires an endomyocardial biopsy

The Japanese Circulation Society Task Force Committee on Acute and Chronic Myocarditis published guidelines (Circ J 2011;75:734) for the diagnosis of eosinophilic myocarditis which includes eosinophilia > 500 / μL, cardiac symptoms, elevated cardiac enzymes, electrocardiogram (ECG) changes, and cardiac dysfunction on ultrasonography, especially in the setting of unremarkable coronary angiography

Radiology description

Features are similar to those described in infective myocarditis

Radiology images

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Transthoracic cardiac echocardiograms

MRI, TIRM

Pericardial effusion of 1.2 cm

MRI, IR, FLASH

Subendocardial delayed enhancement

Increased septal wall thickness

Prognostic factors

Most patients recover spontaneously with no known sequela
A small percentage of patients, mostly children and young adults, present with fulminant disease at onset and may progress rapidly to sudden death

Case reports

15 year old adolescent with eosinophilic myocarditis (Cardiol Young 2013;23:277)
30 year old man with recurrent lymphocytic myocarditis and ulcerative colitis (Eur J Med Res 2014;19:11)
47 year old man with acute myocarditis and successful clearance of human parainfluenza virus type 2 viraemia (J Clin Virol 2013;56:37)
54 year old man with acute eosinophilic myocarditis mimicking myocardial infarction (Tex Heart Inst J 2009;36:355)
72 year old man with idiopathic giant cell myocarditis (Indian J Pathol Microbiol 2003;46:241)
76 year old man with eosinophilic myocarditis (BMC Res Notes 2013;6:538)
Three cases of sudden death occurring in systemic sarcoidosis with myocardial involvement (N Z Med J 1989;102:501)

Treatment

Treatment of myocarditis includes supportive therapy for symptoms of acute heart failure and withdrawal of the offending agent, if applicable

Gross description

Cardiac hypertrophy may be present with associated ventricular dilation
The affected myocardium may appear pale, sometimes with hemorrhagic foci

Microscopic (histologic) description

Lymphocytic myocarditis:
- A focal or diffuse lymphohistiocytic infiltrate (mostly T cell type) within myocardial fibers
- Myocyte necrosis is typically present; interstitial fibrosis of varying degree is commonly seen
- Presence of edema should not be used as a criterion for diagnosis of myocarditis
Giant cell myocarditis:
- Diffuse infiltration of myocardium by a heterogeneous infiltrate composed of abundant lymphocytes, eosinophils, plasma cells and scattered prominent giant cells
- There are no well defined granulomas
- It has a more fulminant course (J Card Fail 2002;8:74, Semin Arthritis Rheum 2000;30:1)
Eosinophilic myocarditis:
- Mixed inflammatory cell infiltrate consisting of many eosinophils with histiocytes, lymphocytes and plasma cells; myocardial necrosis is not common and interstitial fibrosis is typically absent or minimal
- Eosinophilic myocarditis associated with hypereosinophilic syndrome is characterized by peripheral eosinophilia greater than 1,500 / μL over 6 months, without a known cause and with an indolent course (Can J Cardiol 2006;22:1233)
Hypersensitivity myocarditis (HSM):
- Due to drug exposure; less necrosis, more prominent perivascular infiltrate, vasculitis and liver involvement
Necrotising eosinophilic myocarditis:
- Extensive myocardial necrosis due to release of major basic protein from degranulated eosinophils
Sarcoid myocarditis:
- Noncaseating granulomas on endomyocardial biopsy performed in a patient with a dilated cardiomyopathy is virtually pathognomonic (J Am Coll Cardiol 2003;41:322, Prog Cardiovasc Dis 2010;52:336)