Page 469 - Textbook of Pathology, 6th Edition

3. TOXIC MYOCARDITIS. A number of acute bacterial 9. FUNGAL MYOCARDITIS. Patients with immuno- 453
infections produce myocarditis by toxins e.g. in diphtheria, deficiency, cancer and other chronic debilitating diseases are
typhoid fever and pneumococcal pneumonia. more prone to develop fungal myocarditis. These include:
candidiasis, aspergillosis, blastomycosis, actinomyosis,
Grossly, the appearance is similar to that seen in viral cryptococcosis, coccidioidomycosis and histoplasmosis.
myocarditis.
Histologically, there are small foci of coagulative necrosis II. IDIOPATHIC (FIEDLER’S) MYOCARDITIS
in the muscle which are surrounded by nonspecific acute
and chronic inflammatory infiltrate. Idiopathic or Fiedler’s myocarditis is an isolated myocarditis
unaccompanied by inflammatory changes in the
Toxic myocarditis manifests clinically by cardiac endocardium or pericardium and occurs without the usual
arrhythmias or acute cardiac failure due to involvement of apparent causes. The condition is rapidly progressive and
the conduction system. It may cause sudden death. causes sudden severe cardiac failure or sudden death.
4. INFECTIVE GRANULOMATOUS MYOCARDITIS. Grossly, the heart is soft and flabby. The cardiac chambers
Tuberculosis, brucellosis and tularaemia are some examples are generally dilated and sometimes show hypertrophy.
of bacterial infections characterised by granulomatous There are yellow-grey focal lesions throughout the
inflammation in the myocardium. Sarcoidosis, though not a myocardium. Mural thrombi are commonly present.
bacterial infection, has histological resemblance to other
granulomatous myocarditis. Tuberculous myocarditis is rare Histologically, two forms of idiopathic myocarditis are
and occurs either by haematogenous spread or by extension described: diffuse type and giant cell (idiopathic
from tuberculous pericarditis. The condition must be granulomatous) type.
distinguished from idiopathic granulomatous (giant cell) i) Diffuse type is more common of the two. It is
myocarditis (described later). characterised by diffuse non-specific inflammatory infil-
trate consisting of lymphocytes, plasma cells, macro-
5. SYPHILITIC MYOCARDITIS. Syphilitic involvement of phages, eosinophils and a few polymorphs in the inter-
the myocardium may occur in 2 forms—a gummatous lesion stitial tissue without formation of granulomas. Late stage
consisting of granulomatous inflammation which is more shows healing by fibrosis. CHAPTER 16
common, and a primary non-specific myocarditis which is rare. ii) Giant cell type or idiopathic granulomatous type is
The syphilitic gummas in the myocardium may be single or characterised by formation of non-caseating granulomas
multiple and may be grossly discernible. The gummas may consisting of macrophages, lymphocytes, plasma cells and
affect the conduction system of the heart. multinucleate giant cells. The giant cells are of foreign
6. RICKETTSIAL MYOCARDITIS. Myocarditis occurs body or Langhans’ type or of myogenic origin. The
quite frequently in scrub typhus (R. tsutsugamushi) and Rocky granulomas do not show presence of acid-fast bacilli or
Mountain typhus fever caused by spotted rickettsii. spirochaetes. Some have suggested relationship of this The Heart
condition with sarcoidosis but sarcoid granulomas are
Microscopically, there is interstitial oedema and focal or known to occur in the myocardium secondary to
patchy infiltration by inflammatory cells which include generalised sarcoidosis.
lymphocytes, plasma cells, macrophages, mast cells and
eosinophils but necrosis and degeneration are generally
not present. III. MYOCARDITIS IN CONNECTIVE TISSUE DISEASES
Inflammatory involvement of the myocardium occurs in a
7. PROTOZOAL MYOCARDITIS. Chagas’ disease and number of connective tissue diseases such as rheumatoid
toxoplasmosis are the two protozoal diseases causing arthritis, lupus erythematosus, polyarteritis nodosa,
myocarditis. Chagas’ disease caused by Trypanosoma cruzi dermatomyositis and scleroderma. The pathologic changes
frequently attacks myocardium besides involving the skeletal in the heart muscle are similar to the changes seen in other
muscle and the central nervous system. Toxoplasmosis organs in these conditions as described elsewhere in relevant
caused by intracellular protozoan, Toxoplasma gondii, chapters.
sometimes causes myocarditis in children and adults.

Microscopically, both these conditions show focal IV. MISCELLANEOUS TYPES OF MYOCARDITIS
degeneration and necrosis of the myocardium, oedema Apart from the above forms of myocarditis, miscellaneous
and cellular infiltrate consisting of histiocytes, plasma group consists of myocarditis caused by a variety of agents—
cells, lymphocytes and a few polymorphs.The organisms physical and chemical agents, drugs and metabolic
are found in the muscle fibres. derangements.

8. HELMINTHIC MYOCARDITIS. Echinococcus granulosus 1. Physical agents. Physical agents like contusion of the
and Trichinella spiralis are the two intestinal helminths which myocardium, heat stroke, cardiac surgery and irradiation can
may cause myocarditis. Echinococcus rarely produces hydatid initiate non-specific myocarditis. The features consist of an
cyst in the myocardium while the larvae of Trichinella in infiltrate of neutrophils, eosinophils and mononuclear cells
trichinosis cause heavy inflammation in the myocardium as and shows contraction-band necrosis of the myocardial
well as in the interstitial tissue. fibres.