Page 293 - Concise Pathology for Exam Preparation ( PDFDrive )

278 SECTION II Diseases of Organ Systems

Infective myocarditis

This is the most common type of myocarditis. It results from direct invasion of causative
organisms or their toxins into the myocardium or a destructive immune response to their
antigens. Common causes include
• Viral
• Seen in 5% of viral infections due to direct viral cytotoxicity or a destructive cell-
mediated immune reaction
• Myocardium is pale and flabby; focal or patchy necrosis and mural thrombi may be
seen on gross examination. Microscopy shows oedema and infiltration by neutro-
phils, which in the later stages are replaced by lymphocytes and macrophages
• Bacterial
• Myocardium shows abscesses
• Exudate is chiefly composed of neutrophils, lymphocytes, plasma cells and macro-
phages
• Coagulative necrosis may be seen
• Helminthic
Echinococcus granulosus and Trichinella spiralis are generally implicated.
• Fungal
Seen in immune deficiency, cancer and chronic debilitating diseases
• Protozoal (Chagas disease)
Mixed inflammation around parasitized myofibres is seen.
Q. Enumerate and describe the various types of cardiomyopathies.

Ans. Cardiomyopathy (CMP) is a heterogeneous group of diseases associated with me-
chanical and electrical dysfunction of the myocardium. Cardiomyopathies may be local-
ized to the heart or may form a part of a systemic disease.
1. Primary cardiomyopathy: Diseases confined to heart muscle. May be genetic or ac-
quired in origin.
Three pathophysiologic categories are encountered (Table 11.7):
(a) Dilated (congestive) CMP
(b) Hypertrophic (obstructive) CMP
(c) Restrictive/obliterative or infiltrative CMP
Further, restrictive cardiomyopathy includes the following entities:
(i) Cardiac amyloidosis
(ii) Endocardial fibroelastosis
(iii) Endomyocardial fibrosis
(iv) Loeffler endocarditis
2. Secondary cardiomyopathy: The myocardial involvement is seen as a component of a
systemic or a multiorgan disorder, as in
(a) Nutritional deficiencies (alcoholic CMP and beriberi)
(b) Toxic chemicals (cobalt, arsenic, lithium and hydrocarbons)

TABLE 11.7. Types of CMP
Hypertrophic (obstructive) Restrictive/obliterative or
Features Dilated (congestive) CMP CMP infiltrative CMP
Definition • Systolic dysfunction with dilata- • Diastolic dysfunction (re- • Diastolic dysfunction (re-
tion of all four chambers duced chamber size and im- striction in ventricular fill-
paired diastolic filling) ing due to reduction in the
• 25% patients have left ven- volume of ventricles)
tricular outflow obstruction
Incidence 90% of all CMPs Less common Less common
Age affected 20–50 years 25–40 years Variable

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