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16. A 59-year-old patient receiving chemotherapy with the anthracycline
Adriamycin develops severe heart failure. Sections from an endocardial
biopsy specimen reveal vacuolization of the endoplasmic reticulum of the
myocytes. What type of cardiac damage is Adriamycin most likely to produce?
a. Dilated cardiomyopathy
b. Hyperplastic cardiomyopathy
c. Hypertrophic cardiomyopathy
d. Obliterative cardiomyopathy
e. Restrictive cardiomyopathy
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The answer is a. The cardiomyopathies
(CMPs) may be classified into primary and secondary forms. The primary
forms are mainly idiopathic (unknown cause). Most of the secondary cardiomyopathies
result in a dilated cardiomyopathy that is characterized by
congestion and four-chamber dilation with hypertrophy. The walls are
either of normal thickness or they may be thinner than normal. This results
in a flabby, globular, banana-shaped heart that is hypocontracting. The
microscopic appearance is not distinctive. The ventricles may contain
mural thrombi. The causes of secondary dilated CMP are many and include
alcoholism (the most common cause in the United States), metabolic disorders,
and toxins. Examples of the latter include cobalt, which has been
used in beer as a foam stabilizer; anthracyclines; cocaine; and iron, the
deposition of which is seen in patients with hemochromatosis. The anthracycline
Adriamycin, which is used in chemotherapy, causes lipid peroxidation
of myofiber membranes. One final form of DCM develops in the last
trimester of pregnancy or the first 6 months after delivery. About half of
these patients recover full cardiac function.
Other forms of cardiomyopathies include a hypertrophic form, a
restrictive form, and an obliterative form. In hypertrophic CMP the major
gross abnormality is within the interventricular septum, which is usually
thicker than the left ventricle. Constrictive (restrictive) CMP is associated
with amyloidosis, sarcoidosis, endomyocardial disease, or storage diseases.
These abnormalities produce a stiff, hypocontracting heart.
