PRIMARY CARDIOMYOPATHIES (DIAGNOSIS OF EXCLUSION)
cardiomyopathy (most common form) is cardiac enlargement with dilatationof
all 4 chambers, resulting in progressive congestive heart failure (typical mode
of presentation). The cause is genetic in 20–50% of cases, but some cases are
related to alcohol, medications (Adriamycin [doxorubicin]), cocaine, viral
myocarditis (Cox-sackievirus B and enteroviruses), parasitic infections (Chagas
disease), iron overload or pregnancy.
cases of all types, the underlying etiology leads to destruction of myocardial
con-tractility, which affects systolic function. Echocardiogram typically shows
decreased ejection fraction. Complications include mural thrombi and cardiac
arrhythmias; prognosis is poor with 5-year survival of 25%. Treatment is heart
transplantation. There is myocyte hypertrophy with interstitial fibrosis on
microscopy, and eccentric hypertrophy seen on gross examination.
cardiomyopathy (also called asymmetrical septal hypertrophy, andidiopathic
hypertrophic subaortic stenosis [IHSS]) is a common cause of sudden cardiac
death in young athletes. The condition is an asymmetrical hypertrophy of
cardiac muscle that causes decreased compliance affecting diastolic function.
Hypertrophic cardiomyopathy can be an autosomal dominant disorder (>50% of
cases) or idiopathic. The muscle hypertrophy is due to the increased synthesis
of actin and myosin, and on microscopic examination, the cardiac muscle fibers
are hypertrophied and in disarray. Hypertrophic cardiomyopathy is most
prominent in the ventricular septum, where it can obstruct the ventricular
outflow tract. This can potentially lead to death during severe exercise when
the cardiac outflow tract collapses, preventing blood from exiting the heart.
Restrictive cardiomyopathy (uncommon
form) is caused by diseases which producerestriction of cardiac filling during
diastole; etiologies include amyloidosis, sarcoid-osis, endomyocardial
fibroelastosis, and Loeffler endomyocarditis. In all of these diseases,
increased deposition of material leads to decreased compliance, affecting
diastolic function. On gross examination, the ventricles are not enlarged and
the cavities are not dilated. Microscopy will reflect the underlying cause.
Arrhythmogenic right ventricular
cardiomyopathy causes thinning of the right ven-tricle due to autosomal
dominant mutations that encode desmosomal junctional proteins. On microscopy,
there is fatty infiltration of the myocardium.