Hypertrophic cardiomyopathy histopathology
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Editors-In-Chief: C. Michael Gibson, M.S., M.D. [1], Cafer Zorkun, M.D. [2], Martin S. Maron, M.D., and Barry J. Maron, M.D.
Overview
On histopathologic examination, hypertrophic cardiomyopathy is characterized by both myocardial disarray and by periarteriolar fibrosis. Myocardial disarray can be associated with aberrant impulse conduction and arrhythmias, and periarteriolar fibrosis can be associated with myocardial ischemia.
Histopathologic Abnormalities
Myocardial Disarray
A cardiomyopathy is any disease that primarily affects the muscle of the heart. In HCM, the normal alignment of muscle cells is disrupted (there is a swirling pattern to the arrangement of the muscle cells), a phenomenon known as myocardial disarray. HCM is believed to be due to a mutation in one of many genes that results in a mutated myosin heavy chain, one of the components of the myocyte (the muscle cell of the heart). Histopathologically, the cardiac sarcomere is abnormal resulting in hypertrophy of the left ventricle in the absence of other disorders that could produce the condition such as hypertension, amyloid or aortic stenosis.
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Myocardial disarray with swirling pattern of myocytes
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Variants of hypertrophic cardiomyopathy
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White areas of fibrosis or scar in a patient with HCM which may contribute in part to arrhythmias
Periarteriolar Fibrosis
Compared to normal arterioles on the left, the arterioles from a patient with hyertension (middle) show moderate periarteriolar thickening and fibrosis. Shown on the right is a patient with HCM in which there is even more signficant periarteriolar thickening and fibrosis. This thickening of the wall of the intramyocardial arterioles leads to an increased wall/lumen ratio, subendocardial ischemia and impaired coronary flow reserve. Patients who subsequently died in one series had abnormal coronary flow reserve on PET scanning at baseline indicating that ischemia may play a role, at least in part, in subsequent mortality.
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Normal arteriole
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Hypertensive arteriole with wall thickening and myocyte hypertrophy
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Arteriole in HCM patient with periarteriole fibrosis and thicknening
