Idiopathic cardiomyopathy: The pathologic roles of arteriolopathy

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Structural alterations and pathologic features of arteriolopathy of the heart were studied in 12 patients with idiopathic cardiomyopathy, five with hypertrophic cardiomyopathy (HOCM), and seven with congestive cardiomyopathy (COCM). The patients, six men and six women, ranged in age from 25 to 66 years. Diagnoses of idiopathic cardiomyopathy were confirmed clinically and at autopsy. Heart weights ranged from 350 to 700 g. Dilatative hypertrophy of both ventricles was observed in four patients, dilatation of both ventricles in six patients, and concentric hypertrophy of the left ventricle in two patients. The ventricular septa ranged in thickness from 7 to 27 mm, and the septal:free wall ratios ranged form 1.0 to 1.8. The lumens of extramural coronary arteries showed less than 30 per cent narrowing. Sections of the heart and all body organs were examined. The myocardia showed microscopic areas of hypertrophy, degeneration and disorganization of muscle cells, interstitial fibrosis, and various features of arteriolopathy. Histometric studies showed that hypertrophy of muscle cells was greater in HOCM than in COCM, that the content of connective tissue in the myocardium was higher in COCM, and that interstitial fibrosis was greater in the epicardial zone than in the endocardial zone in COCM but was greater in the endocardial zone in HOCM. Of the arteriolar changes, those of smooth muscle cells and internal elastic lamina were observed most frequently; no arteriolar narrowing or stenosis was observed in either HOCM or COCM. The correlation between the frequency of arteriolopathy (loss of smooth muscle cells in the media) and myocardial interstitial fibrosis was significant in COCM (P less than 0.05) but not in HOCM. No significant correlations were found between arteriolopathy and age, the duration of symptoms, the cause of death, the heart weight, the thickness of the septum or posterior free wall, the septal:free wall ratio, the presence of disorganized cells in the septum, mural thrombi, the mean muscle cell diameter, or the extent of very hypertrophic cells (P greater than 0.05) in either HOCM or COCM.