Histopathological study of the papillary muscles and apex cordis of the hypertrophied left ventricle.

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Abstract
Hypertrophy of the papillary muscle and apex cordis of the left ventricle was studied histopathologically using 84 hearts obtained at autopsy. The hearts were divided into three groups: a hypertrophy group (heart weight more than 350 g); a borderline group (heart weight between 350 and 300 g) and a control group (heart weight less than 300 g). The size of the papillary muscle increased with increase in heart weight. Derangement of myocyte linings and fibrosis at the papillary muscle base became apparent with hypertrophy. In addition derangement and fibrosis extended from the internal to middle layers of the free wall with progressing hypertrophy. Derangement seemed to precede hypertrophy and fibrosis. A cluster of huge myocyte-like Purkinje''s cells were associated with the center of the derangement. At the apex, criss-cross derangement developed from right and left side derangement with increasing hypertrophy. It is speculated that the focal derangement plays an important role in producing hypertrophy in response to mechanical stress with subsequent development of hypertrophy and fibrosis with some asymmetry.