Myocardial fibre calcification.

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Abstract
Three [human] cases of myocardial fiber calcification found at post-mortem examination are described. In 1 case, there was antemortem hypercalcemia and hyperphosphatemia and the case was clearly an example of metastatic calcification. In the other 2 cases, there was ischemic myocardial necrosis and calcification was seen in fibers which were not overtly necrotic, but which were both in proximity to (the majority) and remote from the necrotic zones. Since renal failure with hyperphosphatemia was present in both cases, these were considered to be examples of augmented (by the hyperphosphatemia) dystrophic calcification. The histological, histochemical and ultrastructural features were identical in the 3 cases. Hydroxyapatite formation was observed initially in mitochondria, followed by spillage of crystals into the cytosol and ultimately into the interstitium. The fundamental lesion is a dysfunction of the fiber membrane; the similarity of this reaction with the calcification seen in skeletal muscle fibers in various myopathies is noted and a unifying hypothesis of the mechanism of skeletal and cardiac muscle fiber calcification is thereby suggested.