Myofibrillar degeneration--a common type of myocardial lesion and its selective identification by a modified luxol fast blue stain.

Myofibrillar degeneration is a very common form of myocardial damage. It occurs as a disseminated lesion after various forms of injury (e.g. association with cardiovascular surgery, raised intracranial pressure). As a localized alteration it surrounds the coagulation necrosis of infarcts. The present study introduces a modification of the Luxol Fast Blue (LFB) stain as a specific marker of myofibrillar degeneration. In formalin-fixed and paraffin-embedded myocardium of human autopsies and biopsies two LFB-reaction types are demonstrable: A) irregular blue transverse bands and B) a diffuse blue staining of the entire myocyte. The first type corresponds to the cross band lesion typical of myofibrillar degeneration. By electron microscopy it consists of dense aggregations of disorganized myofilaments. The second form exhibits diffusely LFB-coloured cells and ultrastructurally an irregular felt-like splitting of myofibrils. The latter represents another, until now unrecognized type of myofibrillar degeneration which is not clearly detectable when using other staining methods. Since a coagulation necrosis is only faintly LFB-positive, this method is not suitable for the detection of early stages of infarcts. The obvious advantages of the LFB-method are: detection of type, amount and distribution pattern of myofibrillar degeneration in low-power-views, even if myocytes are cut transversely, high sensitivity, easy handling and reliability. The affinity of damaged cells for the LFB-stain seems to be related to the pathogenesis of myofibrillar degeneration, in which abundant Ca++-influx plays a primary role.