Variability of haematoxylin - basic fuchsin - picric acid (HBFP) staining of infarcted myocardium due to tissue storage.

Early myocardial infarction is usually detected (3) The effect of storage and drying on the timgrossly by utilising the nitro-blue tetrazolium (NBT) ing of the differentiation step was also technique.1 The normal areas stain dark blue and studied. infarcted areas which lack the dehydrogenase enzyme remain unstained. In 1971, Lie et aI2 described a non-enzymatic histochemical method, the haematoxylin-basic fuchsin-picric acid (HBFP) technique, for demonstrating early stages of myocardial infarction. They found positive staining of infarcted myocardium from dogs as early as 30 minutes after coronary artery ligation and positive staining of infarcted human hearts as early as 6 hours following fatal coronary occlusion. The HBFP technique is sensitive to early myocardial changes and can be carried out on formalinfixed paraffin-embedded tissue. Although technically much care is required, it provides a vivid contrast between infarcted and normal fibres. There are several factors believed to affect HBFP positivity,'such as aging of unstained sections in room air,4 and the precise timing of the differentiation step of this stain. This paper reports the results of the investigation of some of these factors.