Myocardial disarray. A critical review.

Myocardial disarray or disorganisation is at present a contentious topic, not least because its value as a clinical marker for hypertrophic cardiomyopathy has changed considerably over the years. Initially observed as one of the features of asymmetric septal hypertrophy, disarray has since been promoted as its pathognomonic histological feature, regarded by some observers as the morphological manifestation of a genetically transmitted myocardial defect. Recently, however, it has become evident that myocardial disarray is not limited to hypertrophic cardiomyopathy, but is encountered in hearts with both congenital and acquired conditions, and is also observed in normal hearts. The specificity of disarray for hypertrophic cardiomyopathy is thus seriously questioned. Latterly, it has been suggested that disarray, judged from through-and-through sections of the ventricular midseptum is a highly specific and sensitive marker of hypertrophic cardiomyopathy when considered in quantitative rather than qualitative fashion. The present study sets out to answer the question whether disarray could be the histological expression of the normal but intricate fibre architecture of the heart, a consideration also initiated by debatable definitions of normality and abnormality of myocardial histology. Gross fibre dissections in five normal hearts showed that many sites occurred in which disarray was a natural phenomenon. In five more hearts it was found that the plane of section of a tissue block might profoundly influence the histology. In fact, tissue cubicles sampled from different faces showed a change in histology in the vast majority. Thus the diagnostic significance of myocardial disarray as a marker of hypertrophic cardiomyopathy in the clinical setting almost vanishes; a change in orientation of a tissue section may actually turn "normality" into "disarray".