Myocardial fiber disarray and ventricular septal hypertrophy in asymmetrical hypertrophy of the heart.

ALTHOUGH TWO NINETEENTH CENTURY French pathologists1 2 and an early twentieth century German pathologist3 described cardiac pathological findings compatible with what we know today as "6asymmetrical hypertrophy of the heart," it remained for Donald Teare to bring attention to this entity in 1958.4 In nine cases of sudden death, Teare described a marked hypertrophy and thickening of the interventricular septum at postmortem examination. In five of these cases the hypertrophic process also involved-the anterior wall of the left ventricle. By contrast, the posterior left ventricular wall appeared not to be involved. The process was truly asymmetric.4 Microscopic examination of the hypertrophic areas of the myocardium revealed myocardial fiber disarray (a very bizarre form of myocardial fiber hypertrophy) and significant amounts of interstitial fibrosis. Teare's report, together with that of Lord Brock,5 opened the flood gates to voluminous literature on this fascinating, sometimes controversial, but always stimulating, entity. Much has been written on the clinical, hemodynamic, angiographic, pathophysiologic, pharmacodynamic, therapeutic and pathologic aspects. And more is yet to come. Like a rejected lover, asymmetrical cardiac hypertrophy has been called many things. To distinguish it from other cardiomyopathies, the term hypertrophic cardiomyopathy6 seems appropriate. When obstruction to left ventricular outflow is present (hypertrophic obstructive cardiomyopathy), the terms hypertrophic7 or muscular8 9 subaortic stenosis have been applied. It should be noted, however, that muscular or hypertrophic subaortic stenosis may be caused not only by asymmetric cardiac hypertrophy, but also by concentric left ventricular hypertrophy.'0' 11 In fact, it has recently been described in the absence of any apparent left ventricular hypertrophy." Until recently the presence of ventricular septal hypertrophy and/or myocardial fiber disarray on microscopy were generally considered to be specific for asymmetrical hypertrophy of the heart. Such is no longer the case. Thickening of the interventricular septum has been described in fetuses and in some