EDITORIAL Hypertrophic cardiomyopathy: a 1987 viewpoint

characterized by symmetric or asymmetric hyper-trophy of the left and/or right ventricle (table 1). * It is a primary disorder of heart muscle in which the site and extent of the hypertrophic process are important in determining the disease manifestations.' Ventricular (asymmetric) septal hypertrophy is the commonest form ofHCM (table 1) and is characterized by abnormalities of systolic and diastolic function as well as rhythm disturbances. Systole is characterized by the presence or absence of an intraventricular pres-sure gradient, which when present may be persistent (gradient at rest), labile (spontaneously variable), or latent (provocable).", 2 Diastole is characterized by ab-normalities of ventricular relaxation3 and passive chamber stiffness.4 Patients with extensive hyper-trophy are more likely to manifest the abnormalities of systolic and diastolic function, as well as being more prone to atrial and ventricular arrhythmias and sudden death.' During the almost three decades that HCM has been recognized as a clinical entity with regard to the sig-nificant morbidity and mortality, our knowledge and understanding of the diastolic and rhythm abnor-malities have advanced in a fairly orderly, if perhaps modest, fashion. Such is not the case, however, with interpretation of the significance of the systolic intra-ventricular pressure differences. Most investigators accept that the characteristic pressure gradient, caused by prolonged mitral leaflet-septal contact, represents obstruction to left ventricular outflow and offer these patients surgical relief of the obstruction if they are unresponsive to medical therapy."'`5,6 However