Cardiac Function in Primary Myocardial Disorders*-Part II

The data presented indicate that myocardial function in primary cardiomyopathy falls into three main groups: congestive, constrictive, and hypertrophic obstructive. However, clear-cut differences between the congestive and constrictive groups do not always exist, though the hypertrophic obstructive group appears to be different. In the congestive and constrictive groups the absence of any obvious cause for the heart disease and the finding of round-cell infiltration and fibrosis at necropsy in some would harmonize with an infective origin for many, though the histological and virological studies gave no support for this. Nevertheless, myocarditis or infective cardiomyopathy has long been accepted as an entity. Possibly infection damages the delicate contractile elements of the myocardium and interferes with the biochemical and biophysical phenomena essential for efficient function. In some way also the toxic agent might prevent the hypertrophy that occurs readily with most other forms of heart disease. By contrast, the third group, hypertrophic obstructive cardiomyopathy, shows very marked differences from the other two, which strongly suggest another pathogenesis. A positive family history, massive ventricular hypertrophy, reduced ventricular compliance, disturbed contraction and systolic outflow gradients