Beta-adrenergic blockade in hypertrophic obstructive cardiomyopathy.

Hypertrophic obstructive cardiomyopathy is a disorder of ventricular muscle characterized by asymmetrical hypertrophy and unusually rapid ventricular ejection of a normal stroke volume (Goodwin et al., 1960; Braunwald et al., 1964). The presence of a systolic gradient between the left ventricle and the aorta has been taken as evidence of obstruction of the ventricular outflow tract, but recent observations suggest that the.pressure gradient may be due to continuing contraction in areas of the ventricle which have been completely emptied early in systole (Criley et al., 1965). The hypertrophy also leads to a restrictive effect with a high ventricular filling pressure. On clinical and haemodynamic grounds the presentation may be purely "obstructive," occasionally purely restrictive, or, more often, a mixed form with varying combinations of obstruction and restriction.