Propranolol in management of muscular subaortic stenosis.

Muscular subaortic stenosis (Wigle, Heimbecker, and Gunton, 1962) is one of the names used to describe functional ventricular obstruction which simulates aortic valve stenosis. Other workers (Brock, 1957, 1959; Teare, 1958; Morrow and Braunwald, 1959; Brent et al., 1960; Brockenbrough, Braunwald, and Morrow, 1961; Goodwin et al., 1960) have also emphasized the functional nature of the myocardial obstruction. Criley et al. (1965) developed a new concept ofthe condition, illustrating seven patients in whom there was a pressure gradient without obstruction. Braunwald and Ebert (1962) and others have shown that increased beta-adrenergic stimulation increased the apparent obstruction to flow, from both the right and the left ventricle in muscular subaortic stenosis. It has been shown that digitalis has a similar action (Braunwald, Brockenbrough, and Frye, 1962). Cohen et al. (1964) studied the acute effect of beta-adrenergic blockade in patients with muscular subaortic stenosis using pronethalol during cardiac catheterization,and later Cherian et al. (1966) showed that propranolol would prevent the increase in dynamic obstruction which occurred with exercise or isoprenaline infusion. It was noted that propranolol had very little or no effect on the hiemodynamics at rest. The importance of the adrenergic nervous system in this condition was reinforced by the findings of Everson Pearse (1964), who examined operative specimens of ventricular septal myocardium from two patients and showed an increased amount of noradrenaline in the hypertrophied muscle. This observation of increased noradrenaline store has been confirmed in one patient submitted to ventriculomyotomy at the Royal Melbourne Hospital (G. Burnstock, personal communication, 1966).