Cardiac output after beta-adrenergic blockade in ischaemic heart disease.

The suggestion that blockade of the cardiac sympathetic nerves might be helpful in patients with angina pectoris has received some experimental support (Apthorp, Chamberlain, and Hayward, 1964; Hamer et al., 1964). The increased myocardial contractility during exercise is produced by stimulation of beta-adrenergic sympathetic fibres (Ahlquist, 1948) which are specifically blocked by pronethalol and propranolol (Dornhorst and Robinson, 1962; Black et al., 1964). These drugs have been shown to decrease myocardial contractility under a variety of circumstances, and it seems likely that the consequent reduction in myocardial work might be responsible for their beneficial effect in angina pectoris. In order to assess the mechanisms by which exercise tolerance is increased after beta-adrenergic blockade, we have undertaken a study of the effects of propranolol on cardiovascular function at rest and during exercise in a series of patients with ischvmic heart disease.