Beta-adrenergic blockers are increasingly used in the treatment of angina pectoris (Hamer et al., 1964Srivastava, Dewar, and Newell, 1964; Gillam andPrichard, 1965, 1966;Keelan, 1965;Rabkin et al., 1966;Wolfson et al., 1966), cardiac arrhythmias (Stock and Dale, 1963;Ginn, Irons, and Orgain, 1965;Harrison, Griffin, and Fiene, 1965;Bath, 1966;Harris, 1966;Rowlands, Howitt, and Markman, 1965;Schamroth, 1966;Szekely et al., 1966), and some other less common conditions (Harrison et al., 1964). The danger of inducing or aggravating heart failure by beta-blockade remains a matter of controversy (Stephen, 1966). Whereas this risk has been considered as relatively small and acceptable by Snow (1965Snow ( , 1966, undesirable side-effects and sometimes severe complications related to the depressant action of propranolol on myocardial contractility have been reported, in isolated instances with fatal outcome (Fleckenstein et al., 1964;Vogel, 1965;Scheu, 1966;Luthy and Hegglin, 1966). This risk undoubtedly represents an important drawback to this kind of therapy.In the present study, propranolol was given intravenously to patients with organic disease of the left heart, and its circulatory effects were assessed during the course of standard pre-operative catheterization of the heart. In a second stage of this study, these effects were compared with those of CIBA 39,089-Ba, a new specific beta-adrenergic blocking agent. Fig. 1 shows the chemical structures of isoprenaline, propranolol, and CIBA 39,089-Ba. Fig. 2 shows that the two drugs are apparently equipotent beta-blockers in terms of their negative chronotropic effect. This study Received March 30, 1967. suggests that propranolol depresses myocardial contractility, and this effect correlates well with the severity of the heart disease. CIBA 39,089-Ba has a negative chronotropic effect fairly similar to that of propranolol, but produces a significantly less marked depression of myocardial contractility.
RESULTSThe results are shown in Tables III and IV and in Fig. 3-7. Both drugs slowed the heart rate to much the same extent. At rest, the heart rate was reduced from 77 to 64 beats/min. (-16%) after BLE I