Springer Online Journal Archives 1860-2000
Summary Antiischemic effects of β1-blocking agents are based on intrinsic negative inotropic and chronotropic properties. Partial β1-agonistic activity, although useful in preserving cardiac function, may counteract such antischemic properties by modulating the intrinsic negative cardiac effects of beta-blockade. To investigate the acute hemodynamic and antiischemic profile of epanolol, a cardioselective β1-antagonist and partial agonist, 20 patients with left coronary artery disease underwent two incremental atrial pacing tests, 45 minutes before (APST I) and 15 minutes after (APST II) 4 mg intravenous epanolol, administered over 5 minutes. Additional measurements were carried out at 1, 3, 5, 10, and 15 minutes after epanolol, at basal and fixed heart rates. Epanolol immediately reduced heart rate with a maximum of 10% at 15 minutes and decreased contractility (Vmax) by 7% (both p〈.05), whereas cardiac output fell temporarily by 9% (p〈.05). Other hemodynamic parameters did not change, except for a significant 11% reduction in myocardial oxygen demand. Despite comparable pacing conditions, both the double product and contractility decreased significantly less during APST II, resulting in a 17% lower myocardial oxygen consumption (p〈.05). Myocardial ischemia was markedly reduced, indicated by normalization of lactate metabolism [lactate extraction 16±7% vs. −7±8% (APST I)], less ST depression (21%), and modulation of LV end-diastolic pressure postpacing (all p〈.05 vs. APST I), whereas angina was absent or less in 14 patients. None of the patients reported an adverse effect. Thus, under resting conditions intravenous epanolol induces moderate, short-lasting negative chronotropic and inotropic effects, but does not alter cardiac pump function or vascular resistance, reflecting its additional β1-agonistic properties. Alternatively, during pacing it still reduces ischemia through negative inotropic effects and diminishes myocardial oxygen demand, reflecting its β1-antagonistic profile.
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