THE EFFECT OF THE PARTIAL BETA-1-ADRENOCEPTOR AGONIST XAMOTEROL ON HEMODYNAMICS AND MYOCARDIAL ENERGETICS IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

Abstract

Xamoterol, a new partial beta-1-adrenoceptor agonist, was evaluated in respect to its hemodynamic and energetic effects when given acutely i.v. (0.2 mg/kg body weight) to 10 patients with idiopathic dilated cardiomyopathy. Hemodynamically, a small drop in left ventricular end-systolic volume index (from 105 +/- 38 to 91 +/- 48 ml/m2; p < 0.05) and end-diastolic volume index (from 168 +/- 44 to 152 +/- 41 ml/m2; p < 0.05) and an increase in maximum rate of left ventricular pressure rise (from 1,003 +/- 358 to 1,283 +/- 398 mm Hg/s; p < 0.001) was observed. The systolic stress-time integral was only slightly reduced after injection of xamoterol, from 107 +/- 28 to 94 +/- 35 x 10(3) dyn.s/cm2 (NS). Other conventional hemodynamic variables did not change significantly. Myocardial oxygen consumption per beat increased from 125 +/- 39-mu-l/beat/100 g to 153 +/- 62-mu-l/beat/100 g (p < 0.05). The ratio of myocardial oxygen consumption per beat and stress-time integral-as an inverse measure of left ventricular contraction economy-increased significantly, from 132 +/- 62 to 192 +/- 115-mu-l/beat/10(3) dyn.s/cm2 (p < 0.02) after injection of xamoterol, whereas left ventricular efficiency decreased from 17.6 +/- 7.8 to 13.8 +/- 6.5% (p < 0.05). Thus, in idiopathic dilated cardiomyopathy, xamoterol exhibited only minor hemodynamic effects whereas myocardial contraction economy and efficiency were significantly reduced.