[Effects of acute beta-adrenoceptor blockage (metoprolol i.v.) on plasma norepinephrine concentration and hemodynamics in postmyocardial infarction patients].
The effect of acute beta-adrenoceptor blockage (Metoprolol) (M), 0.1 mg/kg i.v.) on left ventricular performance has been investigated at rest and during exercise in 15 patients with 2--3 months old transmural myocardial infarctions. Coronary venous and arterial norepinephrine (NE) concentrations were determined. There was no significant change in arterial and coronary venous NE concentrations (0.27 and 0.22 ng/ml, respectively) after blockage of beta-adrenoceptors (0.36 vs 0.26 ng/ml), which caused a fall of stroke volume from 79 to 68 ml, a reduction of ejection fraction from 62 to 55% and of circumferential fibre shortening form 1.2 to 0.9 circ/sec. During physical exercise the plasma NE concentration in the arterial (0.51 ng/ml) and coronary venous (0.6 ng/ml) blood increased significantly and increased even further to 0.65 and 0.76 ng/ml, respectively, following administration of Metoprolol. The arterio-coronary sinus difference in NE concentrations demonstrate a release of NE from the myocardium. As compared to control values, heart rate following Metoprolol was lower (116 vs 106/min), mean PCV pressure was slightly increased (from 21 to 23 mm Hg) and there was a fall of cardiac index from 6.3 to 5.2 l/min X m2. It is likely that the increased sympathetic activity after Metoprolol and during exercise is a compensatory reaction due to the hemodynamic effects of blockade of beta-adrenoceptors. Further studies are in preparation in order to find out if this is only a transient phenomenon during the early adaptation phase after blockade of beta-adrenoceptors.
D000328:Adult; D000792:Angiography; D001794:Blood Pressure / Q000187:drug effects; D003331:Coronary Vessels; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy; D009638:Norepinephrine / Q000097:blood; D005082:Physical Exertion; D011412:Propanolamines / Q000627:therapeutic use*
D011412:Propanolamines; D008790:Metoprolol; D009638:Norepinephrine
Wirkungen einer akuten Blockade adrenerger beta-Rezeptoren aug Noradrenalinkonzentration und Hämodynamik bei Patienten nach Myokardinfarkt.