Birkeland S, Westby J, Hexeberg E
Department of Surgery, University of Bergen, Haukeland Hospital, Norway.
J Cardiovasc Pharmacol. 1994 Jan;23(1):66-71. doi: 10.1097/00005344-199401000-00008.
beta-Adrenergic blockade alleviates myocardial ischemia, probably largely through heart rate (HR) reduction. We hypothesized that the negative inotropic effect of beta-blockade, which is believed to be potentially dangerous, is attenuated in underperfused hearts with an acute coronary artery occlusion. We studied the effect of intravenous propranolol (1 mg/kg i.v.) in feline hearts with acute circumflex coronary artery (LCX) occlusion by cross-oriented segments in normally perfused and mildly underperfused left ventricular (LV) anterior wall. A control group (n = 10) was compared with a stenosis group (n = 9) in which the mean coronary perfusion pressure was reduced (91 +/- 4 g vs. 136 +/- 5 mm Hg, p < 0.01). End-systolic pressure-length (ESP-ESL) relations during dynamic afterload increase and preload reduction were calculated to evaluate regional inotropy. HR and LV peak systolic blood pressure (LVSP) decreased in both groups after beta-blockade (p < 0.05). Subendocardial and mid-myocardial blood flow measured by radiolabeled microspheres decreased in the control group (p < 0.05) but was unchanged in the stenosis group. Systolic shortening of circumferential segments also decreased in the control group (p < 0.05) but was unchanged in the stenosis group. ESP-ESL relations of circumferential segments shifted markedly rightward in the control group, whereas a modest rightward shift was noted in the stenosis group. This study in feline heart with acute LCX occlusion showed an attenuated negative inotropic effect of beta-blockade in underperfused LV anterior wall.
β-肾上腺素能阻滞剂可减轻心肌缺血，可能主要是通过降低心率（HR）来实现。我们推测，β-阻滞剂的负性肌力作用虽被认为具有潜在危险性，但在急性冠状动脉闭塞导致灌注不足的心脏中会减弱。我们通过正常灌注和轻度灌注不足的左心室（LV）前壁交叉定向节段，研究了静脉注射普萘洛尔（1 mg/kg静脉注射）对猫急性冠状动脉回旋支（LCX）闭塞心脏的影响。将对照组（n = 10）与狭窄组（n = 9）进行比较，狭窄组的平均冠状动脉灌注压降低（91±4 g vs. 136±5 mmHg，p < 0.01）。计算动态后负荷增加和前负荷降低期间的收缩末期压力-长度（ESP-ESL）关系，以评估局部心肌收缩力。β-阻滞剂治疗后两组的心率和左心室收缩压峰值（LVSP）均降低（p < 0.05）。对照组中通过放射性微球测量的内膜下和心肌中层血流量减少（p < 0.05），而狭窄组则无变化。对照组中环周节段的收缩期缩短也减少（p < 0.05），而狭窄组无变化。对照组中环周节段的ESP-ESL关系明显右移，而狭窄组仅出现适度右移。这项对猫急性LCX闭塞心脏的研究表明，β-阻滞剂在灌注不足的LV前壁中的负性肌力作用减弱。
