Geary G G, Norris R M
Coronary Care Unit, Green Lane Hospital, Auckland, New Zealand.
Cardiovasc Res. 1988 Aug;22(8):527-36. doi: 10.1093/cvr/22.8.527.
Changes in myocardial segment length (ultrasonic crystals) and myocardial blood flow (15(3) microns microspheres) were studied during 5 min occlusions of the left anterior descending coronary artery in open chest anaesthetised dogs, and the effects of occlusion without intervention were compared with those of occlusion during bilateral vagal nerve stimulation (n = 11) and occlusion after administration of 1 mg.kg-1 propranolol (n = 9) in the same dogs. Delineation of the perfusion beds of occluded and non-occluded arteries at necropsy verified placement of the crystals at the centres and immediately within the borders of the ischaemic areas. In untreated animals (n = 6) systolic shortening during occlusion decreased by 160(2)% (dyskinesis) in the centre zone and by 61(1)% (hypokinesis) in the border zone of ischaemia, myocardial blood flow decreased by 96(2)% in the centre and 81(2)% at the border, and the changes were reproducible over three successive occlusions. Postsystolic shortening (after peak decline of left ventricular pressure) was reproducible in control animals over three occlusions, was similar in magnitude to the magnitude of dyskinesis (centre zone) or to the degree of hypokinesis (border zone), and persisted after the release of occlusion. Vagal stimulation and propranolol decreased dyskinesis during occlusion but did not affect postsystolic shortening or collateral blood flow within the ischaemic zones. If postsystolic shortening of dyskinetic centre zone segments represents residual active shortening of these segments, as is suggested by other evidence, these results suggest that the oxygen sparing effects for very ischaemic myocardium of vagal stimulation and propranolol do not include a significant reduction in residual active shortening.
在开胸麻醉犬中，研究了左前降支冠状动脉闭塞5分钟期间心肌节段长度（超声晶体）和心肌血流（15（3）微米微球）的变化，并将未干预情况下的闭塞效应与双侧迷走神经刺激期间的闭塞效应（n = 11）以及同一批犬给予1 mg.kg-1普萘洛尔后闭塞的效应（n = 9）进行了比较。尸检时对闭塞和未闭塞动脉的灌注床进行描绘，证实晶体放置在缺血区域的中心及紧邻边缘处。在未治疗的动物（n = 6）中，闭塞期间中心区域的收缩期缩短减少了160（2）%（运动障碍），缺血边缘区域减少了61（1）%（运动减弱），中心区域的心肌血流减少了96（2）%，边缘区域减少了81（2）%，并且在连续三次闭塞中这些变化均可重现。对照动物在三次闭塞中收缩期后缩短（左心室压力峰值下降后）均可重现，其幅度与运动障碍（中心区域）的幅度或运动减弱（边缘区域）的程度相似，并且在闭塞解除后仍持续存在。迷走神经刺激和普萘洛尔减少了闭塞期间的运动障碍，但不影响收缩期后缩短或缺血区域内的侧支血流。如果运动障碍中心区域节段的收缩期后缩短代表这些节段的残余主动缩短，正如其他证据所提示的那样，这些结果表明，迷走神经刺激和普萘洛尔对严重缺血心肌的氧节省效应并不包括显著减少残余主动缩短。
