Watanabe J, Maruyama Y, Ashikawa K, Isoyama S, Satoh S, Suzuki H, Shimizu Y, Ino-oka E, Takishima T
Jpn Circ J. 1986 Mar;50(3):248-57. doi: 10.1253/jcj.50.248.
By measuring ECG ST segment deviation and regional mechanical dysfunction, we assessed the effects of an alteration in afterload pressure on regional myocardial ischemia due to a partial coronary occlusion of the left circumflex coronary artery (CFX). Eight isolated, perfused and paced dog hearts were loaded with an artificial arterial system which simulated the aortic input impedance of the dog arterial tree. Afterload pressure was altered by stepwise changes in peripheral resistance (Rp), while left ventricular end-diastolic pressure (LVEDP) and heart rate were kept constant. Coronary perfusion pressure (CPP) was kept equal to mean aortic pressure (AoP). ECG and myocardial systolic segment shortening (SS) were measured in both areas perfused by the CFX and the left anterior descending coronary artery (LAD). In the presence of CFX stenosis, mean AoP decreased from 96 +/- 7 to 46 +/- 7 mmHg following a decrease in Rp and cardiac output increased progressively from 465 +/- 30 to 1055 +/- 100 ml/min. In this situation, CFX coronary blood flow decreased from 75 +/- 2 to 28 +/- 6 ml/100 g/min. Epicardial ECG in the ischemic region showed two types of ST segment deviation after CFX stenosis: ST segment elevation and ST segment depression. Moreover, following afterload reduction, these individual ECG ST segment changes showed further deviations. The levels of mean AoP, below which further ST segment deviations significantly occurred, were as follows: 71 +/- 6 mmHg in ST segment elevation cases and 52 +/- 7 mmHg in ST segment depression cases. Myocardial systolic segment shortening in the ischemic region also significantly decreased following CFX stenosis (91 +/- 8% of pre-ischemic control, p less than 0.05). Then, during afterload reduction, SS in the CFX area appeared to be bimodal and it definitely decreased when mean AoP was 46 +/- 7 mmHg. To enhance the sensitivity of detection of further mechanical dysfunction throughout afterload reduction following regional myocardial ischemia, we calculated percentage values of the SS in the CFX area to the SS in the LAD area at each Rp. By this normalization, mechanical dysfunction was found when mean AoP was below 67 +/- 5 mmHg. These results suggest that reduction in afterload pressure below a certain level aggravated the regional ischemia, despite an increase in cardiac output, and to detect this change in the ischemic region during afterload reduction, ECG ST segment deviation seems to be a useful indicator.(ABSTRACT TRUNCATED AT 400 WORDS)
通过测量心电图ST段偏移和局部机械功能障碍，我们评估了后负荷压力改变对因左旋支冠状动脉（CFX）部分性冠状动脉闭塞所致局部心肌缺血的影响。八只离体、灌注并起搏的犬心脏连接了一个模拟犬动脉树主动脉输入阻抗的人工动脉系统。通过逐步改变外周阻力（Rp）来改变后负荷压力，同时保持左心室舒张末期压力（LVEDP）和心率恒定。冠状动脉灌注压（CPP）保持与平均主动脉压（AoP）相等。在CFX和左前降支冠状动脉（LAD）灌注的区域均测量心电图和心肌收缩段缩短（SS）。在存在CFX狭窄的情况下，随着Rp降低，平均AoP从96±7 mmHg降至46±7 mmHg，心输出量从465±30 ml/min逐渐增加至1055±100 ml/min。在这种情况下，CFX冠状动脉血流量从75±2 ml/100 g/min降至28±6 ml/100 g/min。缺血区域的心外膜心电图在CFX狭窄后显示出两种类型的ST段偏移：ST段抬高和ST段压低。此外，在后负荷降低后，这些个体心电图ST段变化显示出进一步的偏移。进一步出现明显ST段偏移时的平均AoP水平如下：ST段抬高病例为71±6 mmHg，ST段压低病例为52±7 mmHg。CFX狭窄后缺血区域的心肌收缩段缩短也显著降低（缺血前对照的91±8%，p<0.05）。然后，在后负荷降低期间，CFX区域的SS似乎呈双峰状，当平均AoP为46±7 mmHg时明确降低。为提高在局部心肌缺血后负荷降低过程中检测进一步机械功能障碍的敏感性，我们计算了每个Rp时CFX区域SS与LAD区域SS的百分比值。通过这种标准化，当平均AoP低于67±5 mmHg时发现存在机械功能障碍。这些结果表明，尽管心输出量增加，但后负荷压力降至一定水平以下会加重局部缺血，并且在检测后负荷降低期间缺血区域的这种变化时，心电图ST段偏移似乎是一个有用的指标。（摘要截选至400字）
