Ohtsuka S, Kakihana M, Watanabe H, Sugishita Y
Department of Internal Medicine, University of Tsukuba, Japan.
J Am Coll Cardiol. 1994 Nov 1;24(5):1406-14. doi: 10.1016/0735-1097(94)90127-9.
This study investigated the long-term effects of decreased aortic distensibility on the heart in relation to coronary perfusion.
Aortic distensibility is decreased in patients with atherosclerosis and hypertension and in the elderly. However, the effect of a long-term decrease in aortic distensibility on coronary perfusion has not been fully investigated.
Twelve anesthetized dogs underwent thoracotomy and were allocated to two groups: Group I included six control dogs with a normal aorta; Group II included six dogs with decreased aortic distensibility produced by banding the descending aorta. After 4 to 6 weeks, the dogs had a second operation to measure coronary artery flow and transmural flow distribution. Because the effect of decreased aortic distensibility on coronary perfusion may be affected by ventricular contractility, measurements were performed at baseline and during increased ventricular contraction induced by isoproterenol infusion.
At baseline, arterial compliance was reduced by 35% in Group II, but there was no change in total mean arterial resistance. Hemodynamic variables, regional wall motion and coronary flow were also similar in both groups. However, during isoproterenol infusion, coronary flow increased more in Group II than in Group I (p < 0.01), and the coronary flow reserve ratio (maximal peak hyperemic flow divided by rest flow) decreased more in Group II than in Group I (mean [+/- SD] 1.9 +/- 0.4 vs. 2.4 +/- 0.3, p < 0.05). Moreover, although the transmural flow distribution was similar in the two groups at baseline, during isoproterenol infusion the endocardial flow increased less in Group II than in Group I (p < 0.05), and the endocardial/epicardial flow ratio was significantly decreased in Group II compared with Group I (mean [+/- SD] 0.70 +/- 0.18 vs. 0.99 +/- 0.22, p < 0.05). The subendocardial electrocardiogram showed ST segment elevation during isoproterenol infusion in Group II (p < 0.05) but not in Group I.
These results demonstrate that during increased ventricular contraction, chronically decreased aortic distensibility contributes to a further decrease in the coronary flow reserve ratio, impairs endocardial blood flow and may induce subendocardial ischemia even in the absence of coronary artery stenosis.
本研究调查了主动脉扩张性降低对心脏的长期影响及其与冠状动脉灌注的关系。
动脉粥样硬化、高血压患者以及老年人的主动脉扩张性降低。然而，主动脉扩张性长期降低对冠状动脉灌注的影响尚未得到充分研究。
12只麻醉犬接受开胸手术，分为两组：第一组包括6只主动脉正常的对照犬；第二组包括6只通过结扎降主动脉导致主动脉扩张性降低的犬。4至6周后，犬接受第二次手术以测量冠状动脉血流和透壁血流分布。由于主动脉扩张性降低对冠状动脉灌注的影响可能受心室收缩性影响，因此在基线以及异丙肾上腺素输注诱导心室收缩增强期间进行测量。
在基线时，第二组的动脉顺应性降低了35%，但总平均动脉阻力无变化。两组的血流动力学变量、局部室壁运动和冠状动脉血流也相似。然而，在输注异丙肾上腺素期间，第二组的冠状动脉血流增加幅度大于第一组（p<0.01），第二组的冠状动脉血流储备率（最大充血峰值血流除以静息血流）降低幅度大于第一组（平均值[±标准差]1.9±0.4对2.4±0.3，p<0.05）。此外，尽管两组在基线时透壁血流分布相似，但在输注异丙肾上腺素期间，第二组的心内膜血流增加幅度小于第一组（p<0.05），与第一组相比，第二组的心内膜/心外膜血流比值显著降低（平均值[±标准差]0.70±0.18对0.99±0.22，p<0.05）。第二组在输注异丙肾上腺素期间心内膜下心电图显示ST段抬高（p<0.05），而第一组未出现。
这些结果表明，在心室收缩增强期间，长期降低的主动脉扩张性会导致冠状动脉血流储备率进一步降低，损害心内膜血流，甚至在无冠状动脉狭窄的情况下也可能诱发心内膜下缺血。
