Evaluation of Subendocardial Microcirculatory Hemodynamics by High-Speed Needle-Probe CCD Microscope

本研究旨在验证我们的假设，即增强α-受体交感神经刺激通过抑制冠状动脉晃动现象调节冠状动脉紧张性来改善血管内膜下缺血。因此，我们用针式CCD活体显微镜直接观察了麻醉下开胸的杂种狗的血管内微动脉搏动性直径变化和微循环。在暴露左冠状动脉间隔支后，我们用20 MHz 80通道超声多普勒流量计测量壁内血流。用针式CCD活体显微镜从左心耳经二尖瓣口插入左心室，观察内膜下小动脉。为了进行比较，还观察了心外膜小动脉。通过右心室起搏控制心率。冠状动脉灌注压控制主动脉缩窄术。在不同起搏频率（140、200、250 bpm）下，观察心脏电生理参数的变化 ...更多信息 在以下条件下，在测量壁内血流的同时制作内皮小动脉; 1）基础情况，2）持续静脉注射去甲肾上腺素（NE，0.25 μ g/kg/min），3）NE + α受体阻滞剂（酚苄明，0.5mg/kg）。在140 bpm的速率下，α-受体阻断可使NE持续给药时逆行血流明显增加，舒张期前向血流无明显变化。至于内膜下流量，其在140 bpm的速率下增加，在200 bpm的速率下没有显示出任何变化，在250 bpm的速率下减少。在任何心率下，α-受体阻滞剂均能显著增加逆行血流和晃动率。阻断α受体后，心内膜下和心外膜下的搏动均表现出明显的荷电，用针型CCD活体显微镜观察了α受体交感神经刺激下心脏跳动时心内膜下小动脉搏动直径的变化。结果发现，刺激α受体可抑制心动过速时的晃动现象，维持心内膜下血流。少

This study is to test our hypothesis that enhancement of alpha-receptor sympathetic nerve stimulation improves subendocardial ischaemia by its inhibitory effect on coronary slosh phenomenon adjusting coronary tonus. We, therefore, directly observed pulsatile diameter changes and microcirculation of subendocardial arterioles with our needle type CCD intravital microscope.Open chest mongrel dogs under anaesthesia were used in the experiment. We measured intramural blood flow with a 20 Mhz 80-channeled ultrasound Doppler flowmeter after exposing septal branches of the left coronary artery. The needle type CCD intravital microscope was inserted from the left appendage into the left ventricle via mitral valve and the subendocardial arterioles were observed. To make comparison, epicardial arterioles were observed too. Heart rate was controlled by right ventricular pacing. Coronary perfusion pressure was controlled aortic banding. Under various pacing rates (140,200,250 bpm), observation of e … More ndocardial arterioles were made while measuring intramural blood flow under the following conditions ; 1) basal condition, 2) continuous intravenous injection of norepinephrine (NE,0.25 mug/kg/min), 3) NE plus alpha-receptor blockade (phenoxybenzamine, 0.5 mg/kg).At the rate of 140 bpm, alpha-receptor blockade caused remarkable increase of retrograde flow during continuous administration of NE.Diastolic forward flow did not show any significant change. As for the subendocardial flow volume, it increased at the rate of 140 bpm, did not show any change at the rate of 200 bpm and decreased at the rate of 250 bpm. At any heart rate, there was an increase of significan retrograde flow and slosh ratio by alpha-receptor blockade. Pulsatililty of both subendocardium and subepicardium showed significant charges after alpha-receptor blockade.The needle type CCD intravital microscopy enabled to observe pulsatile diameter changes of subendocardial arterioles of a beating heart under alpha-receptor sympathetic nerve stimulation. It was found that alpha-receptor stimulation inhibited slosh phenomenon and maintained the subendocardial blood flow during tachycardia. Less