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受体交感神经刺激可通过抑制冠脉晃动现象来调节冠脉紧张度，从而改善心内膜下缺血。因此，我们用我们的针式CCD活体显微镜直接观察心内膜下小动脉的搏动直径变化和微循环。实验采用麻醉开胸杂种犬。显露左冠状动脉间隔支后，用20 Mhz 80通道超声多普勒血流仪测量壁内血流量。将针式CCD活体显微镜从左心耳经二尖瓣置入左室，观察心内膜下小动脉。为了进行比较，还观察了心外膜小动脉。采用右室起搏控制心率。冠脉灌注压控制主动脉环扎术。在不同起搏频率(140、200、250次/分)下，观察e-…在1)基础状态下，2)持续静脉注射去甲肾上腺素(NE，0.25µg/kg/min)，3)去甲肾上腺素(NE)加α受体阻滞剂(苯氧苯甲胺，0.5 mg/kg)，在每分钟140次的频率下，α受体阻滞剂使持续给药时的逆行血流量显著增加。心内膜下血流量以140次/分的速度增加，200次/分的速度无变化，250次/分的速度减少。在任何心率下，α受体阻滞剂均可使逆行血流和晃动率显著增加。α受体阻断后，心内膜下和心外膜下的搏动均有明显变化，针式CCD活体显微镜可观察到α受体交感神经刺激下心脏心内膜下小动脉搏动直径的变化。在心动过速时，刺激α受体可抑制晃动现象，维持心内膜下血流量。较少

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