微小心筋灌流分布の灌流液依存性 (血液vs. Tyrode溶液)

-分子トレーサ法による検討-

抄録

We compared the spatial patterns of regional myocardial flows between crystalloid and blood perfused hearts, we measured within-layer regional myocardial flow distributions of Tyrode- and blood-perfused hearts using a molecular flow tracer, tritiated-desmethylimipramine (HDMI). Isolated rat hearts were perfused with Tyrode solution (Tyrd; n=7) or blood (Bld; n=14) at the 100 mmHg head pressure. After the peak reactive flow following 30 s flow-shutoff-reperfusion was measured, HDMI (2μCi) was injected into the perfusion line. A 60 s continuous injection was performed in seven and a bolus injection in seven hearts out of the fourteen Bld hearts and in Tyrd hearts. The left ventricular free wall was then sliced into 10 μm thick slices from subepi- to subendocardium. The distribution of HDMI density, i. e., within-layer relative flow, was measured in twenty-eight slices per heart by quantitative digital radiography with 100μm pixels. The coefficient of variation of flows (CV=SD of pixel tracer density/mean tracer density) was used to quantitate perfusion heterogeneity. In Tyrd and Bld, perfusion rates were 13.6±2.7 and 2.8±0.6 ml/min/g, respectively. The maximum percent increase of flow rate after the reperfusion was larger in Bld than in Tyrd (71±21% vs. 15±9%). CV was considerably higher in Bld than in Tyrd. In Bld, the continuous tracer injection yielded a smaller CV than the bolus injection. These CV differences were consistent over the resolution range of 100-800, μm. These data suggest that more preserved higher vasomotor tone and therefore higher flow resistance in blood-perfused hearts will be responsible for higher flow heterogeneity. The reduced CV under continuous tracer injection in blood-perfused hearts implies the short-term, temporal fluctuation of vasomotor tone and/or stochastic behaviors of the corpuscles in microvessels.