ダブル分子トレーサを利用した低酸素潅流心における心筋潅流不均一性の解析  [in Japanese] Microheterogeneity of myocardial perfusion in isolated rabbit hearts under hypoxia -digitalradiographic study using a double molecular flow tracer-  [in Japanese]

新しく開発したダブル分子トレーサ法により、低酸素潅流時におけるウサギ・ランゲンドルフ心(n=6)の心筋微小潅流の不均一性を評価した。分子トレーサにはデスメチルイミプラミン(DMI)を利用した。正常酸素潅流時にヨード125標識DMI、低酸素潅流時にトリチウム標識DMIを逆行性投与した後、左室自由壁の連続切片(10μm厚)を作製し、毛細管内皮に取り込まれた両者の分布をサプトラクション・デジタルラジオグラフィにより計測・比較した(空間分解能400μm)。潅流不均一性の指標であるトレーサ分布の変動係数(=SD/mean)は低酸素潅流下で88%増加した(0.16±0.03vs.0.30±0.11, P<0.05)。また、両トレーサ分布の相互相関はr=0.79±0.08(P<0.05)、相関直線の傾きは1.5±0.6を示し、局所領域間の潅流量の差は増大した。低酸素潅流下の微小心筋レベルにおいて、低潅流領域から高潅流領域への潅流シフト(coronary steal)が生じていることが示唆された。

To examine the effect of hypoxic perfusion on microregional myocardial perfusion, we measured the within-layer regional flow distribution by quantitative digitalradiography combined with a double-tracer deposition technique. In isolated Tyrode-perfused rabbit hearts (n=6), ^<125>I- and ^3H-labeled desmethylimipramine (IDMI, HDMI) were injected during normoxic and hypoxic perfusion, respectively. The left ventricular free wall was processed into 10-μm-thick slices in parallel with the epicardial surface. Tracer density distributions of IDMI (relative flow distribution during normoxia) and HDMI (relative flow distribution during hypoxia) were resolved into 400-μm pixel regions, comparable in size to myocardial microcirculatory units governed by the smallest arterioles. The flow heterogeneity assessed with the coefficient of variation of regional flows (CV=standard deviation of regional flow/mean flow) increased by 88% from 0.16±0.03 to 0.30±0.11 (P<0.05). Nevertheless, there was a moderate correlation between regional flows during the two states (r=0.79±0.08, P<0.05), indicating that the spatial pattern of flow distribution was rather maintained after hypoxic perfusion. In conclusion, hypoxia increased microregional flow heterogeneity through the augmentation of regional flow differences between originally high- and low-flow regions. The coronary steal phenomenon from originally low- to high-flow regions would occur at a microcirculatorv unit level.