The coronary laser angioplasty is the method to recanalize obstructed coronary arteries with laser energy. Excimer laser which is pulsed ultraviolet laser, is expected for the application to the small arteries such as coronary arteries in which thermal damages is critical. In order to realize the coronary laser angioplasty with excimer laser, the fiber transmission, the endoscopic irradiation and the development of endoscopic system for the coronary artery were tried. Excimer laser could be transmitted through the fiber for ultra violet beam transmission (Sumitomo Electr. Ind.) and atheroma was ablated through 400 μm core diameter fiber. The maximum transmitted power was about 6 mJ/pulse and the transmission efficiency was about 80%. Atheroma was observed as like as small lump under endoscopic observation, and excimer laser could destruct atheroma through the fiber under endoscopic view. In order to realize endoscopic application of excimer laser to the coronary arteries, the endoscope was designed from the point of percutaneous approach method to the coronary arteries, and 1.5 mm diameter of endoscope with single channel for laser fiber was developed experimentally. The endoscope could be inserted deeply into the coronary arteries of goat, and the laser irradiation could be performed under endoscopic observation. The possibility of visual coronary laser angioplasty with excimer laser was demonstrated with this endoscope.

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我々は1.06μm連続発振型Nd: YAGレーザー (1.06μm Nd: YAG) をPercutaneous transluminal laser angioplasty (PTLA) に使用しているが, 1,32μm連続発振型Nd: YAGレーザー(1.32μm Nd: YAG) もPTLAに使用可能である。これら2種のレーザーの動脈壁に対する蒸散効果の比較を, 直径0.4mmの石英ベアーファイバーと直径1.8mmのセラミックチップ付きプローブを用いて定量的に行った。37℃の生理的食塩水中で腸骨動脈壁に2種のレーザーを照射し, 生じた蒸散孔の大きさを計測した。実験の結果, レーザー照射による蒸散孔の体積については. ベアーファイバーの場合には1.06μm Nd: YAG, 1.32μm Nd: YAGで有為差が見られなかったが、セラミックチップ付きプローフの場合には20W 3秒以上の高エネルギー照射条件では1.32μm Nd: YAGの方が蒸散体積が明らかに大きかった。また蒸散孔の深さについては, いずれのプローブを用いた場合でも1.06μm Nd: YAGの方が1.32μm Nd: YAGよりも大きい傾向が見られ, 蒸散面積については, いずれのプローブを構いた場合でも1.32μm Nd: YAGの方が大きい傾向が見られた。1.32μm Nd: YAGは、1.06μm Nd: YAGと比べて蒸散孔の面積が広く深さは浅いため. 臨床に用いる際には安全性が高く有用であると推察される。

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This study was performed to examine the amount and the route of administration of hematoporphyrin derivative (HpD), and check the possibility of safely inducing regression of atherosclerotic foci using a new fiber with photodynamic therapy (PDT). Nine rabbits with experimentally induced atherosclerotic lesions were divided into 3 groups. Groups A and B consisted of 6 rabbits, given respectively 5mg/kg and 1.7mg/kg HpD intravenously. Group C was composed of 3 rabbits, given 1.7mg/kg HpD through a Dispatch catheter. Twenty-four hours after HpD administration, the aortas of Group A and B were examined by fluorescent microscopy and fluorescence spectrum analysis. Immediately after HpD administration, the aortas of Group C were examined in the same way. In Group C, the fluorescent microscope revealed the strongest intensity of reddish orange HpD fluorescence in the intima in atherosclerotic lesions, and a spectral peak at 630nm, indicating the presence of HpD, was higher than in Group A and B. These findings suggest that the local administration of HpD using the Dispatch catheter is extremely effective.
Next, nine new atherosclerotic rabbits were prepared. They were given 5mg/kg HpD intravenously. Twenty-four hours after HpD administration, the aortas of all the rabbits were exposed to a 200-milliwatt output argon-pumped dye laser beam at 630nm for ten minutes through a 0.8mm-diameter plastic fiber that was introduced from their femoral arteries. The new fiber had enough flexibility for clinical use and could transmit the laser beam in all directions from its tip coated with magnesium oxide. Three rabbits were sacrificed immediately after laser irradiation, referred to PDT-0 rabbits. Six rabbits were sacrificed at lweek and 2 weeks after irradiation ( PDT-1 and PDT-2 ). The irradiated regions were observed histopathologically. In the PDT-0 rabbits, the intimal cells were damaged and endothelial cells disappeared. In the PDT-1 and PDT-2 rabbits, most intimal cells were necrotic and the intima disappeared.The ratio of intimal thickness and medial thickness in irradiated regions was significantly decreased compared with nontreated regions. The internal area of the aortas in irradiated regions was significantly increased compared with nontreated regions. These findings suggest that PDT using a new plastic fiber is effective and may be used for human coronary arteries.

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