Atsushi Utsumi

Efficacy of argon-laser-mediated hot-balloon angioplasty

To overcome the abrupt closure and late restenosis after percutaneous transluminal coronary angioplasty (PTCA), new technology termed hot balloon angioplasty has been considered. A novel laser-heated hot balloon catheter has been developed to address these problems. Its feasibility and acute thermal effects in the porcine coronary arteries in vitro was studied. As the balloon material was teflon (heat-resistant up to 240 degree(s)C). The temperature of the balloon could rise abruptly. So, intima~media were welded while marked thermal injury was not detected in adventitial tissue.

Acute effects of short-term intimal heating by laser-heated thermal balloon angioplasty in canine stenotic femoral arteries in vivo

Short-term intimal heating may be effective to improve luminal geometry without deep medial injury which can induce restenosis. We developed a new laser-heated thermal balloon catheter which can quickly raise and lower the balloon temperature. To investigate the acute effect of short-term thermal balloon angioplasty (STBA) for stenotic lesions, we performed STBA following balloon angioplasty (BA) in 8 canine stenotic femoral arteries. Cw Nd:YAG laser delivery (10 W, 15 s) induced the maximum temperature of 83 degree(s)C on average. Angiography and angioscopy were performed at pre-BA, post-BA and post-STBA. The angiographical mean stenotic diameter was 1.8 mm at pre-BA, 2.2 mm* at post-BA, 2.9 mm** at post-STBA (*:p < 0.05 pre-BA vs post-BA, **:p < 0.05 pre- and post-BA vs post-STBA). The angioscopic observation revealed intimal flaps and tears in 7 lesions after BA. The luminal geometry after STBA was symmetrically expanded. However, the intimal injury was still observed although the intimal flaps were partly sealed by STBA. These results suggested that the dilatation mechanism of STBA for stenotic lesions might be attributed to preventing elastic recoil rather than to sealing intimal fragments induced by BA.

Parametric study for laser hot balloon angioplasty to suppress chronic restenosis: animal experiment

To suppress restenosis after the percutaneous transluminal coronary angioplasty (PTCA), we experimentally investigated the optimum parameter setting on the combination of the balloon temperature and heating duration of our laser hot balloon catheter in rabbit model. The rabbit femoral arteries were treated by our laser hot balloon of 2.5 mm in diameter with various balloon temperatures and durations at the range from 60 to 90 deg., and from 15 to 30 seconds, respectively. The histological examination showed that high temperature (greater than 70 deg.) was necessary to suppress hyperplasia of the vessel in chronic phase. The angiography of pre- and post-treatment and of 2 months after the treatment showed that high temperature with short heating duration (15-30 s) was the best setting for chronic patency of the treated vessels. The laser hot balloon angioplasty with the above mentioned parameter setting might realize significant improvement on chronic patency after PTCA.

CO laser angioplasty using contact irradiation

We successfully demonstrated usefulness of CO laser angioplasty. We investigated in vivo CO laser angioplasty using contact irradiation under visualization by a thin endoscope in atheromatous rabbit aorta, which was temporary filled by saline during the irradiation. 4W, 4s contact irradiation via 400μm As-S glass fiber to atheromatous aorta wall made a fine ablation hole with the minimum heat injuries to remained vascular tissue. A small amount of char was found on ZnSe contact tip after approximately 20 irradiations. But no damage was occurred in the tip. We think the visualization in the arterial lumen by the thin endoscope may be useful for pre-diagnosis and targeting of laser therapy.

Laser Angioplasty Using Carbon Monoxide Lasers

In this paper, we demonstrate the possibility as well as usefulness of the usage of CO lasers for the laser coronary angioplasty. CO lasers, approximately 5μm of their wavelength, have strong ablation capacity to water-containing living tissue due to intensive attenuation by water. Accordingly, a precise ablation of intravascular obstruction without a perforation may be possible by the CO laser irradiation. As a fundamental study, the design of the fiber energy delivery of CO lasers for the coronary angioplasty and the ablation effect of the CO laser irradiation to human atheroma are revealed. The CO laser irradiation method in the flushing medium of a coronary angioscope is also discussed.

Infrared glass fiber cables for CO laser medical applications

We developed the medical fiber cables which were designed for CO laser therapy, i.e., angioplasty and endoscopic therapy. As-S chalcogenide glass fibers were used for CO laser delivery. A 230 micrometers core-diameter fiber was used for the angioplasty laser cable. The outer diameter of this cable was 600 micrometers . The total length and insertion length of the angioplasty laser cable were 2.5 m and 1.0 m, respectively. Typically, 2.0 W of fiber output was used in the animal experiment in vivo for the ablation of the model plaque which consisted of human atheromatous aorta wall. The transmission of the angioplasty laser cable was approximately 35%, because the reflection loss occurred at both ends of the fiber and window. Meanwhile, the core diameter of the energy delivery fiber for the endoscopic therapy was 450 micrometers . The outer diameter of this cable was 1.7 mm. Approximately 4.5 W of fiber output was used for clinical treatment of pneumothorax through a pneumoscope. Both types of the cables had the ultra-thin thermocouples for temperature monitoring at the tip of the cables. This temperature monitoring was extremely useful to prevent the thermal destruction of the fiber tip. Moreover, the As-S glass fibers were completely sealed by the CaF2 windows and outer tubes. Therefore, these cables were considered to have sufficient safety properties for medical applications. These laser cables were successfully used for the in vivo animal experiments and/or actual clinical therapies.

Combined guidance technique using angioscope and fluoroscope images for CO laser angioplasty: in-vivo animal experiment

The combined guidance technique using angioscope and fluoroscope (i.e. angiography) images for CO laser angioplasty was demonstrated in vivo animal experiment. The newly developed total occlusion model which has been produced by a long term transplantation of ChitinR tube in canine femoral artery was ablated by the contact irradiation of CO laser. A thin laser angioscope catheter, 5F in outer diameter, was inserted from total carotid artery to femoral artery by selective catheterization technique under fluoroscopy. A thin CO laser cable of which diameter was less than 0.6mm was advanced from the tip of the angioscope catheter. A As-S chalcogenide glass fiber of which diameter was 200micrometers was installed in the laser cable. The laser cable connected to the CO laser device which was developed for medical use. The angioscope catheter and laser cable could be seen by the fluoroscopy. The authors used the angioscope image of the occlusion end and the angiography image to check the direction of ablation hole. The simultaneous use of these images which include quite different kinds of information was extremely useful for the safety guidance of laser angioplasty for total occlusion. The histological specimen from the ablated occlusion showed that the repetitive ablation procedure made a larger lumen than the laser cable diameter.

State of the art of CO laser angioplasty system

A unique percutaneous transluminal coronary angioplasty system new IR therapy laser with IR glass fiber delivery under novel angioscope guidance was described. Carbon monoxide (CO) laser emission of 5 mm in wavelength was employed as therapy laser to achieve precise ablation of atheromatous plaque with a flexible As-S IR glass fiber for laser delivery. We developed the first medical CO laser as well as As-S IR glass fiber cable. We also developed 5.5 Fr. thin angioscope catheter with complete directional manipulatability at its tip. The system control unit could manage to prevent failure irradiations and fiber damages. This novel angioplasty system was evaluated by a stenosis model of mongrel dogs. We demonstrated the usefulness of our system to overcome current issues on laser angioplasty using multifiber catheter with over-the-guidewire system.

CO laser angioplasty system: efficacy of manipulatable laser angioscope catheter

A percutaneous transluminal coronary angioplasty system using a unique combination of CO laser (5 micrometers ) and As-S infrared glass fiber under the guidance of a manipulatable laser angioscope catheter is described. The ablation and guidance functions of this system are evaluated. The angioplasty treatment procedure under angioscope guidance was studied by in vitro model experiment and in vivo animal experiment. The whole angioplasty system is newly developed. That is, a transportable compact medical CO laser device which can emit up to 10 W, a 5 F manipulatable laser angioscope catheter, a thin CO laser cable of which the diameter is 0.6 mm, an angioscope imaging system for laser ablation guidance, and a system controller were developed. Anesthetized adult mongrel dogs (n equals 5) with an artificial complete occlusion in the femoral artery and an artificial human vessel model including occluded or stenotic coronary artery were used. The manipulatability of the catheter was drastically improved (both rotation and bending), therefore, precise control of ablation to expand stenosis was obtained. A 90% artificial stenosis made of human yellow plaque in 4.0 mm diameter in the vessel was expanded to 70% stenosis by repetitive CO laser ablations of which total energy was 220 J. All procedures were performed and controlled under angioscope visualization.

New Percutaneous Transluminal Coronary Angioscope

A new thin coronary angioscope which has a inflatable balloon at its distal tip is described in this paper. This angioscope is formed into very thin flexible catheter, less than 4F(1.33mm) in sheath outer diameter at the catheter tip. The angioscope contains two penetrated lumina which utilize for either flushing blood or manipulating of a guiding wire. A selective intracoronary visualization in left anterior descending coronary artery (LAD) and circumuflex(CX) of dogs up to 15kg in their weight were carried out during up to 20s until occurring of ST segment change of the electro-cardiogram(ECG).