title: Optimal conditions for cardiac catheter ablation using photodynamic therapy.
abstract: OBJECTIVE
  Photodynamic therapy (PDT) is based on non-thermal injury mediated by singlet oxygen species and is used clinically in cancer therapy. In our continuing efforts to apply this technology to cardiac catheter ablation, we clarified the optimal condition for creating PDT-mediated lesions using a laser catheter.
  
  
  RESULTS
  In a total of 35 canines, we applied a laser directly to the epicardium of the beating heart during open-chest surgery at 15 min after administration of a photosensitizer, talaporfin sodium. We evaluated the lesion size (depth and width) using hematoxylin-eosin staining under varying conditions as follows: laser output (5, 10, 20 W/cm(2)), irradiation time (0-60 s), photosensitizer concentration (0, 2.5, 5 mg/kg), blood oxygen concentration (103.5 ± 2.1 vs. 548.0 ± 18.4 torr), and contact force applied during irradiations (low: <20 g, high: >20 g). A laser irradiation at 20 W/cm(2) for 60 s under 5 mg/kg (29 µg/mL) of photosensitizer induced a lesion 8.7 ± 0.8 mm deep and 5.2 ± 0.2 mm wide. The lesion size was thus positively correlated to the laser power, irradiation time, and photosensitizer concentration, and was independent of the applied contact force and oxygen concentration. In addition, the concentration of the photosensitizer strongly correlated with the changes in the pulse oximetry data and fluorescence of the backscattering laser, suggesting that a clinically appropriate condition could be estimated in real time.
  
  
  CONCLUSIONS
  Photodynamic therapy-mediated cardiac lesions might be controllable by regulating the photosensitizer concentration, laser output, and irradiation time.
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan kimura@z7.keio.jp.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Takatsuki
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Shunichiro
authors.initials: S
authors.lastname: Miyoshi
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Mei
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Emiyu
authors.initials: E
authors.lastname: Ogawa
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Katsumata
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Nishiyama
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nishiyama
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tanimoto
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Aizawa
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Tsunenori
authors.initials: T
authors.lastname: Arai
authors.affiliation: Department of Cardiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuda
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D003131:Combined Modality Therapy / Q000379:methods; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D053685:Laser Therapy / Q000379:methods*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D011166:Porphyrins / Q000008:administration & dosage*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000601:surgery*
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C053434:Talaporfin
keywords: Ablation; Arrhythmia; Photodynamic therapy; Talaporfin sodium