title: Myocardial electrical conduction block induced by photosensitization reaction in exposed porcine hearts in vivo.
abstract: OBJECTIVE
  This study proposes photosensitization reaction for non-thermal cardiac ablation in arrhythmia therapy. Acute and chronic phase experiments were conducted in exposed porcine hearts to demonstrate the photosensitization reaction-induced myocardial electrical conduction block in vivo.
  
  
  METHODS
  The porcine left atrial appendage was exposed under an open-chest procedure. Then, a water-soluble chlorin photosensitizer, NPe6, was injected into the pigs intravenously at 5 or 10  mg/kg. About 15 or 30 minutes after the injection, a 663-nm continuous-wave diode laser was irradiated on the surface of the atrial appendage through a silica optical fiber. The laser energy was delivered to the tissue point by point at an energy density of 50-208 J/cm(2).
  
  
  RESULTS
  Acute and chronic tissue damages as a result of the photosensitization reaction were determined by electrophysiology and histology, respectively. The change in the myocardial conduction time between two electrodes was measured immediately after the completion of the 35-mm irradiation line between the electrodes. The conduction delay of 35.5 milliseconds might be due to the change in the conduction pathway induced by transmural acute conduction block with the photosensitization reaction. The tissue temperature increase in the irradiated area was approximately 12.8°C. Azan-staining revealed about 1-mm transmural fibrosis of the atrial appendage at 2 weeks after the irradiation (50 J/cm(2)).
  
  
  CONCLUSIONS
  The results suggest that the photosensitization reaction might induce acute and chronic myocardial electrical conduction block. Cardiac ablation with the photosensitization reaction might be a non-temperature-mediated methodology for arrhythmia therapy.
authors: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Hiyoshi, Kohoku-ku, Yokohama, Japan. arisa@a3.keio.jp
authors: Arisa
authors: A
authors: Ito
authors: Shunichiro
authors: S
authors: Miyoshi
authors: Takehiro
authors: T
authors: Kimura
authors: Seiji
authors: S
authors: Takatsuki
authors: Kotaro
authors: K
authors: Fukumoto
authors: Keiichi
authors: K
authors: Fukuda
authors: Tsunenori
authors: T
authors: Arai
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000188:drug therapy*; D016279:Atrial Function, Left; D022062:Electrophysiologic Techniques, Cardiac; D005240:Feasibility Studies; D005260:Female; D006321:Heart / Q000502:physiology; D006325:Heart Atria / Q000473:pathology; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D009206:Myocardium / Q000737:chemistry / Q000473:pathology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011166:Porphyrins / Q000493:pharmacokinetics / Q000627:therapeutic use*; D013552:Swine
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C053434:Talaporfin