title: Dependence of damage within 10min to myocardial cells by a photodynamic reaction with a high concentration of talaporfin sodium outside cells in vitro on parameters of laser irradiation.
abstract: BACKGROUND
  To investigate the immediate occurrence of irreparable severe damage to myocardial cells up to 10min after a photodynamic reaction with a high concentration of photosensitizer outside cells, we measured the damage response time and the parameters that govern the response time via rat myocardial Ca(2+) concentration. In our proposed method for catheter ablation of tachyarrhythmia by photodynamic reaction, there are two components to the electrical conduction block: an immediate electrical conduction block of several tens of seconds to several minutes, and a permanent electrical conduction block.
  
  
  METHODS
  Rat myocardial intracellular Ca(2+) concentration changes before, during and after the photodynamic reaction with a high concentration of photosensitizer outside myocardial cells were continuously observed using a Fluo-4 AM Ca(2+) probe. Talaporfin sodium with 663-nm excitation was used to induce the photodynamic reaction. Talaporfin concentration was 10-30μg/ml, radiant exposure was 10-40J/cm(2), and irradiance was 30-290mW/cm(2). We evaluated the response time of irreparable severe damage to myocardial cells, according to Ca(2+) concentration.
  
  
  RESULTS
  The response time of the defined severe damage occurrence to myocardial cells ranged from 200 to 500s. The response time decreased with increasing irradiance and photosensitizer concentration, but exhibited no significant change with total radiant exposure.
  
  
  CONCLUSIONS
  We found that severe myocardial cell damage caused by a photodynamic reaction with a high concentration of photosensitizer outside cells occurred within a few minutes, which might be useful for catheter ablation for tachyarrhythmia that needs immediate response during the ablation procedure.
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama, 223-8522, Japan. Electronic address: e.ogawa@appi.keio.ac.jp.
authors.forename: Emiyu
authors.initials: E
authors.lastname: Ogawa
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama, 223-8522, Japan. Electronic address: arisa.i@arai.appi.keio.ac.jp.
authors.forename: Arisa
authors.initials: A
authors.lastname: Ito
authors.affiliation: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama, 223-8522, Japan. Electronic address: tsunearai@appi.keio.ac.jp.
authors.forename: Tsunenori
authors.initials: T
authors.lastname: Arai
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D053685:Laser Therapy / Q000379:methods*; D008027:Light; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D011166:Porphyrins / Q000008:administration & dosage*; D011829:Radiation Dosage; D051381:Rats
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C053434:Talaporfin; D002118:Calcium
keywords: Catheter ablation; Extracellular photodynamic reaction; Myocardial cell; Response time; Talaporfin sodium