title: Histologic analysis of transmyocardial channels: comparison of CO2 and holmium:YAG lasers.
abstract: BACKGROUND
  Transmyocardial laser revascularization using different lasers is being tested in the treatment of refractory angina. We conducted comparative analysis of the acute and chronic myocardial effects of these different lasers.
  
  
  METHODS
  Transmyocardial channels were made in normal dog hearts with either a holmium:yttrium-aluminum garnet or a CO2 laser. Channels were examined histologically 6 to 24 hours, 2 to 3 weeks, and 6 weeks after creation.
  
  
  RESULTS
  Regardless of the laser source, the channels were occluded by thrombus within 6 to 24 hours. Subsequently, organization and neovascularization of the channel region occurred. Thermoacoustic damage was initially greater with the holmium:yttrium-aluminum garnet laser, but the channel appearances were indistinguishable from those made with the CO2 laser by 6 weeks.
  
  
  CONCLUSIONS
  Histologically, the myocardial effects of the CO2 and holmium:yttrium-aluminum garnet lasers are similar and differ predominantly in the amount of acute thermoacoustic injury. Channels are rapidly occluded by thrombus and are replaced by neovascularized collagen. This suggests that the physiologic effects of these two lasers may be similar and that mechanisms other than blood flow through chronic patent channels should be considered as contributing to the clinical benefits observed with this procedure.
authors.affiliation: Department of Pathology, Columbia-Presbyterian Medical Center, New York, New York, USA.
authors.forename: P E
authors.initials: PE
authors.lastname: Fisher
authors.forename: T
authors.initials: T
authors.lastname: Khomoto
authors.forename: C M
authors.initials: CM
authors.lastname: DeRosa
authors.forename: H M
authors.initials: HM
authors.lastname: Spotnitz
authors.forename: C R
authors.initials: CR
authors.lastname: Smith
authors.forename: D
authors.initials: D
authors.lastname: Burkhoff
mesh_terms: D000818:Animals; D006348:Cardiac Surgical Procedures; D003331:Coronary Vessels / Q000473:pathology; D004285:Dogs; D053685:Laser Therapy / Q000295:instrumentation*; D009204:Myocardial Revascularization / Q000295:instrumentation* / Q000379:methods; D009206:Myocardium / Q000473:pathology*; D018919:Neovascularization, Physiologic