title: Laser-mediated reversal of cardiac expansion after myocardial infarction.
abstract: OBJECTIVE
  A complication of transmural myocardial infarction is infarct expansion, which can lead to the development of heart failure. However, the necrotic muscle is replaced by collagen, a material known to shrink when heated. Thus, the hypothesis was that thermally-induced scar shrinkage could reverse infarct expansion.
  
  
  METHODS
  Four weeks after transmural infarcts were produced by coronary occlusion, rats were randomized to control or treatment with a neodymium:yttrium-aluminum-garnet laser. The epicardial scar surface was irradiated until shrinkage was observed. Thirty minutes later, hearts were excised and fixed at a distending pressure of 15 mm Hg, left ventricular cavity volume was measured, and histologic analysis was performed.
  
  
  RESULTS
  Cavity volume was reduced by laser treatment (0.72 +/- 0.07 ml vs. 0.54 +/- 0.05 ml; P= 0.044). In addition, treatment resulted in thicker scars, a leftward shift of the heart's electrical axis, and straightening of collagen fibers.
  
  
  CONCLUSIONS
  Laser treatment resulted in thermally-mediated scar shrinkage, which reversed infarct expansion and reduced cavity volume.
authors.affiliation: Heart Institute, Good Samaritan Hospital, and Cardiology Section, Department of Medicine, University of Southern California, Los Angeles, California 90017, USA. pwhittaker@dnamail.com
authors.forename: P
authors.initials: P
authors.lastname: Whittaker
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002921:Cicatrix / Q000532:radiotherapy; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000528:radiation effects; D006339:Heart Rate; D053685:Laser Therapy; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D009206:Myocardium / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley