Laser-mediated reversal of cardiac expansion after myocardial infarction

Background and Objectives: 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. Study Design/Materials and 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 Mg, left ventricular cavity volume was measured, and histologic analysis was performed. Results: Cavity volume was reduced by laser treatment (0.72 +/- 0.07 mi vs. 0.54 +/- 0.05 mi; P = 0.044). In addition, treatment resulted in thicker scars, a leftward shift of the heart's electrical axis, and straightening of collagen fibers. Conclusion: Laser treatment resulted in thermally-mediated scar shrinkage, which reversed infarct expansion and reduced cavity volume. Lasers Surg, Med. 25:198-206, 1999. (C) 1999 Wiley-Liss, Inc.