ELECTRON-MICROSCOPIC FINDINGS AFTER TRANSMYOCARDIAL LASER REVASCULARIZATION IN AN ACUTE ISCHEMIC PIG MODEL

Objective: The clinical benefit in terms of angina reduction after tra nsmyocardial laser revascularization (TMLR) in patients with diffuse c oronary artery disease who are not candidates for conventional procedu res has been proved. The exact mechanisms of TMLR however, are still u nknown. The aim of this study was to investigate the cellular changes in relation to intramyocardial partial oxygen pressure (p(ti)O(2)) aft er TMLR in a model of acute ischemia in pigs by electron microscopical methods (TEM). Methods: Seven pigs were included in this study (five animals with acute myocardial ischemia and additional-TMLR and two ani mals with acute myocardial ischemia and without TMLR for control). Acu te ischemia was induced by ligation of diagonal branches of the left a rterior descending artery (LAD). Intramyocardial partial oxygen pressu re was measured before induction of ischemia and thereafter continuous ly for up to 6 h in all animals. Biopsies of all animals were taken be fore induction of ischemia and thereafter at 30 min. 3 and 6 h. Analys is of the myocardial ultrastructure was focused on mitochondria, cell nucleus, T-tubules and myofibrils. Results: Ultrastructural changes we re seen in all animals. At 6 h after induction of ischemia, mitochondr ia showed a destruction of the internal as well as the external membra ne and of the cristae. The nuclei showed margination of the chromatin. Myofibrils were characterized by ruptures in the Z-stripes. Lipid dro plets as an indicator of ischemia could be identified. PtiO2 between 4 0 and 80 mmHg before intervention decreased down to 0-2 mmHg within th e first 9 min after diagonal branch ligation and did not increase even after TMLR. Conclusions: In this acute ischemic model using pigs, TEM evaluation following TMLR proves irreversible changes of the myocardi al ultrastructure. Furthermore, TMLR was not able to increase ischemic ally induced decrease of p(ti)O(2). These data provide some evidence t hat TMLR thus, may not be able to ameliorate acute ischemia at least i n the pig model. Further investigations are needed to investigate the effect of TMLR in chronic myocardial ischemia. (C) 1997 Elsevier Scien ce B.V. All rights reserved.