STATE-OF-THE-ART - TRANSCUTANEOUS AND PERCUTANEOUS MYOCARDIAL REVASCULARIZATION

Traditional approaches to improve myocardial perfusion in patients wit h coronary artery disease previously have applied methods to restore b lood flow through the existing coronary vessels. In contrast laser myo cardial revascularization techniques rely on the creation of new myoca rdial channels to produce effects leading to improved perfusion and re duction in angina. Laser transmyocardial revascularization (TMR) is pe rformed via open thoracotomy to access the epicardial surface, is rela tively safe, and appears to have a beneficial effect on myocardial per fusion. Percutaneous myocardial revascularization (PMR), however, uses transmission of laser energy along a flexible, fiber-optic catheter, thus permitting creation of laser channels from the endocardial surfac e of the left ventricle via a femoral artery approach. Tissue response s to lasers are dependent upon the energy used and its means of delive ry, thermal, mechanical, or chemical effects of laser channel creation may all impact on the myocardium, although stimulation of angiogenic growth factors, with consequent neovascularization appears to be the p rincipal underlying mechanism responsible for improvement in myocardia l perfusion. Patients with severe, chronic angina refractory to drug t herapies and in whom standard surgical or angioplasty revascularizatio n approaches are not possible may be candidate for TMR or PMR techniqu es. Clinical studies of TMR have described reductions in angina class, hospital admissions, and the number of myocardial myocardial perfusio n defects. PMR studies have reported improvements in angina class, inc reased exercise duration, and trends toward improvement in radionuclid e perfusion defects. Randomized trials are underway and will provide m ore definitive insights into the future clinical role of laser myocard ial revascularization techniques.