Direct myocardial revascularization: Surgical and catheter-based approaches

During the last decade, direct myocardial revascularization has evolved as a potential therapeutic approach to enhancing tissue perfusion and alleviating symptoms in patients with advanced coronary artery disease not amenable to conventional revascularization techniques. The current experimental and clinical data derive mostly from surgical (transepicardial) and catheter-based (transendocardial) laser direct myocardial revascularization studies. Utilization of nonlaser energy sources, such as radiofrequency and various mechanical channeling devices, has been studied primarily in animals. Altogether, the experimental findings concerning the different direct myocardial revascularization approaches suggest a common mechanistic paradigm in which localized, controlled tissue injury initiates an inflammatory process accompanied by an angiogenic response that may lead to increased collateral blood vessel formation within and adjacent to the injury site. Although clinical results have consistently suggested improved angina symptoms and exercise performance, objective changes in myocardial perfusion imaging studies are largely indeterminate. Thus, an alternative mechanism-myocardial denervation-was suggested. The most recent-and the only double-blind-direct myocardial revascularization study reported to date has raised the disturbing possibility of placebo of placebo effects contributing importantly to the subjective benefits demonstrated in earlier surgical and catheter-based, nonblinded clinical trials. Therefore, although direct myocardial revascularization may constitute an exciting new therapeutic strategy for patients with a wide variety of refractory ischemic heart diseases, further investigation is necessary before a conclusion can be reached concerning the true therapeutic merits of this approach.