Microperfusion enhancement after TMLR in chronically ischemic porcine hearts

Transmyocardial revascularization devices: technology update

Transmyocardial laser revascularization (TMR) emerged as treatment modality for patients with diffuse coronary artery disease not amendable to percutaneous or surgical revascularization. The procedure entails the creation of laser channels within ischemic myocardium in an effort to better perfuse these areas. Currently, two laser devices are approved by the US Food and Drug Administration for TMR – holmium:yttrium–aluminum–garnet and CO₂. The two devices differ in regard to energy outputs, wavelengths, ability to synchronize with the heart cycle, and laser–tissue interactions. These differences have led to studies showing different efficacies between the two laser devices. Over 50,000 procedures have been performed worldwide using TMR. Improvements in angina stages, quality of life, and perfusion of the myocardium have been demonstrated with TMR. Although several mechanisms for these improvements have been suggested, evidence points to new blood vessel formation, or angiogenesis, within the treated myocardium, as the major contributory factor. TMR has been used as sole therapy and in combination with coronary artery bypass grafting. Clinical studies have demonstrated that TMR is both safe and effective in angina relief long term. The objective of this review is to present the two approved laser devices and evidence for the safety and efficacy of TMR, along with future directions with this technology.

Intraoperative CD133+ cell transplantation during coronary artery bypass grafting in ischemic cardiomyopathy

If traditional treatment of coronary artery disease has failed, intramyocardial transplantation of CD133+ stem cells with the potential to improve myocardial function is an alternative approach to treating ischemic cardiomyopathy. The INSTEM trial aims at evaluating safety and feasibility of isolation and subsequent intramyocardial transplantation of CD133+ cells in combination with coronary artery bypass grafting (CABG). Patients suffering from severe ischemic cardiomyopathy (ejection fraction ≫15% and ≪35%) are enrolled in this trial. Bone marrow is harvested from the iliac crest and CD133+ cells are purified up to 99%. The myocardial region of interest is pre-treated by transmyocardial laser revascularization in order to trigger homing of transplanted cells. Autologous bone marrow CD133+ cells (up to 30×10(6) cells) are injected into predefined myocardial regions. Cardiac function prior to as well as three, six and 12 months after cell transplantation is assessed by echocardiography. Neither operative mortalities nor any cardiac deaths during follow-up occurred. Left ventricular ejection fraction improved from 25%±5% preoperatively to 40%±8% after six months. Our method of intraoperative CD133+ cell isolation while performing CABG and subsequent transmyocardial cell transplantation is feasible and safe. Although the follow-up has not yet been completed we propose this procedure to be a promising causal therapy of severe ischemic cardiomyopathy.

Transmyocardial laser revascularization

It has been almost a decade since transmyocardial laser revascularization (TMR) was approved for clinical use in the United States. The safety of TMR was demonstrated initially with nonrandomized studies in which TMR was used as the only treatment for patients with severe angina. TMR efficacy was proven after multiple randomized controlled trials. These revealed significant angina relief compared to maximum medical therapy in patients with diffuse coronary disease not amenable to conventional revascularization. In light of these results, TMR has been used as an adjunct to coronary artery bypass grafting (CABG). By definition, patients treated with this combined therapy have more severe coronary disease and comorbidities that are associated with end-stage atherosclerosis. Combination CABG + TMR has resulted in symptomatic improvement without additional risk. The likely mechanism whereby TMR has provided benefit is the angiogenesis engendered by the laser-tissue interaction. Improved perfusion and concomitant improvement in myocardial function have been observed post-TMR. Additional therapies to enhance the angiogenic response include combining TMR with stem cell-based treatments, which appear to be promising future endeavors.

Mechanisms and Results of Transmyocardial Laser Revascularization

Transmyocardial laser revascularization (TMR) is a technique that has been performed on over 10,000 patients around the world. Most of the patients were not suffering from heart failure. TMR is principally used for the treatment of angina, but in patients with significant reversible ischemia that is not amenable to conventional therapy, TMR may also improve myocardial function. The results of using TMR as a treatment for angina show a dramatic improvement in symptoms and quality of life. This paper reviews the current status of TMR techniques, mechanisms and results.

35 years of experimental research in transmyocardial revascularization: what have we learned?

In the past 35 years many experimental studies have been performed to investigate the revascularization potential of transmyocardial revascularization and the possible working mechanisms underlying the observed clinical improvement in angina pectoris after this treatment. In this review of the experimental literature, the various methods that have been used to create transmyocardial channels and the most supported hypotheses on the working mechanism (channel patency, angiogenesis and myocardial denervation) are discussed and evaluated.