Does laser type impact myocardial function following transmyocardial laser revascularization?

Abstract

Background Transmyocardial laser revascularization (TMR) is currently clinically performed with either a CO2 or Ho:YAG laser for the treatment of severe angina. While both lasers provide symptomatic relief, there are significant differences in the laser–tissue interactions specific to each device that may impact their ability to enhance the perfusion of myocardium and thereby improve contractile function of the ischemic heart. Methods A porcine model of chronic myocardial ischemia was employed. After collecting baseline functional data with cine magnetic resonance imaging (MRI) and dobutamine stress echo (DSE), 14 animals underwent TMR with either a CO2 or Ho:YAG laser. Transmural channels were created with each laser in a distribution of 1/cm2 in the ischemic zone. Six weeks post-treatment repeat MRI as well as DSE were obtained after which the animals were sacrificed. Histology was preformed to characterize the laser–tissue interaction. Results CO2 TMR led to improvement in wall thickening in the ischemic area as seen with cine MRI (40.3% vs. baseline, P < 0.05) and DSE (20.2% increase vs. baseline, P < 0.05). Ho:YAG treated animals had no improvement in wall thickening by MRI (−11.6% vs. baseline, P = .67) and DSE (−16.7% vs. baseline, P = 0.08). Correlative semi-quantitative histology revealed a significantly higher fibrosis index in Ho:YAG treated myocardium versus CO2 (1.81 vs. 0.083, P < 0.05). Conclusions In a side-by-side comparison CO2 TMR resulted in improved function of ischemic myocardium as assessed by MRI and echocardiography. Ho:YAG TMR led to no improvement in regional function likely due to concomitant increase in fibrosis in the lasered area.

A Chronic Cardiac Ischemia Model in Swine Using an Ameroid Constrictor

“…Ameroid constrictors have been used extensively to create animal models of chronic myocardial ischemia, chronic myocardial infarction, and heart failure 5 6 7 9 10 11 12 13 15 16 17 18 19 22 . Although these models can be created through the use of stents, hydraulic occluders, or fixed stenosis occluders, the prevalence of ameroid use in scientific literature allows researchers to more accurately compare the results of their work with previously published studies 5 6 7 9 10 11 12 13 15 16 17 18 19 22 . Another advantage of using the ameroid constrictor is that the procedure is relatively straightforward and can be performed successfully by anyone with reasonable surgical skills, and requires no specialized instruments.…”

“…Once placed around an artery (usually the left anterior descending coronary artery (LAD) or the left circumflex coronary artery (LCX)), the casein material absorbs the surrounding fluid causing the inner lumen to narrow gradually, mimicking the slow stenosis of an artery and resulting finally in full occlusion 9 13 14 . This procedure used by itself or in conjunction with other methods results in a region of chronic myocardial ischemia and/or infarction of the left ventricle of the heart that has been useful for developing and evaluating new imaging techniques 8 10 15 , therapeutic treatments 7 16 17 18 and surgical procedures 19 20 .…”

Remodeling an infarcted heart: novel hybrid treatment with transmyocardial revascularization and stem cell therapy

“…However, it has also been argued that despite increased myocardial damage, it is this damage itself that is paradoxically responsible for the repair and remodeling of ischemic myocardium. Despite these observed repair mechanisms, Estvold and colleagues argued that increased fibrosis associated with the Ho:YAG device led to decreased improvements in ventricular wall thickening and function compared to the CO 2 laser system (Estvold et al 2010 ). Therefore, debate still exists over the extent of injury incurred by these laser devices and their subsequent effects on cardiac function.…”

Transmyocardial Revascularization Enhances Mesenchymal Stem Cell Engraftment in Infarcted Hearts through SCF–c-Kit and SDF-1–CXCR4 Signaling Axes

“…89 The two laser systems have been compared side-by-side in a study by Horvath and colleagues. 90 In a porcine model of chronic myocardial ischemia, TMR was performed using either a CO 2 laser or a Ho:YAG laser. Six weeks later, the hearts that were treated with CO 2 laser showed improvement in ischemic wall thickening, whereas the ones treated with Early on in the development of TMR, it was thought that TMR worked by creating channels, which would stay patent and allow direct myocardial perfusion, like amphibian hearts.…”