Recovery and viability of an acute myocardial infarct after transmyocardial laser revascularization

Photobiomodulation Regulation as One Promising Therapeutic Approach for Myocardial Infarction

Myocardial infarction refers to myocardial necrosis caused by acute or persistent coronary ischemia and hypoxia. It is considered to be one of the significant crises threatening human health in the world. Following myocardial infarction, collagen gradually replaces the original tissue due to the loss of many cardiomyocytes, myocardial contractile function decreases, and myocardial fibrosis eventually leads to heart failure. Phototherapy is a new treatment which has shown superior efficacy on the nerve, skeletal muscle, skin, and other tissues. Likewise, there is growing evidence that phototherapy also has many positive effects on the heart. Therefore, this article introduces the progress of research on phototherapy as a new therapeutic strategy in the treatment of myocardial infarction. The wavelength of photobiomodulation in the treatment of myocardial infarction is specific, and the influence of light source power and light duration on the tissue presents a bell-shaped distribution. Under these conditions, phototherapy can promote ATP synthesis and angiogenesis, inhibit the inflammatory response, improve heart function, reduce infarct size, and protect myocardium. In addition, we summarized the molecular mechanisms of phototherapy. According to the location of photoreceptors, they can be divided into mitochondrial and nonmitochondrial parts.

Transmyocardial Laser Revascularization: Saudi Experience

One hundred transmyocardial revascularization procedures were performed between February 1994 and January 1996, using the C02 Heart Laser on 90 patients with stable angina and 10 with unstable angina. This was the sole therapy in 98 cases and utilized in combination with open-heart surgery in 2 others. Most patients (96) had this procedure without having undergone previous coronary artery bypass graft surgery; 66 patients were deemed to have nongraftable vessels, while 34 patients had coronary artery anatomy that was favorable to bypass graft surgery but elected to undergo laser revascularization instead. The majority (86%) were male and ages ranged from 30 to 82 (mean 55) years. At 12 months after the procedure, 92% of patients reported that they were free of angina, while mean exercise tolerance increased from 7 minutes preoperatively to 15 minutes, and metabolic equivalent units rose from 4.8 to 10.2. The average increase in Karnofsky performance score was 51%, and oxygen consumption improved by 93%. The increase in left ventricular ejection fraction was not statistically significant. Most patients resumed work within 18 days of the procedure. Consumption of antianginal medication was reduced to minimal in 83% of the patients at the end of one year. There were 10 deaths in the series, chiefly in patients with extremely low ejection fractions. We conclude that the application of this rapidly evolving procedure as a primary therapy in ungraftable patients, appears to be safe and deserving further study.

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.

The promise and challenges of cardiac stem cell therapy

After an extensive myocardial infarction, restoration of heart function depends on the ability of the heart to promote regeneration and prevent adverse ventricular remodeling. Preclinical research demonstrated that the transplantation of healthy stem cells restored heart function, but the stem cells obtained from older animals or patients were not as efficacious as those from younger individuals. In this paper, we review the successes and limitations discovered in preclinical studies and clinical trials examining cell therapy for damaged hearts. After the modest successes of the early clinical trials, research is now exploring the benefits of enhanced stem cell therapy. Cell based gene therapy markedly improves the angiogenesis achieved. Rejuvenating aged stems cells prior to transplantation restores the functional benefits attained. Transplanting healthy allogeneic stem cells from young donors into aged individuals can restore function if rejection can be prevented. Finally, modulating the cellular environment in aged individuals permits the full functional benefits of stem cell therapy to be realized. Significant challenges remain, but these approaches show promise that cell therapy may become routine therapy to improve functional recovery of older patients after an extensive myocardial infarction.

Intramyocardial partial oxygen pressure in patients undergoing transmyocardial laser revascularization and bypass surgery

OBJECTIVE

Numerous investigations could not clarify the exact mechanism of transmyocardial laser revascularization (TMLR). The aim of this study was to investigate, whether TMLR leads to an increase of myocardial oxygenation in comparison to patients undergoing coronary artery bypass grafting (CABG).

DESIGN

Twelve patients (TMLR group) underwent TMLR alone with an 800 W CO2 laser through a left anterior thoracotomy. Seventeen patients (CABG group) underwent standard CABG. Myocardial oxygenation was determined by measuring intramyocardial partial oxygen pressure (ptiO2 ). PtiO2 was measured online and mean values at 1, 24, 32, and 48 h postoperatively were compared with baseline before intervention. Parameters influencing ptiO2 (arterial pO2, hemodynamic parameters, hemoglobin) were recorded.

RESULTS

Mean baseline ptiO2 was significantly lower in the TMLR group compared with the CABG group (p < 0.05). In both groups ptiO2 increased significantly in the postoperative course, whereby ptiO2 in the TMLR group was significantly lower compared with the CABG group.

CONCLUSION

Although the exact mechanism of action of TMLR remains unclear, ptiO2 and thus oxygen supply in the myocardium increased in patients undergoing TMLR at least in the early postoperative course. However, ptiO2 increased to a lesser extent compared with CABG.

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.

Combined transmyocardial revascularization and cell-based angiogenic gene therapy increases transplanted cell survival

We hypothesized that pretreatment of an infarcted heart by mechanical transmyocardial revascularization (TMR) before transplantation of bone marrow cells (BMCs) or BMC-expressing angiogenic growth factors would increase transplanted BMC survival and enhance myocardial repair. Female Lewis rats underwent coronary ligation 3 wk before creation of 10 needle TMR channels (3 groups) or no TMR (3 groups), followed by transplantation of 3 × 106male donor BMCs, BMC transfected with vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and insulin-like growth factor-1 (IGF-1) (BMC + VBI), or medium alone. At 1, 3, and 7 days, we evaluated transplanted cell survival, vascular densities, and left ventricular (LV) function ( N = 4 per group × 6 groups × 3 time points). At 3 days, vascular densities in the scar were increased by TMR + BMC + VBI and by BMC + VBI ( P < 0.05), and at 7 days, vascular densities were greatest in rats receiving TMR + BMC + VBI ( P < 0.05). Transplanted cell survival at 3 and 7 days was increased by TMR and by BMC + VBI. Combined therapy with TMR + BMC + VBI resulted in the greatest cell survival at 3 days ( P < 0.05) versus BMC. After 7 days, LV ejection fraction (LVEF) was lowest in rats receiving neither BMC nor TMR and greatest in rats receiving TMR + BMC + VBI ( P = 0.004). We concluded that mechanical pretreatment of infarcted myocardium by TMR enhances the effect of subsequent cell-based gene therapy on transplanted cell survival, angiogenesis, and LV function. Scar pretreatment with TMR combined with cell-based multigene therapy may maximize myocardial repair.

Transmyocardial Laser Revascularization Enhances Blood Flow within Bypass Grafts

OBJECTIVE

: Early benefits from transmyocardial laser revascularization (TMR) may be related to acute sympathetic denervation. This study hypothesized that TMR as an adjunct to off-pump coronary artery bypass (OPCAB) would improve myocardial runoff in the TMR-treated regions and increase graft flow.

METHODS

: Graft blood flow was measured in 145 consecutive OPCAB patients. In patients with graft flow <40 mL/min (n = 25), the myocardial region served by the graft was treated with TMR. Blood flow was reassessed 10 minutes after TMR and compared with graft flow in the nontreated regions. Postoperative outcomes, transcardiac thrombin production, coagulation activation, myocardial, and inflammatory markers were assessed. A control group not treated with TMR (n = 14) was selected with similar graft flows and other baseline characteristics.

RESULTS

: Risk factors, comorbidities, and preoperative medications were similar in all groups. TMR led to a 48% increase in bypass graft flow in 12 patients, but no significant change in flow in the remainder (n = 13). The control group also showed no change in graft flow measured during the same time-points. Compared with those that did not respond to TMR, responders showed a greater drop in pH during warm ischemia caused by distal anastomoses during OPCAB and significantly higher transcardiac gradients of F1.2, IL-8, TNFα, and VCAM.

CONCLUSIONS

: TMR acutely improves venous bypass graft flow in regions with more severe myocardial acidosis and inflammation during and after OPCAB. Acute sympathetic denervation after TMR may provide mechanistic insight into the early clinical benefits of TMR as an adjunct to OPCAB.

The prospective clinical and scintigraphic assessment of patients with preserved left ventricular systolic function after transmyocardial laser revascularisation

AIM

To analyse the clinical outcome and myocardial perfusion and function after transmyocardial revascularisation (TMR) in patients with normal left ventricular function and multivessel coronary artery disease non-amenable for standard revascularisation.

METHOD AND RESULTS

Twenty three severely symptomatic patients (CCS score median 4) with normal left ventricular systolic function but coronaries non-amenable for either PTCA or CABG were subjected to TMR. The angina score, left ventricular systolic and diastolic function in radionuclide ventriculography at rest, exercise tolerance and myocardial perfusion--Thallium-201 SPECT (adenosine stress 74 and 37 MBq under nitrate cover) were evaluated before and 3, 6, 12 months post-operatively. After an average of 40 +/- 12 (range 14-56) TMR channels angina score decreased significantly (p< 0.0001) and the exercise tolerance increased (from 6.0 +/- 4.5 to 9.1 +/- 4.6 after 6 months, p< 0.05) in 21 patients. During the follow up period two patients had a myocardial infarction and one committed suicide after 6 months. Ejection fraction dropped significantly only after 1 year post-TMR from 70 +/- 13 to 63 +/- 0.13%, p < 0.05. The overall perfusion improved initially in 14 patients with subsequent deterioration in time. The changes in segmental perfusion were not associated with the symptomatic improvement.

CONCLUSION

Transmyocardial revascularisation in patients with normal ejection fraction may improve the angina class, exercise tolerance and overall but not segmental perfusion and does not show any immediate effect on left ventricular function.

Improvement of myocardial contractility in a porcine model of chronic ischemia using a combined transmyocardial revascularization and gene therapy approach

OBJECTIVES

The purpose of this study was to investigate whether a novel fibroblast growth factor-2 gene formulation, providing a localized and sustained availability of the adenoviral vector from a collagen-based matrix, in combination with CO 2 transmyocardial laser revascularization would lead to an enhanced angiogenic response and improved myocardial function.

METHODS

Fibroblast growth factor-2 gene was delivered by means of an adenoviral vector (adenoviral fibroblast growth factor-2) formulated in a collagen-based matrix. The ischemic areas of 33 animals were then treated. Group 1 was treated with CO 2 transmyocardial laser revascularization; group 2 was treated with intramyocardial injections of adenoviral fibroblast growth factor-2 in a collagen-based matrix; group 3 had a combination treatment of matrix adenoviral fibroblast growth factor-2 and CO 2 transmyocardial laser revascularization; and group 4 received injections with saline-formulated adenoviral fibroblast growth factor-2. Baseline left ventricular function was assessed by echocardiography and cine magnetic resonance imaging. Studies were repeated 6 weeks after treatment. Vascular development was assessed using anti-alpha-actin immunohistochemistry.

RESULTS

Matrix adenoviral fibroblast growth factor-2 + transmyocardial laser revascularization-treated areas had a 105% increase in arteriolar development versus either treatment alone ( P < .05) and a 390% increase compared with saline-formulated adenoviral fibroblast growth factor-2 treatment alone ( P < .05). Contractility was significantly improved in matrix adenoviral fibroblast growth factor-2 + transmyocardial laser revascularization-treated areas as measured by myocardial wall thickening. This functional improvement was confirmed by cine magnetic resonance imaging, in which a 90% increase in the contractility of the treated segments was demonstrated after matrix adenoviral fibroblast growth factor-2 + transmyocardial laser revascularation. The other treatments provided significantly less restoration of myocardial function.

CONCLUSIONS

The increase in angiogenesis as a result of matrix adenoviral fibroblast growth factor-2 gene therapy in combination with CO 2 transmyocardial laser revascularization is greater than that seen in either therapy alone. A concomitant improvement in myocardial function was seen as a result of this angiogenic response.

Cellular Destruction Following Transmyocardial Laser Revascularization (TMR)

During transmyocardial revascularization, cellular destruction of cardiomyocytes occurs as a result of the high-energy laser. However, the features of myocardial cellular destruction are unclear. The present study was undertaken to examine the structural characteristics of cell death in the myocardium following transmyocardial revascularization. Myocardial specimens from 3 male patients who had died within 11 days following laser revascularization were collected within 1 h of death and were analyzed by immunohistochemistry and electron microscopy. For immunohistochemistry, antibodies to pro-apoptotic proteins CPP32 and BAX were used. Immunohistochemical examination demonstrated the presence of cells expressing both CPP32 and BAX along the laser channel. Electron microscopic analysis revealed that the lining surface of laser channels consisted of condensed acellular debris and dead cells. No endothelialization of channels was noted. The lumen of laser channels were surrounded by a rim of acellular debris with several outer concentric rims of cardiomyocytes showing features of cellular destruction. The present study identified features of both necrotic and apoptotic cellular death following laser revascularization.

Implantation of Endothelial Progenitor Cells into Laser-Induced Channels in Rat Ischemia Hindlimb Augments Neovascularization

The aim of this study was to investigate the effect of transmuscle laser revascularization (TMR) in combination with endothelial progenitor cell grafting on neovascularization of ischemic hindlimbs of nude rats. Mononuclear cells (MNCs) isolated from human umbilical cord blood (HUCB) by density gradient centrifugation were expanded in vitro. Spindle-shaped attaching (AT) cells and cord-like structures were developed from culture of MNCs. Acetylated low-density lipoprotein (Ac-LDL) incorporation by AT cells was performed. Phenotypic characterization was assessed by immunocytochemistry, and flow cytometry analysis. EPCs were labeled with 1, 1'-dioctadecyl-1 to 3,3, 3', 3'- tetramethyl-indocarbocyanine perchlorate (DiI) before being injected into the Nd:YAG laser channels or ischemic region. An acute ischemic limb model was created with the following four groups of nude rats by ligating the right external iliac artery: TMR + EPC group: rats with local transplantation of EPCs into laser channels; TMR group: those with transmuscular channels created without EPCs; EPC group: those with EPCs injected into the ischemic hindlimb; control group: an ischemic model without TMR or EPCs. All rats underwent femoral artery ultrasonic blood flow measurements of the ischemic and nonischemic limbs to obtain a flow ratio (femoral artery flow index [FAFI]: right femoral artery flow/left femoral artery flow) immediately after ligation of the artery (at baseline) and 28 days postoperation, and the ischemic limb muscle was sampled for histochemical and immunohistologic analysis. AT cells expressed AC 133 and endothelial cell (ECs) markers (KDR, CD34, CD31, and von Willebrand factor) and exhibited function similar to that of ECs as estimated by Ac-LDL incorporation. Flow cytometric analysis revealed that AT cells were positive for CD34 (62% +/- 7%) and AC133 (57.2% +/- 9.8%) at day 7 of culture. Twenty-eight days after the operation, the FAFI was significantly higher in the TMR+EPC group and EPC group than that in the control group. It was significantly higher in the TMR+EPC group, EPC group, and TMR group than that at their respective baselines. The FAFI in the control group was unchanged and no difference in FAFI was found between the TMR group and control group, and among the TMR+EPC, TMR, and EPC groups. TMR+EPC, TMR, and EPC treatment resulted in an increased number of capillaries in the treated regional area compared to the control group. Nd: YAG-laser transmuscle revascularization combined with the EPC grafting can significantly ameliorate perfusion and augment neovascularization in this ischemic hindlimb model of nude rats.

Transmyocardial Revascularization

Low-powered lasers were first used in the 1980s to produce transventricular channels as an adjunct to coronary artery bypass surgery. High-powered lasers, which were introduced in the 1990s, are powerful enough to create transmyocardial channels with minimal damage to surrounding tissues. Clinical studies were first carried out in patients with inoperable coronary artery disease and angina pectoris refractory to medical therapy. Based on these studies, the Food and Drug Administration granted approval of transmyocardial revascularization (TMR) as a sole therapy. Recently, TMR has been combined with coronary artery bypass surgery and 2 types of laser systems are currently available which have not been compared. The results of clinical trials provide contrasting findings regarding benefit, and the procedure is associated with potential morbidity and mortality risk. Furthermore, the mechanism of action of TMR remains undefined. Additional studies need to be done with TMR to assess whether it is a useful treatment or an addition to the list of placebo therapies initially thought to have been of benefit in the therapy for angina pectoris.

What is the Optimal Channel Density for Transmyocardial Laser Revascularization?

BACKGROUND

Transmyocardial laser revascularization (TMR) has demonstrated reproducible relief of angina in patients with end-stage coronary disease. However, the optimum dose or channel density has not been elucidated.

METHODS

Using a porcine model of chronic myocardial ischemia, 14 animals were treated with CO2 TMR and randomized as follows: group 1 was 1 channel per 2 cm2; group 2 was 1 channel per 1 cm2; and group 3 was 2 channels per 1 cm2. Left ventricular myocardial viability and function were assessed by magnetic resonance imaging (MRI) and echocardiography pretreatment, and repeated 6 weeks later.

RESULTS

The MRI assessment of group 1 (1 channel/2 cm2) and group 2 (1 channel/cm2) demonstrated similar improvement in segmental contractility posttreatment of 12.11% +/- 5.15% and 12.47% +/- 9.51%, respectively. In contrast, group 3 (2 channels/cm2) showed significantly worse segmental contractility posttreatment: -18.52% +/- 7.16% (p = 0.01). Echocardiographic imaging revealed significant improvements in wall thickening in the ischemic zone for group 1 at 0.91 +/- 0.07 cm pretreatment versus 1.30 +/- 0.09 cm posttreatment, (p = 0.01); and for group 2 at 0.93 +/- 0.11 cm versus 1.42 +/- 0.18 cm, (p = 0.01). No significant improvement in wall thickening was seen in group 3 (0.84 +/- 0.06 cm versus 0.88 +/- 0.09 cm, p = n.s.).

CONCLUSIONS

These data corroborate the empiric finding of an effective therapeutic dose range for TMR, 1 channel per 1 to 2 cm2. These results also demonstrate a detrimental effect when channel density is increased above the clinical standard of 1 channel per cm2 to a density of 2 channels per 1 cm2.

[Long-term results of percutaneous transmyocardial laser revascularization therapy at the University of Vienna Medical Center]

INTRODUCTION

Percutaneous transmyocardial laser revascularization (PTMR) was used for treating patients with therapy refractory angina pectoris who are not amenable for angioplasty or bypass surgery ("no-option patients"). The aim of this study was to evaluate the short- and long-term results of PTMR-interventions performed at the University of Vienna between February 1999 and May 2000.

PATIENTS AND METHODS

Twenty-four "no-option" patients underwent PTMR. The chronically ischemic myocardial areas were determined by perfusion scintigraphy; after coronary angiography and contrast ventriculography 10 patients were treated with the Biosense laser using 3D-NOGA-mapping guidance and 14 patients with the Eclipse laser using biplane fluoroscopic guidance. After an average follow-up period (FUP) of 7.7 +/- 4.2 months, all patients underwent perfusion scintigraphy, coronary angiography and contrast ventriculography. Global and regional left ventricular (LV) function were calculated by the area-length method.

RESULTS

The ischemic myocardial areas of the patients were treated with an average of 16 laser points. In one patient, an intramural hematoma caused by the Biosense laser catheter was observed, in another patient the ventricular wall was perforated by the Eclipse laser (both events were resolved conservatively); during the in-hospital stay 2 patients suffered from severe angina pectoris and in one patient a pacemaker was implanted. During the 7-month-FUP one patient had a myocardial infarction; in one patient a stent implantation, in another one coronary bypass surgery had to be performed (in not-lasered areas), 2 patients died. Thus, the composite MACE rate was 33.3%. Angina class improved significantly during the FUP, but a trend to deterioration of global ejection fraction was observed. The rest and late rest myocardial perfusion remained unchanged.

CONCLUSION

While the angina class of the patients improved significantly, no significant change of myocardial perfusion but a trend to deterioration of LV function after the FUP were observed.

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.

A mathematical model for the laser treatment of heart disease

Transmyocardial laser revascularisation (TMLR) is used to treat patients with severe coronary artery disease. A laser is used to create narrow tunnels within ischemic heart muscle in an attempt to reperfuse the area with oxygenated blood directly from the left-ventricular chamber. It has been hypothesised that initially blood flow through the patent tunnels plays an important role in the efficacy of the treatment (J. Am. College Cordiol. 25(1) (1995) 258) and Waters (J. Fluid Mech. 433 (2001) 193) developed a simple mathematical model to show that this blood flow enhances the quantity of oxygenated blood drawn into the tunnel and the subsequent delivery of oxygen to the tissue. To date, however, the optimum parameter values for this clinical technique have not been determined, e.g. the radius of the laser-drilled tunnels and their relative spacing. We present a mathematical model to determine the distribution of oxygen for a wide range of the governing parameters. Our results indicate that the tunnel radius has a significant effect on the degree of tissue reperfusion and predictions for the optimum tunnel spacing are made.

Evaluation of myocardial perfusion and left ventricular function six months after percutaneous transmyocardial laser revascularization: Comparison of two Ho-YAG laser systems with the same wavelength, but different energy delivery and navigation systems

BACKGROUND AND OBJECTIVES

Myocardial perfusion and left ventricular function (LVF) were assessed after percutaneous transmyocardial laser revascularization (PTMR) in patients not amenable to conventional revascularization, with a comparison of two laser systems.

STUDY DESIGN/MATERIALS AND METHODS

PTMR was performed with an Eclipse laser in 15 patients, and with a Biosense DMR in 10 patients. (201)Thallium scintigraphy, coronary angiography, and ventriculography were performed at baseline and at the 7.5+/-4.3-month follow-up. All patients in the Biosense DMR group and 10 in the Eclipse group underwent NOGA mapping before PTMR and after follow-up.

RESULTS

The event-free survival rates were comparable, and the angina scores of all patients improved significantly, but more so in the Biosense DMR group than in the Eclipse group (1.2+/-1.1 vs. 2.3+/-0.9, P < 0.05). Both, the electrical activity assessed by NOGA mapping and the normalized (201)thallium uptake at redistribution improved significantly in the treated segments after Biosense DMR, while the global LVF decreased insignificantly in the Eclipse group.

CONCLUSIONS

PTMR resulted in significant improvements in the clinical symptoms, but the electrical activity improved only in the Biosense DMR group, without transforming to a better LVF.

Laser myocardial revascularization modulates expression of angiogenic, neuronal, and inflammatory cytokines in a porcine model of chronic myocardial ischemia

BACKGROUND

Controversy exists whether transmyocardial laser revascularization (TMR) is associated with angiogenesis or neuromodulation and whether these are time-dependent phenomena. Accordingly, we performed a time-course analysis of the expression of angiogenic and neuronal factors following experimental percutaneous TMR.

METHODS AND RESULTS

Five weeks after placing ameroid constrictors on the circumflex coronary artery, 16 pigs underwent left ventricular mapping guided TMR using Ho:YAG laser (2 J x 1 pulse) at 30 sites directed at the ischemic zones and 11 animals were ischemic controls. Histology and immunostaining were obtained at 1 and 2 weeks (4 TMR and 3 controls at each time point) and at 4 weeks (8 TMR and 5 controls) for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), nerve growth factor (betaNGF), substance P (SP), and monocyte chemoattractant protein-1 (MCP-1). Immunoreactivity was scored using a digital image analysis system. Factor VIII staining was used for blood vessel counting. Enhanced regional expression of VEGF, bFGF and MCP-1 in the TMR group was noted at 1 and 2 weeks with a threefold increase at 4 weeks following TMR compared to controls. BetaNGF expression in the TMR group was enhanced at 1 and 2 weeks with subsequent decline at 4 weeks to the controls level. SP expression was not significantly different between groups at all time points. There was a twofold increase in the number of blood vessels in the TMR group at 4 weeks, which was not apparent earlier.

CONCLUSIONS

These immunohistological findings suggest that cytokines expression compatible with angiogenesis and neuromodulation occurs early after TMR. Up-regulation of angiogenic and inflammatory cytokines may be more sustained than neuromodulation.

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.

Transmyocardial coil implants: a novel approach to transmyocardial revascularization

BACKGROUND

Transmyocardial laser revascularization (TMLR) has potential benefit for patients with end-stage coronary artery disease and intractable angina not amenable to conventional revascularization techniques. Neovascularization has been proposed to occur around the laser channels. Our aim was to determine the feasibility of a novel nonlaser myocardial revascularization technique and its effect on angiogenesis in a nonischemic porcine model.

METHODS

In the first phase, six transmyocardial stainless steel coil implants (TMI) were deployed to the lateral wall of the left ventricle in each of 6 pigs. The animals were sacrificed at 8 and 12 weeks, with a single animal dying prematurely at 4 weeks, and the myocardium was assessed for new vessel growth. In the second phase, 8 implants were deployed in each of 12 pigs with regular fluoroscopic follow-up until sacrifice at 2 weeks to assess implant stability.

RESULTS

The deployment procedure was safe and feasible with no complications evident. A significant increase in new vessels at implant sites with 5.43 +/- 3.67, 4.97 +/- 2.44, and 3.57 +/- 2.29 seen per high power field at 12, 8, and 4 weeks, respectively, compared to 1.00 +/- 1.06 (p < 0.0001) in control myocardium. There was no evidence of implant migration in Phase 2.

CONCLUSIONS

TMIs can feasibly be deployed in the nonischemic pig model with a high success rate. The presence of angiogenesis at the implant site and the maintenance of this reaction for 3 months implies that TMI may offer an alternative to TMLR while providing a platform for delivery of angiogenic factors.

Attenuation of infarct size in rats and dogs after myocardial infarction by low-energy laser irradiation

BACKGROUND AND OBJECTIVE

The aim of the present study was to investigate the possibility that low-energy laser irradiation attenuates infarct size formation after induction of chronic myocardial infarction (MI) in small and large experimental animals.

STUDY DESIGN/MATERIALS AND METHODS

Laser irradiation was applied to the infarcted area of rats and dogs at various power densities (2.5 to 20 mW/cm(2)) after occlusion of the coronary artery.

RESULTS

In infarcted laser-irradiated rats that received laser irradiation immediately and 3 days after MI at energy densities of 2.5, 6, and 20 mW/cm(2), there was a 14%, 62% (significant; P < 0.05), and 2.8% reduction of infarct size (14 days after MI) relative to non--laser-irradiated rats, respectively. In dogs, a 49% (significant; P < 0.01) reduction of infarct size was achieved.

CONCLUSION

The results of the present study indicate that delivery of low-energy laser irradiation to infarcted myocardium in rats and dogs has a profound effect on the infarct size after MI.

Potential use of ultrasound in creating transmyocardial channels

Although the mechanisms of the clinical benefits of transmyocardial laser revascularization (TMLR) are considered to be angiogenesis with increased perfusion, denervation and placebo effect, it is unknown whether laser energy is a prerequisite in obtaining these beneficial effects. The present study investigated whether it is possible to create transmyocardial channels and induce angiogenesis by ultrasound. Myocardium was penetrated with an ultrasonically activated surgical blade by advancing the blade tip perpendicularly to the left ventricular free wall of the beating heart of 6 mongrel dogs. The power of ultrasound was set at either the lowest or highest of the system. The animals were killed 30 min (acute; n=3) and 2 weeks (chronic; n=3) after channel creation. Holmium:YAG laser, which is currently used for clinical TMLR, was used to create myocardial channels in 4 other dogs, which were also killed 30 min (n=2) and 2 weeks (n=2) after channel creation. The areas of acute channel core, acute thermal damage and chronic fibrosis were compared between the laser and ultrasound channels by Masson's trichrome stain. Factor VIII and proliferating cell nuclear antigen (PCNA) immunostaining were carried out on the samples obtained from chronic animals. The density of vessels and that of proliferating vascular endothelial cells and vascular smooth muscle cells around the channels were measured. The area of acute core was larger in the lowest and highest outputs of ultrasound than in laser channels (0.78+/-0.09, 1.0+/-0.12 vs 0.38+/-0.04 mm2; p<0.01). The area of acute damage in both laser and the highest output of ultrasound channels was greater than in the channels produced by the lowest output of ultrasound (4.43+/-0.28, 4.63+/-0.44 vs 2.90+/-0.29 mm2; p<0.01). The ratio of acute damage area to acute core area was greater in laser channels than in either type of ultrasound channel (16.86+/-1.66 vs 6.04+/-0.67, 7.86+/-1.07; p<0.01) and the area of chronic fibrosis was greater (3.23+/-0.20 vs 1.59+/-0.18, 2.24+/-0.20 mm2; p<0.01). Factor VIII and PCNA immunostaining revealed new vessels not only inside the areas of chronic fibrosis, but also in the surrounding myocardium, in both laser and ultrasound channels. Ultrasound created transmyocardial channels histologically similar to laser channels and angiogenesis was induced in the normal myocardium surrounding ultrasound channels.

Anatomy and clinical significance of ventricular Thebesian veins

An injection study was carried out in sheep hearts to compare the anatomy and distribution of Thebesian veins (venae cordis minimae) in the ventricles. The left azygos, middle cardiac, small cardiac, and anterior cardiac veins were ligated in 36 hearts, and India ink was injected into the right coronary artery or the left coronary artery or the coronary sinus. Examination revealed foramina Thebesii in both of these cardiac chambers. Myocardial tissue samples were taken, and 12 were subsequently studied histologically to confirm the presence of Thebesian veins. A greater number of Thebesian veins were observed in the right ventricle than in the left (P < 0.05). To identify any larger communications between the coronary arteries and cardiac chambers (arterioluminal), and between the coronary veins and cardiac chambers (venoluminal), gelatine was injected in 16 hearts. Arterioluminal vessels were identified only in the right ventricle, whereas venoluminal vessels were present in both ventricles. Venoluminal vessels are most likely responsible for the non-nutritive shunting of cardioplegic solutions delivered via the coronary sinus during surgery. Thebesian veins play a role in the drainage of blood, contributing towards right to left shunting of deoxygenated blood. It has also been suggested, although not proven, that they are able to supply blood to the myocardium in coronary arterial occlusion, thus acting as a natural form of nutrient channel. Thebesian veins may be confused with artificial nutrient channels constructed by transmyocardial laser revascularization, a possibility that should be considered during histological evaluation of this technique.

Changes in myocardial perfusion after transmyocardial laser revascularization in patients with end-stage angina pectoris

The purpose of the present study was to analyze the effects of transmyocardial laser revascularization (TMLR) on myocardial perfusion. The value of (99m)Tc-MIBI scintigraphy in the detection of changes in perfusion of the lased and nonlased segments was assessed as well. In 15 patients before TMLR and then 3 and 6 months afterwards, MIBI scintigraphy and a stress test were carried out. At the beginning of the study, all patients were classified as having angina pectoris class III or IV (according to the criteria of the Canadian Cardiac Society); their ejection fraction was >30%. The parameters of the stress test increased significantly in 70% of the patients. Cardiac scintigraphy revealed improved perfusion of 33.7% of the transient defects within 3 months after TMLR which persisted at 6 months with a clear trend towards further improvement in the lased segments. TMLR has been found to be particularly beneficial in patients in whom other invasive methods of treatment cannot be applied.

A review of the literature: transmyocardial laser revascularization

BACKGROUND AND OBJECTIVE

Transmyocardial laser revascularization is an investigational procedure that improves chronic angina that is not amenable to other forms of therapy. The theorized mechanism is an increased supply of oxygenated blood to the myocardium via the creation of left ventricular transmural channels. The objective of this review is to facilitate an understanding of the current work published in the literature on the subject of transmyocardial laser revascularization.

METHODS

Using Melvyl Medline, all pertinent literature associated with transmyocardial laser revascularization was sought and reviewed.

CONCLUSION

The research in transmyocardial laser revascularization is growing. The results of the current work in animals is conflicting with some showing a benefit from this procedure and others that refute its effectiveness. This may be the outcome of differing methodology, which has yet to be evaluated. Although the results of human trials are positive, the overall effectiveness in comparison with the conventional forms of therapy has not been addressed. It is, therefore, a procedure worthy of continued study.

Acute and chronic effects of transmyocardial laser revascularization in the nonischemic pig myocardium by using three laser systems

BACKGROUND AND OBJECTIVE

Transmyocardial laser revascularization (TMLR) improves symptoms in patients with coronary heart disease. It is based on the hypothesis of direct perfusion of ischemic myocardium by means of laser-created channels. Three different lasers were used to study alternative effects on myocardium.

STUDY DESIGN/MATERIALS AND METHODS

The present study was conducted to evaluate comprehensively and compare the short and long-term tissue effects and the basic interaction mechanisms of CO2, Ho:YAG, and Er:YAG laser radiation with myocardium. The dynamics of laser-induced impacts in gel used as tissue phantom was visualized by time-resolved flash photography. Pressure measurements performed during perforation of myocardium in vitro revealed the explosive character of the ablation process. Channels made into the left ventricle of normal pig hearts were examined immediately and 6 weeks after creation.

RESULTS

Regardless of laser source, all channels became occluded within 6 weeks by scar. Minimal acute thermal damage by Er:YAG laser corresponded to smaller scars. Pulsed Ho:YAG caused stronger tissue tearing than continuous wave CO2 irradiation. An increased volume density of intramyocardial vessels was found about the scars 6 weeks after treatment with all lasers.

CONCLUSION

The laser sources permitted to study outcome of pressure effects and thermal damage in vivo. There were only minor differences between the three laser systems used. Rapid channel occlusion suggests that rather than revascularization, subsidiary physiologic tissue effects elicited by the thermal, oxidative, or mechanical action of the laser impact may contribute to the beneficial clinical effects of TMLR.

Effect of transmyocardial laser revascularization on chronic ischemic hearts in sheep

BACKGROUND

We investigated the effect of transmyocardial laser revascularization (TMR) on myocardial function and regional blood flow in an animal model of ischemic heart disease.

METHODS

Chronic ischemia was induced in 11 sheep by the application of coronary stenosis on the left anterior descending (LAD) and circumflex coronary artery (LCX). Ten weeks later, in six of them, transmyocardial channels were created in the anterior free wall and in the posterior wall of the left ventricle. Five animals served as controls. The myocardial function was assessed by echocardiography taken at baseline and every 2 weeks after coronary stenosis and after TMR. Myocardial perfusion was measured by colored microspheres, injected at baseline, immediately after coronary stenosis, before and after TMR, and at 20 weeks after coronary stenosis. The hearts were retrieved at 20 weeks for light microscopic examination.

RESULTS

The left ventricular end-diastolic and end-systolic cavity area was elevated 20 weeks after coronary stenosis in the control and TMR groups. There was no difference between groups (analysis of variance; ANOVA, non-significant). The wall thickening fraction (WTF) decreased progressively and significantly after coronary stenosis in both groups. The WTF was further acutely reduced by TMR, and recovered gradually to the pre-TMR level. No significant difference in WTF was observed between the TMR and control groups. The resting myocardial blood flow was significantly increased by TMR at 20 weeks (P=0.03). Light microscopic examination revealed channel patency in 49% of the laser scars at 10 weeks post-TMR. A dense capillary network was observed at the edges of the surrounding scar.

CONCLUSIONS

In an experimental model of ischemic heart disease, TMR developed angiogenesis in the lased channels, but, however, failed to improve myocardial function.

Ultrastructural and immunohistochemical analysis of early myocardial changes following transmyocardial laser revascularization

BACKGROUND AND AIM OF THE STUDY

Transmyocardial laser revascularization (TMR) has demonstrated significant relief in patients presenting with refractory angina. However, the mechanism by which TMR improves clinical symptoms is unclear. This study analyzes the early immunohistochemical and ultrastructural features of the human myocardium following TMR.

METHODS

Specimens of myocardium that contained laser channels were removed in toto at autopsy from three male patients, ages 41, 57, and 65 (mean age 55.8) who had died 1 to 11 days (mean 6.8) following laser revascularization. Consecutive parallel sections of specimens were stained with cell-type specific antibodies to CD3 (to identify T-lymphocytes), CD68 (macrophages), Factor VIII (endothelial cells), and myosin (myocytes). Additionally, adjacent areas of myocardium that contained laser channels were processed and analyzed by transmission electron microscopy.

RESULTS

The internal lining surface of laser channels was composed of vacuolized and condensed myocardial debris. No obvious connections were noted between laser channels and the ventricular cavity. No endothelialization of channels was observed, whereas the adjacent noninjured myocardium demonstrated microvessels lined by well-preserved endothelial cells. The laser channels were surrounded by zones of necrotic cardiomyocytes.

CONCLUSIONS

Our observations suggest that laser channels are not lined by endothelial cells during the early stages following TMR. Mechanisms other than direct myocardial perfusion from the ventricular cavity by patent endothelialized channels may explain the immediate relief from angina provided by TMR.

Transmyocardial laser revascularization with excimer laser: clinical results at 1 year

BACKGROUND

Transmyocardial laser revascularization, a new strategy for the treatment of diffuse ischemic heart disease, uses laser technology for the theoretical purpose of forming transmyocardial channels in the heart to increase perfusion to ischemic zones. This report summarizes our initial clinical experience with the procedure.

METHODS

Excimer transmyocardial laser revascularization was performed in a reversibly ischemic region of the heart in 15 patients. Ischemia and myocardial viability were evaluated by assessment of symptoms and of results of radionuclide single photon emission computed tomography imaging, exercise tolerance testing, and 24-hour Holter monitoring.

RESULTS

No adverse events occurred as a result of the laser revascularization, although 1 patient with preoperative ventricular arrhythmias died 48 hours postoperatively as a result of refractory ventricular tachycardia. Angina class decreased significantly from base line values in patients who had undergone the procedure (mean Canadian Cardiovascular Association angina class, 3.5+/-0.5 at base line, 1.6+/-0.6 at 1 month, 1.5+/-0.8 at 3 months, 1.9+/-0.9 at 6 months, 1.8+/-0.8 at 12 months; p<0.002), and nitroglycerin requirements were similarly decreased in patients who had undergone laser revascularization (mean g/wk of sublingual nitroglycerin, 19+/-4 at baseline, 5+/-3 at 1 month, 4+/-2 at 3 months, 4+/-2 at 6 months, 2+/-1 at 12 months; p<0.02). Exercise tolerance testing demonstrated increase in exercise duration compared with base line values (mean minutes, 7.4+/-3.1 at base line, 8.0+/-3.9 at 1 month, 8.5+/-4.4 at 3 months, and 9.0+/-3.9 at 12 months; p>0.05); those increases were not large enough to be statistically significant, however.

CONCLUSIONS

Our data are consistent with the concept that excimer transmyocardial laser revascularization in individuals with significant ischemic heart disease appears to be well tolerated, can be performed safely, and may lead to a reduction in ischemic symptomatology.

Long- and short-term effects of transmyocardial laser revascularization in acute myocardial ischemia

BACKGROUND AND OBJECTIVE

This study examined the effect of transmyocardial laser revascularization (TMLR) on infarct size and global and regional left ventricular (LV) function.

STUDY DESIGN/MATERIALS AND METHODS

Acute ischemia was induced in 24 dogs by ligating the left anterior descending artery. TMLR was done through a left thoracotomy in 12 dogs. The 12 control dogs had ligation only. Global and regional LV function were measured before ligation, then at 6 hours or 3 months after ligation. We calculated the volumetric ratio of damaged myocardium to myocardium at risk (Vd/Vr).

RESULTS

At 6 hours, global compensation despite regional dyskinesia was universal; Vd/Vr was the same in control and TMLR dogs. At 3 months, global function during stress was significantly higher in TMLR dogs than in control dogs (P < .05); regional contractions were synergic only in TMLR dogs; mean Vd/Vr was significantly lower in TMLR dogs.

CONCLUSION

TMLR limits infarct expansion and improves long-term global and regional function after acute ischemia.

Transmyocardial revascularization with CO2 laser in patients with refractory angina pectoris. Clinical results from the Norwegian randomized trial

OBJECTIVES

The purpose of the study was to evaluate clinical effects, exercise performance and effect on maximal oxygen consumption (MVO2) of transmyocardial revascularization with CO2-laser (TMR) in patients with refractory angina pectoris.

BACKGROUND

Transmyocardial laser revascularization is a new method to treat patients with refractory angina pectoris not eligible for conventional revascularization. Few randomized studies comparing TMR with conventional treatment have been published.

METHODS

One hundred patients with refractory angina not eligible for conventional revascularization were block-randomized in a 1:1 ratio to receive continued optimal medical treatment (MT) or TMR in addition to MT. The patients were evaluated at baseline and at three and 12 months with end points to symptoms, exercise capacity and MVO2.

RESULTS

Transmyocardial laser revascularization resulted in significant relief in angina symptoms after three and 12 months compared to baseline. Time to chest pain during exercise increased from baseline by 78 s after three months (p = NS) and 66 s (p < 0.01) after 12 months in the TMR group, whereas total exercise time and MVO2 were unchanged. No significant changes were observed in the MT group. Perioperative mortality was 4%. One year mortality was 12% in the TMR group and 8% in the MT group (p = NS.)

CONCLUSIONS

Transmyocardial laser revascularization was performed with low perioperative mortality and caused significant symptomatic improvement, but no improvement in exercise capacity.

Transmyocardial laser revascularization combined with coronary artery bypass grafting: a multicenter, blinded, prospective, randomized, controlled trial

OBJECTIVE

We sought to assess the safety and efficacy of transmyocardial revascularization combined with coronary artery bypass grafting in patients not amenable to complete revascularization by coronary bypass alone.

METHODS

A total of 263 patients whose standard of care was coronary artery bypass grafting and who had one or more ischemic areas not amenable to bypass grafting were prospectively randomized to receive coronary bypass of suitable vessels plus transmyocardial revascularization to areas not graftable (n = 132) or coronary bypass alone with nongraftable areas left unrevascularized (n = 131). Group preoperative demographics and operative characteristics were similar.

RESULTS

The operative mortality rate after coronary bypass/transmyocardial revascularization was 1.5% (2/132) versus 7.6% (10/131) after coronary bypass alone (P =.02). Patients undergoing both coronary bypass and transmyocardial revascularization required less postoperative inotropic support (30% vs 55%, P =.0001) and had a trend toward fewer insertions of intra-aortic balloon pumps (4% vs 8%, P =.13) than did patients having coronary bypass alone. Multivariable predictors of operative mortality were coronary artery bypass alone (odds ratio, 5.3; 95% confidence interval, 1.1-25.7; P =.04) and increased age (odds ratio, 1.1; 95% confidence interval, 1. 0-1.2; P =.03). One-year Kaplan-Meier survival (95% vs 89%, P =.05) and freedom from major adverse cardiac events defined as death or myocardial infarction (92% vs 86%, P =.09) favored the combination of coronary bypass and transmyocardial revascularization. Baseline to 12-month improvement in angina and exercise treadmill scores was similar between groups.

CONCLUSIONS

In a prospective, randomized, multicenter trial, transmyocardial revascularization combined with coronary artery bypass grafting in patients not amenable to complete revascularization by coronary bypass alone was safe; however, angina relief and exercise treadmill improvement were indistinguishable between groups at 12 months of follow-up. Operative and 1-year survival benefits observed after adjunctive transmyocardial revascularization require confirmation by a larger validation study, which is ongoing.

Myocardial laser revascularization: the controversy and the data

The clinical and experimental data relevant to the theoretical mechanisms and clinical results of laser myocardial revascularization are reviewed. Both transmyocardial and percutaneous approaches are considered. Both types result in a reduction in anginal symptoms in patients refractory to conventional therapy and are likely to act through common pathways. The proximate mechanisms for the transmyocardial revascularization effect most likely relate to myocardial inflammation, secondary stimulation of growth factors, and denervation of the myocardium.

Transmyocardial laser revascularization: current status

Transmyocardial laser revascularization (TMLR) has been widely evaluated for treatment of the ischemic myocardium either in conjunction with coronary artery bypass grafting or as sole therapy. Clinically, it has shown significant improvement for angina symptoms, but the mechanism by which this modality works is unknown at this time. The original premise on which transmyocardial revascularization was established depended on its ability to essentially generate channels that would directly carry blood from the ventricle into the ischemic myocardium. This theory, however, has not been substantiated, so other mechanisms have been postulated. This article gives a historical perspective on the advent of transmyocardial revascularization and the many animal and human studies that have paved the way for its clinical use. Current controversies are examined, along with the new advances in laser technology and where the future of TMLR is headed.

Evaluation of transmyocardial laser revascularization (TMLR) by gated myocardial perfusion scintigraphy

TMLR is a novel treatment for patients with coronary artery disease. It comprises the creation of transmyocardial channels thought to improve myocardial perfusion. Gated Tc-99m sestamibi scintigraphy was used to evaluate changes in myocardial perfusion after TMLR. Twelve patients underwent TMLR using a carbon dioxide laser. Sestamibi scans were carried out following a standard protocol prior to and 1, 3, 6, and 12 months after TMLR. Both visual and semi-quantitative assessment showed improvement in 4 patients, deterioration in 2 patients, and no change in the remaining 6 patients each. However, visual and semi-quantitative assessment were concordant in 6 patients and discordant in 6 patients. In 3 of these, semi-quantitative assessment suggested a better outcome, and in 3 patients visual assessment gave better results. Our findings in a small group of patients suggest that about a third benefited from TMLR. Gated myocardial perfusion scintigraphy using technetium-99m sestamibi is suitable for visual evaluation of changes in the lased area over time, but does not allow semi-quantitative evaluation in the patient population typically treated with TMLR. Further investigations using optimized imaging protocols, including positron emission tomography and three dimensional image presentation, are warranted.

Transmyocardial revascularization with a carbon dioxide laser in patients with end-stage coronary artery disease

BACKGROUND

The construction of subendocardial channels to perfuse ischemic areas of the myocardium has been investigated since the 1950s. We assessed the safety and efficacy of transmyocardial revascularization with a carbon dioxide laser in patients with refractory angina and left ventricular free-wall ischemia that was not amenable to direct coronary revascularization.

METHODS

In a prospective, controlled, multicenter trial, we randomly assigned 91 patients to undergo transmyocardial revascularization and 101 patients to receive continued medical treatment. The severity of angina (according to the Canadian Cardiovascular Society [CCS] classification), quality of life, and cardiac perfusion (as assessed by thallium-201 scanning) were evaluated at base line and 3, 6, and 12 months after randomization.

RESULTS

At 12 months, angina had improved by at least two CCS classes in 72 percent of the patients assigned to transmyocardial revascularization, as compared with 13 percent of the patients assigned to medical treatment who continued medical treatment (P<0.001). Patients in the transmyocardial-revascularization group also had a significantly improved quality of life as compared with the medical-treatment group. Myocardial perfusion improved by 20 percent in the transmyocardial-revascularization group and worsened by 27 percent in the medical-treatment group (P=0.002). In the first year of follow-up, 2 percent of patients assigned to undergo transmyocardial revascularization were hospitalized because of unstable angina, as compared with 69 percent of patients assigned to medical treatment (P<0.001). The perioperative mortality rate associated with transmyocardial revascularization was 3 percent. The rate of survival at 12 months was 85 percent in the transmyocardial-revascularization group and 79 percent in the medical-treatment group (P=0.50).

CONCLUSIONS

In patients with angina refractory to medical treatment and coronary artery disease that precluded coronary-artery bypass surgery or percutaneous transluminal coronary angioplasty, transmyocardial revascularization improved cardiac perfusion and clinical status over a 12-month period.

Transmyocardial laser revascularisation compared with continued medical therapy for treatment of refractory angina pectoris: a prospective randomised trial. ATLANTIC Investigators. Angina Treatments-Lasers and Normal Therapies in Comparison

BACKGROUND

Transmyocardial revascularisation (TMR) is an operative treatment for refractory angina pectoris when bypass surgery or percutaneous transluminal angioplasty is not indicated. We did a prospective randomised trial to compare TMR with continued medication.

METHODS

We recruited 182 patients from 16 US centres with Canadian Cardiovascular Society Angina (CCSA) score III (38%) or IV (62%), reversible ischaemia, and incomplete response to other therapies. Patients were randomly assigned TMR and continued medication (n=92) or continued medication alone (n=90). Baseline assessments were angina class, exercise tolerance, Seattle angina questionnaire for quality of life, and dipyridamole thallium stress test. We reassessed patients at 3 months, 6 months, and 12 months, with independent masked angina assessment at 12 months.

FINDINGS

At 12 months, total exercise tolerance increased by a median of 65 s in the TMR group compared with a 46 s decrease in the medication-only group (p<0.0001, median difference 111 s). Independent CCSA score was II or lower in 47.8% in the TMR group compared with 14.3% in the medication-only group (p<0.001). Each Seattle angina questionnaire index increased in the TMR group significantly more than in the medication-only group (p<0.001).

INTERPRETATION

TMR lowered angina scores, increased exercise tolerance time, and improved patients' perceptions of quality of life. This operative treatment provided clinical benefits in patients with no other therapeutic options.

Transmyocardial laser revascularisation has no beneficial effect on high energy phosphates and lactate content during acute myocardial ischaemia in pigs

OBJECTIVE

Transmyocardial laser revascularisation (TMLR) is used to treat endstage coronary heart disease. There is evidence that angina is significantly reduced after TMLR. However, the precise mechanism by which symptoms disappear remains unknown. The objective of the present study was to examine the potential effects of TMLR on high-energy phosphates and myocardial perfusion in an acute ischaemic model.

METHOD

Five male landrace pigs (42 +/- 1.8 kg) had TMLR of the anterolateral wall of the left ventricle using a 1000 W CO2 laser (PLC, USA). Thereafter the anterior descending coronary artery was occluded with a tourniquet. After 90 min of ischaemia, drill-biopsies were taken from ischaemic and non-ischaemic areas as well as from laser channels. The specimens were snap-frozen in liquid nitrogen. Subsequently, methylene blue was injected into the left atrium to study tissue distribution. The hearts were excised and the patency of channels was examined visually.

RESULTS

Coronary artery occlusion resulted in immediate blue discoloration in both TMLR and control areas. There was no subendocardial methylene blue staining around laser channels. Inspection of hearts showed occlusion of laser channels due to thrombus formation at both endo- and epicardial levels. ATP-metabolites significantly increased in ischaemic areas compared to non-ischaemic areas. Furthermore there was significant upregulation of purine-content in ischaemic regions even in areas with laser channels.

CONCLUSIONS

In our acute model there was early occlusion of the channels after TMLR. We suggest that clinical improvement after this procedure is not due to increased myocardial oxygen delivery, since high energy phosphate levels and lactate content remained unchanged.

Cardiac sympathetic denervation after transmyocardial laser revascularization

BACKGROUND

Transmyocardial laser revascularization (TMR) has been shown to improve refractory angina not amenable to conventional coronary interventions. However, the mechanism of action remains controversial, because improved myocardial perfusion has not been consistently demonstrated. We hypothesized that TMR relieves angina by causing myocardial sympathetic denervation.

METHODS AND RESULTS

PET imaging of resting and stress myocardial perfusion with [13N]ammonia (NH3) and of sympathetic innervation with [11C]hydroxyephedrine (HED) was performed before and after TMR in 8 patients with class IV angina ineligible for CABG or PTCA. A mean of 50+/-11 channels were created in the left ventricle (LV) with a holmium:YAG laser. A semiautomated program was used to determine NH3 uptake and HED retention in the LV. Perfusion and innervation defects were defined as the percentage of LV with tracer uptake or retention >2 SD below normal mean values. All patients experienced improvement in their angina by 2.4+/-0.5 angina classes after surgery, P=0.008. Sympathetic innervation defects exceeded resting perfusion defects in all patients before TMR (34.6+/-27.3% for HED versus 9.4+/-10.8% for NH3, P=0.008). TMR did not significantly affect resting or stress myocardial perfusion but increased the extent of sympathetic denervation in 6 of 8 patients by 27.5+/-15.9%, P=0.03. In the remaining 2 patients, both sympathetic denervation and stress perfusion defects decreased after surgery.

CONCLUSIONS

TMR causes decreased myocardial HED uptake in most patients without significant change in resting or stress myocardial perfusion, suggesting that the improvement in angina may be at least in part due to sympathetic denervation.