Holmium:YAG laser transmyocardial revascularization relieves angina and improves functional status

Clinical outcomes meta-analysis: measuring subendocardial perfusion and efficacy of transmyocardial laser revascularization with nuclear imaging

INTRODUCTION

Randomized and nonrandomized clinical trials have tried to assess whether or not TMR patients experience an increase in myocardial perfusion. However there have been inconsistencies reported in the literature due to the use of different nuclear imaging modalities to test this metric. The primary purpose of this meta-analysis was to determine whether SPECT, MUGA and PET scans demonstrate changes in myocardial perfusion between lased and non-lased subjects and whether laser type affects myocardial perfusion. The secondary purpose was to examine the overall effect of laser therapy on clinical outcomes including survival, hospital re-admission and angina reduction.

METHODS

Sixteen studies were included in the primary endpoint analysis after excluding all other non-imaging TMR papers. Standardized mean difference was used as the effect size for all quantitative outcomes and log odds ratio was used as the effect size for all binary outcomes.

RESULTS

Statistically significant improvements in myocardial perfusion were observed between control and treatment groups in myocardial perfusion at 6-month follow up using PET imaging with a porcine model. However non-significant differences were observed in patients at 3 and 12 months using SPECT, PET or MUGA scans. Both CO₂ and Ho:YAG laser systems demonstrated an increase in myocardial perfusion however this effect was not statistically significant. In addition both laser types displayed statistically significant decreases in patient angina at 3, 6 and 12 months but non-significant increases in survival rates and decreases in hospital re-admissions.

CONCLUSION

In order to properly assess myocardial perfusion in TMR subjects, subendocardial perfusion needs to be analyzed via nuclear imaging. PET scans can provide this level of sensitivity and should be utilized in future studies to monitor and detect perfusion changes in lased and non-lased subjects.

Newer Therapies for Management of Stable Ischemic Heart Disease With Focus on Refractory Angina

Ischemic heart disease remains a major public health problem nationally and internationally. Stable ischemic heart disease (SIHD) is one of the clinical manifestations of ischemic heart disease and is generally characterized by episodes of reversible myocardial demand/supply mismatch, related to ischemia or hypoxia, which are usually inducible by exercise, emotion, or other stress and reproducible-but which may also be occurring spontaneously. Improvements in the treatment of acute coronary syndromes along with increasing prevalence of cardiovascular risk factors, including diabetes and obesity, have led to increasing population of patients with SIHD. A significant number of these continue to have severe angina despite medical management and revascularization procedures performed and may progress to refractory angina. This article reviews the newer therapies in the treatment of SIHD with special focus in treating patients with refractory angina.

Treatment of Inoperable Coronary Disease and Refractory Angina: Spinal Stimulators, Epidurals, Gene Therapy, Transmyocardial Laser, and Counterpulsation

Intractable angina from refractory coronary disease is a severe form of myocardial ischemia for which revascularization provides no prognostic benefit. Inoperable coronary disease is also accompanied by a “vicious cycle” of myocardial dystrophy from a chronic alteration of the cardiac sympathetic tone and sensitization of damaged cardiac tissues. Several adjunctive treatments have demonstrated efficacy when revascularization is either unsuccessful or contraindicated. Spinal cord stimulation modifies the neurologic input and output of the heart by delivering a very low dose of electrical current to the dorsal columns of the high thoracic spinal cord. Neural fibers then release CGRP and other endogenous peptides to the coronary circulation reducing myocardial oxygen demand and enhancing vasodilation of collaterals to improve the myocardial blood flow of the most diseased regions of the heart. Randomized study has shown the survival data at five years is comparable to bypass for high-risk patients. Transmyocardial laser revascularization creates small channels into ischemic myocardium in an effort to enhance flow though studies have shown no improvement in prognosis over medical therapy alone. Enhanced external counterpulsation uses noninvasive pneumatic compression of the legs to improve diastolic filling of the coronary vessels and promote development of collateral flow. The compressor regimen requires thirty-five hours of therapy over a seven-week treatment period. Therapeutic angiogenesis requires injection of cytokines to promote neovascularization and improve myocardial perfusion into the regions affected by chronic ischemia. Phase 3 trials are pending. High thoracic epidural blockade produces a rapid and potent sympatholysis, coronary vasodilation and reduced myocardial oxygen demand in refractory coronary disease. This technique can be used as an adjunct to bypass surgery or medical therapy in chronic or acute unstable angina. Epidurals are easy to perform and often available for outpatient or inpatient use. The rapid anti-ischemic effect may complement therapeutic angiogenesis or other interventions with delayed onset to clinical benefit. A new era for interventional and implant cardiology is beginning to emerge as more clinicians, including cardiologists, gradually learn new procedures to safely provide more therapeutic options for patients suffering refractory angina.

Transmyocardial Revascularization: Peril and Potential

Transmyocardial laser revascularization is a technique for the treatment of patients with chronic angina pectoris that is refractory to medical therapy and who are not eligible for surgical intervention. Percutaneous myocardial revascularization is a less-invasive catheter-based procedure that has been adapted from transmyocardial laser revascularization. Six prospective randomized clinical trials have been performed with transmyocardial laser revascularization and 5 have been performed using percutaneous myocardial revascularization. All of the transmyocardial laser revascularization and 4 of the percutaneous myocardial revascularization studies showed a significant improvement in angina class; however, results for improved survival, increased exercise tolerance, improved ejection fraction, and improved myocardial perfusion were less definitive. Transmyocardial laser revascularization has significant potential for morbidity and mortality. This article summarizes the results of the randomized trials, explains the current theories for the mechanism of transmyocardial laser revascularization, and discusses its current role in treatment for patients, considering the evidence that currently exists.

Alternative therapy for medically refractory angina: enhanced external counterpulsation and transmyocardial laser revascularization

Medically refractory angina pectoris (RAP) is defined by presence of severe angina with objective evidence of ischemia and failure to relieve symptoms with coronary revascularization. Medication and invasive revascularization are the most common approaches for treating coronary artery disease (CAD). Although symptoms are eliminated or alleviated by these invasive approaches, the disease and its causes are present after treatment. New treatment approaches are needed to prevent the disease from progressing and symptoms from recurring. External enhanced counterpulsation therapy provides a treatment modality in the management of CAD and can complement invasive revascularization procedures. Data support that it should be considered a first-line treatment of RAP.

Transmyocardial laser revascularization versus medical therapy for refractory angina

BACKGROUND

This is an update of a review previously published in 2009. Chronic angina and advanced forms of coronary disease are increasingly more frequent. In spite of the improvement in the efficacy of available revascularization treatments, a subgroup of patients continue suffering from refractory angina. Transmyocardial laser revascularization (TMLR) has been proposed to improve the clinical situation of these patients.

OBJECTIVES

To assess the effects (both benefits and harms) of TMLR versus optimal medical treatment in people with refractory angina who are not candidates for percutaneous coronary angioplasty or coronary artery bypass graft, in alleviating angina severity, reducing mortality and improving ejection fraction.

SEARCH METHODS

We searched the following resources up to June 2014: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the metaRegister of Controlled Trials database, ClinicalTrials.gov, and the WHO International Clinical Trials Registry. We applied no languages restrictions. We also checked reference lists of relevant papers.

SELECTION CRITERIA

We selected studies if they fulfilled the following criteria: randomized controlled trials (RCTs) of TMLR, by thoracotomy, in patients with Canadian Cardiovascular Society or New York Heart Association angina grade III-IV who were excluded from other revascularization procedures.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data for each trial about the population and interventions compared and assessed the risk of bias of the studies, evaluating randomisation sequence generation, allocation concealment, blinding (of participants, personnel and outcome assessors), incomplete outcome data, selective outcome reporting, and other potential sources of bias.

MAIN RESULTS

From a total of 502 references, we retrieved 47 papers for more detailed evaluation. We selected 20 papers, reporting data from seven studies, which included 1137 participants, of which 559 were randomized to TMLR. Participants and professionals were not blinded, which suggests high risk of performance bias. Overall, 43.8% of participants in the treatment group decreased two angina classes, as compared with 14.8% in the control group: odds ratio (OR) 4.63, 95% confidence interval (CI) 3.43 to 6.25), and heterogeneity was present. Mortality by intention-to-treat analysis was similar in both groups at 30 days (4.0% in the TMLR group and 3.5% in the control group), and one year (12.2% in the TMLR group and 11.9% in the control group). However, the 30-day mortality as-treated was 6.8% in the TMLR group and 0.8% in the control group (pooled OR was 3.76, 95% CI 1.63 to 8.66), mainly due to a higher mortality in participants crossing from standard treatment to TMLR. The assessment of subjective outcomes, such as improvement in angina, was affected by a high risk of bias and this may explain the differences found. Other adverse events such as myocardial infarction, arrhythmias or heart failure, were not considered in this review, as they were not predefined outcomes in trials design and they show a high inconsistency across studies. No new trials on transmyocardial laser revascularization have been published in the last ten years and it is very unlikely that new research will be undertaken in this field.

AUTHORS' CONCLUSIONS

This review shows that risks associated with TMLR outweigh the potential clinical benefits. Subjective outcomes are subject to high risk of bias and no differences were found in survival, but a significant increase in postoperative mortality and other safety outcomes suggests that the procedure may pose unacceptable risks.

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.

Improved myocardial perfusion after transmyocardial laser revascularization in a patient with microvascular coronary artery disease

We report the case of a 59-year-old woman who presented with symptoms of angina that was refractory to medical management. Although her cardiac catheterization revealed microvascular coronary artery disease, her symptoms were refractory to optimal medical management that included ranolazine. After undergoing transmyocardial revascularization, her myocardial ischemia completely resolved and her symptoms dramatically improved. This case suggests that combination of ranolazine and transmyocardial revascularization can be applied to patients with microvascular coronary artery disease.

Long-term outcomes after transmyocardial revascularization

BACKGROUND

Two independent reports documented substantially higher operative mortality associated with transmyocardial revascularization (TMR) when used in isolation than that reported in the premarket clinical trials. To clarify the state of the art, this article assesses temporal trends in the use of TMR, short-term and long-term outcomes, and outcomes stratified by procedure type (TMR only and TMR + coronary artery bypass graft [CABG]) and by the 2 specific TMR devices.

METHODS

The study population included all patients undergoing TMR in isolation or in combination with CABG at 435 cardiothoracic hospitals in the United States participating in the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (ACSD) from January 2000 through November 2006 (n = 15,386). Analysis of long-term outcomes was accomplished through linkage to Medicare claims data. Short-term and long-term (7 years) adverse outcomes were assessed and compared between the 2 TMR device types.

RESULTS

The use of TMR in conjunction with CABG surgery is increasing. This study showed modest differences in short-term morbidity and mortality between the 2 devices. In combination with CABG, after risk adjustment, patients treated with the holmium:YAG laser (experienced a higher rate of operative mortality (3.5% vs 2.5%; adjusted hazard ratio 1.39, 95% confidence level 1.03 to 1.87) but no difference in the composite short-term rate of major morbidity or mortality, compared with the Heart Laser CO2 transmyocardial revascularization system (PLC Medical Systems, Inc, Milford, MA). However, there were no clinically meaningful differences in long-term results.

CONCLUSIONS

Modest differences in short-term morbidity and mortality between the 2 devices suggest the usefulness of further research.

Does laser type impact myocardial function following transmyocardial laser revascularization?

BACKGROUND

Transmyocardial laser revascularization (TMR) is currently clinically performed with either a CO(2) 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 CO(2) or Ho:YAG laser. Transmural channels were created with each laser in a distribution of 1/cm(2) 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

CO(2) 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 CO(2) (1.81 vs. 0.083, P < 0.05).

CONCLUSIONS

In a side-by-side comparison CO(2) 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.

Effects of Transmyocardial Revascularization on Myocardial Perfusion and Systolic Function Assessed by Nuclear and Magnetic Resonance Imaging Methods

OBJECTIVE

There is no obvious explanation, except placebo, to the symptomatic effect of transmyocardial laser revascularization (TMR) in patients with refractory angina. Whether TMR improves myocardial perfusion or relieves symptoms without altering cardiac function is not clarified.

METHODS

One hundred patients with refractory angina were randomized 1:1 to TMR (CO2 laser) and medical treatment, or medical treatment alone. Technetium 99m (99mTc)-tetrofosmin myocardial perfusion tomography (SPECT), quantitative myocardial perfusion gated SPECT (QGSPECT), technetium 99m (99mTc) multiple gated acquisition radionuclide ventriculografi (MUGA) and cine-magnetic resonance imaging (cine-MRI) were performed at baseline and after 3 and 12 months.

RESULTS

Following TMR, a slight reduction in left ventricular ejection fraction (LVEF) (p < 0.05) was observed (MUGA and QGSPECT) compared to baseline. Inclusion of incomplete studies (QGSPECT) revealed a significant reduction in LVEF and increase in left ventricular end-diastolic volume (LVEDV) (p < 0.05) compared to a control group. Otherwise, no between-group comparisons showed statistically significant differences.

CONCLUSION

TMR did not improve myocardial perfusion, but led to a reduction in LVEF and increase in LVEDV, however not significantly different from the control group.

Myocardial Laser Revascularization in the Year 2000 as seen by a Norwegian Specialist Panel. The Process of Evaluating and Implementing New Methods in Clinical Practice

OBJECTIVE

In Norway "Transmyocardial laser revascularization" as a routine method was prohibited by the Ministry of Health in 1995 due to lacking evidence of treatment effect and concerns about procedural morbidity and mortality. In 1999 Norwegian health authorities asked for a re-evaluation of the method based on a systematic review of literature.

METHODS

Medline and Embase were searched and a total of 267 articles were identified. Publications were classified by an expert panel according to type of study and importance for the project.

RESULTS

Based on the literature review the panel concluded that heart laser treatment does not have a life-saving effect, nor does it improve myocardial function. However, the method has a considerable short-term symptomatic effect, the mechanism of which is not understood. Neoangiogenesis, denervation and placebo may play a role. Based on the report the Norwegian health authorities recommended use of this method be restricted to scientific trials only.

CONCLUSIONS

Based on a systematic literature review it was concluded that the only documented effect of heart laser treatment is symptom relief, the mechanism for which is unclear. It could partly or totally be a placebo effect. A conflict of interest may arise when new technologies are to be implemented in health care. The communication between professionals evaluating scientific results and decision makers is challenging. Quality assurance of this process may be obtained by use of expert panels working under the auspices of an official institution.

Transmyocardial laser revascularization versus medical therapy for refractory angina

BACKGROUND

Chronic angina and advanced forms of coronary disease are increasingly more frequent. Although the improved efficacy of available revascularization treatments, a subgroup of patients present with refractory angina. Transmyocardial laser revascularization (TMLR) has been proposed to improve the clinical situation of these patients.

OBJECTIVES

To assess the efficacy and safety of TMLR versus optimal medical treatment in patients with refractory angina in alleviating the severity of angina and improving survivorship and heart function.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 2 2007), MEDLINE (January 2006 to June 2007), EMBASE ( 2004 to June 2007) and ongoing studies were sought using the metaRegister of Controlled Trials database (mRCT) and ClinicalTrials.gov databases. No languages restrictions were applied. Reference lists of relevant papers were also checked.

SELECTION CRITERIA

Studies were selected if they fulfilled the following criteria: randomized controlled trials of TMLR, by thoracotomy, in patients with angina grade III-IV who were excluded from other revascularization procedures. From a total of 181 references, 20 papers were selected, reporting data from seven studies.

DATA COLLECTION AND ANALYSIS

Two reviewers abstracted data from selected papers; . The reviewers performed independently both quality assessment and data extraction. Selected studies present methodological weaknesses. None of them fulfilled all the quality criteria.

MAIN RESULTS

Seven studies (1137 participants of which 559 randomized to TMLR) were included. Overall, 43.8 % of patients in the treatment group decreased two angina classes as compared with 14.8 % in the control group, odds ratio (OR) of 4.63 (95% confidence interval (CI) 3.43 to 6.25), and heterogeneity was statistically significant. Mortality by intention-to-treat analysis at both 30 days (4.0 % in the TMLR group and 3.5 % in the control group) and 1 year (12.2 % in the TMLR group and 11.9 % in the control group) was similar in both groups. The 30-days mortality as treated was 6.8% in TMLR group and 0.8% in the control group, showing a statistically significant difference. The pooled OR was 3.76 (95% CI 1.63 to 8.66), because of the higher mortality in patients crossing from standard treatment to TMLR.

AUTHORS' CONCLUSIONS

There is insufficient evidence to conclude that the clinical benefits of TMLR outweigh the potential risks. The procedure is associated with a significant early mortality.

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.

Angiogenic therapy for coronary artery and peripheral arterial disease

Neovascularization in chronically ischemic adult cardiac and skeletal muscle results from the processes of angiogenesis, arteriogenesis and vasculogenesis. Therapeutic angiogenesis describes an emerging field of cardiovascular medicine whereby new blood vessels are induced to grow to supply oxygen and nutrients to cardiac or skeletal muscle rendered ischemic as a result of progressive atherosclerosis. Various techniques have been utilized to promote new blood vessel growth in the heart and extremities, including mechanical means such as surgical or percutaneous myocardial laser revascularization, angiogenic growth factor therapies involving members of the vascular endothelial growth factor and fibroblast growth factor families, and more recently, cellular-based therapies using stem cells known as endothelial progenitor cells or angioblasts. The following review discusses each of these treatment strategies in detail including both preclinical and clinical data for their use in peripheral arterial and coronary artery disease.

Perioperative management of patients undergoing transmyocardial laser revascularization

Advanced revascularization strategies continue to uncover a growing number of patients with symptomatic diffuse coronary artery disease. Transmyocardial laser revascularization (TMR) provides significant benefit in terms of improved quality of life and more complete revascularization for these difficult to treat patients when TMR is used as sole therapy or in combination with coronary artery bypass grafting. The safe clinical application of this important procedure relies on diligent perioperative management with appropriate patient selection, intraoperative care that avoids myocardial ischemia, and postoperative pain control along with expeditious reinstitution of antianginal medications. The treatment paradigms learned with the safe application of TMR should prove useful as new therapies to extend our revascularization options are developed.

Clinical results of sole therapy TMR treatment

The safety and efficacy of transmyocardial laser revascularization (TMR) is best demonstrated by the data collected from several multi-institutional randomized controlled trials. These trials are an important link between the preclinical data and the most common use of TMR (TMR + Coronary Artery Bypass Grafting). In addition to significant symptomatic relief both short- and long-term objective data were also garnered in these studies. A review of the history, study design, and outcomes is provided.

Evolving treatment strategies for chronic refractory angina

Chronic refractory angina is a term used to describe patients who, despite optimal medical therapy, have both angina and objective evidence of ischaemia. It is estimated that 5-15% of the 12 million patients with chronic angina in the US meet the criteria for having refractory angina. This review focuses on the following evolving pharmacological therapies for chronic refractory angina: L-arginine, ivabradine, ranolazine, nicorandil and trimetazidine. Evolving devices and invasive procedures including enhanced external counterpulsation, spinal cord stimulation, and transmyocardial revascularisation are also briefly discussed.

A Blinded, Randomized, Placebo-Controlled Trial of Percutaneous Laser Myocardial Revascularization to Improve Angina Symptoms in Patients With Severe Coronary Disease

OBJECTIVES

This study was a randomized, patient- and evaluator-blinded, placebo-controlled trial in patients treated using percutaneous myocardial laser revascularization.

BACKGROUND

Previous studies using similar therapies have been confounded by placebo bias.

METHODS

A total of 298 patients with severe angina were randomly assigned to receive low-dose or high-dose myocardial laser channels or no laser channels, blinded as a sham procedure. The primary end point was the change in exercise duration from baseline examination to six months.

RESULTS

The incidence of 30-day death, stroke, myocardial infarction, coronary revascularization, or left ventricular perforation occurred in two patients in the placebo, eight patients in the low-dose, and four patients in the high-dose groups (p = 0.12); 30-day myocardial infarction incidence was higher in patients receiving either low-dose or high-dose laser (nine patients) compared with placebo (no patients, p = 0.03). At six months, there were no differences in the change in exercise duration between those receiving a sham (28.0 s, n = 100), low-dose laser (33.2 s, n = 98), or high-dose laser (28.0 s, n = 98, p = 0.94) procedure. There were also no differences in the proportion of patients improving to better than Canadian Cardiovascular Society class III angina symptoms at six months. The follow-up visual summed stress single-photon-emission computed tomography scores were not significantly different from baseline in any group and were no different between groups. The modest improvement in angina symptoms assessed by the Seattle Angina Questionnaire also was not statistically different among the arms.

CONCLUSIONS

Treatment with percutaneous myocardial laser revascularization provides no benefit beyond that of a similar sham procedure in patients blinded to their treatment status.

Meta-analysis of survival and relief of angina pectoris after transmyocardial revascularization

A meta-analysis of 7 randomized trials involving 1,053 patients was performed to evaluate the effect of transmyocardial laser revascularization as the sole procedural intervention on survival and angina relief. At 1 year, transmyocardial laser revascularization produced a significant improvement in angina class (p <0.0001) but no improvement in survival (p = 0.75).

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.

Current and future treatment strategies for refractory angina

Patients with refractory angina are not candidates for revascularization and have both class III or IV angina and objective evidence of ischemia despite optimal medical therapy. An estimated 300,000 to 900,000 patients in the United States have refractory angina, and 25,000 to 75,000 new cases are diagnosed each year. This review focuses on treatment strategies for refractory angina and includes the mechanism of action and clinical trial data for each strategy. The pharmacological agents that have been used are ranolazine, ivabradine, nicorandil, L-arginine, testosterone, and estrogen; currently, only L-arginine, testosterone, and estrogen are approved by the Food and Drug Administration. Results with the noninvasive treatments of enhanced external counterpulsation and transcutaneous electrical nerve stimulation are provided. Invasive treatment strategies including spinal cord stimulation, transmyocardial revascularization, percutaneous myocardial revascularization, and gene therapy are also reviewed.

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.

Transmyocardial laser revascularization

Transmyocardial laser revascularization (TMR) has been performed on over 12,000 patients worldwide. Since 1990, the treatment has provided significant angina relief for symptomatic end-stage coronary disease that is refractory to medical therapy. Seventy-five percent of patients treated with TMR have demonstrated a decrease of two or more angina classes postoperatively. As a result, TMR has provided a significant improvement in quality of life for patients, resulting in fewer hospital admissions and decreased dependency on medications. Two different wavelengths of light, carbon dioxide (CO(2)) and holmium yttrium-aluminum-garnet (Ho:YAG), have been employed. Results obtained using these lasers differ. The CO(2) laser has demonstrated a perfusion benefit as well as long-term improvement in quality of life and angina relief. The Ho:YAG laser has not demonstrated these results. These differences may, in part, explain the failure of percutaneous myocardial laser revascularization. This catheter-based approach was not as successful as TMR due to its partial thickness treatment of the myocardium as well as its use of the Ho:YAG laser. In addition to the patients with end-stage coronary disease who undergo TMR as sole therapy, there are an increasing number of patients who have been treated with a combination of coronary artery bypass grafting and TMR. This provides a more complete revascularization than leaving territories ungrafted. Further enhancement of the angiogenic response seen after TMR may be seen by the addition of gene therapy to TMR treatment.

From controlled trials to clinical practice

OBJECTIVES

We sought to examine trends in the use and outcomes of transmyocardial revascularization (TMR) in community practice. We also identified important risk factors for TMR and compared outcomes of TMR combined with coronary artery bypass graft surgery (TMR + CABG) versus bypass alone in patients receiving incomplete revascularization.

BACKGROUND

Although it is approved for use as a stand-alone procedure, there are limited data on the outcomes of (TMR + CABG).

METHODS

We identified 3,717 patients receiving TMR at 173 U.S. hospitals participating in the Society of Thoracic Surgeons (STS) National Cardiac Database. Baseline characteristics and outcomes in these patients were compared with those from six published randomized TMR trials. Multivariable logistic regression was used to identify clinical risk factors for mortality with TMR. Risk-adjusted mortality was also compared for TMR + CABG relative to CABG only in patients not amenable to complete traditional revascularization.

RESULTS

Between January 1998 and December 2001, the number of STS hospitals performing TMR and total procedural counts increased markedly, driven predominately by more TMR + CABG cases. Overall mortality rates for TMR-alone and TMR + CABG were 6.4% and 4.2%, respectively. Operative risks were significantly higher in those patients with recent myocardial infarction, unstable angina, and depressed ventricular function. Among patients receiving incomplete revascularization, TMR + CABG was not associated with decreased mortality risk compared with CABG alone, adjusted odds ratio 1.11 (95% confidence interval 0.74 to 1.67).

CONCLUSIONS

The use of TMR, and in particular, TMR + CABG, is expanding in community practice. Although procedural risks are high, there is room for optimization through improved patient selection and timing of the procedure. Further studies of TMR + CABG are needed given its growing use and unclear benefits.

Mid-term results of combined transmyocardial laser revascularization and coronary artery bypass

BACKGROUND

Transmyocardial laser revascularization is increasingly used to treat intractable angina in the absence of graftable vessels; however, its role in combination with coronary artery bypass grafting remains undefined. The aim of this pilot study was to investigate the outcome of the combination therapy at mid-term follow-up.

METHODS

Patients (n = 20) who had elective coronary artery bypass with one or more nongraftable coronary arteries were prospectively randomized to have either coronary artery bypass grafting alone or combination coronary artery bypass grafting plus transmyocardial laser revascularization with a holmium:YAG (yttrium-aluminum-garnet) laser to nongraftable areas. All patients had an exercise tolerance test preoperatively and at 6, 18, and 36 months follow-up. Stress echocardiography was performed on 17 patients at 18 months postoperatively, and regional wall motion score index was calculated in lased and nonlased nonrevascularizable myocardium of the left ventricle at rest and with dobutamine stress.

RESULTS

Both groups of patients were similar in preoperative demographics and operative data. There was no perioperative death. There was no difference between the two groups in angina scoring at 6, 18, and 36 months follow-up. Exercise tolerance improved by a mean of 46.8 +/- 20.0 seconds in the coronary artery bypass grafting group versus 199.2 +/- 66.5 seconds per patient in the coronary artery bypass grafting plus transmyocardial laser revascularization group (p = 1.8 x10(-6)) at 6 months; this benefit was maintained at 18 months (157 +/- 46.3 versus 61 +/- 39.2 seconds; p = 4 x10(-4)) but was lost at 36 months (57.2. +/- 42.1 versus 68.1 +/- 46.7 seconds; p = 0.70). The mean values for wall motion score index in the lased and nonlased regions at each stage of dobutamine stress at 18 months after surgery were not statistically significant.

CONCLUSIONS

The combination of coronary artery bypass and transmyocardial laser revascularization improved exercise tolerance in patients in whom complete revascularization could not be achieved by bypass grafting alone in the short term, but this benefit was lost by 36 months postoperatively. The transient improvement in exercise tolerance cannot be explained by changes in contractility in the lased areas.

Transmyocardial laser revascularization: epicardial ECG detection provides efficient R-wave triggering during mobilization of the heart

OBJECTIVE

In order to achieve an accurate intraoperative ECG detection, a new technique in detecting the trigger-signal was developed. In contrast to the traditional three-lead ECG-configuration, the left leg electrode was connected to a transient epicardial pacemaker electrode on the left-ventricular surface.

BACKGROUND DATA

The Holmium:YAG-Laser for Transmyocardial Laser Revascularization (TMLR) is R-wave-triggered, providing the release of energy only during the refractory period of the heart cycle. However, an exact ECG-triggering during mobilization of the apex and/or posterior wall is difficult to achieve by using conventional ECG-configuration, therefore increasing the risk for mistriggering and induction of arrhythmias during TMLR.

MATERIALS AND METHODS

Two groups of patients, all undergoing stand alone TMLR-procedures via left minithoracotomy, were compared. Ten patients were operated with the conventional ECG configuration (group 1) and ten patients with the modified epicardial ECG configuration (group 2).

RESULTS

In patients of group 1, as a result of a loss of the trigger signal or due to the triggering of artifacts, the incidence of correctly triggered QRS-complexes was 56% of all documented QRS-complexes. In contrast, an excellent triggering was observed in 98% (p < 0.001) in group 2, resulting in a reduction of laser operative time by 35% (p < 0.001) and a decrease in the incidence of intraoperative ventricular fibrillation (0 vs. 3).

CONCLUSION

In conclusion, this new ECG configuration is a simple but effective method in achieving an excellent ECG signal during all stages of TMLR. As a consequence, a reduction in operative time and incidence of ventricular fibrillation can be achieved.

Myocardial laser revascularization for the treatment of end-stage coronary artery disease

Myocardial laser revascularization is a novel therapeutic technique aimed at delivering oxygenated blood via a series of channels to the ischemic regions of the heart. These channels may be created surgically or via a less invasive percutaneous approach. In patients with end-stage coronary artery disease, both transmyocardial laser revascularization (TMR) and percutaneous myocardial laser revascularization (PMR) have been associated with a reduction in symptoms, improved exercise tolerance, and enhanced quality of life. However, the mechanism of action of laser therapy is incompletely understood, the results of objective cardiac perfusion measurements are inconclusive, and multiple randomized trials have failed to demonstrate an increase in survival. In addition, the positive results seen in TMR trials have been questioned because of a lack of blinding, raising the possibility that the benefit may have been due to the placebo effect. Finally, two recent sham-controlled, randomized clinical trials of PMR have not shown any benefit of the procedure, but instead have highlighted the important role of the placebo effect in the response to PMR. Further research is, therefore, needed to elucidate the value of myocardial laser revascularization.

Diode-pumped fiber lasers: a new clinical tool?

BACKGROUND AND OBJECTIVE

Diode-pumped fiber lasers are a compact and an efficient source of high power laser radiation. These laser systems have found wide recognition in the area of lasers as a result of these very practical characteristics and are now becoming important tools for a large number of applications. In this review, we outline the basic physics of fiber lasers and illustrate how a number of clinical procedures would benefit from their employment.

STUDY DESIGN/MATERIALS AND METHODS

The pump mechanisms, the relevant pump and laser transitions between the energy levels, and the main properties of the output from fiber lasers will be briefly reviewed. The main types of high power fiber lasers that have been demonstrated will be examined along with some recent medical applications that have used these lasers. We will also provide a general review of some important medical specialties, highlighting why these fields would gain from the introduction of the fiber laser.

RESULTS/CONCLUSION

It is established that while the fiber laser is still a new form of laser device and hence not commercially available in a wide sense, a number of important medical procedures will benefit from its general introduction into medicine. With the number of medical and surgical applications requiring high power laser radiation steadily increasing, the demand for more efficient and compact laser systems providing this capacity will grow commensurately. The high power fiber laser is one system that looks like a promising modality to meet this need.

Continued symptomatic improvement three to five years after transmyocardial revascularization with CO(2) laser: a late clinical follow-up of the Norwegian Randomized trial with transmyocardial revascularization

OBJECTIVES

The goals of this study were to assess late clinical outcome and left ventricular ejection fraction (LVEF) after transmyocardial revascularization with CO(2) laser (TMR).

BACKGROUND

During the 1990s TMR emerged as a treatment option for patients with refractory angina not eligible for conventional revascularization. Few reports exist on clinical effects and LVEF >3 years after TMR.

METHODS

One hundred patients with refractory angina not eligible for conventional revascularization were block-randomized 1:1 to receive continued medical treatment or medical treatment combined with TMR. The patients were evaluated at baseline and after 3, 12 and 43 (range: 32 to 60) months with end points to angina, hospitalizations due to acute myocardial infarctions or unstable angina, heart failure and LVEF. Mortality was registered and MOS 36 Short-Form Health Survey answered at baseline and after 3, 6 and 12 months.

RESULTS

Forty-three months after TMR, angina symptoms were still significantly improved, and unstable angina hospitalizations reduced by 55% (p < 0.001). Heart failure treatment (p < 0.01) increased, whereas the number of acute myocardial infarctions, LVEF and mortality was not affected. Quality of life was improved 3, 6 and 12 months after TMR.

CONCLUSIONS

Forty-three months after TMR, angina symptoms and hospitalizations due to unstable angina were significantly reduced, heart failure treatment increased and LVEF and mortality were seemingly unaffected.

A comparison of mechanical and laser transmyocardial revascularization for induction of angiogenesis and arteriogenesis in chronically ischemic myocardium

OBJECTIVES

The purpose of the present study was to compare the use of a mechanical transmyocardial implant (TMI) device with transmyocardial laser revascularization (TMR) for induction of therapeutic angiogenesis and arteriogenesis in the chronically ischemic heart.

BACKGROUND

Prior experimental studies have demonstrated evidence for neovascularization after both mechanical and laser transmyocardial revascularization, although a long-term comparison of the two techniques has not been performed.

METHODS

Using an established model of chronic hibernating myocardium, mini-swine underwent 90% proximal left circumflex (LCx) coronary artery stenosis. One month later, baseline positron emission tomography (PET) and dobutamine stress echocardiography (DSE) were performed to quantitate regional myocardial blood flow (MBF) and function. Animals then underwent TMR with a holmium:yttrium-aluminum-garnet (holmium:YAG) laser (n = 5), TMI (n = 5), or sham redo-thoracotomy (n = 5). In the TMR group, the entire LCx region was treated with transmural laser channels at a density of 1/cm(2). Transmyocardial implants were placed transmurally at a similar density in the LCx region of the TMI group. Six months later, the PET and DSE studies were repeated, and the animals were euthanized.

RESULTS

Six months after TMR, there was a significant increase over baseline in resting MBF to the lased LCx region (68.9 +/- 4.6% vs. 89.3 +/- 3.0% reference non-ischemic septal segments; p < 0.001). This increased MBF was accompanied by a significant improvement in LCx regional wall motion during peak dobutamine stress (p = 0.04). Compared with baseline, there was no change in LCx region MBF six months after either TMI (72.9 +/- 4.8% vs. 85.7 +/- 3.4%; p = 0.10) or sham redo-thoracotomy (75.6 +/- 4.6% vs. 80.1 +/- 5.0%; p > 0.2). Likewise, there was no significant change in rest or stress wall motion by DSE six months postoperatively in either group. Overall vascular density was increased only in the TMR-treated regions six months postoperatively. The difference between groups was most notable for a twofold increase in the number of small arterioles seen in the lased (4.4 +/- 0.3 arterioles per high power field; p < 0.001 vs. both TMI and sham) compared with TMI (2.2 +/- 0.2) and sham (1.9 +/- 0.2)-treated regions.

CONCLUSIONS

Mechanical transmyocardial revascularization with a TMI device does not appear to promote physiologically significant angiogenesis or arteriogenesis in the chronically ischemic porcine heart and cannot be recommended for clinical trials at this time. Infrared laser-mediated injury mechanisms may be important for inducing therapeutic neovascularization with direct myocardial revascularization techniques.

Reoperative transmyocardial laser revascularization for late recurrent angina

Transmyocardial laser revascularization (TMR) reduces anginal class and is indicated for severely symptomatic patients who are not candidates for conventional revascularization. This report describes a 72-year-old man who presented 4 years following initially successful TMR with recurrent angina refractory to maximal medical management. Reoperative TMR was performed with substantial improvement in angina and functional class.

Safety of local delivery of low- and intermediate-dose adenovirus gene transfer vectors to individuals with a spectrum of morbid conditions

To help define the safety profile of the use of adenovirus (Ad) gene transfer vectors in humans, this report summarizes our experience since April 1993 of the local administration of E1(-)/E3(-) Ad vectors to humans using low (<10(9) particle units) or intermediate (10(9)-10(11) particle units) doses. Included in the study are 90 individuals and 12 controls, with diverse comorbid conditions, including cystic fibrosis, colon cancer metastatic to liver, severe coronary artery disease, and peripheral vascular disease, as well as normals. These individuals received 140 different administrations of vector, with up to seven administrations to a single individual. The vectors used include three different transgenes (human cystic fibrosis transmembrane conductance regulator cDNA, E. coli cytosine deaminase gene, and the human vascular endothelial growth factor 121 cDNA) administered by six different routes (nasal epithelium, bronchial epithelium, percutaneous to solid tumor, intradermal, epicardial injection of the myocardium, and skeletal muscle). The total population was followed for 130.4 patient-years. The study assesses adverse events, common laboratory tests, and long-term follow-up, including incidence of death or development of malignancy. The total group incidence of major adverse events linked to an Ad vector was 0.7%. There were no deaths attributable to the Ad vectors per se, and the incidence of malignancy was within that expected for the population. Overall, the observations are consistent with the concept that local administration of low and intermediate doses of Ad vectors appears to be well tolerated.

[Coronary artery bypass graft combined with transmyocardial laser revascularization. Survival and functional class at one-year follow-up]

INTRODUCTION AND OBJECTIVES

The use of Transmyocardial Laser Revascularization (TMLR) as a strategy to treat unstable angina has been reported in many studies. We analyze its safety and effectiveness in combined procedures (CABG + TMLR).

METHODS

A non-randomized, retrospective cohort study was performed from May 4, 1999 to May 25, 2000 in 21 TMLR patients (18 combined CABG + TMLR) and 118 CABG only procedures. Mortality and NYHA analyses were determined by telephone at follow-up.

RESULTS

Three hospital deaths were observed: one isolated TMLR patient, one valvular + CABG + TMLR patient, and one CABG + TMLR patient. A significantly higher incidence of preoperative angina was found in the group of patients with TMLR + CABG, than in the group with only CABG (83 vs 25%; p < 0.001). There were no differences in age, gender, ejection fraction, Parsonnet and EuroSCORE risk estimation, or mortality (5.1% isolated CABG, 5.6% combined). No episode of angina was detected during follow-up in the CABG + TMLR group: 88% patients were NYHA I, and 21% NYHA II.

CONCLUSION

Incomplete coronary revascularization may be complemented with TMLR in the areas in which CABG is not possible without increased mortality. This technique may avoid postoperative unstable angina due to residual ischemic areas.

Excimer laser (308 nm) based transmyocardial laser revascularization: effects of the lasing parameters on myocardial histology

BACKGROUND AND OBJECTIVE

The effect of the excimer laser (308 nm) parameters on transmyocardial revascularization (TMR) channels is not well defined. This study investigates the influence of the pulse repetition rate, the size of the delivery catheter and its advancement speed on the morphology of TMR channels in vivo.

STUDY DESIGN/MATERIALS AND METHODS

Myocardial ablation was performed in a porcine model (N = 27) using multifiber catheters of 1.0 and 1.4 mm in diameter. The catheters were advanced into the myocardium at different speeds (1.27 and 2.54 mm/sec) while ablating at various repetition rates (10-80 Hz). The radiant exposure was kept at 35 mJ/mm(2) throughout the experiments. The channel histology was quantified by digital microscopy.

RESULTS

The channel cross-sectional area and the extent of the thermal damage decrease as the catheter advancement speed exceeds the ablation speed and vice versa. Within the parameters tested, advancement speed of about 1.3 mm/sec and pulse repetition rates of 40 Hz produce channels of size comparable to the catheter's diameter with moderate thermomechanical damage.

CONCLUSIONS

The repetition rate, catheter size, and catheter advancement speed are closely intertwined and crucial to the histological outcome of excimer laser based TMR.

Factors affecting functional outcome after autologous skeletal myoblast transplantation

BACKGROUND

This study assessed the extent to which the initial degree of functional impairment and the number of injected cells may influence the functional improvement provided by autologous skeletal myoblast transplantation into infarcted myocardium.

METHODS

One week after left coronary artery ligation, 44 rats received into the infarcted scar, autologous skeletal myoblasts expanded in vitro for 7 days (mean, 3.5 x 10(6), n = 21), or culture medium alone (controls, n = 23). Left ventricular function was assessed by two-dimensional echocardiography.

RESULTS

When transplanted hearts were stratified according to their baseline ejection fraction, a significant improvement occurred at 2 months in the less than 25% (from 21.4% to 37%), 25% to 35% (from 29% to 43.8%), and in the 35% to 40% (from 37.2% to 41.7%) groups, compared to controls (p = 0.048, 0.0057, and 0.034, respectively), but not in the more than 40% stratum. A significant linear relationship was found between the improvement in ejection fraction and the number of injected myoblasts, both at 1 and 2 months after transplantation (p < 0.0001).

CONCLUSIONS

Autologous myoblast transplantation is functionally effective over a wide range of postinfarct ejection fractions, including in the sickest hearts provided that they are injected with a sufficiently high number of cells.